draft-ietf-hip-rfc5206-bis-00.txt   draft-ietf-hip-rfc5206-bis-01.txt 
Network Working Group P. Nikander Network Working Group P. Nikander
Internet-Draft Ericsson Research NomadicLab Internet-Draft Ericsson Research NomadicLab
Obsoletes: 5206 (if approved) T. Henderson, Ed. Obsoletes: 5206 (if approved) T. Henderson, Ed.
Intended status: Standards Track The Boeing Company Intended status: Standards Track The Boeing Company
Expires: February 23, 2011 C. Vogt Expires: April 21, 2011 C. Vogt
J. Arkko J. Arkko
Ericsson Research NomadicLab Ericsson Research NomadicLab
August 22, 2010 October 18, 2010
End-Host Mobility and Multihoming with the Host Identity Protocol Host Mobility with the Host Identity Protocol
draft-ietf-hip-rfc5206-bis-00 draft-ietf-hip-rfc5206-bis-01
Abstract Abstract
This document defines mobility and multihoming extensions to the Host This document defines mobility extensions to the Host Identity
Identity Protocol (HIP). Specifically, this document defines a Protocol (HIP). Specifically, this document defines a general
general "LOCATOR" parameter for HIP messages that allows for a HIP "LOCATOR" parameter for HIP messages that allows for a HIP host to
host to notify peers about alternate addresses at which it may be notify peers about alternate addresses at which it may be reached.
reached. This document also defines elements of procedure for This document also defines elements of procedure for mobility of a
mobility of a HIP host -- the process by which a host dynamically HIP host -- the process by which a host dynamically changes the
changes the primary locator that it uses to receive packets. While primary locator that it uses to receive packets. While the same
the same LOCATOR parameter can also be used to support end-host LOCATOR parameter can also be used to support end-host multihoming,
multihoming, detailed procedures are left for further study. detailed procedures are out of scope for this document.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on February 23, 2011. This Internet-Draft will expire on April 21, 2011.
Copyright Notice Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 2, line 33 skipping to change at page 3, line 13
than English. than English.
Table of Contents Table of Contents
1. Introduction and Scope . . . . . . . . . . . . . . . . . . . . 4 1. Introduction and Scope . . . . . . . . . . . . . . . . . . . . 4
2. Terminology and Conventions . . . . . . . . . . . . . . . . . 5 2. Terminology and Conventions . . . . . . . . . . . . . . . . . 5
3. Protocol Model . . . . . . . . . . . . . . . . . . . . . . . . 6 3. Protocol Model . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Operating Environment . . . . . . . . . . . . . . . . . . 6 3.1. Operating Environment . . . . . . . . . . . . . . . . . . 6
3.1.1. Locator . . . . . . . . . . . . . . . . . . . . . . . 8 3.1.1. Locator . . . . . . . . . . . . . . . . . . . . . . . 8
3.1.2. Mobility Overview . . . . . . . . . . . . . . . . . . 8 3.1.2. Mobility Overview . . . . . . . . . . . . . . . . . . 8
3.1.3. Multihoming Overview . . . . . . . . . . . . . . . . . 9 3.2. Protocol Overview . . . . . . . . . . . . . . . . . . . . 8
3.2. Protocol Overview . . . . . . . . . . . . . . . . . . . . 9 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) . . . . . . . . . . . . . . . . . . . . . . . . 12 Rekey) . . . . . . . . . . . . . . . . . . . . . . . . 11
3.2.3. Host Multihoming . . . . . . . . . . . . . . . . . . . 12 3.2.3. Using LOCATORs across Addressing Realms . . . . . . . 11
3.2.4. Site Multihoming . . . . . . . . . . . . . . . . . . . 14 3.2.4. Network Renumbering . . . . . . . . . . . . . . . . . 11
3.2.5. Dual host multihoming . . . . . . . . . . . . . . . . 14 3.3. Other Considerations . . . . . . . . . . . . . . . . . . . 12
3.2.6. Combined Mobility and Multihoming . . . . . . . . . . 15 3.3.1. Address Verification . . . . . . . . . . . . . . . . . 12
3.2.7. Using LOCATORs across Addressing Realms . . . . . . . 15 3.3.2. Credit-Based Authorization . . . . . . . . . . . . . . 12
3.2.8. Network Renumbering . . . . . . . . . . . . . . . . . 15 3.3.3. Preferred Locator . . . . . . . . . . . . . . . . . . 13
3.2.9. Initiating the Protocol in R1 or I2 . . . . . . . . . 16 4. LOCATOR Parameter Format . . . . . . . . . . . . . . . . . . . 14
3.3. Other Considerations . . . . . . . . . . . . . . . . . . . 17 4.1. Traffic Type and Preferred Locator . . . . . . . . . . . . 15
3.3.1. Address Verification . . . . . . . . . . . . . . . . . 17 4.2. Locator Type and Locator . . . . . . . . . . . . . . . . . 16
3.3.2. Credit-Based Authorization . . . . . . . . . . . . . . 17 4.3. UPDATE Packet with Included LOCATOR . . . . . . . . . . . 16
3.3.3. Preferred Locator . . . . . . . . . . . . . . . . . . 19 5. Processing Rules . . . . . . . . . . . . . . . . . . . . . . . 16
3.3.4. Interaction with Security Associations . . . . . . . . 19 5.1. Locator Data Structure and Status . . . . . . . . . . . . 16
4. LOCATOR Parameter Format . . . . . . . . . . . . . . . . . . . 22 5.2. Sending LOCATORs . . . . . . . . . . . . . . . . . . . . . 18
4.1. Traffic Type and Preferred Locator . . . . . . . . . . . . 24 5.3. Handling Received LOCATORs . . . . . . . . . . . . . . . . 19
4.2. Locator Type and Locator . . . . . . . . . . . . . . . . . 24 5.4. Verifying Address Reachability . . . . . . . . . . . . . . 21
4.3. UPDATE Packet with Included LOCATOR . . . . . . . . . . . 25 5.5. Changing the Preferred Locator . . . . . . . . . . . . . . 22
5. Processing Rules . . . . . . . . . . . . . . . . . . . . . . . 25 5.6. Credit-Based Authorization . . . . . . . . . . . . . . . . 23
5.1. Locator Data Structure and Status . . . . . . . . . . . . 25 5.6.1. Handling Payload Packets . . . . . . . . . . . . . . . 23
5.2. Sending LOCATORs . . . . . . . . . . . . . . . . . . . . . 26 5.6.2. Credit Aging . . . . . . . . . . . . . . . . . . . . . 25
5.3. Handling Received LOCATORs . . . . . . . . . . . . . . . . 28 6. Security Considerations . . . . . . . . . . . . . . . . . . . 26
5.4. Verifying Address Reachability . . . . . . . . . . . . . . 30 6.1. Impersonation Attacks . . . . . . . . . . . . . . . . . . 27
5.5. Changing the Preferred Locator . . . . . . . . . . . . . . 32 6.2. Denial-of-Service Attacks . . . . . . . . . . . . . . . . 28
5.6. Credit-Based Authorization . . . . . . . . . . . . . . . . 32 6.2.1. Flooding Attacks . . . . . . . . . . . . . . . . . . . 28
5.6.1. Handling Payload Packets . . . . . . . . . . . . . . . 33 6.2.2. Memory/Computational-Exhaustion DoS Attacks . . . . . 28
5.6.2. Credit Aging . . . . . . . . . . . . . . . . . . . . . 34 6.3. Mixed Deployment Environment . . . . . . . . . . . . . . . 29
6. Security Considerations . . . . . . . . . . . . . . . . . . . 35 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29
6.1. Impersonation Attacks . . . . . . . . . . . . . . . . . . 36 8. Authors and Acknowledgments . . . . . . . . . . . . . . . . . 30
6.2. Denial-of-Service Attacks . . . . . . . . . . . . . . . . 37 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 30
6.2.1. Flooding Attacks . . . . . . . . . . . . . . . . . . . 37 9.1. Normative references . . . . . . . . . . . . . . . . . . . 30
6.2.2. Memory/Computational-Exhaustion DoS Attacks . . . . . 37 9.2. Informative references . . . . . . . . . . . . . . . . . . 30
6.3. Mixed Deployment Environment . . . . . . . . . . . . . . . 38 Appendix A. Document Revision History . . . . . . . . . . . . . . 31
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 38
8. Authors and Acknowledgments . . . . . . . . . . . . . . . . . 39
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 39
9.1. Normative references . . . . . . . . . . . . . . . . . . . 39
9.2. Informative references . . . . . . . . . . . . . . . . . . 39
Appendix A. Document Revision History . . . . . . . . . . . . . . 40
1. Introduction and Scope 1. Introduction and Scope
The Host Identity Protocol [RFC4423] (HIP) supports an architecture The Host Identity Protocol [RFC4423] (HIP) 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 must also know at least one IP address at which its peers are host must also know at least one IP address at which its peers are
reachable. Initially, these IP addresses are the ones used during reachable. Initially, these IP addresses are the ones used during
the HIP base exchange [RFC5201]. the HIP base exchange [RFC5201].
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.
The scope of this document encompasses messaging and elements of The scope of this document encompasses messaging and elements of
procedure for basic network-level mobility and simple multihoming, procedure for basic network-level host mobility, leaving more
leaving more complicated scenarios and other variations for further complicated scenarios and other variations for further study. More
study. More specifically: specifically:
This document defines a generalized LOCATOR parameter for use in This document defines a generalized LOCATOR parameter for use in
HIP messages. The LOCATOR parameter allows a HIP host to notify a HIP messages. The LOCATOR parameter allows a HIP host to notify a
peer about alternate addresses at which it is reachable. The peer about alternate addresses at which it is reachable. The
LOCATORs may be merely IP addresses, or they may have additional LOCATORs may be merely IP addresses, or they may have additional
multiplexing and demultiplexing context to aid the packet handling multiplexing and demultiplexing context to aid the packet handling
in the lower layers. For instance, an IP address may need to be in the lower layers. For instance, an IP address may need to be
paired with an ESP Security Parameter Index (SPI) so that packets paired with an ESP Security Parameter Index (SPI) so that packets
are sent on the correct SA for a given address. 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 -- the sequential procedure for end-host mobility of a HIP host -- the sequential
change in the preferred IP address used to reach a host. In change in the preferred IP address used to reach a host. In
particular, message flows to enable successful host mobility, particular, message flows to enable successful host mobility,
including address verification methods, are defined herein. including address verification methods, are defined herein.
However, while the same LOCATOR parameter is intended to support However, while the same LOCATOR parameter is intended to support
host multihoming (parallel support of a number of addresses), and host multihoming (parallel support of a number of addresses), and
experimentation is encouraged, detailed elements of procedure for experimentation is encouraged, detailed elements of procedure for
host multihoming are left for further study. host multihoming are out of scope.
While HIP can potentially be used with transports other than the ESP While HIP can potentially be used with transports other than the ESP
transport format [RFC5202], this document largely assumes the use of transport format [RFC5202], this document largely assumes the use of
ESP and leaves other transport formats for further study. ESP and leaves other transport formats for further study.
There are a number of situations where the simple end-to-end There are a number of situations where the simple end-to-end
readdressing functionality is not sufficient. These include the readdressing functionality is not sufficient. These include the
initial reachability of a mobile host, location privacy, simultaneous initial reachability of a mobile host, location privacy, simultaneous
mobility of both hosts, and some modes of NAT traversal. In these mobility of both hosts, and some modes of NAT traversal. In these
situations, there is a need for some helper functionality in the situations, there is a need for some helper functionality in the
network, such as a HIP rendezvous server [RFC5204]. Such network, such as a HIP rendezvous server [RFC5204]. Such
functionality is out of the scope of this document. We also do not functionality is out of the scope of this document. We also do not
consider localized mobility management extensions (i.e., mobility consider localized mobility management extensions (i.e., mobility
management techniques that do not involve directly signaling the management techniques that do not involve directly signaling the
correspondent node); this document is concerned with end-to-end correspondent node); this document is concerned with end-to-end
mobility. Finally, making underlying IP mobility transparent to the mobility. Making underlying IP mobility transparent to the transport
transport layer has implications on the proper response of transport layer has implications on the proper response of transport congestion
congestion control, path MTU selection, and Quality of Service (QoS). control, path MTU selection, and Quality of Service (QoS).
Transport-layer mobility triggers, and the proper transport response Transport-layer mobility triggers, and the proper transport response
to a HIP mobility or multihoming address change, are outside the to a HIP mobility or multihoming address change, are outside the
scope of this document. scope of this document.
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 RFC 2119 [RFC2119].
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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. With respect to a given peer, a host always has one active data. With respect to a given peer, a host always has one active
Preferred locator, unless there are no active locators. By Preferred locator, unless there are no active locators. By
default, the locators used in the HIP base exchange are the default, the locators used in the HIP base exchange are the
Preferred locators. Preferred locators.
Credit Based Authorization. A host must verify a mobile or Credit Based Authorization. A host must verify a peer host's
multihomed peer's reachability at a new locator. Credit-Based reachability at a new locator. Credit-Based Authorization
Authorization authorizes the peer to receive a certain amount of authorizes the peer to receive a certain amount of data at the new
data at the new locator before the result of such verification is locator before the result of such verification is known.
known.
3. Protocol Model 3. Protocol Model
This section is an overview; more detailed specification follows this This section is an overview; more detailed specification follows this
section. section.
3.1. Operating Environment 3.1. Operating Environment
The Host Identity Protocol (HIP) [RFC5201] is a key establishment and The Host Identity Protocol (HIP) [RFC5201] is a key establishment and
parameter negotiation protocol. Its primary applications are for parameter negotiation protocol. Its primary applications are for
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| --------- | ---------
| | | |
---- --------- ---- ---------
| 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 Mobility and Multihoming (MH) Figure 2: Architecture for HIP Host Mobility (MH)
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" is introduced below.
Consider first the case in which there is no mobility or multihoming, Consider first the case in which there is no mobility or multihoming,
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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 is still single-homed Consider next a mobility event, in which a host moves to another IP
but moves to another IP address. Two things must occur in this case. address. Two things must occur in this case. First, the peer must
First, the peer must be notified of the address change using a HIP be notified of the address change using a HIP UPDATE message.
UPDATE message. Second, each host must change its local bindings at Second, each host must change its local bindings at the HIP sublayer
the HIP sublayer (new IP addresses). It may be that both the SPIs (new IP addresses). It may be that both the SPIs and IP addresses
and IP addresses are changed simultaneously in a single UPDATE; the are changed simultaneously in a single UPDATE; the protocol described
protocol described herein supports this. However, simultaneous herein supports this. However, simultaneous movement of both hosts,
movement of both hosts, notification of transport layer protocols of notification of transport layer protocols of the path change, and
the path change, and procedures for possibly traversing middleboxes procedures for possibly traversing middleboxes are not covered by
are not covered by this document. this document.
Finally, consider the case when a host is multihomed (has more than
one globally routable address) and has multiple addresses available
at the HIP layer as alternative locators for fault tolerance.
Examples include the use of (possibly multiple) IPv4 and IPv6
addresses on the same interface, or the use of multiple interfaces
attached to different service providers. Such host multihoming
generally necessitates that a separate ESP SA is maintained for each
interface in order to prevent packets that arrive over different
paths from falling outside of the ESP anti-replay window [RFC4303].
Multihoming thus makes it possible that the bindings shown on the
right side of Figure 2 are one to many (in the outbound direction,
one HIT pair to multiple SPIs, and possibly then to multiple IP
addresses). However, only one SPI and address pair can be used for
any given packet, so the job of the "MH" block depicted above is to
dynamically manipulate these bindings. Beyond locally managing such
multiple bindings, the peer-to-peer HIP signaling protocol needs to
be flexible enough to define the desired mappings between HITs, SPIs,
and addresses, and needs to ensure that UPDATE messages are sent
along the right network paths so that any HIP-aware middleboxes can
observe the SPIs. This document does not specify the "MH" block, nor
does it specify detailed elements of procedure for how to handle
various multihoming (perhaps combined with mobility) scenarios. The
"MH" block may apply to more general problems outside of HIP.
However, this document does describe a basic multihoming case (one
host adds one address to its initial address and notifies the peer)
and leave more complicated scenarios for experimentation and future
documents.
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 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
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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.
3.1.3. Multihoming Overview
A related operational configuration is host multihoming, in which a
host has multiple locators simultaneously rather than sequentially,
as in the case of mobility. By using the LOCATOR parameter defined
herein, a host can inform its peers of additional (multiple) locators
at which it can be reached, and can declare a particular locator as a
"preferred" locator. Although this document defines a basic
mechanism for multihoming, it does not define detailed policies and
procedures, such as which locators to choose when more than one pair
is available, the operation of simultaneous mobility and multihoming,
source address selection policies (beyond those specified in
[RFC3484]), and the implications of multihoming on transport
protocols and ESP anti-replay windows. Additional definitions of
HIP-based multihoming are expected to be part of future documents.
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 mobility and multihoming. These scenarios assume that HIP is HIP host mobility. These scenarios assume that HIP is being used
being used with the ESP transform [RFC5202], although other scenarios with the ESP transform [RFC5202], although other scenarios may be
may be defined in the future. To understand these usage scenarios, defined in the future. To understand these usage scenarios, the
the reader should be at least minimally familiar with the HIP reader should be at least minimally familiar with the HIP protocol
protocol specification [RFC5201]. However, for the (relatively) specification [RFC5201]. However, for the (relatively) uninitiated
uninitiated reader, it is most important to keep in mind that in HIP reader, it is most important to keep in mind that in HIP the actual
the actual payload traffic is protected with ESP, and that the ESP payload traffic is protected with ESP, and that the ESP SPI acts as
SPI acts as an index to the right host-to-host context. More an index to the right host-to-host context. More specification
specification details are found later in Section 4 and Section 5. details are found later in Section 4 and Section 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. Both of the hosts therefore 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 or The readdressing protocol is an asymmetric protocol where a mobile
multihomed host informs a peer host about changes of IP addresses on host informs a peer host about changes of IP addresses on affected
affected SPIs. The readdressing exchange is designed to be SPIs. The readdressing exchange is designed to be piggybacked on
piggybacked on existing HIP exchanges. The majority of the packets existing HIP exchanges. The majority of the packets on which the
on which the LOCATOR parameters are expected to be carried are UPDATE LOCATOR parameters are expected to be carried are UPDATE packets.
packets. However, some implementations may want to experiment with However, some implementations may want to experiment with sending
sending LOCATOR parameters also on other packets, such as R1, I2, and LOCATOR parameters also on other packets, such as R1, I2, and NOTIFY.
NOTIFY.
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, VERIFIED, or DEPRECATED state. From the perspective of a ACTIVE, VERIFIED, or DEPRECATED state. From the perspective of a
host, newly-learned addresses of the peer must be verified before put host, newly-learned addresses of the peer must be verified before put
into active service, and addresses removed by the peer are put into a into active service, and addresses removed by the peer are put into a
deprecated state. Under limited conditions described below 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
skipping to change at page 12, line 32 skipping to change at page 11, line 32
UPDATE(ESP_INFO, LOCATOR, SEQ, [DIFFIE_HELLMAN]) UPDATE(ESP_INFO, LOCATOR, 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. Host Multihoming 3.2.3. Using LOCATORs across Addressing Realms
A (mobile or stationary) host may sometimes have more than one
interface or global address. The host may notify the peer host of
the additional interface or address by using the LOCATOR parameter.
To avoid problems with the ESP anti-replay window, a host SHOULD use
a different SA for each interface or address used to receive packets
from the peer host when multiple locator pairs are being used
simultaneously rather than sequentially.
When more than one locator is provided to the peer host, the host
SHOULD indicate which locator is preferred (the locator on which the
host prefers to receive traffic). By default, the addresses used in
the base exchange are preferred until indicated otherwise.
In the multihoming case, the sender may also have multiple valid
locators from which to source traffic. In practice, a HIP
association in a multihoming configuration may have both a preferred
peer locator and a preferred local locator, although rules for source
address selection should ultimately govern the selection of the
source locator based on the destination locator.
Although the protocol may allow for configurations in which there is
an asymmetric number of SAs between the hosts (e.g., one host has two
interfaces and two inbound SAs, while the peer has one interface and
one inbound SA), it is RECOMMENDED that inbound and outbound SAs be
created pairwise between hosts. When an ESP_INFO arrives to rekey a
particular outbound SA, the corresponding inbound SA should be also
rekeyed at that time. Although asymmetric SA configurations might be
experimented with, their usage may constrain interoperability at this
time. However, it is recommended that implementations attempt to
support peers that prefer to use non-paired SAs. It is expected that
this section and behavior will be modified in future revisions of
this protocol, once the issue and its implications are better
understood.
Consider the case between two hosts, one single-homed and one
multihomed. The multihomed host may decide to inform the single-
homed host about its other address. It is RECOMMENDED that the
multihomed host set up a new SA pair for use on this new address. To
do this, the multihomed host sends a LOCATOR with an ESP_INFO,
indicating the request for a new SA by setting the OLD SPI value to
zero, and the NEW SPI value to the newly created incoming SPI. A
Locator Type of "1" is used to associate the new address with the new
SPI. The LOCATOR parameter also contains a second Type "1" locator,
that of the original address and SPI. To simplify parameter
processing and avoid explicit protocol extensions to remove locators,
each LOCATOR parameter MUST list all locators in use on a connection
(a complete listing of inbound locators and SPIs for the host). The
multihomed host waits for an ESP_INFO (new outbound SA) from the peer
and an ACK of its own UPDATE. As in the mobility case, the peer host
must perform an address verification before actively using the new
address. Figure 5 illustrates this scenario.
Multi-homed Host Peer Host
UPDATE(ESP_INFO, LOCATOR, SEQ, [DIFFIE_HELLMAN])
----------------------------------->
UPDATE(ESP_INFO, SEQ, ACK, [DIFFIE_HELLMAN,] ECHO_REQUEST)
<-----------------------------------
UPDATE(ACK, ECHO_RESPONSE)
----------------------------------->
Figure 5: Basic Multihoming Scenario
In multihoming scenarios, it is important that hosts receiving
UPDATEs associate them correctly with the destination address used in
the packet carrying the UPDATE. When processing inbound LOCATORs
that establish new security associations on an interface with
multiple addresses, a host uses the destination address of the UPDATE
containing the LOCATOR as the local address to which the LOCATOR plus
ESP_INFO is targeted. This is because hosts may send UPDATEs with
the same (locator) IP address to different peer addresses -- this has
the effect of creating multiple inbound SAs implicitly affiliated
with different peer source addresses.
3.2.4. Site Multihoming
A host may have an interface that has multiple globally routable IP
addresses. Such a situation may be a result of the site having
multiple upper Internet Service Providers, or just because the site
provides all hosts with both IPv4 and IPv6 addresses. The host
should stay reachable at all or any subset of the currently available
global routable addresses, independent of how they are provided.
This case is handled the same as if there were different IP
addresses, described above in Section 3.2.3. Note that a single
interface may experience site multihoming while the host itself may
have multiple interfaces.
Note that a host may be multihomed and mobile simultaneously, and
that a multihomed host may want to protect the location of some of
its interfaces while revealing the real IP address of some others.
This document does not presently specify additional site multihoming
extensions to HIP; further alignment with the IETF shim6 working
group may be considered in the future.
3.2.5. Dual host multihoming
Consider the case in which both hosts would like to add an additional
address after the base exchange completes. In Figure 6, consider
that host1, which used address addr1a in the base exchange to set up
SPI1a and SPI2a, wants to add address addr1b. It would send an
UPDATE with LOCATOR (containing the address addr1b) to host2, using
destination address addr2a, and a new set of SPIs would be added
between hosts 1 and 2 (call them SPI1b and SPI2b -- not shown in the
figure). Next, consider host2 deciding to add addr2b to the
relationship. Host2 must select one of host1's addresses towards
which to initiate an UPDATE. It may choose to initiate an UPDATE to
addr1a, addr1b, or both. If it chooses to send to both, then a full
mesh (four SA pairs) of SAs would exist between the two hosts. This
is the most general case; it often may be the case that hosts
primarily establish new SAs only with the peer's Preferred locator.
The readdressing protocol is flexible enough to accommodate this
choice.
-<- SPI1a -- -- SPI2a ->-
host1 < > addr1a <---> addr2a < > host2
->- SPI2a -- -- SPI1a -<-
addr1b <---> addr2a (second SA pair)
addr1a <---> addr2b (third SA pair)
addr1b <---> addr2b (fourth SA pair)
Figure 6: Dual Multihoming Case in Which Each Host Uses LOCATOR to
Add a Second Address
3.2.6. Combined Mobility and Multihoming
It looks likely that in the future, many mobile hosts will be
simultaneously mobile and multihomed, i.e., have multiple mobile
interfaces. Furthermore, if the interfaces use different access
technologies, it is fairly likely that one of the interfaces may
appear stable (retain its current IP address) while some other(s) may
experience mobility (undergo IP address change).
The use of LOCATOR plus ESP_INFO should be flexible enough to handle
most such scenarios, although more complicated scenarios have not
been studied so far.
3.2.7. Using LOCATORs across Addressing Realms
It is possible for HIP associations to migrate to a state in which It is possible for HIP associations to migrate to a state in which
both parties are only using locators in different addressing realms. both parties are only using locators in different addressing realms.
For example, the two hosts may initiate the HIP association when both For example, the two hosts may initiate the HIP association when both
are using IPv6 locators, then one host may loose its IPv6 are using IPv6 locators, then one host may loose its IPv6
connectivity and obtain an IPv4 address. In such a case, some type connectivity and obtain an IPv4 address. In such a case, some type
of mechanism for interworking between the different realms must be of mechanism for interworking between the different realms must be
employed; such techniques are outside the scope of the present text. employed; such techniques are outside the scope of the present text.
The basic problem in this example is that the host readdressing to The basic problem in this example is that the host readdressing to
IPv4 does not know a corresponding IPv4 address of the peer. This IPv4 does not know a corresponding IPv4 address of the peer. This
may be handled (experimentally) by possibly configuring this address may be handled (experimentally) by possibly configuring this address
information manually or in the DNS, or the hosts exchange both IPv4 information manually or in the DNS, or the hosts exchange both IPv4
and IPv6 addresses in the locator. and IPv6 addresses in the locator.
3.2.8. 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. renumbering is similar to mobility.
3.2.9. Initiating the Protocol in R1 or I2
A Responder host MAY include a LOCATOR parameter in the R1 packet
that it sends to the Initiator. This parameter MUST be protected by
the R1 signature. If the R1 packet contains LOCATOR parameters with
a new Preferred locator, the Initiator SHOULD directly set the new
Preferred locator to status ACTIVE without performing address
verification first, and MUST send the I2 packet to the new Preferred
locator. The I1 destination address and the new Preferred locator
may be identical. All new non-preferred locators must still undergo
address verification once the base exchange completes.
Initiator Responder
R1 with LOCATOR
<-----------------------------------
record additional addresses
change responder address
I2 sent to newly indicated preferred address
----------------------------------->
(process normally)
R2
<-----------------------------------
(process normally, later verification of non-preferred locators)
Figure 7: LOCATOR Inclusion in R1
An Initiator MAY include one or more LOCATOR parameters in the I2
packet, independent of whether or not there was a LOCATOR parameter
in the R1. These parameters MUST be protected by the I2 signature.
Even if the I2 packet contains LOCATOR parameters, the Responder MUST
still send the R2 packet to the source address of the I2. The new
Preferred locator SHOULD be identical to the I2 source address. If
the I2 packet contains LOCATOR parameters, all new locators must
undergo address verification as usual, and the ESP traffic that
subsequently follows should use the Preferred locator.
Initiator Responder
I2 with LOCATOR
----------------------------------->
(process normally)
record additional addresses
R2 sent to source address of I2
<-----------------------------------
(process normally)
Figure 8: LOCATOR Inclusion in I2
The I1 and I2 may be arriving from different source addresses if the
LOCATOR parameter is present in R1. In this case, implementations
simultaneously using multiple pre-created R1s, indexed by Initiator
IP addresses, may inadvertently fail the puzzle solution of I2
packets due to a perceived puzzle mismatch. See, for instance, the
example in Appendix A of [RFC5201]. As a solution, the Responder's
puzzle indexing mechanism must be flexible enough to accommodate the
situation when R1 includes a LOCATOR parameter.
3.3. Other Considerations 3.3. Other Considerations
3.3.1. Address Verification 3.3.1. Address Verification
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, it does not necessarily know whether the other host is LOCATOR, 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].
Likewise, viral software may have compromised the peer host, Likewise, viral software may have compromised the peer host,
skipping to change at page 18, line 20 skipping to change at page 13, line 11
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, Credit-Based Authorization prevents
amplifications. This is accomplished by limiting the data a host can amplifications. This is accomplished by limiting the data a host can
send to an unverified address of a peer by the data recently received send to an unverified address of a peer by the data recently received
from that peer. Redirection-based flooding attacks thus become less from that peer. Redirection-based flooding attacks thus become less
attractive than, for example, pure direct flooding, where the attractive than, for example, pure direct flooding, where the
attacker itself sends bogus packets to the victim. attacker itself sends bogus packets to the victim.
Figure 9 illustrates Credit-Based Authorization: Host B measures the Figure 5 illustrates Credit-Based Authorization: Host B measures the
amount of data recently received from peer A and, when A readdresses, amount of data recently received from peer A and, when A readdresses,
sends packets to A's new, unverified address as long as the sum of sends packets to A's new, unverified address as long as the sum of
the packet sizes does not exceed the measured, received data volume. the packet sizes does not exceed the measured, received data volume.
When insufficient credit is left, B stops sending further packets to When insufficient credit is left, B stops sending further packets to
A until A's address becomes ACTIVE. The address changes may be due A until A's address becomes ACTIVE. The address changes may be due
to mobility, multihoming, or any other reason. Not shown in Figure 9 to mobility, multihoming, or any other reason. Not shown in Figure 5
are the results of credit aging (Section 5.6.2), a mechanism used to are the results of credit aging (Section 5.6.2), a mechanism used to
dampen possible time-shifting attacks. dampen possible time-shifting attacks.
+-------+ +-------+ +-------+ +-------+
| A | | B | | A | | B |
+-------+ +-------+ +-------+ +-------+
| | | |
address |------------------------------->| credit += size(packet) address |------------------------------->| credit += size(packet)
ACTIVE | | ACTIVE | |
|------------------------------->| credit += size(packet) |------------------------------->| credit += size(packet)
skipping to change at page 19, line 28 skipping to change at page 13, line 44
|<-------------------------------| credit -= size(packet) |<-------------------------------| credit -= size(packet)
| | | |
|<-------------------------------| credit -= size(packet) |<-------------------------------| credit -= size(packet)
| X credit < size(packet) | X credit < size(packet)
| | => do not send packet! | | => do not send packet!
+ address verification concludes | + address verification concludes |
address | | address | |
ACTIVE |<-------------------------------| do not change credit ACTIVE |<-------------------------------| do not change credit
| | | |
Figure 9: Readdressing Scenario Figure 5: Readdressing Scenario
3.3.3. Preferred Locator 3.3.3. Preferred Locator
When a host has multiple locators, the peer host must decide which to When a host has multiple locators, the peer host must decide which to
use for outbound packets. It may be that a host would prefer to use for outbound packets. It may be that a host would prefer to
receive data on a particular inbound interface. HIP allows a receive data on a particular inbound interface. HIP allows a
particular locator to be designated as a Preferred locator and particular locator to be designated as a Preferred locator and
communicated to the peer (see Section 4). communicated to the peer (see Section 4).
In general, when multiple locators are used for a session, there is
the question of using multiple locators for failover only or for
load-balancing. Due to the implications of load-balancing on the
transport layer that still need to be worked out, this document
assumes that multiple locators are used primarily for failover. An
implementation may use ICMP interactions, reachability checks, or
other means to detect the failure of a locator.
3.3.4. Interaction with Security Associations
This document specifies a new HIP protocol parameter, the LOCATOR
parameter (see Section 4), that allows the hosts to exchange
information about their locator(s) and any changes in their
locator(s). The logical structure created with LOCATOR parameters
has three levels: hosts, Security Associations (SAs) indexed by
Security Parameter Indices (SPIs), and addresses.
The relation between these levels for an association constructed as
defined in the base specification [RFC5201] and ESP transform
[RFC5202] is illustrated in Figure 10.
-<- SPI1a -- -- SPI2a ->-
host1 < > addr1a <---> addr2a < > host2
->- SPI2a -- -- SPI1a -<-
Figure 10: Relation between Hosts, SPIs, and Addresses (Base
Specification)
In Figure 10, host1 and host2 negotiate two unidirectional SAs, and
each host selects the SPI value for its inbound SA. The addresses
addr1a and addr2a are the source addresses that the hosts use in the
base HIP exchange. These are the "preferred" (and only) addresses
conveyed to the peer for use on each SA. That is, although packets
sent to any of the hosts' interfaces may be accepted on the inbound
SA, the peer host in general knows of only the single destination
address learned in the base exchange (e.g., for host1, it sends a
packet on SPI2a to addr2a to reach host2), unless other mechanisms
exist to learn of new addresses.
In general, the bindings that exist in an implementation
corresponding to this document can be depicted as shown in Figure 11.
In this figure, a host can have multiple inbound SPIs (and, not
shown, multiple outbound SPIs) associated with another host.
Furthermore, each SPI may have multiple addresses associated with it.
These addresses that are bound to an SPI are not used to lookup the
incoming SA. Rather, the addresses are those that are provided to
the peer host, as hints for which addresses to use to reach the host
on that SPI. The LOCATOR parameter is used to change the set of
addresses that a peer associates with a particular SPI.
address11
/
SPI1 - address12
/
/ address21
host -- SPI2 <
\ address22
\
SPI3 - address31
\
address32
Figure 11: Relation between Hosts, SPIs, and Addresses (General Case)
A host may establish any number of security associations (or SPIs)
with a peer. The main purpose of having multiple SPIs with a peer is
to group the addresses into collections that are likely to experience
fate sharing. For example, if the host needs to change its addresses
on SPI2, it is likely that both address21 and address22 will
simultaneously become obsolete. In a typical case, such SPIs may
correspond with physical interfaces; see below. Note, however, that
especially in the case of site multihoming, one of the addresses may
become unreachable while the other one still works. In the typical
case, however, this does not require the host to inform its peers
about the situation, since even the non-working address still
logically exists.
A basic property of HIP SAs is that the inbound IP address is not
used to lookup the incoming SA. Therefore, in Figure 11, it may seem
unnecessary for address31, for example, to be associated only with
SPI3 -- in practice, a packet may arrive to SPI1 via destination
address address31 as well. However, the use of different source and
destination addresses typically leads to different paths, with
different latencies in the network, and if packets were to arrive via
an arbitrary destination IP address (or path) for a given SPI, the
reordering due to different latencies may cause some packets to fall
outside of the ESP anti-replay window. For this reason, HIP provides
a mechanism to affiliate destination addresses with inbound SPIs,
when there is a concern that anti-replay windows might be violated.
In this sense, we can say that a given inbound SPI has an "affinity"
for certain inbound IP addresses, and this affinity is communicated
to the peer host. Each physical interface SHOULD have a separate SA,
unless the ESP anti-replay window is loose.
Moreover, even when the destination addresses used for a particular
SPI are held constant, the use of different source interfaces may
also cause packets to fall outside of the ESP anti-replay window,
since the path traversed is often affected by the source address or
interface used. A host has no way to influence the source interface
on which a peer sends its packets on a given SPI. A host SHOULD
consistently use the same source interface and address when sending
to a particular destination IP address and SPI. For this reason, a
host may find it useful to change its SPI or at least reset its ESP
anti-replay window when the peer host readdresses.
An address may appear on more than one SPI. This creates no
ambiguity since the receiver will ignore the IP addresses during SA
lookup anyway. However, this document does not specify such cases.
When the LOCATOR parameter is sent in an UPDATE packet, then the
receiver will respond with an UPDATE acknowledgment. When the
LOCATOR parameter is sent in an R1 or I2 packet, the base exchange
retransmission mechanism will confirm its successful delivery.
LOCATORs may experimentally be used in NOTIFY packets; in this case,
the recipient MUST consider the LOCATOR as informational and not
immediately change the current preferred address, but can test the
additional locators when the need arises. The use of the LOCATOR in
a NOTIFY message may not be compatible with middleboxes.
4. LOCATOR Parameter Format 4. LOCATOR Parameter Format
The LOCATOR parameter is a critical parameter as defined by The LOCATOR parameter is a critical parameter as defined by
[RFC5201]. It consists of the standard HIP parameter Type and Length [RFC5201]. It 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, Locator Lifetime, and a Locator encoding. A
LOCATOR containing zero Locator fields is permitted but has the LOCATOR containing zero Locator fields is permitted but has the
effect of deprecating all addresses. effect of deprecating all addresses.
skipping to change at page 23, line 32 skipping to change at page 14, line 44
| Traffic Type | Locator Type | Locator Length | Reserved |P| | Traffic Type | Locator Type | Locator Length | Reserved |P|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Locator Lifetime | | Locator Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Locator | | Locator |
| | | |
| | | |
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 12: LOCATOR Parameter Format Figure 6: LOCATOR Parameter Format
Type: 193 Type: 193
Length: Length in octets, excluding Type and Length fields, and Length: Length in octets, excluding Type and Length fields, and
excluding padding. excluding padding.
Traffic Type: Defines whether the locator pertains to HIP signaling, Traffic Type: Defines whether the locator pertains to HIP signaling,
user data, or both. user data, or both.
Locator Type: Defines the semantics of the Locator field. Locator Type: Defines the semantics of the Locator field.
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
skipping to change at page 27, line 41 skipping to change at page 19, line 4
host moves to another link. In any case, link-local addresses MUST host moves to another link. In any case, link-local addresses MUST
NOT be announced to a peer unless that peer is known to be on the NOT be announced to a peer unless that peer is known to be on the
same link. same link.
Once the host has decided on the groups and assignment of addresses Once the host has decided on the groups and assignment of addresses
to the SPIs, it creates a LOCATOR parameter that serves as a complete to the SPIs, it creates a LOCATOR parameter that serves as a complete
representation of the addresses and affiliated SPIs intended for representation of the addresses and affiliated SPIs intended for
active use. We now describe a few cases introduced in Section 3.2. active use. 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 We assume that the Traffic Type for each locator is set to "0" (other
values for Traffic Type may be specified in documents that separate values for Traffic Type may be specified in documents that separate
the HIP control plane from data plane traffic). Other mobility and the HIP control plane from data plane traffic). Other mobility cases
multihoming cases are possible but are left for further are possible but are left for further experimentation.
experimentation.
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 parameter. The ESP_INFO contains the current single LOCATOR 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 contains a single Locator with a "Locator Type" of "1"; LOCATOR contains a single Locator with a "Locator Type" of "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 protocol This packet is retransmitted as defined in the HIP protocol
skipping to change at page 28, line 22 skipping to change at page 19, line 32
single LOCATOR parameter (with a single address). The ESP_INFO single LOCATOR parameter (with a single address). The ESP_INFO
contains the current value of the SPI in the OLD SPI and the new contains the current value of the SPI in the OLD SPI and the new
value of the SPI in the NEW SPI, and a KEYMAT Index as selected value of the SPI in the NEW SPI, and a KEYMAT Index as selected
by local policy. Optionally, the host may choose to initiate a by local policy. Optionally, the host may choose to initiate a
Diffie Hellman rekey by including a DIFFIE_HELLMAN parameter. Diffie Hellman rekey by including a DIFFIE_HELLMAN parameter.
The LOCATOR contains a single Locator with "Locator Type" of "1"; The LOCATOR contains a single Locator with "Locator Type" of "1";
the SPI must match that of the NEW SPI in the ESP_INFO. the SPI must match that of the NEW SPI in the ESP_INFO.
Otherwise, the steps are identical to the case in which no Otherwise, the steps are identical to the case in which no
rekeying is initiated. rekeying is initiated.
3. Host multihoming (addition of an address). We only describe the
simple case of adding an additional address to a (previously)
single-homed, non-mobile host. The host SHOULD set up a new SA
pair between this new address and the preferred address of the
peer host. To do this, the multihomed host creates a new inbound
SA and creates a new SPI. For the outgoing UPDATE message, it
inserts an ESP_INFO parameter with an OLD SPI field of "0", a NEW
SPI field corresponding to the new SPI, and a KEYMAT Index as
selected by local policy. The host adds to the UPDATE message a
LOCATOR with two Type "1" Locators: the original address and SPI
active on the association, and the new address and new SPI being
added (with the SPI matching the NEW SPI contained in the
ESP_INFO). The Preferred bit SHOULD be set depending on the
policy to tell the peer host which of the two locators is
preferred. The UPDATE also contains a SEQ parameter and
optionally a DIFFIE_HELLMAN parameter, and follows rekeying
procedures with respect to this new address. The UPDATE message
SHOULD be sent to the peer's Preferred address with a source
address corresponding to the new locator.
The sending of multiple LOCATORs, locators with Locator Type "0", and The sending of multiple LOCATORs, locators with Locator Type "0", and
multiple ESP_INFO parameters is for further study. Note that the multiple ESP_INFO parameters is for further study. Note that the
inclusion of LOCATOR in an R1 packet requires the use of Type "0" inclusion of LOCATOR in an R1 packet requires the use of Type "0"
locators since no SAs are set up at that point. locators since no SAs are set up at that point.
5.3. Handling Received LOCATORs 5.3. Handling Received LOCATORs
A host SHOULD be prepared to receive a LOCATOR parameter in the A host SHOULD be prepared to receive a LOCATOR parameter in the
following HIP packets: R1, I2, UPDATE, and NOTIFY. following HIP packets: R1, I2, UPDATE, and NOTIFY.
skipping to change at page 31, line 26 skipping to change at page 22, line 16
Note that in the case of receiving a LOCATOR in an R1 and replying Note that in the case of receiving a LOCATOR in an R1 and replying
with an I2 to the new address in the LOCATOR, receiving the with an I2 to the new address in the LOCATOR, receiving the
corresponding R2 is sufficient proof of reachability for the corresponding R2 is sufficient proof of reachability for the
Responder's preferred address. Since further address verification of Responder's preferred address. Since further address verification of
such an address can impede the HIP-base exchange, a host MUST NOT such an address can impede the HIP-base exchange, a host MUST NOT
separately verify reachability of a new Preferred locator that was separately verify reachability of a new Preferred locator that was
received on an R1. received on an R1.
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 13, 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
prepare incoming SA prepare incoming SA
NEW SPI in ESP_INFO (UPDATE) NEW SPI in ESP_INFO (UPDATE)
<----------------------------------- <-----------------------------------
switch to new outgoing SA switch to new outgoing SA
data on new SA data on new SA
-----------------------------------> ----------------------------------->
mark address ACTIVE mark address ACTIVE
Figure 13: 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 Credit-
Based Authorization permits. Credit-Based Authorization is explained Based Authorization permits. Credit-Based Authorization is explained
in Section 5.6. Once address verification succeeds, the status of in Section 5.6. Once address verification succeeds, the status of
the new Preferred locator changes to ACTIVE. the new Preferred locator changes to ACTIVE.
skipping to change at page 33, line 22 skipping to change at page 24, line 9
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 14 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 15 shows the decision chain in the event a packet received. Figure 9 shows the decision chain in the event a packet is
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 14: 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 |
\_________________/ +---------------+ \_________________/ +---------------+
| |
skipping to change at page 34, line 43 skipping to change at page 25, line 43
| |
| Yes | Yes
| |
v v
+---------------+ +---------------+ +---------------+ +---------------+
| Reduce credit | | Send packet | | Reduce credit | | Send packet |
| counter by |----------------> | to preferred | | counter by |----------------> | to preferred |
| packet size | | address | | packet size | | address |
+---------------+ +---------------+ +---------------+ +---------------+
Figure 15: Sending Packets with Credit-Based Authorization Figure 9: Sending Packets with Credit-Based Authorization
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
skipping to change at page 40, line 21 skipping to change at page 31, line 21
in Progress, February 2006. in Progress, February 2006.
Appendix A. Document Revision History Appendix A. Document Revision History
To be removed upon publication To be removed upon publication
+----------+-------------------------------------------------------+ +----------+-------------------------------------------------------+
| Revision | Comments | | Revision | Comments |
+----------+-------------------------------------------------------+ +----------+-------------------------------------------------------+
| draft-00 | Initial version from RFC5206 xml (unchanged). | | draft-00 | Initial version from RFC5206 xml (unchanged). |
| draft-01 | Remove multihoming-specific text; no other changes. |
+----------+-------------------------------------------------------+ +----------+-------------------------------------------------------+
Authors' Addresses Authors' Addresses
Pekka Nikander Pekka Nikander
Ericsson Research NomadicLab Ericsson Research NomadicLab
JORVAS FIN-02420 JORVAS FIN-02420
FINLAND FINLAND
Phone: +358 9 299 1 Phone: +358 9 299 1
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