draft-ietf-hip-rfc5206-bis-14.txt   rfc8046.txt 
Network Working Group T. Henderson, Ed. Internet Engineering Task Force (IETF) T. Henderson, Ed.
Internet-Draft University of Washington Request for Comments: 8046 University of Washington
Obsoletes: 5206 (if approved) C. Vogt Obsoletes: 5206 C. Vogt
Intended status: Standards Track Independent Category: Standards Track Independent
Expires: April 13, 2017 J. Arkko ISSN: 2070-1721 J. Arkko
Ericsson Ericsson
October 10, 2016 February 2017
Host Mobility with the Host Identity Protocol Host Mobility with the Host Identity Protocol
draft-ietf-hip-rfc5206-bis-14
Abstract Abstract
This document defines a mobility extension to the Host Identity This document defines a mobility extension to the Host Identity
Protocol (HIP). Specifically, this document defines a "LOCATOR_SET" Protocol (HIP). Specifically, this document defines a "LOCATOR_SET"
parameter for HIP messages that allows for a HIP host to notify peers parameter for HIP messages that allows for a HIP host to notify peers
about alternate addresses at which it may be reached. This document about alternate addresses at which it may be reached. This document
also defines how the parameter can be used to preserve communications also defines how the parameter can be used to preserve communications
across a change to the IP address used by one or both peer hosts. across a change to the IP address used by one or both peer hosts.
The same LOCATOR_SET parameter can also be used to support end-host The same LOCATOR_SET parameter can also be used to support end-host
multihoming (specified in RFC[Replace with the RFC number for draft- multihoming (as specified in RFC 8047). This document obsoletes RFC
ietf-hip-multihoming]). This document obsoletes RFC 5206. 5206.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
This Internet-Draft will expire on April 13, 2017. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc8046.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction and Scope . . . . . . . . . . . . . . . . . . . 3 1. Introduction and Scope . . . . . . . . . . . . . . . . . . . 4
2. Terminology and Conventions . . . . . . . . . . . . . . . . . 4 2. Terminology and Conventions . . . . . . . . . . . . . . . . . 4
3. Protocol Model . . . . . . . . . . . . . . . . . . . . . . . 5 3. Protocol Model . . . . . . . . . . . . . . . . . . . . . . . 7
3.1. Operating Environment . . . . . . . . . . . . . . . . . . 5 3.1. Operating Environment . . . . . . . . . . . . . . . . . . 7
3.1.1. Locator . . . . . . . . . . . . . . . . . . . . . . . 7 3.1.1. Locator . . . . . . . . . . . . . . . . . . . . . . . 9
3.1.2. Mobility Overview . . . . . . . . . . . . . . . . . . 7 3.1.2. Mobility Overview . . . . . . . . . . . . . . . . . . 9
3.2. Protocol Overview . . . . . . . . . . . . . . . . . . . . 8 3.2. Protocol Overview . . . . . . . . . . . . . . . . . . . . 10
3.2.1. Mobility with a Single SA Pair (No Rekeying) . . . . 9 3.2.1. Mobility with a Single SA Pair (No Rekeying) . . . . 10
3.2.2. Mobility with a Single SA Pair (Mobile-Initiated 3.2.2. Mobility with a Single SA Pair (Mobile-Initiated
Rekey) . . . . . . . . . . . . . . . . . . . . . . . 10 Rekey) . . . . . . . . . . . . . . . . . . . . . . . 12
3.2.3. Mobility messaging through rendezvous server . . . . 11 3.2.3. Mobility Messaging through the Rendezvous Server . . 13
3.2.4. Network Renumbering . . . . . . . . . . . . . . . . . 12 3.2.4. Network Renumbering . . . . . . . . . . . . . . . . . 14
3.3. Other Considerations . . . . . . . . . . . . . . . . . . 12 3.3. Other Considerations . . . . . . . . . . . . . . . . . . 14
3.3.1. Address Verification . . . . . . . . . . . . . . . . 12 3.3.1. Address Verification . . . . . . . . . . . . . . . . 14
3.3.2. Credit-Based Authorization . . . . . . . . . . . . . 13 3.3.2. Credit-Based Authorization . . . . . . . . . . . . . 15
3.3.3. Preferred Locator . . . . . . . . . . . . . . . . . . 14 3.3.3. Preferred Locator . . . . . . . . . . . . . . . . . . 16
4. LOCATOR_SET Parameter Format . . . . . . . . . . . . . . . . 15 4. LOCATOR_SET Parameter Format . . . . . . . . . . . . . . . . 16
4.1. Traffic Type and Preferred Locator . . . . . . . . . . . 16 4.1. Traffic Type and Preferred Locator . . . . . . . . . . . 18
4.2. Locator Type and Locator . . . . . . . . . . . . . . . . 17 4.2. Locator Type and Locator . . . . . . . . . . . . . . . . 19
4.3. UPDATE Packet with Included LOCATOR_SET . . . . . . . . . 17 4.3. UPDATE Packet with Included LOCATOR_SET . . . . . . . . . 19
5. Processing Rules . . . . . . . . . . . . . . . . . . . . . . 17 5. Processing Rules . . . . . . . . . . . . . . . . . . . . . . 19
5.1. Locator Data Structure and Status . . . . . . . . . . . . 18 5.1. Locator Data Structure and Status . . . . . . . . . . . . 19
5.2. Sending the LOCATOR_SET . . . . . . . . . . . . . . . . . 19 5.2. Sending the LOCATOR_SET . . . . . . . . . . . . . . . . . 21
5.3. Handling Received LOCATOR_SETs . . . . . . . . . . . . . 20 5.3. Handling Received LOCATOR_SETs . . . . . . . . . . . . . 22
5.4. Verifying Address Reachability . . . . . . . . . . . . . 22 5.4. Verifying Address Reachability . . . . . . . . . . . . . 24
5.5. Changing the Preferred Locator . . . . . . . . . . . . . 23 5.5. Changing the Preferred Locator . . . . . . . . . . . . . 26
5.6. Credit-Based Authorization . . . . . . . . . . . . . . . 24 5.6. Credit-Based Authorization . . . . . . . . . . . . . . . 26
5.6.1. Handling Payload Packets . . . . . . . . . . . . . . 24 5.6.1. Handling Payload Packets . . . . . . . . . . . . . . 27
5.6.2. Credit Aging . . . . . . . . . . . . . . . . . . . . 26 5.6.2. Credit Aging . . . . . . . . . . . . . . . . . . . . 29
6. Security Considerations . . . . . . . . . . . . . . . . . . . 27 6. Security Considerations . . . . . . . . . . . . . . . . . . . 29
6.1. Impersonation Attacks . . . . . . . . . . . . . . . . . . 28 6.1. Impersonation Attacks . . . . . . . . . . . . . . . . . . 30
6.2. Denial-of-Service Attacks . . . . . . . . . . . . . . . . 29 6.2. Denial-of-Service Attacks . . . . . . . . . . . . . . . . 31
6.2.1. Flooding Attacks . . . . . . . . . . . . . . . . . . 29 6.2.1. Flooding Attacks . . . . . . . . . . . . . . . . . . 31
6.2.2. Memory/Computational-Exhaustion DoS Attacks . . . . . 29 6.2.2. Memory/Computational-Exhaustion DoS Attacks . . . . . 32
6.3. Mixed Deployment Environment . . . . . . . . . . . . . . 30 6.3. Mixed Deployment Environment . . . . . . . . . . . . . . 32
6.4. Privacy Concerns . . . . . . . . . . . . . . . . . . . . 31 6.4. Privacy Concerns . . . . . . . . . . . . . . . . . . . . 33
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 31 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 33
8. Differences from RFC 5206 . . . . . . . . . . . . . . . . . . 31 8. Differences from RFC 5206 . . . . . . . . . . . . . . . . . . 33
9. Authors and Acknowledgments . . . . . . . . . . . . . . . . . 32 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 35
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 33 9.1. Normative References . . . . . . . . . . . . . . . . . . 35
10.1. Normative references . . . . . . . . . . . . . . . . . . 33 9.2. Informative References . . . . . . . . . . . . . . . . . 35
10.2. Informative references . . . . . . . . . . . . . . . . . 34 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 36
Appendix A. Document Revision History . . . . . . . . . . . . . 35 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 37
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 36
1. Introduction and Scope 1. Introduction and Scope
The Host Identity Protocol [RFC7401] (HIP) supports an architecture The Host Identity Protocol (HIP) [RFC7401] supports an architecture
that decouples the transport layer (TCP, UDP, etc.) from the that decouples the transport layer (TCP, UDP, etc.) from the
internetworking layer (IPv4 and IPv6) by using public/private key internetworking layer (IPv4 and IPv6) by using public/private key
pairs, instead of IP addresses, as host identities. When a host uses pairs, instead of IP addresses, as host identities. When a host uses
HIP, the overlying protocol sublayers (e.g., transport layer sockets HIP, the overlying protocol sublayers (e.g., transport-layer sockets
and Encapsulating Security Payload (ESP) Security Associations (SAs)) and Encapsulating Security Payload (ESP) Security Associations (SAs))
are instead bound to representations of these host identities, and are instead bound to representations of these host identities, and
the IP addresses are only used for packet forwarding. However, each the IP addresses are only used for packet forwarding. However, each
host needs to also know at least one IP address at which its peers host needs to also know at least one IP address at which its peers
are reachable. Initially, these IP addresses are the ones used are reachable. Initially, these IP addresses are the ones used
during the HIP base exchange. during the HIP base exchange.
One consequence of such a decoupling is that new solutions to One consequence of such a decoupling is that new solutions to
network-layer mobility and host multihoming are possible. There are network-layer mobility and host multihoming are possible. There are
potentially many variations of mobility and multihoming possible. potentially many variations of mobility and multihoming possible.
skipping to change at page 3, line 47 skipping to change at page 4, line 41
multiplexing and demultiplexing context to aid with the packet multiplexing and demultiplexing context to aid with the packet
handling in the lower layers. For instance, an IP address may handling in the lower layers. For instance, an IP address may
need to be paired with an ESP Security Parameter Index (SPI) so need to be paired with an ESP Security Parameter Index (SPI) so
that packets are sent on the correct SA for a given address. that packets are sent on the correct SA for a given address.
This document also specifies the messaging and elements of This document also specifies the messaging and elements of
procedure for end-host mobility of a HIP host. In particular, procedure for end-host mobility of a HIP host. In particular,
message flows to enable successful host mobility, including message flows to enable successful host mobility, including
address verification methods, are defined herein. address verification methods, are defined herein.
The HIP rendezvous server [I-D.ietf-hip-rfc5204-bis] can be used The HIP rendezvous server (RVS) [RFC8004] can be used to manage
to manage simultaneous mobility of both hosts, initial simultaneous mobility of both hosts, initial reachability of a
reacahability of a mobile host, location privacy, and some modes mobile host, location privacy, and some modes of NAT traversal.
of NAT traversal. Use of the HIP rendezvous server to manage the Use of the HIP RVS to manage the simultaneous mobility of both
simultaneous mobility of both hosts is specified herein. hosts is specified herein.
The following topics are out of scope: The following topics are out of scope:
While the same LOCATOR_SET parameter supports host multihoming While the same LOCATOR_SET parameter supports host multihoming
(simultaneous use of a number of addresses), procedures for host (simultaneous use of a number of addresses), procedures for host
multihoming are out of scope, and are specified in multihoming are out of scope and are specified in [RFC8047].
[I-D.ietf-hip-multihoming].
While HIP can potentially be used with transports other than the While HIP can potentially be used with transports other than the
ESP transport format [RFC7402], this document largely assumes the ESP transport format [RFC7402], this document largely assumes the
use of ESP and leaves other transport formats for further study. use of ESP and leaves other transport formats for further study.
We do not consider localized mobility management extensions (i.e., We do not consider localized mobility management extensions (i.e.,
mobility management techniques that do not involve directly mobility management techniques that do not involve directly
signaling the correspondent node); this document is concerned with signaling the correspondent node); this document is concerned with
end-to-end mobility. end-to-end mobility.
skipping to change at page 4, line 38 skipping to change at page 5, line 37
The main sections of this document are organized as follows. The main sections of this document are organized as follows.
Section 3 provides a summary overview of operations, scenarios, and Section 3 provides a summary overview of operations, scenarios, and
other considerations. Section 4 specifies the messaging parameter other considerations. Section 4 specifies the messaging parameter
syntax. Section 5 specifies the processing rules for messages. syntax. Section 5 specifies the processing rules for messages.
Section 6 describes security considerations for this specification. Section 6 describes security considerations for this specification.
2. Terminology and Conventions 2. Terminology and Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in [RFC2119].
LOCATOR_SET. A HIP parameter containing zero or more Locator fields. LOCATOR_SET. A HIP parameter containing zero or more Locator fields.
Locator. A name that controls how the packet is routed through the locator. A name that controls how the packet is routed through the
network and demultiplexed by the end host. It may include a network and demultiplexed by the end host. It may include a
concatenation of traditional network addresses such as an IPv6 concatenation of traditional network addresses such as an IPv6
address and end-to-end identifiers such as an ESP SPI. It may address and end-to-end identifiers such as an ESP SPI. It may
also include transport port numbers or IPv6 Flow Labels as also include transport port numbers or IPv6 Flow Labels as
demultiplexing context, or it may simply be a network address. demultiplexing context, or it may simply be a network address.
Address. A name that denotes a point-of-attachment to the network. Locator. When capitalized in the middle of a sentence, this term
refers to the encoding of a locator within the LOCATOR_SET
parameter (i.e., the 'Locator' field of the parameter).
Address. A name that denotes a point of attachment to the network.
The two most common examples are an IPv4 address and an IPv6 The two most common examples are an IPv4 address and an IPv6
address. The set of possible addresses is a subset of the set of address. The set of possible addresses is a subset of the set of
possible locators. possible locators.
Preferred locator. A locator on which a host prefers to receive Preferred locator. A locator on which a host prefers to receive
data. Certain locators are labelled as preferred when a host data. Certain locators are labeled as preferred when a host
advertises its locator set to its peer. By default, the locators advertises its locator set to its peer. By default, the locators
used in the HIP base exchange are the preferred locators. The use used in the HIP base exchange are the preferred locators. The use
of preferred locators, including the scenario where multiple of preferred locators, including the scenario where multiple
address scopes and families may be in use, is defined more in address scopes and families may be in use, is defined more in
[I-D.ietf-hip-multihoming] than in this document. [RFC8047] than in this document.
Credit Based Authorization. A mechanism allowing a host to send a Credit-Based Authorization (CBA). A mechanism allowing a host to
certain amount of data to a peer's newly announced locator before send a certain amount of data to a peer's newly announced locator
the result of mandatory address verification is known. before the result of mandatory address verification is known.
3. Protocol Model 3. Protocol Model
This section is an overview; more detailed specification follows this This section is an overview; a more detailed specification follows
section. this section.
3.1. Operating Environment 3.1. Operating Environment
The Host Identity Protocol (HIP) [RFC7401] is a key establishment and HIP [RFC7401] is a key establishment and parameter negotiation
parameter negotiation protocol. Its primary applications are for protocol. Its primary applications are for authenticating host
authenticating host messages based on host identities, and messages based on host identities and establishing SAs for the ESP
establishing security associations (SAs) for the ESP transport format transport format [RFC7402] and possibly other protocols in the
[RFC7402] and possibly other protocols in the future. future.
+--------------------+ +--------------------+ +--------------------+ +--------------------+
| | | | | | | |
| +------------+ | | +------------+ | | +------------+ | | +------------+ |
| | Key | | HIP | | Key | | | | Key | | HIP | | Key | |
| | Management | <-+-----------------------+-> | Management | | | | Management | <-+-----------------------+-> | Management | |
| | Process | | | | Process | | | | Process | | | | Process | |
| +------------+ | | +------------+ | | +------------+ | | +------------+ |
| ^ | | ^ | | ^ | | ^ |
| | | | | | | | | | | |
skipping to change at page 6, line 7 skipping to change at page 7, line 42
| +------------+ | | +------------+ | | +------------+ | | +------------+ |
| | | | | | | |
| | | | | | | |
| Initiator | | Responder | | Initiator | | Responder |
+--------------------+ +--------------------+ +--------------------+ +--------------------+
Figure 1: HIP Deployment Model Figure 1: HIP Deployment Model
The general deployment model for HIP is shown above, assuming The general deployment model for HIP is shown above, assuming
operation in an end-to-end fashion. This document specifies an operation in an end-to-end fashion. This document specifies an
extension to the HIP protocol to enable end-host mobility. In extension to HIP to enable end-host mobility. In summary, these
summary, these extensions to the HIP base protocol enable the extensions to the HIP base protocol enable the signaling of new
signaling of new addressing information to the peer in HIP messages. addressing information to the peer in HIP messages. The messages are
The messages are authenticated via a signature or keyed hash message authenticated via a signature or keyed Hash Message Authentication
authentication code (HMAC) based on its Host Identity. This document Code (HMAC) based on its Host Identity (HI). This document specifies
specifies the format of this new addressing (LOCATOR_SET) parameter, the format of this new addressing (LOCATOR_SET) parameter, the
the procedures for sending and processing this parameter to enable procedures for sending and processing this parameter to enable basic
basic host mobility, and procedures for a concurrent address host mobility, and procedures for a concurrent address verification
verification mechanism. mechanism.
--------- ---------
| TCP | (sockets bound to HITs) | TCP | (sockets bound to HITs)
--------- ---------
| |
--------- ---------
----> | ESP | {HIT_s, HIT_d} <-> SPI ----> | ESP | {HIT_s, HIT_d} <-> SPI
| --------- | ---------
| | | |
---- --------- ---- ---------
| MH |-> | HIP | {HIT_s, HIT_d, SPI} <-> {IP_s, IP_d, SPI} | MH |-> | HIP | {HIT_s, HIT_d, SPI} <-> {IP_s, IP_d, SPI}
---- --------- ---- ---------
| |
--------- ---------
| IP | | IP |
--------- ---------
Figure 2: Architecture for HIP Host Mobility (MH) Figure 2: Architecture for HIP Host Mobility and Multihoming
Figure 2 depicts a layered architectural view of a HIP-enabled stack Figure 2 depicts a layered architectural view of a HIP-enabled stack
using the ESP transport format. In HIP, upper-layer protocols using the ESP transport format. In HIP, upper-layer protocols
(including TCP and ESP in this figure) are bound to Host Identity (including TCP and ESP in this figure) are bound to Host Identity
Tags (HITs) and not IP addresses. The HIP sublayer is responsible Tags (HITs) and not IP addresses. The HIP sublayer is responsible
for maintaining the binding between HITs and IP addresses. The SPI for maintaining the binding between HITs and IP addresses. The SPI
is used to associate an incoming packet with the right HITs. The is used to associate an incoming packet with the right HITs. The
block labeled "MH" is introduced below. block labeled "MH" corresponds to the function that manages the
bindings at the ESP and HIP sublayers for mobility (specified in this
document) and multihoming (specified in [RFC8047]).
Consider first the case in which there is no mobility or multihoming, Consider first the case in which there is no mobility or multihoming,
as specified in the base protocol specification [RFC7401]. The HIP as specified in the base protocol specification [RFC7401]. The HIP
base exchange establishes the HITs in use between the hosts, the SPIs base exchange establishes the HITs in use between the hosts, the SPIs
to use for ESP, and the IP addresses (used in both the HIP signaling to use for ESP, and the IP addresses (used in both the HIP signaling
packets and ESP data packets). Note that there can only be one such packets and ESP data packets). Note that there can only be one such
set of bindings in the outbound direction for any given packet, and set of bindings in the outbound direction for any given packet, and
the only fields used for the binding at the HIP layer are the fields the only fields used for the binding at the HIP layer are the fields
exposed by ESP (the SPI and HITs). For the inbound direction, the exposed by ESP (the SPI and HITs). For the inbound direction, the
SPI is all that is required to find the right host context. ESP SPI is all that is required to find the right host context. ESP
rekeying events change the mapping between the HIT pair and SPI, but rekeying events change the mapping between the HIT pair and SPI, but
do not change the IP addresses. do not change the IP addresses.
Consider next a mobility event, in which a host moves to another IP Consider next a mobility event, in which a host moves to another IP
address. Two things need to occur in this case. First, the peer address. Two things need to occur in this case. First, the peer
needs to be notified of the address change using a HIP UPDATE needs to be notified of the address change using a HIP UPDATE
message. Second, each host needs to change its local bindings at the message. Second, each host needs to change its local bindings at the
HIP sublayer (new IP addresses). It may be that both the SPIs and IP HIP sublayer (new IP addresses). It may be that both the SPIs and IP
addresses are changed simultaneously in a single UPDATE; the protocol addresses are changed simultaneously in a single UPDATE; the protocol
described herein supports this. Although internal notification of described herein supports this. Although internal notification of
transport layer protocols regarding the path change (e.g. to reset transport-layer protocols regarding the path change (e.g., to reset
congestion control variables) may be desired, this specification does congestion control variables) may be desired, this specification does
not address such internal notification. In addition, elements of not address such internal notification. In addition, elements of
procedure for traversing network address translators (NATs) and procedure for traversing network address translators (NATs) and
firewalls, including NATs and firewalls that may understand the HIP firewalls, including NATs and firewalls that may understand HIP, may
protocol, may complicate the above basic scenario and are not covered complicate the above basic scenario and are not covered by this
by this document. document.
3.1.1. Locator 3.1.1. Locator
This document defines a generalization of an address called a This document defines a generalization of an address called a
"locator". A locator specifies a point-of-attachment to the network "locator". A locator specifies a point of attachment to the network
but may also include additional end-to-end tunneling or per-host but may also include additional end-to-end tunneling or a per-host
demultiplexing context that affects how packets are handled below the demultiplexing context that affects how packets are handled below the
logical HIP sublayer of the stack. This generalization is useful logical HIP sublayer of the stack. This generalization is useful
because IP addresses alone may not be sufficient to describe how because IP addresses alone may not be sufficient to describe how
packets should be handled below HIP. For example, in a host packets should be handled below HIP. For example, in a host
multihoming context, certain IP addresses may need to be associated multihoming context, certain IP addresses may need to be associated
with certain ESP SPIs to avoid violating the ESP anti-replay window. with certain ESP SPIs to avoid violating the ESP anti-replay window.
Addresses may also be affiliated with transport ports in certain Addresses may also be affiliated with transport ports in certain
tunneling scenarios. Locators may simply be traditional network tunneling scenarios. Locators may simply be traditional network
addresses. The format of the locator fields in the LOCATOR_SET addresses. The format of the Locator fields in the LOCATOR_SET
parameter is defined in Section 4. parameter is defined in Section 4.
3.1.2. Mobility Overview 3.1.2. Mobility Overview
When a host moves to another address, it notifies its peer of the new When a host moves to another address, it notifies its peer of the new
address by sending a HIP UPDATE packet containing a single address by sending a HIP UPDATE packet containing a single
LOCATOR_SET parameter and a single ESP_INFO parameter. This UPDATE LOCATOR_SET parameter and a single ESP_INFO parameter. This UPDATE
packet is acknowledged by the peer. For reliability in the presence packet is acknowledged by the peer. For reliability in the presence
of packet loss, the UPDATE packet is retransmitted as defined in the of packet loss, the UPDATE packet is retransmitted as defined in the
HIP protocol specification [RFC7401]. The peer can authenticate the HIP specification [RFC7401]. The peer can authenticate the contents
contents of the UPDATE packet based on the signature and keyed hash of the UPDATE packet based on the signature and keyed hash of the
of the packet. packet.
When using ESP Transport Format [RFC7402], the host may at the same When using the ESP transport format [RFC7402], the host may, at the
time decide to rekey its security association and possibly generate a same time, decide to rekey its security association and possibly
new Diffie-Hellman key; all of these actions are triggered by generate a new Diffie-Hellman key; all of these actions are triggered
including additional parameters in the UPDATE packet, as defined in by including additional parameters in the UPDATE packet, as defined
the base protocol specification [RFC7401] and ESP extension in the base protocol specification [RFC7401] and ESP extension
[RFC7402]. [RFC7402].
When using ESP (and possibly other transport modes in the future), When using ESP (and possibly other transport modes in the future),
the host is able to receive packets that are protected using a HIP the host is able to receive packets that are protected using a HIP-
created ESP SA from any address. Thus, a host can change its IP created ESP SA from any address. Thus, a host can change its IP
address and continue to send packets to its peers without necessarily address and continue to send packets to its peers without necessarily
rekeying. However, the peers are not able to send packets to these rekeying. However, the peers are not able to send packets to these
new addresses before they can reliably and securely update the set of new addresses before they can reliably and securely update the set of
addresses that they associate with the sending host. Furthermore, addresses that they associate with the sending host. Furthermore,
mobility may change the path characteristics in such a manner that mobility may change the path characteristics in such a manner that
reordering occurs and packets fall outside the ESP anti-replay window reordering occurs and packets fall outside the ESP anti-replay window
for the SA, thereby requiring rekeying. for the SA, thereby requiring rekeying.
3.2. Protocol Overview 3.2. Protocol Overview
In this section, we briefly introduce a number of usage scenarios for In this section, we briefly introduce a number of usage scenarios for
HIP host mobility. These scenarios assume that HIP is being used HIP host mobility. These scenarios assume that HIP is being used
with the ESP transform [RFC7402], although other scenarios may be with the ESP transform [RFC7402], although other scenarios may be
defined in the future. To understand these usage scenarios, the defined in the future. To understand these usage scenarios, the
reader should be at least minimally familiar with the HIP protocol reader should be at least minimally familiar with the HIP
specification [RFC7401] and with the use of ESP with HIP [RFC7402]. specification [RFC7401] and with the use of ESP with HIP [RFC7402].
According to these specifications, the data traffic in a HIP session According to these specifications, the data traffic in a HIP session
is protected with ESP, and the ESP SPI acts as an index to the right is protected with ESP, and the ESP SPI acts as an index to the right
host-to-host context. More specification details are found later in host-to-host context. More specification details are found later in
Section 4 and Section 5. Sections 4 and 5.
The scenarios below assume that the two hosts have completed a single The scenarios below assume that the two hosts have completed a single
HIP base exchange with each other. Both of the hosts therefore have HIP base exchange with each other. Therefore, both of the hosts have
one incoming and one outgoing SA. Further, each SA uses the same one incoming and one outgoing SA. Further, each SA uses the same
pair of IP addresses, which are the ones used in the base exchange. pair of IP addresses, which are the ones used in the base exchange.
The readdressing protocol is an asymmetric protocol where a mobile The readdressing protocol is an asymmetric protocol where a mobile
host informs a peer host about changes of IP addresses on affected host informs a peer host about changes of IP addresses on affected
SPIs. The readdressing exchange is designed to be piggybacked on SPIs. The readdressing exchange is designed to be piggybacked on
existing HIP exchanges. In support of mobility, the LOCATOR_SET existing HIP exchanges. In support of mobility, the LOCATOR_SET
parameter is carried in UPDATE packets. parameter is carried in UPDATE packets.
The scenarios below at times describe addresses as being in either an The scenarios below at times describe addresses as being in either an
ACTIVE, UNVERIFIED, or DEPRECATED state. From the perspective of a ACTIVE, UNVERIFIED, or DEPRECATED state. From the perspective of a
host, newly-learned addresses of the peer needs to be verified before host, newly learned addresses of the peer need to be verified before
put into active service, and addresses removed by the peer are put put into active service, and addresses removed by the peer are put
into a deprecated state. Under limited conditions described below into a deprecated state. Under limited conditions described below
(Section 5.6), an UNVERIFIED address may be used. The addressing (Section 5.6), an UNVERIFIED address may be used. The addressing
states are defined more formally in Section 5.1. states are defined more formally in Section 5.1.
Hosts that use link-local addresses as source addresses in their HIP Hosts that use link-local addresses as source addresses in their HIP
handshakes may not be reachable by a mobile peer. Such hosts SHOULD handshakes may not be reachable by a mobile peer. Such hosts SHOULD
provide a globally routable address either in the initial handshake provide a globally routable address either in the initial handshake
or via the LOCATOR_SET parameter. or via the LOCATOR_SET parameter.
3.2.1. Mobility with a Single SA Pair (No Rekeying) 3.2.1. Mobility with a Single SA Pair (No Rekeying)
A mobile host sometimes needs to change an IP address bound to an A mobile host sometimes needs to change an IP address bound to an
interface. The change of an IP address might be needed due to a interface. The change of an IP address might be needed due to a
change in the advertised IPv6 prefixes on the link, a reconnected PPP change in the advertised IPv6 prefixes on the link, a reconnected PPP
link, a new DHCP lease, or an actual movement to another subnet. In link, a new DHCP lease, or an actual movement to another subnet. In
order to maintain its communication context, the host needs to inform order to maintain its communication context, the host needs to inform
its peers about the new IP address. This first example considers the its peers about the new IP address. This first example considers the
case in which the mobile host has only one interface, one IP address case in which the mobile host has only one interface, one IP address
in use within the HIP session, a single pair of SAs (one inbound, one in use within the HIP session, a single pair of SAs (one inbound, one
outbound), and no rekeying occurs on the SAs. We also assume that outbound), and no rekeying occurring on the SAs. We also assume that
the new IP addresses are within the same address family (IPv4 or the new IP addresses are within the same address family (IPv4 or
IPv6) as the previous address. This is the simplest scenario, IPv6) as the previous address. This is the simplest scenario,
depicted in Figure 3. Note that the conventions for message depicted in Figure 3. Note that the conventions for message
parameter notations in figures (use of parentheses and brackets) is parameter notations in figures (use of parentheses and brackets) is
defined in Section 2.2 of [RFC7401]. defined in Section 2.2 of [RFC7401].
Mobile Host Peer Host Mobile Host Peer Host
UPDATE(ESP_INFO, LOCATOR_SET, SEQ) UPDATE(ESP_INFO, LOCATOR_SET, SEQ)
-----------------------------------> ----------------------------------->
UPDATE(ESP_INFO, SEQ, ACK, ECHO_REQUEST) UPDATE(ESP_INFO, SEQ, ACK, ECHO_REQUEST)
<----------------------------------- <-----------------------------------
UPDATE(ACK, ECHO_RESPONSE) UPDATE(ACK, ECHO_RESPONSE)
-----------------------------------> ----------------------------------->
Figure 3: Readdress without Rekeying, but with Address Check Figure 3: Readdress without Rekeying but with Address Check
The steps of the packet processing are as follows: The steps of the packet processing are as follows:
1. The mobile host may be disconnected from the peer host for a 1. The mobile host may be disconnected from the peer host for a
brief period of time while it switches from one IP address to brief period of time while it switches from one IP address to
another; this case is sometimes referred to in the literature as another; this case is sometimes referred to in the literature as
a "break-before-make" case. The host may also obtain its new IP a "break-before-make" case. The host may also obtain its new IP
address before loosing the old one ("make-before-break" case). address before losing the old one ("make-before-break" case). In
In either case, upon obtaining a new IP address, the mobile host either case, upon obtaining a new IP address, the mobile host
sends a LOCATOR_SET parameter to the peer host in an UPDATE sends a LOCATOR_SET parameter to the peer host in an UPDATE
message. The UPDATE message also contains an ESP_INFO parameter message. The UPDATE message also contains an ESP_INFO parameter
containing the values of the old and new SPIs for a security containing the values of the old and new SPIs for a security
association. In this case, the OLD SPI and NEW SPI parameters association. In this case, both the OLD SPI and NEW SPI
both are set to the value of the preexisting incoming SPI; this parameters are set to the value of the preexisting incoming SPI;
ESP_INFO does not trigger a rekeying event but is instead this ESP_INFO does not trigger a rekeying event but is instead
included for possible parameter-inspecting firewalls on the path included for possible parameter-inspecting firewalls on the path
([RFC5207] specifies some such firewall scenarios in which the ([RFC5207] specifies some such firewall scenarios in which the
HIP-aware firewall may want to associate ESP flows to host HIP-aware firewall may want to associate ESP flows to host
identities). The LOCATOR_SET parameter contains the new IP identities). The LOCATOR_SET parameter contains the new IP
address (Locator Type of "1", defined below) and a locator address (embedded in a Locator Type of "1", defined below) and a
lifetime. The mobile host waits for this UPDATE to be lifetime associated with the locator. The mobile host waits for
acknowledged, and retransmits if necessary, as specified in the this UPDATE to be acknowledged, and retransmits if necessary, as
base specification [RFC7401]. specified in the base specification [RFC7401].
2. The peer host receives the UPDATE, validates it, and updates any 2. The peer host receives the UPDATE, validates it, and updates any
local bindings between the HIP association and the mobile host's local bindings between the HIP association and the mobile host's
destination address. The peer host MUST perform an address destination address. The peer host MUST perform an address
verification by placing a nonce in the ECHO_REQUEST parameter of verification by placing a nonce in the ECHO_REQUEST parameter of
the UPDATE message sent back to the mobile host. It also the UPDATE message sent back to the mobile host. It also
includes an ESP_INFO parameter with the OLD SPI and NEW SPI includes an ESP_INFO parameter with both the OLD SPI and NEW SPI
parameters both set to the value of the preexisting incoming SPI, parameters set to the value of the preexisting incoming SPI and
and sends this UPDATE (with piggybacked acknowledgment) to the sends this UPDATE (with piggybacked acknowledgment) to the mobile
mobile host at its new address. This UPDATE also acknowledges host at its new address. This UPDATE also acknowledges the
the mobile host's UPDATE that triggered the exchange. The peer mobile host's UPDATE that triggered the exchange. The peer host
host waits for its UPDATE to be acknowledged, and retransmits if waits for its UPDATE to be acknowledged, and retransmits if
necessary, as specified in the base specification [RFC7401]. The necessary, as specified in the base specification [RFC7401]. The
peer MAY use the new address immediately, but it MUST limit the peer MAY use the new address immediately, but it MUST limit the
amount of data it sends to the address until address verification amount of data it sends to the address until address verification
completes. completes.
3. The mobile host completes the readdress by processing the UPDATE 3. The mobile host completes the readdress by processing the UPDATE
ACK and echoing the nonce in an ECHO_RESPONSE, containing the ACK ACK and echoing the nonce in an ECHO_RESPONSE, containing the ACK
of the peer's UPDATE. This UPDATE is not protected by a of the peer's UPDATE. This UPDATE is not protected by a
retransmission timer because it does not contain a SEQ parameter retransmission timer because it does not contain a SEQ parameter
requesting acknowledgment. Once the peer host receives this requesting acknowledgment. Once the peer host receives this
ECHO_RESPONSE, it considers the new address to be verified and ECHO_RESPONSE, it considers the new address to be verified and
can put the address into full use. can put the address into full use.
While the peer host is verifying the new address, the new address is While the peer host is verifying the new address, the new address is
marked as UNVERIFIED in the interim, and the old address is marked as UNVERIFIED (in the interim), and the old address is
DEPRECATED. Once the peer host has received a correct reply to its DEPRECATED. Once the peer host has received a correct reply to its
UPDATE challenge, it marks the new address as ACTIVE and removes the UPDATE challenge, it marks the new address as ACTIVE and removes the
old address. old address.
3.2.2. Mobility with a Single SA Pair (Mobile-Initiated Rekey) 3.2.2. Mobility with a Single SA Pair (Mobile-Initiated Rekey)
The mobile host may decide to rekey the SAs at the same time that it The mobile host may decide to rekey the SAs at the same time that it
notifies the peer of the new address. In this case, the above notifies the peer of the new address. In this case, the above
procedure described in Figure 3 is slightly modified. The UPDATE procedure described in Figure 3 is slightly modified. The UPDATE
message sent from the mobile host includes an ESP_INFO with the OLD message sent from the mobile host includes an ESP_INFO with the OLD
skipping to change at page 11, line 19 skipping to change at page 13, line 16
UPDATE(ESP_INFO, LOCATOR_SET, SEQ, [DIFFIE_HELLMAN]) UPDATE(ESP_INFO, LOCATOR_SET, SEQ, [DIFFIE_HELLMAN])
-----------------------------------> ----------------------------------->
UPDATE(ESP_INFO, SEQ, ACK, [DIFFIE_HELLMAN,] ECHO_REQUEST) UPDATE(ESP_INFO, SEQ, ACK, [DIFFIE_HELLMAN,] ECHO_REQUEST)
<----------------------------------- <-----------------------------------
UPDATE(ACK, ECHO_RESPONSE) UPDATE(ACK, ECHO_RESPONSE)
-----------------------------------> ----------------------------------->
Figure 4: Readdress with Mobile-Initiated Rekey Figure 4: Readdress with Mobile-Initiated Rekey
3.2.3. Mobility messaging through rendezvous server 3.2.3. Mobility Messaging through the Rendezvous Server
Section 6.11 of [RFC7401] specifies procedures for sending HIP UPDATE Section 6.11 of [RFC7401] specifies procedures for sending HIP UPDATE
packets. The UPDATE packets are protected by a timer subject to packets. The UPDATE packets are protected by a timer subject to
exponential backoff and resent UPDATE_RETRY_MAX times. It may be, exponential backoff and resent UPDATE_RETRY_MAX times. It may be,
however, that the peer is itself in the process of moving when the however, that the peer is itself in the process of moving when the
local host is trying to update the IP address bindings of the HIP local host is trying to update the IP address bindings of the HIP
association. This is sometimes called the "double-jump" mobility association. This is sometimes called the "double-jump" mobility
problem; each host's UPDATE packets are simultaneously sent to a problem; each host's UPDATE packets are simultaneously sent to a
stale address of the peer, and the hosts are no longer reachable from stale address of the peer, and the hosts are no longer reachable from
one another. one another.
The HIP Rendezvous Extension [I-D.ietf-hip-rfc5204-bis] specifies a The HIP Rendezvous Extension [RFC8004] specifies a rendezvous service
rendezvous service that permits the I1 packet from the base exchange that permits the I1 packet from the base exchange to be relayed from
to be relayed from a stable or well-known public IP address location a stable or well-known public IP address location to the current IP
to the current IP address of the host. It is possible to support address of the host. It is possible to support double-jump mobility
double-jump mobility with this rendezvous service if the following with this rendezvous service if the following extensions to the
extensions to the specifications of [I-D.ietf-hip-rfc5204-bis] and specifications of [RFC8004] and [RFC7401] are followed.
[RFC7401] are followed.
1. The mobile host sending an UPDATE to the peer, and not receiving 1. The mobile host sending an UPDATE to the peer, and not receiving
an ACK, MAY resend the UPDATE to a rendezvous server (RVS) of the an ACK, MAY resend the UPDATE to an RVS of the peer, if such a
peer, if such a server is known. The host MAY try the RVS of the server is known. The host MAY try the RVS of the peer up to
peer up to UPDATE_RETRY_MAX times as specified in [RFC7401]. The UPDATE_RETRY_MAX times as specified in [RFC7401]. The host MAY
host MAY try to use the peer's RVS before it has tried try to use the peer's RVS before it has tried UPDATE_RETRY_MAX
UPDATE_RETRY_MAX times to the last working address (i.e. the RVS times to the last working address (i.e., the RVS MAY be tried in
MAY be tried in parallel with retries to the last working parallel with retries to the last working address). The
address). The aggressiveness of a host replicating its UPDATEs aggressiveness of a host replicating its UPDATEs to multiple
to multiple destinations, to try candidates in parallel instead destinations, to try candidates in parallel instead of serially,
of serially, is a policy choice outside of this specification. is a policy choice outside of this specification.
2. A rendezvous server supporting the UPDATE forwarding extensions 2. An RVS supporting the UPDATE forwarding extensions specified
specified herein MUST modify the UPDATE in the same manner as it herein MUST modify the UPDATE in the same manner as it modifies
modifies the I1 packet before forwarding. Specifically, it MUST the I1 packet before forwarding. Specifically, it MUST rewrite
rewrite the IP header source and destination addresses, recompute the IP header source and destination addresses, recompute the IP
the IP header checksum, and include the FROM and RVS_HMAC header checksum, and include the FROM and RVS_HMAC parameters.
parameters.
3. A host receiving an UPDATE packet MUST be prepared to process the 3. A host receiving an UPDATE packet MUST be prepared to process the
FROM and RVS_HMAC parameters, and MUST include a VIA_RVS FROM and RVS_HMAC parameters and MUST include a VIA_RVS parameter
parameter in the UPDATE reply that contains the ACK of the UPDATE in the UPDATE reply that contains the ACK of the UPDATE SEQ.
SEQ.
4. An initiator receiving a VIA_RVS in the UPDATE reply should 4. An Initiator receiving a VIA_RVS in the UPDATE reply should
initiate address reachability tests (described later in this initiate address reachability tests (described later in this
document) towards the end host's address and not towards the document) towards the end host's address and not towards the
address included in the VIA_RVS. address included in the VIA_RVS.
This scenario requires that hosts using rendezvous servers also take This scenario requires that hosts using RVSs also take steps to
steps to update their current address bindings with their rendezvous update their current address bindings with their RVS upon a mobility
server upon a mobility event. [I-D.ietf-hip-rfc5204-bis] does not event. [RFC8004] does not specify how to update the RVS with a
specify how to update the rendezvous server with a client host's new client host's new address. Section 3.2 of [RFC8003] describes how a
address. [I-D.ietf-hip-rfc5203-bis] Section 3.2 describes how a host host may send a REG_REQUEST in either an I2 packet (if there is no
may send a REG_REQUEST in either an I2 packet (if there is no active active association) or an UPDATE packet (if such association exists).
association) or an UPDATE packet (if such association exists). According to procedures described in [RFC8003], if a mobile host has
According to procedures described in [I-D.ietf-hip-rfc5203-bis], if a an active registration, it may use mobility updates specified herein,
mobile host has an active registration, it may use mobility updates within the context of that association, to readdress the association.
specified herein, within the context of that association, to
readdress the association.
3.2.4. Network Renumbering 3.2.4. Network Renumbering
It is expected that IPv6 networks will be renumbered much more often It is expected that IPv6 networks will be renumbered much more often
than most IPv4 networks. From an end-host point of view, network than most IPv4 networks. From an end-host point of view, network
renumbering is similar to mobility, and procedures described herein renumbering is similar to mobility, and procedures described herein
also apply to notify a peer of a changed address. also apply to notify a peer of a changed address.
3.3. Other Considerations 3.3. Other Considerations
skipping to change at page 12, line 51 skipping to change at page 14, line 44
When a HIP host receives a set of locators from another HIP host in a When a HIP host receives a set of locators from another HIP host in a
LOCATOR_SET, it does not necessarily know whether the other host is LOCATOR_SET, it does not necessarily know whether the other host is
actually reachable at the claimed addresses. In fact, a malicious actually reachable at the claimed addresses. In fact, a malicious
peer host may be intentionally giving bogus addresses in order to peer host may be intentionally giving bogus addresses in order to
cause a packet flood towards the target addresses [RFC4225]. cause a packet flood towards the target addresses [RFC4225].
Therefore, the HIP host needs to first check that the peer is Therefore, the HIP host needs to first check that the peer is
reachable at the new address. reachable at the new address.
Address verification is implemented by the challenger sending some Address verification is implemented by the challenger sending some
piece of unguessable information to the new address, and waiting for piece of unguessable information to the new address and waiting for
some acknowledgment from the Responder that indicates reception of some acknowledgment from the Responder that indicates reception of
the information at the new address. This may include the exchange of the information at the new address. This may include the exchange of
a nonce, or the generation of a new SPI and observation of data a nonce or the generation of a new SPI and observation of data
arriving on the new SPI. More details are found in Section 5.4 of arriving on the new SPI. More details are found in Section 5.4 of
this document. this document.
An additional potential benefit of performing address verification is An additional potential benefit of performing address verification is
to allow NATs and firewalls in the network along the new path to to allow NATs and firewalls in the network along the new path to
obtain the peer host's inbound SPI. obtain the peer host's inbound SPI.
3.3.2. Credit-Based Authorization 3.3.2. Credit-Based Authorization
Credit-Based Authorization (CBA) allows a host to securely use a new CBA allows a host to securely use a new locator even though the
locator even though the peer's reachability at the address embedded peer's reachability at the address embedded in the locator has not
in the locator has not yet been verified. This is accomplished based yet been verified. This is accomplished based on the following three
on the following three hypotheses: hypotheses:
1. A flooding attacker typically seeks to somehow multiply the 1. A flooding attacker typically seeks to somehow multiply the
packets it generates for the purpose of its attack because packets it generates for the purpose of its attack because
bandwidth is an ample resource for many victims. bandwidth is an ample resource for many victims.
2. An attacker can often cause unamplified flooding by sending 2. An attacker can often cause unamplified flooding by sending
packets to its victim, either by directly addressing the victim packets to its victim, either by directly addressing the victim
in the packets, or by guiding the packets along a specific path in the packets or by guiding the packets along a specific path by
by means of an IPv6 Routing header, if Routing headers are not means of an IPv6 Routing header, if Routing headers are not
filtered by firewalls. filtered by firewalls.
3. Consequently, the additional effort required to set up a 3. Consequently, the additional effort required to set up a
redirection-based flooding attack (without CBA and return redirection-based flooding attack (without CBA and return
routability checks) would pay off for the attacker only if routability checks) would pay off for the attacker only if
amplification could be obtained this way. amplification could be obtained this way.
On this basis, rather than eliminating malicious packet redirection On this basis, rather than eliminating malicious packet redirection
in the first place, Credit-Based Authorization prevents in the first place, CBA prevents amplifications. This is
amplifications. This is accomplished by limiting the data a host can accomplished by limiting the data a host can send to an unverified
send to an unverified address of a peer by the data recently received address of a peer by the data recently received from that peer.
from that peer. Redirection-based flooding attacks thus become less Redirection-based flooding attacks thus become less attractive than,
attractive than, for example, pure direct flooding, where the for example, pure direct flooding, where the attacker itself sends
attacker itself sends bogus packets to the victim. bogus packets to the victim.
Figure 5 illustrates Credit-Based Authorization: Host B measures the Figure 5 illustrates CBA: Host B measures the amount of data recently
amount of data recently received from peer A and, when A readdresses, received from peer A and, when A readdresses, sends packets to A's
sends packets to A's new, unverified address as long as the sum of new, unverified address as long as the sum of the packet sizes does
the packet sizes does not exceed the measured, received data volume. not exceed the measured, received data volume. When insufficient
When insufficient credit is left, B stops sending further packets to credit is left, B stops sending further packets to A until A's
A until A's address becomes ACTIVE. The address changes may be due address becomes ACTIVE. The address changes may be due to mobility,
to mobility, multihoming, or any other reason. Not shown in Figure 5 multihoming, or any other reason. Not shown in Figure 5 are the
are the results of credit aging (Section 5.6.2), a mechanism used to results of credit aging (Section 5.6.2), a mechanism used to dampen
dampen possible time-shifting attacks. possible time-shifting attacks.
+-------+ +-------+ +-------+ +-------+
| A | | B | | A | | B |
+-------+ +-------+ +-------+ +-------+
| | | |
address |------------------------------->| credit += size(packet) address |------------------------------->| credit += size(packet)
ACTIVE | | ACTIVE | |
|------------------------------->| credit += size(packet) |------------------------------->| credit += size(packet)
|<-------------------------------| do not change credit |<-------------------------------| do not change credit
| | | |
skipping to change at page 14, line 45 skipping to change at page 16, line 43
to accomplish this, if the sender knows roughly its round-trip time to accomplish this, if the sender knows roughly its round-trip time
(RTT) and current sending rate to the host, is to allow enough credit (RTT) and current sending rate to the host, is to allow enough credit
to support maintaining the sending rate for a duration corresponding to support maintaining the sending rate for a duration corresponding
to two or three RTTs. to two or three RTTs.
3.3.3. Preferred Locator 3.3.3. Preferred Locator
When a host has multiple locators, the peer host needs to decide When a host has multiple locators, the peer host needs to decide
which to use for outbound packets. It may be that a host would which to use for outbound packets. It may be that a host would
prefer to receive data on a particular inbound interface. HIP allows prefer to receive data on a particular inbound interface. HIP allows
a particular locator to be designated as a Preferred locator and a particular locator to be designated as a preferred locator and
communicated to the peer (see Section 4). communicated to the peer (see Section 4).
4. LOCATOR_SET Parameter Format 4. LOCATOR_SET Parameter Format
The LOCATOR_SET parameter has a type number value that is considered The LOCATOR_SET parameter has a type number value that is considered
to be a 'critical parameter' as per the definition in [RFC7401]; such to be a "critical parameter" as per the definition in [RFC7401]; such
parameter types MUST be recognized and processed by the recipient. parameter types MUST be recognized and processed by the recipient.
The parameter consists of the standard HIP parameter Type and Length The parameter consists of the standard HIP parameter Type and Length
fields, plus zero or more Locator sub-parameters. Each Locator sub- fields, plus zero or more Locator sub-parameters. Each Locator sub-
parameter contains a Traffic Type, Locator Type, Locator Length, parameter contains a Traffic Type, Locator Type, Locator Length,
Preferred locator bit, Locator Lifetime, and a Locator encoding. A preferred locator bit ("P" bit), Locator Lifetime, and a Locator
LOCATOR_SET containing zero Locator fields is permitted but has the encoding. A LOCATOR_SET containing zero Locator fields is permitted
effect of deprecating all addresses. but has the effect of deprecating all addresses.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Traffic Type | Locator Type | Locator Length | Reserved |P| | Traffic Type | Locator Type | Locator Length | Reserved |P|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Locator Lifetime | | Locator Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 16, line 19 skipping to change at page 18, line 10
Locator Length: Defines the length of the Locator field, in units of Locator Length: Defines the length of the Locator field, in units of
4-byte words (Locators up to a maximum of 4*255 octets are 4-byte words (Locators up to a maximum of 4*255 octets are
supported). supported).
Reserved: Zero when sent, ignored when received. Reserved: Zero when sent, ignored when received.
P: Preferred locator. Set to one if the locator is preferred for P: Preferred locator. Set to one if the locator is preferred for
that Traffic Type; otherwise, set to zero. that Traffic Type; otherwise, set to zero.
Locator Lifetime: Locator lifetime, in seconds. Locator Lifetime: Lifetime of the locator, in seconds.
Locator: The locator whose semantics and encoding are indicated by Locator: The locator whose semantics and encoding are indicated by
the Locator Type field. All Locator sub-fields are integral the Locator Type field. All sub-fields of the Locator field are
multiples of four octets in length. integral multiples of four octets in length.
The Locator Lifetime indicates how long the following locator is The Locator Lifetime (lifetime) indicates how long the following
expected to be valid. The lifetime is expressed in seconds. Each locator is expected to be valid. The lifetime is expressed in
locator MUST have a non-zero lifetime. The address is expected to seconds. Each locator MUST have a non-zero lifetime. The address is
become deprecated when the specified number of seconds has passed expected to become deprecated when the specified number of seconds
since the reception of the message. A deprecated address SHOULD NOT has passed since the reception of the message. A deprecated address
be used as a destination address if an alternate (non-deprecated) is SHOULD NOT be used as a destination address if an alternate
available and has sufficient address scope. (non-deprecated) is available and has sufficient address scope.
4.1. Traffic Type and Preferred Locator 4.1. Traffic Type and Preferred Locator
The following Traffic Type values are defined: The following Traffic Type values are defined:
0: Both signaling (HIP control packets) and user data. 0: Both signaling (HIP control packets) and user data.
1: Signaling packets only. 1: Signaling packets only.
2: Data packets only. 2: Data packets only.
The "P" bit, when set, has scope over the corresponding Traffic Type. The "P" bit, when set, has scope over the corresponding Traffic Type.
That is, when a "P" bit is set for Traffic Type "2", for example, it That is, when a "P" bit is set for Traffic Type "2", for example, it
means that the locator is preferred for data packets. If there is a means that the locator is preferred for data packets. If there is a
conflict (for example, if the "P" bit is set for an address of Type conflict (for example, if the "P" bit is set for an address of Type
"0" and a different address of Type "2"), the more specific Traffic "0" and a different address of Type "2"), the more specific Traffic
Type rule applies (in this case, "2"). By default, the IP addresses Type rule applies (in this case, "2"). By default, the IP addresses
used in the base exchange are Preferred locators for both signaling used in the base exchange are preferred locators for both signaling
and user data, unless a new Preferred locator supersedes them. If no and user data, unless a new preferred locator supersedes them. If no
locators are indicated as preferred for a given Traffic Type, the locators are indicated as preferred for a given Traffic Type, the
implementation may use an arbitrary destination locator from the set implementation may use an arbitrary destination locator from the set
of active locators. of active locators.
4.2. Locator Type and Locator 4.2. Locator Type and Locator
The following Locator Type values are defined, along with the The following Locator Type values are defined, along with the
associated semantics of the Locator field: associated semantics of the Locator field:
0: An IPv6 address or an IPv4-in-IPv6 format IPv4 address [RFC4291] 0: An IPv6 address or an IPv4-in-IPv6 format IPv4 address [RFC4291]
(128 bits long). This locator type is defined primarily for non- (128 bits long). This Locator Type is defined primarily for
ESP-based usage. non-ESP-based usage.
1: The concatenation of an ESP SPI (first 32 bits) followed by an 1: The concatenation of an ESP SPI (first 32 bits) followed by an
IPv6 address or an IPv4-in-IPv6 format IPv4 address (an additional IPv6 address or an IPv4-in-IPv6 format IPv4 address (an
128 bits). This IP address is defined primarily for ESP-based additional 128 bits). This IP address is defined primarily for
usage. ESP-based usage.
4.3. UPDATE Packet with Included LOCATOR_SET 4.3. UPDATE Packet with Included LOCATOR_SET
A number of combinations of parameters in an UPDATE packet are A number of combinations of parameters in an UPDATE packet are
possible (e.g., see Section 3.2). In this document, procedures are possible (e.g., see Section 3.2). In this document, procedures are
defined only for the case in which one LOCATOR_SET and one ESP_INFO defined only for the case in which one LOCATOR_SET and one ESP_INFO
parameter is used in any HIP packet. Any UPDATE packet that includes parameter are used in any HIP packet. Any UPDATE packet that
a LOCATOR_SET parameter SHOULD include both an HMAC and a includes a LOCATOR_SET parameter SHOULD include both an HMAC and a
HIP_SIGNATURE parameter. HIP_SIGNATURE parameter.
The UPDATE MAY also include a HOST_ID parameter (which may be useful The UPDATE MAY also include a HOST_ID parameter (which may be useful
for HIP-aware firewalls inspecting the HIP messages for the first for HIP-aware firewalls inspecting the HIP messages for the first
time). If the UPDATE includes the HOST_ID parameter, the receiving time). If the UPDATE includes the HOST_ID parameter, the receiving
host MUST verify that the HOST_ID corresponds to the HOST_ID that was host MUST verify that the HOST_ID corresponds to the HOST_ID that was
used to establish the HIP association, and the HIP_SIGNATURE MUST used to establish the HIP association, and the HIP_SIGNATURE MUST
verify with the public key associated with this HOST_ID parameter. verify with the public key associated with this HOST_ID parameter.
The relationship between the announced Locators and any ESP_INFO The relationship between the announced Locators and any ESP_INFO
parameters present in the packet is defined in Section 5.2. This parameters present in the packet is defined in Section 5.2. This
document does not support any elements of procedure for sending more document does not support any elements of procedure for sending more
than one LOCATOR_SET or ESP_INFO parameter in a single UPDATE. than one LOCATOR_SET or ESP_INFO parameter in a single UPDATE.
5. Processing Rules 5. Processing Rules
This section describes rules for sending and receiving the This section describes rules for sending and receiving the
LOCATOR_SET parameter, testing address reachability, and using LOCATOR_SET parameter, testing address reachability, and using CBA on
Credit-Based Authorization (CBA) on UNVERIFIED locators. UNVERIFIED locators.
5.1. Locator Data Structure and Status 5.1. Locator Data Structure and Status
Each locator announced in a LOCATOR_SET parameter is represented by a Each locator announced in a LOCATOR_SET parameter is represented by a
piece of state that contains the following data: piece of state that contains the following data:
o the actual bit pattern representing the locator, o the actual bit pattern representing the locator,
o the lifetime (seconds), o the lifetime (seconds),
o the status (UNVERIFIED, ACTIVE, DEPRECATED), o the status (UNVERIFIED, ACTIVE, DEPRECATED),
o the Traffic Type scope of the locator, and o the Traffic Type scope of the locator, and
o whether the locator is preferred for any particular scope. o whether the locator is preferred for any particular scope.
The status is used to track the reachability of the address embedded The status is used to track the reachability of the address embedded
within the LOCATOR_SET parameter: within the LOCATOR_SET parameter:
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o the status (UNVERIFIED, ACTIVE, DEPRECATED), o the status (UNVERIFIED, ACTIVE, DEPRECATED),
o the Traffic Type scope of the locator, and o the Traffic Type scope of the locator, and
o whether the locator is preferred for any particular scope. o whether the locator is preferred for any particular scope.
The status is used to track the reachability of the address embedded The status is used to track the reachability of the address embedded
within the LOCATOR_SET parameter: within the LOCATOR_SET parameter:
UNVERIFIED indicates that the reachability of the address has not UNVERIFIED: indicates that the reachability of the address has not
been verified yet, been verified yet,
ACTIVE indicates that the reachability of the address has been ACTIVE: indicates that the reachability of the address has been
verified and the address has not been deprecated, verified and the address has not been deprecated, and
DEPRECATED indicates that the locator lifetime has expired. DEPRECATED: indicates that the locator's lifetime has expired.
The following state changes are allowed: The following state changes are allowed:
UNVERIFIED to ACTIVE The reachability procedure completes UNVERIFIED to ACTIVE: The reachability procedure completes
successfully. successfully.
UNVERIFIED to DEPRECATED The locator lifetime expires while the UNVERIFIED to DEPRECATED: The locator's lifetime expires while the
locator is UNVERIFIED. locator is UNVERIFIED.
ACTIVE to DEPRECATED The locator lifetime expires while the locator ACTIVE to DEPRECATED: The locator's lifetime expires while the
is ACTIVE. locator is ACTIVE.
ACTIVE to UNVERIFIED There has been no traffic on the address for ACTIVE to UNVERIFIED: There has been no traffic on the address for
some time, and the local policy mandates that the address some time, and the local policy mandates that the address
reachability needs to be verified again before starting to use it reachability needs to be verified again before starting to use it
again. again.
DEPRECATED to UNVERIFIED The host receives a new lifetime for the DEPRECATED to UNVERIFIED: The host receives a new lifetime for the
locator. locator.
A DEPRECATED address MUST NOT be changed to ACTIVE without first A DEPRECATED address MUST NOT be changed to ACTIVE without first
verifying its reachability. verifying its reachability.
Note that the state of whether or not a locator is preferred is not Note that the state of whether or not a locator is preferred is not
necessarily the same as the value of the Preferred bit in the Locator necessarily the same as the value of the preferred bit in the Locator
sub-parameter received from the peer. Peers may recommend certain sub-parameter received from the peer. Peers may recommend certain
locators to be preferred, but the decision on whether to actually use locators to be preferred, but the decision on whether to actually use
a locator as a preferred locator is a local decision, possibly a locator as a preferred locator is a local decision, possibly
influenced by local policy. influenced by local policy.
In addition to state maintained about status and remaining lifetime In addition to state maintained about status and remaining lifetime
for each locator learned from the peer, an implementation would for each locator learned from the peer, an implementation would
typically maintain similar state about its own locators that have typically maintain similar state about its own locators that have
been offered to the peer. been offered to the peer.
An unbounded locator lifetime can be signified by setting the value A locator lifetime that is unbounded (does not expire) can be
of the lifetime field to the maximum (unsigned) value. signified by setting the value of the lifetime field to the maximum
(unsigned) value.
Finally, the locators used to establish the HIP association are by Finally, the locators used to establish the HIP association are by
default assumed to be the initial preferred locators in ACTIVE state, default assumed to be the initial preferred locators in ACTIVE state,
with an unbounded lifetime. with an unbounded lifetime.
5.2. Sending the LOCATOR_SET 5.2. Sending the LOCATOR_SET
The decision of when to send the LOCATOR_SET is a local policy issue. The decision of when to send the LOCATOR_SET is a local policy issue.
However, it is RECOMMENDED that a host send a LOCATOR_SET whenever it However, it is RECOMMENDED that a host send a LOCATOR_SET whenever it
recognizes a change of its IP addresses in use on an active HIP recognizes a change of its IP addresses in use on an active HIP
association, and assumes that the change is going to last at least association and assumes that the change is going to last at least for
for a few seconds. Rapidly sending LOCATOR_SETs that force the peer a few seconds. Rapidly sending LOCATOR_SETs that force the peer to
to change the preferred address SHOULD be avoided. change the preferred address SHOULD be avoided.
The sending of a new LOCATOR_SET parameter replaces the locator The sending of a new LOCATOR_SET parameter replaces the locator
information from any previously sent LOCATOR_SET parameter, and information from any previously sent LOCATOR_SET parameter;
therefore if a host sends a new LOCATOR_SET parameter, it needs to therefore, if a host sends a new LOCATOR_SET parameter, it needs to
continue to include all active locators. Hosts MUST NOT announce continue to include all active locators. Hosts MUST NOT announce
broadcast or multicast addresses in LOCATOR_SETs. broadcast or multicast addresses in LOCATOR_SETs.
We now describe a few cases introduced in Section 3.2. We assume We now describe a few cases introduced in Section 3.2. We assume
that the Traffic Type for each locator is set to "0" (other values that the Traffic Type for each locator is set to "0" (other values
for Traffic Type may be specified in documents that separate the HIP for Traffic Type may be specified in documents that separate the HIP
control plane from data plane traffic). Other mobility cases are control plane from data-plane traffic). Other mobility cases are
possible but are left for further study. possible but are left for further study.
1. Host mobility with no multihoming and no rekeying. The mobile 1. Host mobility with no multihoming and no rekeying. The mobile
host creates a single UPDATE containing a single ESP_INFO with a host creates a single UPDATE containing a single ESP_INFO with a
single LOCATOR_SET parameter. The ESP_INFO contains the current single LOCATOR_SET parameter. The ESP_INFO contains the current
value of the SPI in both the OLD SPI and NEW SPI fields. The value of the SPI in both the OLD SPI and NEW SPI fields. The
LOCATOR_SET contains a single Locator with a "Locator Type" of LOCATOR_SET contains a single Locator with a Locator Type of "1";
"1"; the SPI MUST match that of the ESP_INFO. The Preferred bit the SPI MUST match that of the ESP_INFO. The preferred bit
SHOULD be set and the "Locator Lifetime" is set according to SHOULD be set and the "Locator Lifetime" is set according to
local policy. The UPDATE also contains a SEQ parameter as usual. local policy. The UPDATE also contains a SEQ parameter as usual.
This packet is retransmitted as defined in the HIP specification
This packet is retransmitted as defined in the HIP protocol [RFC7401]. The UPDATE should be sent to the peer's preferred IP
specification [RFC7401]. The UPDATE should be sent to the peer's address with an IP source address corresponding to the address in
preferred IP address with an IP source address corresponding to the LOCATOR_SET parameter.
the address in the LOCATOR_SET parameter.
2. Host mobility with no multihoming but with rekeying. The mobile 2. Host mobility with no multihoming but with rekeying. The mobile
host creates a single UPDATE containing a single ESP_INFO with a host creates a single UPDATE containing a single ESP_INFO with a
single LOCATOR_SET parameter (with a single address). The single LOCATOR_SET parameter (with a single address). The
ESP_INFO contains the current value of the SPI in the OLD SPI and ESP_INFO contains the current value of the SPI in the OLD SPI,
the new value of the SPI in the NEW SPI, and a KEYMAT Index as the new value of the SPI in the NEW SPI, and a KEYMAT Index as
selected by local policy. Optionally, the host may choose to selected by local policy. Optionally, the host may choose to
initiate a Diffie Hellman rekey by including a DIFFIE_HELLMAN initiate a Diffie-Hellman rekey by including a DIFFIE_HELLMAN
parameter. The LOCATOR_SET contains a single Locator with parameter. The LOCATOR_SET contains a single Locator with a
"Locator Type" of "1"; the SPI MUST match that of the NEW SPI in Locator Type of "1"; the SPI MUST match that of the NEW SPI in
the ESP_INFO. Otherwise, the steps are identical to the case in the ESP_INFO. Otherwise, the steps are identical to the case in
which no rekeying is initiated. which no rekeying is initiated.
5.3. Handling Received LOCATOR_SETs 5.3. Handling Received LOCATOR_SETs
A host SHOULD be prepared to receive a single LOCATOR_SET parameter A host SHOULD be prepared to receive a single LOCATOR_SET parameter
in a HIP UPDATE packet. Reception of multiple LOCATOR_SET parameters in a HIP UPDATE packet. Reception of multiple LOCATOR_SET parameters
in a single packet, or in HIP packets other than UPDATE, is outside in a single packet, or in HIP packets other than UPDATE, is outside
of the scope of this specification. of the scope of this specification.
Because a host sending the LOCATOR_SET may send the same parameter in Because a host sending the LOCATOR_SET may send the same parameter in
different UPDATE messages to different destination addresses, different UPDATE messages to different destination addresses,
including possibly the rendezvous server of the host, the host including possibly the RVS of the host, the host receiving the
receiving the LOCATOR_SET MUST be prepared to handle the possibility LOCATOR_SET MUST be prepared to handle the possibility of duplicate
of duplicate LOCATOR_SETs sent to more than one of the host's LOCATOR_SETs sent to more than one of the host's addresses. As a
addresses. As a result, the host MUST detect and avoid reprocessing result, the host MUST detect and avoid reprocessing a LOCATOR_SET
a LOCATOR_SET parameter that is redundant with a LOCATOR_SET parameter that is redundant with a LOCATOR_SET parameter that has
parameter that has been recently received and processed. been recently received and processed.
This document describes sending both ESP_INFO and LOCATOR_SET This document describes sending both ESP_INFO and LOCATOR_SET
parameters in an UPDATE. The ESP_INFO parameter is included when parameters in an UPDATE. The ESP_INFO parameter is included when
there is a need to rekey or key a new SPI, and is otherwise included there is a need to rekey or key a new SPI, and is otherwise included
for the possible benefit of HIP-aware NATs and firewalls. The for the possible benefit of HIP-aware NATs and firewalls. The
LOCATOR_SET parameter contains a complete listing of the locators LOCATOR_SET parameter contains a complete listing of the locators
that the host wishes to make or keep active for the HIP association. that the host wishes to make or keep active for the HIP association.
In general, the processing of a LOCATOR_SET depends upon the packet In general, the processing of a LOCATOR_SET depends upon the packet
type in which it is included. Here, we describe only the case in type in which it is included. Here, we describe only the case in
which ESP_INFO is present and a single LOCATOR_SET and ESP_INFO are which ESP_INFO is present and a single LOCATOR_SET and ESP_INFO are
sent in an UPDATE message; other cases are for further study. The sent in an UPDATE message; other cases are for further study. The
steps below cover each of the cases described in Section 5.2. steps below cover each of the cases described in Section 5.2.
The processing of ESP_INFO and LOCATOR_SET parameters is intended to The processing of ESP_INFO and LOCATOR_SET parameters is intended to
be modular and support future generalization to the inclusion of be modular and support future generalization to the inclusion of
multiple ESP_INFO and/or multiple LOCATOR_SET parameters. A host multiple ESP_INFO and/or multiple LOCATOR_SET parameters. A host
SHOULD first process the ESP_INFO before the LOCATOR_SET, since the SHOULD first process the ESP_INFO before the LOCATOR_SET, since the
ESP_INFO may contain a new SPI value mapped to an existing SPI, while ESP_INFO may contain a new SPI value mapped to an existing SPI, while
a Type "1" locator will only contain a reference to the new SPI. a Locator Type of "1" will only contain a reference to the new SPI.
When a host receives a validated HIP UPDATE with a LOCATOR_SET and When a host receives a validated HIP UPDATE with a LOCATOR_SET and
ESP_INFO parameter, it processes the ESP_INFO as follows. The ESP_INFO parameter, it processes the ESP_INFO as follows. The
ESP_INFO parameter indicates whether an SA is being rekeyed, created, ESP_INFO parameter indicates whether an SA is being rekeyed, created,
deprecated, or just identified for the benefit of HIP-aware NATs and deprecated, or just identified for the benefit of HIP-aware NATs and
firewalls. The host examines the OLD SPI and NEW SPI values in the firewalls. The host examines the OLD SPI and NEW SPI values in the
ESP_INFO parameter: ESP_INFO parameter:
1. (no rekeying) If the OLD SPI is equal to the NEW SPI and both 1. (no rekeying) If the OLD SPI is equal to the NEW SPI and both
correspond to an existing SPI, the ESP_INFO is gratuitous correspond to an existing SPI, the ESP_INFO is gratuitous
skipping to change at page 21, line 48 skipping to change at page 23, line 44
If none of the above cases apply, a protocol error has occurred and If none of the above cases apply, a protocol error has occurred and
the processing of the UPDATE is stopped. the processing of the UPDATE is stopped.
Next, the locators in the LOCATOR_SET parameter are processed. For Next, the locators in the LOCATOR_SET parameter are processed. For
each locator listed in the LOCATOR_SET parameter, check that the each locator listed in the LOCATOR_SET parameter, check that the
address therein is a legal unicast or anycast address. That is, the address therein is a legal unicast or anycast address. That is, the
address MUST NOT be a broadcast or multicast address. Note that some address MUST NOT be a broadcast or multicast address. Note that some
implementations MAY accept addresses that indicate the local host, implementations MAY accept addresses that indicate the local host,
since it may be allowed that the host runs HIP with itself. since it may be allowed that the host runs HIP with itself.
The below assumes that all locators are of Type "1" with a Traffic The below assumes that all Locators are of Type "1" with a Traffic
Type of "0"; other cases are for further study. Type of "0"; other cases are for further study.
For each Type "1" address listed in the LOCATOR_SET parameter, the For each Type "1" address listed in the LOCATOR_SET parameter, the
host checks whether the address is already bound to the SPI host checks whether the address is already bound to the SPI
indicated. If the address is already bound, its lifetime is updated. indicated. If the address is already bound, its lifetime is updated.
If the status of the address is DEPRECATED, the status is changed to If the status of the address is DEPRECATED, the status is changed to
UNVERIFIED. If the address is not already bound, the address is UNVERIFIED. If the address is not already bound, the address is
added, and its status is set to UNVERIFIED. Mark all addresses added, and its status is set to UNVERIFIED. Mark all addresses
corresponding to the SPI that were NOT listed in the LOCATOR_SET corresponding to the SPI that were NOT listed in the LOCATOR_SET
parameter as DEPRECATED. parameter as DEPRECATED.
As a result, at the end of processing, the addresses listed in the As a result, at the end of processing, the addresses listed in the
LOCATOR_SET parameter have either a state of UNVERIFIED or ACTIVE, LOCATOR_SET parameter have a state of either UNVERIFIED or ACTIVE,
and any old addresses on the old SA not listed in the LOCATOR_SET and any old addresses on the old SA not listed in the LOCATOR_SET
parameter have a state of DEPRECATED. parameter have a state of DEPRECATED.
Once the host has processed the locators, if the LOCATOR_SET Once the host has processed the locators, if the LOCATOR_SET
parameter contains a new Preferred locator, the host SHOULD initiate parameter contains a new preferred locator, the host SHOULD initiate
a change of the Preferred locator. This requires that the host first a change of the preferred locator. This requires that the host first
verifies reachability of the associated address, and only then verify reachability of the associated address, and only then change
changes the Preferred locator; see Section 5.5. the preferred locator; see Section 5.5.
If a host receives a locator with an unsupported Locator Type, and If a host receives a locator with an unsupported Locator Type, and
when such a locator is also declared to be the Preferred locator for when such a locator is also declared to be the preferred locator for
the peer, the host SHOULD send a NOTIFY error with a Notify Message the peer, the host SHOULD send a NOTIFY error with a Notify Message
Type of LOCATOR_TYPE_UNSUPPORTED, with the Notification Data field Type of LOCATOR_TYPE_UNSUPPORTED, with the Notification Data field
containing the locator(s) that the receiver failed to process. containing the locator(s) that the receiver failed to process.
Otherwise, a host MAY send a NOTIFY error if a (non-preferred) Otherwise, a host MAY send a NOTIFY error if a (non-preferred)
locator with an unsupported Locator Type is received in a LOCATOR_SET locator with an unsupported Locator Type is received in a LOCATOR_SET
parameter. parameter.
A host MAY add the source IP address of a received HIP packet as a A host MAY add the source IP address of a received HIP packet as a
candidate locator for the peer even if it is not listed in the peer's candidate locator for the peer even if it is not listed in the peer's
LOCATOR_SET, but it SHOULD prefer locators explicitly listed in the LOCATOR_SET, but it SHOULD prefer locators explicitly listed in the
LOCATOR_SET. LOCATOR_SET.
5.4. Verifying Address Reachability 5.4. Verifying Address Reachability
A host MUST verify the reachability of an UNVERIFIED address. The A host MUST verify the reachability of an UNVERIFIED address. The
status of a newly learned address MUST initially be set to UNVERIFIED status of a newly learned address MUST initially be set to UNVERIFIED
unless the new address is advertised in a R1 packet as a new unless the new address is advertised in an R1 packet as a new
Preferred locator. A host MAY also want to verify the reachability preferred locator. A host MAY also want to verify the reachability
of an ACTIVE address again after some time, in which case it would of an ACTIVE address again after some time, in which case it would
set the status of the address to UNVERIFIED and reinitiate address set the status of the address to UNVERIFIED and reinitiate address
verification. A typical verification that is protected by verification. A typical verification that is protected by
retransmission timers is to include an ECHO REQUEST within an UPDATE retransmission timers is to include an ECHO REQUEST within an UPDATE
sent to the new address. sent to the new address.
A host typically starts the address-verification procedure by sending A host typically starts the address-verification procedure by sending
a nonce to the new address. A host MAY choose from different message a nonce to the new address. A host MAY choose from different message
exchanges or different nonce values so long as it establishes that exchanges or different nonce values so long as it establishes that
the peer has received and replied to the nonce at the new address. the peer has received and replied to the nonce at the new address.
skipping to change at page 23, line 21 skipping to change at page 25, line 20
random value. A host MAY also use other message exchanges as random value. A host MAY also use other message exchanges as
confirmation of the address reachability. confirmation of the address reachability.
In some cases, it MAY be sufficient to use the arrival of data on a In some cases, it MAY be sufficient to use the arrival of data on a
newly advertised SA as implicit address reachability verification as newly advertised SA as implicit address reachability verification as
depicted in Figure 7, instead of waiting for the confirmation via a depicted in Figure 7, instead of waiting for the confirmation via a
HIP packet. In this case, a host advertising a new SPI as part of HIP packet. In this case, a host advertising a new SPI as part of
its address reachability check SHOULD be prepared to receive traffic its address reachability check SHOULD be prepared to receive traffic
on the new SA. on the new SA.
Mobile host Peer host Mobile Host Peer Host
UPDATE(ESP_INFO, LOCATOR_SET, ...) UPDATE(ESP_INFO, LOCATOR_SET, ...)
----------------------------------> ---------------------------------->
prepare incoming SA prepare incoming SA
UPDATE(ESP_INFO, ...) with new SPI UPDATE(ESP_INFO, ...) with new SPI
<----------------------------------- <-----------------------------------
switch to new outgoing SA switch to new outgoing SA
data on new SA data on new SA
-----------------------------------> ----------------------------------->
mark address ACTIVE mark address ACTIVE
UPDATE(ACK, ECHO_RESPONSE) later arrives UPDATE(ACK, ECHO_RESPONSE) later arrives
-----------------------------------> ----------------------------------->
Figure 7: Address Activation Via Use of a New SA Figure 7: Address Activation via Use of a New SA
When address verification is in progress for a new Preferred locator, When address verification is in progress for a new preferred locator,
the host SHOULD select a different locator listed as ACTIVE, if one the host SHOULD select a different locator listed as ACTIVE, if one
such locator is available, to continue communications until address such locator is available, to continue communications until address
verification completes. Alternatively, the host MAY use the new verification completes. Alternatively, the host MAY use the new
Preferred locator while in UNVERIFIED status to the extent Credit- preferred locator while in UNVERIFIED status to the extent CBA
Based Authorization permits. Credit-Based Authorization is explained permits. CBA is explained in Section 5.6. Once address verification
in Section 5.6. Once address verification succeeds, the status of succeeds, the status of the new preferred locator changes to ACTIVE.
the new Preferred locator changes to ACTIVE.
5.5. Changing the Preferred Locator 5.5. Changing the Preferred Locator
A host MAY want to change the Preferred outgoing locator for A host MAY want to change the preferred outgoing locator for
different reasons, e.g., because traffic information or ICMP error different reasons, e.g., because traffic information or ICMP error
messages indicate that the currently used preferred address may have messages indicate that the currently used preferred address may have
become unreachable. Another reason may be due to receiving a become unreachable. Another reason may be due to receiving a
LOCATOR_SET parameter that has the "P" bit set. LOCATOR_SET parameter that has the "P" bit set.
To change the Preferred locator, the host initiates the following To change the preferred locator, the host initiates the following
procedure: procedure:
1. If the new Preferred locator has ACTIVE status, the Preferred 1. If the new preferred locator has an ACTIVE status, the preferred
locator is changed and the procedure succeeds. locator is changed and the procedure succeeds.
2. If the new Preferred locator has UNVERIFIED status, the host 2. If the new preferred locator has an UNVERIFIED status, the host
starts to verify its reachability. The host SHOULD use a starts to verify its reachability. The host SHOULD use a
different locator listed as ACTIVE until address verification different locator listed as ACTIVE until address verification
completes if one such locator is available. Alternatively, the completes if one such locator is available. Alternatively, the
host MAY use the new Preferred locator, even though in UNVERIFIED host MAY use the new preferred locator, even though in UNVERIFIED
status, to the extent Credit-Based Authorization permits. Once status, to the extent CBA permits. Once address verification
address verification succeeds, the status of the new Preferred succeeds, the status of the new preferred locator changes to
locator changes to ACTIVE and its use is no longer governed by ACTIVE, and its use is no longer governed by CBA.
Credit-Based Authorization.
3. If the peer host has not indicated a preference for any address, 3. If the peer host has not indicated a preference for any address,
then the host picks one of the peer's ACTIVE addresses randomly then the host picks one of the peer's ACTIVE addresses randomly
or according to local policy. This case may arise if, for or according to local policy. This case may arise if, for
example, ICMP error messages that deprecate the Preferred locator example, ICMP error messages that deprecate the preferred locator
arrive, but the peer has not yet indicated a new Preferred arrive, but the peer has not yet indicated a new preferred
locator. locator.
4. If the new Preferred locator has DEPRECATED status and there is 4. If the new preferred locator has a DEPRECATED status and there is
at least one non-deprecated address, the host selects one of the at least one non-deprecated address, the host selects one of the
non-deprecated addresses as a new Preferred locator and non-deprecated addresses as a new preferred locator and
continues. If the selected address is UNVERIFIED, the address continues. If the selected address is UNVERIFIED, the address
verification procedure described above will apply. verification procedure described above will apply.
5.6. Credit-Based Authorization 5.6. Credit-Based Authorization
To prevent redirection-based flooding attacks, the use of a Credit- To prevent redirection-based flooding attacks, the use of a CBA
Based Authorization (CBA) approach MUST be used when a host sends approach MUST be used when a host sends data to an UNVERIFIED
data to an UNVERIFIED locator. The following algorithm addresses the locator. The following algorithm addresses the security
security considerations for prevention of amplification and time- considerations for prevention of amplification and time-shifting
shifting attacks. Other forms of credit aging, and other values for attacks. Other forms of credit aging, and other values for the
the CreditAgingFactor and CreditAgingInterval parameters in CreditAgingFactor and CreditAgingInterval parameters in particular,
particular, are for further study, and so are the advanced CBA are for further study, and so are the advanced CBA techniques
techniques specified in [CBA-MIPv6]. specified in [CBA-MIPv6].
5.6.1. Handling Payload Packets 5.6.1. Handling Payload Packets
A host maintains a "credit counter" for each of its peers. Whenever A host maintains a "credit counter" for each of its peers. Whenever
a packet arrives from a peer, the host SHOULD increase that peer's a packet arrives from a peer, the host SHOULD increase that peer's
credit counter by the size of the received packet. When the host has credit counter by the size of the received packet. When the host has
a packet to be sent to the peer, and when the peer's Preferred a packet to be sent to the peer, and when the peer's preferred
locator is listed as UNVERIFIED and no alternative locator with locator is listed as UNVERIFIED and no alternative locator with
status ACTIVE is available, the host checks whether it can send the status ACTIVE is available, the host checks whether it can send the
packet to the UNVERIFIED locator. The packet SHOULD be sent if the packet to the UNVERIFIED locator. The packet SHOULD be sent if the
value of the credit counter is higher than the size of the outbound value of the credit counter is higher than the size of the outbound
packet. If the credit counter is too low, the packet MUST be packet. If the credit counter is too low, the packet MUST be
discarded or buffered until address verification succeeds. When a discarded or buffered until address verification succeeds. When a
packet is sent to a peer at an UNVERIFIED locator, the peer's credit packet is sent to a peer at an UNVERIFIED locator, the peer's credit
counter MUST be reduced by the size of the packet. The peer's credit counter MUST be reduced by the size of the packet. The peer's credit
counter is not affected by packets that the host sends to an ACTIVE counter is not affected by packets that the host sends to an ACTIVE
locator of that peer. locator of that peer.
Figure 8 depicts the actions taken by the host when a packet is Figure 8 depicts the actions taken by the host when a packet is
received. Figure 9 shows the decision chain in the event a packet is received. Figure 9 shows the decision chain in the event a packet is
sent. sent.
Inbound Inbound
packet Packet
| |
| +----------------+ +---------------+ | +----------------+ +---------------+
| | Increase | | Deliver | | | Increase | | Deliver |
+-----> | credit counter |-------------> | packet to | +-----> | credit counter |-------------> | packet to |
| by packet size | | application | | by packet size | | application |
+----------------+ +---------------+ +----------------+ +---------------+
Figure 8: Receiving Packets with Credit-Based Authorization Figure 8: Receiving Packets with Credit-Based Authorization
Outbound Outbound
packet Packet
| _________________ | _________________
| / \ +---------------+ | / \ +---------------+
| / Is the preferred \ No | Send packet | | / Is the preferred \ No | Send packet |
+-----> | destination address |-------------> | to preferred | +-----> | destination address |-------------> | to preferred |
\ UNVERIFIED? / | address | \ UNVERIFIED? / | address |
\_________________/ +---------------+ \_________________/ +---------------+
| |
| Yes | Yes
| |
v v
skipping to change at page 26, line 29 skipping to change at page 28, line 29
/ Does an ACTIVE \ Yes | Send packet | / Does an ACTIVE \ Yes | Send packet |
| destination address |-------------> | to ACTIVE | | destination address |-------------> | to ACTIVE |
\ exist? / | address | \ exist? / | address |
\_________________/ +---------------+ \_________________/ +---------------+
| |
| No | No
| |
v v
_________________ _________________
/ \ +---------------+ / \ +---------------+
/ Credit counter \ No | | / Is credit counter \ No | |
| >= |-------------> | Drop or | | >= |-------------> | Drop or |
\ packet size? / | buffer packet | \ packet size? / | buffer packet |
\_________________/ +---------------+ \_________________/ +---------------+
| |
| Yes | Yes
| |
v v
+---------------+ +---------------+ +---------------+ +---------------+
| Reduce credit | | Send packet | | Reduce credit | | Send packet |
| counter by |----------------> | to preferred | | counter by |----------------> | to preferred |
skipping to change at page 27, line 7 skipping to change at page 29, line 14
5.6.2. Credit Aging 5.6.2. Credit Aging
A host ensures that the credit counters it maintains for its peers A host ensures that the credit counters it maintains for its peers
gradually decrease over time. Such "credit aging" prevents a gradually decrease over time. Such "credit aging" prevents a
malicious peer from building up credit at a very slow speed and using malicious peer from building up credit at a very slow speed and using
this, all at once, for a severe burst of redirected packets. this, all at once, for a severe burst of redirected packets.
Credit aging may be implemented by multiplying credit counters with a Credit aging may be implemented by multiplying credit counters with a
factor, CreditAgingFactor (a fractional value less than one), in factor, CreditAgingFactor (a fractional value less than one), in
fixed time intervals of CreditAgingInterval length. Choosing fixed-time intervals of CreditAgingInterval length. Choosing
appropriate values for CreditAgingFactor and CreditAgingInterval is appropriate values for CreditAgingFactor and CreditAgingInterval is
important to ensure that a host can send packets to an address in important to ensure that a host can send packets to an address in
state UNVERIFIED even when the peer sends at a lower rate than the state UNVERIFIED even when the peer sends at a lower rate than the
host itself. When CreditAgingFactor or CreditAgingInterval are too host itself. When CreditAgingFactor or CreditAgingInterval are too
small, the peer's credit counter might be too low to continue sending small, the peer's credit counter might be too low to continue sending
packets until address verification concludes. packets until address verification concludes.
The parameter values proposed in this document are as follows: The parameter values proposed in this document are as follows:
CreditAgingFactor 7/8 CreditAgingFactor 7/8
CreditAgingInterval 5 seconds CreditAgingInterval 5 seconds
These parameter values work well when the host transfers a file to These parameter values work well when the host transfers a file to
the peer via a TCP connection and the end-to-end round-trip time does the peer via a TCP connection, and the end-to-end round-trip time
not exceed 500 milliseconds. Alternative credit-aging algorithms may does not exceed 500 milliseconds. Alternative credit-aging
use other parameter values or different parameters, which may even be algorithms may use other parameter values or different parameters,
dynamically established. which may even be dynamically established.
6. Security Considerations 6. Security Considerations
The HIP mobility mechanism provides a secure means of updating a The HIP mobility mechanism provides a secure means of updating a
host's IP address via HIP UPDATE packets. Upon receipt, a HIP host host's IP address via HIP UPDATE packets. Upon receipt, a HIP host
cryptographically verifies the sender of an UPDATE, so forging or cryptographically verifies the sender of an UPDATE, so forging or
replaying a HIP UPDATE packet is very difficult (see [RFC7401]). replaying a HIP UPDATE packet is very difficult (see [RFC7401]).
Therefore, security issues reside in other attack domains. The two Therefore, security issues reside in other attack domains. The two
we consider are malicious redirection of legitimate connections as we consider are malicious redirection of legitimate connections as
well as redirection-based flooding attacks using this protocol. This well as redirection-based flooding attacks using this protocol. This
can be broken down into the following: can be broken down into the following:
1) Impersonation attacks 1) Impersonation attacks
- direct conversation with the misled victim - direct conversation with the misled victim
- man-in-the-middle attack - man-in-the-middle (MitM) attack
2) DoS attacks 2) Denial-of-service (DoS) attacks
- flooding attacks (== bandwidth-exhaustion attacks) - flooding attacks (== bandwidth-exhaustion attacks)
* tool 1: direct flooding * tool 1: direct flooding
* tool 2: flooding by botnets * tool 2: flooding by botnets
* tool 3: redirection-based flooding * tool 3: redirection-based flooding
- memory-exhaustion attacks - memory-exhaustion attacks
- computational-exhaustion attacks - computational-exhaustion attacks
3) Privacy concerns 3) Privacy concerns
We consider these in more detail in the following sections. We consider these in more detail in the following sections.
In Section 6.1 and Section 6.2, we assume that all users are using In Sections 6.1 and 6.2, we assume that all users are using HIP. In
HIP. In Section 6.3 we consider the security ramifications when we Section 6.3, we consider the security ramifications when we have both
have both HIP and non-HIP hosts. HIP and non-HIP hosts.
6.1. Impersonation Attacks 6.1. Impersonation Attacks
An attacker wishing to impersonate another host will try to mislead An attacker wishing to impersonate another host will try to mislead
its victim into directly communicating with them, or carry out a man- its victim into directly communicating with them or carry out a MitM
in-the-middle (MitM) attack between the victim and the victim's attack between the victim and the victim's desired communication
desired communication peer. Without mobility support, such attacks peer. Without mobility support, such attacks are possible only if
are possible only if the attacker resides on the routing path between the attacker resides on the routing path between its victim and the
its victim and the victim's desired communication peer, or if the victim's desired communication peer or if the attacker tricks its
attacker tricks its victim into initiating the connection over an victim into initiating the connection over an incorrect routing path
incorrect routing path (e.g., by acting as a router or using spoofed (e.g., by acting as a router or using spoofed DNS entries).
DNS entries).
The HIP extensions defined in this specification change the situation The HIP extensions defined in this specification change the situation
in that they introduce an ability to redirect a connection, both in that they introduce an ability to redirect a connection, both
before and after establishment. If no precautionary measures are before and after establishment. If no precautionary measures are
taken, an attacker could potentially misuse the redirection feature taken, an attacker could potentially misuse the redirection feature
to impersonate a victim's peer from any arbitrary location. However, to impersonate a victim's peer from any arbitrary location. However,
the authentication and authorization mechanisms of the HIP base the authentication and authorization mechanisms of the HIP base
exchange [RFC7401] and the signatures in the UPDATE message prevent exchange [RFC7401] and the signatures in the UPDATE message prevent
this attack. Furthermore, ownership of a HIP association is securely this attack. Furthermore, ownership of a HIP association is securely
linked to a HIP HI/HIT. If an attacker somehow uses a bug in the linked to a HIP HI/HIT. If an attacker somehow uses a bug in the
skipping to change at page 29, line 9 skipping to change at page 31, line 21
be accepted as a legitimate update. UPDATE packets use HMAC and are be accepted as a legitimate update. UPDATE packets use HMAC and are
signed. Even when an attacker can snoop packets to obtain the SPI signed. Even when an attacker can snoop packets to obtain the SPI
and HIT/HI, they still cannot forge an UPDATE packet without and HIT/HI, they still cannot forge an UPDATE packet without
knowledge of the secret keys. Also, replay attacks on the UPDATE knowledge of the secret keys. Also, replay attacks on the UPDATE
packet are prevented as described in [RFC7401]. packet are prevented as described in [RFC7401].
6.2. Denial-of-Service Attacks 6.2. Denial-of-Service Attacks
6.2.1. Flooding Attacks 6.2.1. Flooding Attacks
The purpose of a denial-of-service attack is to exhaust some resource The purpose of a DoS attack is to exhaust some resource of the victim
of the victim such that the victim ceases to operate correctly. A such that the victim ceases to operate correctly. A DoS attack can
denial-of-service attack can aim at the victim's network attachment aim at the victim's network attachment (flooding attack), its memory,
(flooding attack), its memory, or its processing capacity. In a or its processing capacity. In a flooding attack, the attacker
flooding attack, the attacker causes an excessive number of bogus or causes an excessive number of bogus or unwanted packets to be sent to
unwanted packets to be sent to the victim, which fills their the victim, which fills their available bandwidth. Note that the
available bandwidth. Note that the victim does not necessarily need victim does not necessarily need to be a node; it can also be an
to be a node; it can also be an entire network. The attack functions entire network. The attack functions the same way in either case.
the same way in either case.
An effective DoS strategy is distributed denial of service (DDoS). An effective DoS strategy is distributed denial of service (DDoS).
Here, the attacker conventionally distributes some viral software to Here, the attacker conventionally distributes some viral software to
as many nodes as possible. Under the control of the attacker, the as many nodes as possible. Under the control of the attacker, the
infected nodes (e.g. nodes in a botnet), jointly send packets to the infected nodes (e.g., nodes in a botnet) jointly send packets to the
victim. With such an 'army', an attacker can take down even very victim. With such an "army", an attacker can take down even very
high bandwidth networks/victims. high bandwidth networks/victims.
With the ability to redirect connections, an attacker could realize a With the ability to redirect connections, an attacker could realize a
DDoS attack without having to distribute viral code. Here, the DDoS attack without having to distribute viral code. Here, the
attacker initiates a large download from a server, and subsequently attacker initiates a large download from a server and subsequently
uses the HIP mobility mechanism to redirect this download to its uses the HIP mobility mechanism to redirect this download to its
victim. The attacker can repeat this with multiple servers. This victim. The attacker can repeat this with multiple servers. This
threat is mitigated through reachability checks and credit-based threat is mitigated through reachability checks and CBA. When
authorization. Reachability checks, which when conducted using HIP conducted using HIP, reachability checks can leverage the built-in
can leverage the built-in authentication properties of HIP, can authentication properties of HIP. They can also prevent redirection-
prevent redirection-based flooding attacks. However, the delay of based flooding attacks. However, the delay of such a check can have
such a check can have a noticeable impact on application performance. a noticeable impact on application performance. To reduce the impact
To reduce the impact of the delay, credit-based authorization can be of the delay, CBA can be used to send a limited number of packets to
used to send a limited number of packets to the new address while the the new address while the validity of the IP address is still in
validity of the IP address is still in question. Both strategies do question. Both strategies do not eliminate flooding attacks per se,
not eliminate flooding attacks per se, but they preclude: (i) their but they preclude: (i) their use from a location off the path towards
use from a location off the path towards the flooded victim; and (ii) the flooded victim; and (ii) any amplification in the number and size
any amplification in the number and size of the redirected packets. of the redirected packets. As a result, the combination of a
As a result, the combination of a reachability check and credit-based reachability check and CBA lowers a HIP redirection-based flooding
authorization lowers a HIP redirection-based flooding attack to the attack to the level of a direct flooding attack in which the attacker
level of a direct flooding attack in which the attacker itself sends itself sends the flooding traffic to the victim.
the flooding traffic to the victim.
6.2.2. Memory/Computational-Exhaustion DoS Attacks 6.2.2. Memory/Computational-Exhaustion DoS Attacks
We now consider whether or not the proposed extensions to HIP add any We now consider whether or not the proposed extensions to HIP add any
new DoS attacks (consideration of DoS attacks using the base HIP new DoS attacks (consideration of DoS attacks using the base HIP
exchange and updates is discussed in [RFC7401]). A simple attack is exchange and updates is discussed in [RFC7401]). A simple attack is
to send many UPDATE packets containing many IP addresses that are not to send many UPDATE packets containing many IP addresses that are not
flagged as preferred. The attacker continues to send such packets flagged as preferred. The attacker continues to send such packets
until the number of IP addresses associated with the attacker's HI until the number of IP addresses associated with the attacker's HI
crashes the system. Therefore, a HIP association SHOULD limit the crashes the system. Therefore, a HIP association SHOULD limit the
skipping to change at page 30, line 18 skipping to change at page 32, line 29
forms of memory/computationally exhausting attacks via the HIP UPDATE forms of memory/computationally exhausting attacks via the HIP UPDATE
packet are handled in the base HIP document [RFC7401]. packet are handled in the base HIP document [RFC7401].
A central server that has to deal with a large number of mobile A central server that has to deal with a large number of mobile
clients MAY consider increasing the SA lifetimes to try to slow down clients MAY consider increasing the SA lifetimes to try to slow down
the rate of rekeying UPDATEs or increasing the cookie difficulty to the rate of rekeying UPDATEs or increasing the cookie difficulty to
slow down the rate of attack-oriented connections. slow down the rate of attack-oriented connections.
6.3. Mixed Deployment Environment 6.3. Mixed Deployment Environment
We now assume an environment with both HIP and non-HIP aware hosts. We now assume an environment with hosts that are both HIP and non-HIP
Four cases exist. aware. Four cases exist:
1. A HIP host redirects its connection onto a non-HIP host. The 1. A HIP host redirects its connection onto a non-HIP host. The
non-HIP host will drop the reachability packet, so this is not a non-HIP host will drop the reachability packet, so this is not a
threat unless the HIP host is a MitM that could somehow respond threat unless the HIP host is a MitM that could somehow respond
successfully to the reachability check. successfully to the reachability check.
2. A non-HIP host attempts to redirect their connection onto a HIP 2. A non-HIP host attempts to redirect their connection onto a HIP
host. This falls into IPv4 and IPv6 security concerns, which are host. This falls into IPv4 and IPv6 security concerns, which are
outside the scope of this document. outside the scope of this document.
3. A non-HIP host attempts to steal a HIP host's session (assume 3. A non-HIP host attempts to steal a HIP host's session (assume
that Secure Neighbor Discovery is not active for the following). that Secure Neighbor Discovery is not active for the following).
The non-HIP host contacts the service that a HIP host has a The non-HIP host contacts the service that a HIP host has a
connection with and then attempts to change its IP address to connection with and then attempts to change its IP address to
steal the HIP host's connection. What will happen in this case steal the HIP host's connection. What will happen in this case
is implementation dependent but such a request should fail by is implementation dependent, but such a request should fail by
being ignored or dropped. Even if the attack were successful, being ignored or dropped. Even if the attack were successful,
the HIP host could reclaim its connection via HIP. the HIP host could reclaim its connection via HIP.
4. A HIP host attempts to steal a non-HIP host's session. A HIP 4. A HIP host attempts to steal a non-HIP host's session. A HIP
host could spoof the non-HIP host's IP address during the base host could spoof the non-HIP host's IP address during the base
exchange or set the non-HIP host's IP address as its preferred exchange or set the non-HIP host's IP address as its preferred
address via an UPDATE. Other possibilities exist, but a solution address via an UPDATE. Other possibilities exist, but a solution
is to prevent the local redirection of sessions that were is to prevent the local redirection of sessions that were
previously using an unverified address, but outside of the previously using an unverified address, but outside of the
existing HIP context, into the HIP SAs until the address change existing HIP context, into the HIP SAs until the address change
skipping to change at page 31, line 15 skipping to change at page 33, line 24
6.4. Privacy Concerns 6.4. Privacy Concerns
The exposure of a host's IP addresses through HIP mobility extensions The exposure of a host's IP addresses through HIP mobility extensions
may raise privacy concerns. The administrator of a host may be may raise privacy concerns. The administrator of a host may be
trying to hide its location in some context through the use of a VPN trying to hide its location in some context through the use of a VPN
or other virtual interfaces. Similar privacy issues also arise in or other virtual interfaces. Similar privacy issues also arise in
other frameworks such as WebRTC and are not specific to HIP. other frameworks such as WebRTC and are not specific to HIP.
Implementations SHOULD provide a mechanism to allow the host Implementations SHOULD provide a mechanism to allow the host
administrator to block the exposure of selected addresses or address administrator to block the exposure of selected addresses or address
ranges. While this issue may be more relevant in a host multihoming ranges. While this issue may be more relevant in a host multihoming
scenario in which multiple IP addresses might be exposed scenario in which multiple IP addresses might be exposed [RFC8047],
([I-D.ietf-hip-multihoming]), it is worth noting also here that it is worth noting also here that mobility events might cause an
mobility events might cause an implementation to try to inadvertently implementation to try to inadvertently use a locator that the
use a locator that the adminstrator would rather avoid exposing to administrator would rather avoid exposing to the peer host.
the peer host.
7. IANA Considerations 7. IANA Considerations
[RFC5206], obsoleted by this document, specified an allocation for a [RFC5206], obsoleted by this document, specified an allocation for a
LOCATOR parameter in the HIP Parameters registry, with a type value LOCATOR parameter in the "Parameter Types" subregistry of the "Host
of 193. This document requests IANA to rename the parameter to Identity Protocol (HIP) Parameters" registry, with a type value of
'LOCATOR_SET' and to update the reference from [RFC5206] to this 193. IANA has renamed the parameter to "LOCATOR_SET" and has updated
specification. the reference from [RFC5206] to this specification.
[RFC5206], obsoleted by this document, specified an allocation a [RFC5206], obsoleted by this document, specified an allocation for a
LOCATOR_TYPE_UNSUPPORTED type in the Notify Message Type registry, LOCATOR_TYPE_UNSUPPORTED type in the "Notify Message Types" registry,
with a type value of 46. This document requests IANA to update the with a type value of 46. IANA has updated the reference from
reference from [RFC5206] to this specification. [RFC5206] to this specification.
8. Differences from RFC 5206 8. Differences from RFC 5206
This section summarizes the technical changes made from [RFC5206]. This section summarizes the technical changes made from [RFC5206].
This section is informational, intended to help implementors of the This section is informational, intended to help implementors of the
previous protocol version. If any text in this section contradicts previous protocol version. If any text in this section contradicts
text in other portions of this specification, the text found outside text in other portions of this specification, the text found outside
of this section should be considered normative. of this section should be considered normative.
This document specifies extensions to the HIP Version 2 protocol, This document specifies extensions to the HIP Version 2 protocol,
while [RFC5206] specifies extensions to the HIP Version 1 protocol. while [RFC5206] specifies extensions to the HIP Version 1 protocol.
[RFC7401] documents the differences between these two protocol [RFC7401] documents the differences between these two protocol
versions. versions.
[RFC5206] included procedures for both HIP host mobility and basic [RFC5206] included procedures for both HIP host mobility and basic
host multihoming. In this document, only host mobility procedures host multihoming. In this document, only host mobility procedures
are included; host multihoming procedures are now specified in are included; host multihoming procedures are now specified in
[I-D.ietf-hip-multihoming]. In particular, multihoming-related [RFC8047]. In particular, multihoming-related procedures related to
procedures related to the exposure of multiple locators in the base the exposure of multiple locators in the base exchange packets; the
exchange packets, the transmission, reception, and processing of transmission, reception, and processing of multiple locators in a
multiple locators in a single UPDATE packet, handovers across IP single UPDATE packet; handovers across IP address families; and other
address families, and other multihoming-related specification has multihoming-related specifications have been removed.
been removed.
The following additional changes have been made: The following additional changes have been made:
o The LOCATOR parameter in [RFC5206] has been renamed to o The LOCATOR parameter in [RFC5206] has been renamed to
LOCATOR_SET. LOCATOR_SET.
o Specification text regarding the handling of mobility when both o Specification text regarding the handling of mobility when both
hosts change IP addresses at nearly the same time (a 'double-jump' hosts change IP addresses at nearly the same time (a "double-jump"
mobility scenario) has been added. mobility scenario) has been added.
o Specification text regarding the mobility event in which the host o Specification text regarding the mobility event in which the host
briefly has an active new locator and old locator at the same time briefly has an active new locator and old locator at the same time
(a 'make-before-break' mobility scenario) has been added. (a "make-before-break" mobility scenario) has been added.
o Specification text has been added to note that a host may add the o Specification text has been added to note that a host may add the
source IP address of a received HIP packet as a candidate locator source IP address of a received HIP packet as a candidate locator
for the peer even if it is not listed in the peer's LOCATOR_SET, for the peer even if it is not listed in the peer's LOCATOR_SET,
but that it should prefer locators explicitly listed in the but that it should prefer locators explicitly listed in the
LOCATOR_SET. LOCATOR_SET.
o This document clarifies that the HOST_ID parameter may be included o This document clarifies that the HOST_ID parameter may be included
in UPDATE messages containing LOCATOR_SET parameters, for the in UPDATE messages containing LOCATOR_SET parameters, for the
possible benefit of HIP-aware firewalls. possible benefit of HIP-aware firewalls.
skipping to change at page 32, line 41 skipping to change at page 34, line 52
o The previous specification mentioned that it may be possible to o The previous specification mentioned that it may be possible to
include multiple LOCATOR_SET and ESP_INFO parameters in an UPDATE. include multiple LOCATOR_SET and ESP_INFO parameters in an UPDATE.
This document only specifies the case of a single LOCATOR_SET and This document only specifies the case of a single LOCATOR_SET and
ESP_INFO parameter in an UPDATE. ESP_INFO parameter in an UPDATE.
o The previous specification mentioned that it may be possible to o The previous specification mentioned that it may be possible to
send LOCATOR_SET parameters in packets other than the UPDATE. send LOCATOR_SET parameters in packets other than the UPDATE.
This document only specifies the use of the UPDATE packet. This document only specifies the use of the UPDATE packet.
o This document describes a simple heuristic for setting the credit o This document describes a simple heuristic for setting the credit
value for Credit-Based Authorization. value for CBA.
o This specification mandates that a host must be able to receive o This specification mandates that a host must be able to receive
and avoid reprocessing redundant LOCATOR_SET parameters that may and avoid reprocessing redundant LOCATOR_SET parameters that may
have been sent in parallel to multiple addresses of the host. have been sent in parallel to multiple addresses of the host.
9. Authors and Acknowledgments 9. References
Pekka Nikander and Jari Arkko originated this document, and Christian
Vogt and Thomas Henderson (editor) later joined as co-authors. Greg
Perkins contributed the initial draft of the security section. Petri
Jokela was a co-author of the initial individual submission.
Credit-Based Authorization was originally introduced in [SIMPLE-CBA],
and portions of this document have been adopted from that earlier
draft.
The authors thank Jeff Ahrenholz, Baris Boyvat, Rene Hummen, Miika
Komu, Mika Kousa, Jan Melen, and Samu Varjonen for improvements to
the document.
10. References
10.1. Normative references
[I-D.ietf-hip-rfc5203-bis]
Laganier, J. and L. Eggert, "Host Identity Protocol (HIP)
Registration Extension", draft-ietf-hip-rfc5203-bis-11
(work in progress), August 2016.
[I-D.ietf-hip-rfc5204-bis] 9.1. Normative References
Laganier, J. and L. Eggert, "Host Identity Protocol (HIP)
Rendezvous Extension", draft-ietf-hip-rfc5204-bis-08 (work
in progress), August 2016.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, DOI 10.17487/RFC4291, February Architecture", RFC 4291, DOI 10.17487/RFC4291, February
2006, <http://www.rfc-editor.org/info/rfc4291>. 2006, <http://www.rfc-editor.org/info/rfc4291>.
skipping to change at page 34, line 5 skipping to change at page 35, line 33
Henderson, "Host Identity Protocol Version 2 (HIPv2)", Henderson, "Host Identity Protocol Version 2 (HIPv2)",
RFC 7401, DOI 10.17487/RFC7401, April 2015, RFC 7401, DOI 10.17487/RFC7401, April 2015,
<http://www.rfc-editor.org/info/rfc7401>. <http://www.rfc-editor.org/info/rfc7401>.
[RFC7402] Jokela, P., Moskowitz, R., and J. Melen, "Using the [RFC7402] Jokela, P., Moskowitz, R., and J. Melen, "Using the
Encapsulating Security Payload (ESP) Transport Format with Encapsulating Security Payload (ESP) Transport Format with
the Host Identity Protocol (HIP)", RFC 7402, the Host Identity Protocol (HIP)", RFC 7402,
DOI 10.17487/RFC7402, April 2015, DOI 10.17487/RFC7402, April 2015,
<http://www.rfc-editor.org/info/rfc7402>. <http://www.rfc-editor.org/info/rfc7402>.
10.2. Informative references [RFC8003] Laganier, J. and L. Eggert, "Host Identity Protocol (HIP)
Registration Extension", RFC 8003, DOI 10.17487/RFC8003,
October 2016, <http://www.rfc-editor.org/info/rfc8003>.
[RFC8004] Laganier, J. and L. Eggert, "Host Identity Protocol (HIP)
Rendezvous Extension", RFC 8004, DOI 10.17487/RFC8004,
October 2016, <http://www.rfc-editor.org/info/rfc8004>.
9.2. Informative References
[CBA-MIPv6] [CBA-MIPv6]
Vogt, C. and J. Arkko, "Credit-Based Authorization for Vogt, C. and J. Arkko, "Credit-Based Authorization for
Mobile IPv6 Early Binding Updates", February 2005. Mobile IPv6 Early Binding Updates", Work in Progress,
draft-vogt-mobopts-credit-based-authorization-00, February
[I-D.ietf-hip-multihoming] 2005.
Henderson, T., Vogt, C., and J. Arkko, "Host Multihoming
with the Host Identity Protocol", draft-ietf-hip-
multihoming-11 (work in progress), September 2016.
[RFC4225] Nikander, P., Arkko, J., Aura, T., Montenegro, G., and E. [RFC4225] Nikander, P., Arkko, J., Aura, T., Montenegro, G., and E.
Nordmark, "Mobile IP Version 6 Route Optimization Security Nordmark, "Mobile IP Version 6 Route Optimization Security
Design Background", RFC 4225, DOI 10.17487/RFC4225, Design Background", RFC 4225, DOI 10.17487/RFC4225,
December 2005, <http://www.rfc-editor.org/info/rfc4225>. December 2005, <http://www.rfc-editor.org/info/rfc4225>.
[RFC5206] Nikander, P., Henderson, T., Ed., Vogt, C., and J. Arkko, [RFC5206] Nikander, P., Henderson, T., Ed., Vogt, C., and J. Arkko,
"End-Host Mobility and Multihoming with the Host Identity "End-Host Mobility and Multihoming with the Host Identity
Protocol", RFC 5206, DOI 10.17487/RFC5206, April 2008, Protocol", RFC 5206, DOI 10.17487/RFC5206, April 2008,
<http://www.rfc-editor.org/info/rfc5206>. <http://www.rfc-editor.org/info/rfc5206>.
[RFC5207] Stiemerling, M., Quittek, J., and L. Eggert, "NAT and [RFC5207] Stiemerling, M., Quittek, J., and L. Eggert, "NAT and
Firewall Traversal Issues of Host Identity Protocol (HIP) Firewall Traversal Issues of Host Identity Protocol (HIP)
Communication", RFC 5207, DOI 10.17487/RFC5207, April Communication", RFC 5207, DOI 10.17487/RFC5207, April
2008, <http://www.rfc-editor.org/info/rfc5207>. 2008, <http://www.rfc-editor.org/info/rfc5207>.
[RFC8047] Henderson, T., Ed., Vogt, C., and J. Arkko, "Host
Multihoming with the Host Identity Protocol", RFC 8047,
DOI 10.17487/RFC8047, February 2017,
<http://www.rfc-editor.org/info/rfc8047>.
[SIMPLE-CBA] [SIMPLE-CBA]
Vogt, C. and J. Arkko, "Credit-Based Authorization for Vogt, C. and J. Arkko, "Credit-Based Authorization for
Concurrent Reachability Verification", February 2006. Concurrent Reachability Verification", Work in Progress,
draft-vogt-mobopts-simple-cba-00, February 2006.
Appendix A. Document Revision History Acknowledgments
To be removed upon publication Pekka Nikander and Jari Arkko originated this document; Christian
Vogt and Thomas Henderson (editor) later joined as coauthors. Greg
Perkins contributed the initial text of the security section. Petri
Jokela was a coauthor of the initial individual submission.
+----------+--------------------------------------------------------+ CBA was originally introduced in [SIMPLE-CBA], and portions of this
| Revision | Comments | document have been adopted from that earlier document.
+----------+--------------------------------------------------------+
| draft-00 | Initial version from RFC5206 xml (unchanged). | The authors thank Jeff Ahrenholz, Baris Boyvat, Rene Hummen, Miika
| | | Komu, Mika Kousa, Jan Melen, and Samu Varjonen for improvements to
| draft-01 | Remove multihoming-specific text; no other changes. | the document.
| | |
| draft-02 | Update references to point to -bis drafts; no other |
| | changes. |
| | |
| draft-03 | issue 4: add make before break use case |
| | |
| | issue 6: peer locator exposure policies |
| | |
| | issue 10: rename LOCATOR to LOCATOR_SET |
| | |
| | issue 14: use of UPDATE packet's IP address |
| | |
| draft-04 | Document refresh; no other changes. |
| | |
| draft-05 | Document refresh; no other changes. |
| | |
| draft-06 | Document refresh; no other changes. |
| | |
| draft-07 | Document refresh; IANA considerations updated. |
| | |
| draft-08 | Remove sending LOCATOR_SET in R1, I2, and NOTIFY |
| | (multihoming) |
| | |
| | State that only one LOCATOR_SET parameter may be sent |
| | in an UPDATE packet (according to this draft) |
| | (multihoming) |
| | |
| | Remove text about cross-family handovers (multihoming) |
| | |
| draft-09 | Add specification text regarding double-jump mobility |
| | procedures. |
| | |
| draft-10 | issue 21: clarified that HI MAY be included in UPDATE |
| | for benefit of middleboxes |
| | |
| | changed one informative reference from RFC 4423-bis to |
| | RFC 7401 |
| | |
| | removed discussion about possible multiple LOCATOR_SET |
| | and ESP_INFO parameters in an UPDATE (per previous |
| | mailing list discussion) |
| | |
| | removed discussion about handling LOCATOR_SET |
| | parameters in packets other than UPDATE (per previous |
| | mailing list discussion) |
| | |
| draft-11 | Editorial improvements from WGLC |
| | |
| draft-12 | Update author affiliations and IPR boilerplate to |
| | trust200902 |
| | |
| draft-13 | Editorial improvements to IANA considerations section. |
| | |
| | Moved citation of [SIMPLE-CBA] to Section 9 and |
| | slightly updated text for redirection-based flooding |
| | attacks in the Security Considerations section. |
| | |
| | Editorial improvements based on last call comments. |
| | |
| draft-14 | Added section to summarize changes from RFC5206. |
| | |
| | Replace references to 'middleboxes' with more specific |
| | 'NATs and firewalls'. |
| | |
| | Describe a simple heuristic for setting the credit |
| | value based on sending rate and RTT. |
| | |
| | Add subsection about privacy concerns of locator |
| | exposure to the Security Considerations section. |
| | |
| | Clarify that a host must be able to receive and avoid |
| | reprocessing redundant LOCATOR_SET parameters that may |
| | have been sent in parallel to multiple addresses of |
| | the host. |
| | |
| | Clarify that multicast or broadcast addresses must not |
| | be announced in a LOCATOR_SET. |
| | |
| | Editorial improvements based on last call comments. |
+----------+--------------------------------------------------------+
Authors' Addresses Authors' Addresses
Thomas R. Henderson (editor) Thomas R. Henderson (editor)
University of Washington University of Washington
Campus Box 352500 Campus Box 352500
Seattle, WA Seattle, WA
USA United States of America
EMail: tomhend@u.washington.edu Email: tomhend@u.washington.edu
Christian Vogt Christian Vogt
Independent Independent
3473 North First Street 3473 North First Street
San Jose, CA 95134 San Jose, CA 95134
USA United States of America
EMail: mail@christianvogt.net Email: mail@christianvogt.net
Jari Arkko Jari Arkko
Ericsson Ericsson
JORVAS FIN-02420 Jorvas, FIN-02420
FINLAND Finland
Phone: +358 40 5079256 Phone: +358 40 5079256
EMail: jari.arkko@piuha.net Email: jari.arkko@piuha.net
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