draft-ietf-softwire-mesh-multicast-23.txt   draft-ietf-softwire-mesh-multicast-24.txt 
Softwire WG M. Xu Softwire WG M. Xu
Internet-Draft Y. Cui Internet-Draft Y. Cui
Intended status: Standards Track J. Wu Intended status: Standards Track J. Wu
Expires: March 19, 2019 Tsinghua University Expires: June 21, 2019 Tsinghua University
S. Yang S. Yang
Shenzhen University Shenzhen University
C. Metz C. Metz
Cisco Systems Cisco Systems
September 15, 2018 December 18, 2018
IPv4 Multicast over an IPv6 Multicast in Softwire Mesh Network IPv4 Multicast over an IPv6 Multicast in Softwire Mesh Network
draft-ietf-softwire-mesh-multicast-23 draft-ietf-softwire-mesh-multicast-24
Abstract Abstract
During the transition to IPv6, there will be scenarios where a During the transition to IPv6, there will be scenarios where a
backbone network internally running one IP address family (referred backbone network internally running one IP address family (referred
to as the internal IP or I-IP family), connects client networks to as the internal IP or I-IP family), connects client networks
running another IP address family (referred to as the external IP or running another IP address family (referred to as the external IP or
E-IP family). In such cases, the I-IP backbone needs to offer both E-IP family). In such cases, the I-IP backbone needs to offer both
unicast and multicast transit services to the client E-IP networks. unicast and multicast transit services to the client E-IP networks.
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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-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
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 March 19, 2019. This Internet-Draft will expire on June 21, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 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
(https://trustee.ietf.org/license-info) in effect on the date of (https://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
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5.3. Source Address Mapping . . . . . . . . . . . . . . . . . 9 5.3. Source Address Mapping . . . . . . . . . . . . . . . . . 9
5.4. Routing Mechanism . . . . . . . . . . . . . . . . . . . . 9 5.4. Routing Mechanism . . . . . . . . . . . . . . . . . . . . 9
6. Control Plane Functions of AFBR . . . . . . . . . . . . . . . 10 6. Control Plane Functions of AFBR . . . . . . . . . . . . . . . 10
6.1. E-IP (*,G) and (S,G) State Maintenance . . . . . . . . . 10 6.1. E-IP (*,G) and (S,G) State Maintenance . . . . . . . . . 10
6.2. I-IP (S',G') State Maintenance . . . . . . . . . . . . . 10 6.2. I-IP (S',G') State Maintenance . . . . . . . . . . . . . 10
6.3. E-IP (S,G,rpt) State Maintenance . . . . . . . . . . . . 11 6.3. E-IP (S,G,rpt) State Maintenance . . . . . . . . . . . . 11
6.4. Inter-AFBR Signaling . . . . . . . . . . . . . . . . . . 11 6.4. Inter-AFBR Signaling . . . . . . . . . . . . . . . . . . 11
6.5. SPT Switchover . . . . . . . . . . . . . . . . . . . . . 13 6.5. SPT Switchover . . . . . . . . . . . . . . . . . . . . . 13
6.6. Other PIM Message Types . . . . . . . . . . . . . . . . . 13 6.6. Other PIM Message Types . . . . . . . . . . . . . . . . . 13
6.7. Other PIM States Maintenance . . . . . . . . . . . . . . 13 6.7. Other PIM States Maintenance . . . . . . . . . . . . . . 13
7. Data Plane Functions of the AFBR . . . . . . . . . . . . . . 13 7. Data Plane Functions of the AFBR . . . . . . . . . . . . . . 14
7.1. Process and Forward Multicast Data . . . . . . . . . . . 14 7.1. Process and Forward Multicast Data . . . . . . . . . . . 14
7.2. TTL . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 7.2. TTL or Hop Count . . . . . . . . . . . . . . . . . . . . 14
7.3. Fragmentation . . . . . . . . . . . . . . . . . . . . . . 14 7.3. Fragmentation . . . . . . . . . . . . . . . . . . . . . . 14
8. Packet Format and Translation . . . . . . . . . . . . . . . . 14 8. Packet Format and Translation . . . . . . . . . . . . . . . . 14
9. Softwire Mesh Multicast Encapsulation . . . . . . . . . . . . 15 9. Softwire Mesh Multicast Encapsulation . . . . . . . . . . . . 15
10. Security Considerations . . . . . . . . . . . . . . . . . . . 16 10. Security Considerations . . . . . . . . . . . . . . . . . . . 16
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 16 12. Normative References . . . . . . . . . . . . . . . . . . . . 16
12.1. Normative References . . . . . . . . . . . . . . . . . . 16 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 18
12.2. Informative References . . . . . . . . . . . . . . . . . 17 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17
1. Introduction 1. Introduction
During the transition to IPv6, there will be scenarios where a During the transition to IPv6, there will be scenarios where a
backbone network internally running one IP address family (referred backbone network internally running one IP address family (referred
to as the internal IP or I-IP family), connects client networks to as the internal IP or I-IP family), connects client networks
running another IP address family (referred to as the external IP or running another IP address family (referred to as the external IP or
E-IP family). E-IP family).
One solution is to leverage the multicast functions inherent in the One solution is to leverage the multicast functions inherent in the
skipping to change at page 3, line 34 skipping to change at page 3, line 34
backbone network. backbone network.
This could be accomplished by re-using the multicast VPN approach This could be accomplished by re-using the multicast VPN approach
outlined in [RFC6513]. MVPN-like schemes can support the softwire outlined in [RFC6513]. MVPN-like schemes can support the softwire
mesh scenario and achieve a "many-to-one" mapping between the E-IP mesh scenario and achieve a "many-to-one" mapping between the E-IP
client multicast trees and the transit core multicast trees. The client multicast trees and the transit core multicast trees. The
advantage of this approach is that the number of trees in the I-IP advantage of this approach is that the number of trees in the I-IP
backbone network scales less than linearly with the number of E-IP backbone network scales less than linearly with the number of E-IP
client trees. Corporate enterprise networks, and by extension client trees. Corporate enterprise networks, and by extension
multicast VPNs, have been known to run applications that create too multicast VPNs, have been known to run applications that create too
many (S,G) states [RFC7761][RFC7899]. Aggregation at the edge many (S,G) states, which is source specific states related with a
contains the (S,G) states for customer's VPNs and these need to be specified multicast group [RFC7761][RFC7899]. Aggregation at the
maintained by the network operator. The disadvantage of this edge contains the (S,G) states for customer's VPNs and these need to
be maintained by the network operator. The disadvantage of this
approach is the possibility of inefficient bandwidth and resource approach is the possibility of inefficient bandwidth and resource
utilization when multicast packets are delivered to a receiving AFBR utilization when multicast packets are delivered to a receiving AFBR
with no attached E-IP receivers. with no attached E-IP receivers.
[RFC8114] provides a solution for delivering IPv4 multicast services [RFC8114] provides a solution for delivering IPv4 multicast services
over an IPv6 network. But it mainly focuses on the DS-lite [RFC6333] over an IPv6 network. But it mainly focuses on the DS-lite [RFC6333]
scenario, where IPv4 addresses assigned by a broadband service scenario, where IPv4 addresses assigned by a broadband service
provider are shared among customers. This document describes a provider are shared among customers. This document describes a
detailed solution for the IPv4-over-IPv6 softwire mesh scenario, detailed solution for the IPv4-over-IPv6 softwire mesh scenario,
where client networks run IPv4 and the backbone network runs IPv6. where client networks run IPv4 and the backbone network runs IPv6.
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+--------+ | | | | +--------+ +--------+ | | | | +--------+
|Receiver+---+ E-IP | | E-IP +--+Receiver| |Receiver+---+ E-IP | | E-IP +--+Receiver|
+--------+ |network | |network | +--------+ +--------+ |network | |network | +--------+
+--------+ +--------+ +--------+ +--------+
Figure 1: Softwire Mesh Multicast Framework Figure 1: Softwire Mesh Multicast Framework
2. Requirements Language 2. Requirements Language
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", "NOT RECOMMENDED", "MAY", and
document are to be interpreted as described in [RFC2119]. "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Terminology 3. Terminology
Terminology used in this document: Terminology used in this document:
o Address Family Border Router (AFBR) - A router interconnecting two o Address Family Border Router (AFBR) - A router interconnecting two
or more networks using different IP address families. Besides, in or more networks using different IP address families. Additionally,
the context of softwire mesh multicast, the AFBR runs E-IP and I-IP in the context of softwire mesh multicast, the AFBR runs E-IP and
control planes to maintain E-IP and I-IP multicast states I-IP control planes to maintain E-IP and I-IP multicast states
respectively and performs the appropriate encapsulation/decapsulation respectively and performs the appropriate encapsulation/decapsulation
of client E-IP multicast packets for transport across the I-IP core. of client E-IP multicast packets for transport across the I-IP core.
An AFBR will act as a source and/or receiver in an I-IP multicast An AFBR will act as a source and/or receiver in an I-IP multicast
tree. tree.
o Upstream AFBR: An AFBR that is located on the upper reaches of a o Upstream AFBR: An AFBR that is closer to the source of a multicast
multicast data flow. data flow.
o Downstream AFBR: An AFBR that is located on the lower reaches of a o Downstream AFBR: An AFBR that is closer to a receiver of a
multicast data flow. multicast data flow.
o I-IP (Internal IP): This refers to IP address family that is o I-IP (Internal IP): This refers to IP address family that is
supported by the core network. In this document, the I-IP is IPv6. supported by the core network. In this document, the I-IP is IPv6.
o E-IP (External IP): This refers to the IP address family that is o E-IP (External IP): This refers to the IP address family that is
supported by the client network(s) attached to the I-IP transit core. supported by the client network(s) attached to the I-IP transit core.
In this document, the E-IP is IPv4. In this document, the E-IP is IPv4.
o I-IP core tree: A distribution tree rooted at one or more AFBR o I-IP core tree: A distribution tree rooted at one or more AFBR
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+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| mPrefix46 | group address | | mPrefix46 | group address |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
Figure 3: IPv4-Embedded IPv6 Multicast Address Format Figure 3: IPv4-Embedded IPv6 Multicast Address Format
An IPv6 multicast prefix (mPrefix46) is provisioned on each AFBR. An IPv6 multicast prefix (mPrefix46) is provisioned on each AFBR.
AFBRs will prepend the prefix to an IPv4 multicast group address when AFBRs will prepend the prefix to an IPv4 multicast group address when
translating it to an IPv6 multicast group address. translating it to an IPv6 multicast group address.
The construction of the mPrefix46 for SSM is the same as the The construction of the mPrefix46 for Source-Specific Multicast (SSM)
construction of the mPrefix64 described in Section 5 of [RFC8114]. is the same as the construction of the mPrefix64 described in
Section 5 of [RFC8114].
With this scheme, each IPv4 multicast address can be mapped into an With this scheme, each IPv4 multicast address can be mapped into an
IPv6 multicast address (with the assigned prefix), and each IPv6 IPv6 multicast address (with the assigned prefix), and each IPv6
multicast address with the assigned prefix can be mapped into an IPv4 multicast address with the assigned prefix can be mapped into an IPv4
multicast address. The group address translation algorithm can be multicast address. The group address translation algorithm can be
referred in Section 5.2 of [RFC8114]. referred in Section 5.2 of [RFC8114].
5.3. Source Address Mapping 5.3. Source Address Mapping
There are two kinds of multicast: ASM and SSM. Considering that the There are two kinds of multicast: Any-Source Multicast (ASM) and SSM.
I-IP network and E-IP network may support different kinds of Considering that the I-IP network and E-IP network may support
multicast, the source address translation rules needed to support all different kinds of multicast, the source address translation rules
possible scenarios may become very complex. But since SSM can be needed to support all possible scenarios may become very complex.
implemented with a strict subset of the PIM-SM protocol mechanisms But since SSM can be implemented with a strict subset of the PIM-SM
[RFC7761], we can treat the I-IP core as SSM-only to make it as protocol mechanisms [RFC7761], we can treat the I-IP core as SSM-only
simple as possible. There then remain only two scenarios to be to make it as simple as possible. There then remain only two
discussed in detail: scenarios to be discussed in detail:
o E-IP network supports SSM o E-IP network supports SSM
One possible way to make sure that the translated PIMv6 message One possible way to make sure that the translated PIMv6 message
reaches upstream AFBR is to set S' to a virtual IPv6 address that reaches upstream AFBR is to set S' to a virtual IPv6 address that
leads to the upstream AFBR. The unicast adddress translation leads to the upstream AFBR. The unicast adddress translation
should be achieved according to [RFC6052] should be achieved according to [RFC6052]
o E-IP network supports ASM o E-IP network supports ASM
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are cleared (See Section 4.9.5.1 of [RFC7761]). As a result, the are cleared (See Section 4.9.5.1 of [RFC7761]). As a result, the
source list entries in (*,G) messages can be translated into source list entries in (*,G) messages can be translated into
source list entries in (S',G') messages by clearing both the WC source list entries in (S',G') messages by clearing both the WC
and RPT bits at downstream AFBRs, and vice-versa for the reverse and RPT bits at downstream AFBRs, and vice-versa for the reverse
translation at upstream AFBRs. translation at upstream AFBRs.
5.4. Routing Mechanism 5.4. Routing Mechanism
With mesh multicast, PIMv6 messages originating from a downstream With mesh multicast, PIMv6 messages originating from a downstream
AFBR need to be propogated to the correct upstream AFBR, and every AFBR need to be propogated to the correct upstream AFBR, and every
AFBR needs the /96 prefix in "IPv4-Embedded IPv6 Virtual Source AFBR needs the /96 prefix in "IPv4-Embedded IPv6 Source Address
Address Format". Format" [RFC6052].
To achieve this, every AFBR MUST announce the address of one of its To achieve this, every AFBR MUST announce the address of one of its
E-IPv4 interfaces in the "v4" field alongside the corresponding E-IPv4 interfaces in the "v4" field [RFC6052] alongside the
uPreifx64. The announcement MUST be sent to the other AFBRs through corresponding uPreifx46. The announcement MUST be sent to the other
MBGP [RFC4760]. Every uPrefix46 that an AFBR announces MUST be AFBRs through MBGP [RFC4760]. Every uPrefix46 that an AFBR announces
unique. "uPrefix46" is an IPv6 prefix, and the distribution MUST be unique. "uPrefix46" is an IPv6 prefix, and the distribution
mechanism is the same as the traditional mesh unicast scenario. mechanism is the same as the traditional mesh unicast scenario.
As the "v4" field is an E-IP address, and BGP messages are not As the "v4" field is an E-IP address, and BGP messages are not
tunneled through softwires or any other mechanism specified in tunneled through softwires or any other mechanism specified in
[RFC5565], AFBRs MUST be able to transport and encode/decode BGP [RFC5565], AFBRs MUST be able to transport and encode/decode BGP
messages that are carried over the I-IP, and whose NLRI and NH are of messages that are carried over the I-IP, and whose NLRI and NH are of
the E-IP address family. the E-IP address family.
In this way, when a downstream AFBR receives an E-IP PIM (S,G) In this way, when a downstream AFBR receives an E-IP PIM (S,G)
message, it can translate this message into (S',G') by looking up the message, it can translate this message into (S',G') by looking up the
IP address of the corresponding AFBR's E-IP interface. Since the IP address of the corresponding AFBR's E-IP interface. Since the
uPrefix46 of S' is unique, and is known to every router in the I-IP uPrefix46 of S' is unique, and is known to every router in the I-IP
network, the translated message will be forwarded to the network, the translated message will be forwarded to the
corresponding upstream AFBR, and the upstream AFBR can translate the corresponding upstream AFBR, and the upstream AFBR can translate the
message back to (S,G). message back to (S,G).
When a downstream AFBR receives an E-IP PIM (*,G) message, S' can be When a downstream AFBR receives an E-IP PIM (*,G) message, S' can be
generated according to the format specified in Figure 3, with the generated with the "source address" field set to * (wildcard value).
"source address" field set to * (wildcard value). The translated The translated message will be forwarded to the corresponding
message will be forwarded to the corresponding upstream AFBR. Since upstream AFBR. Since every PIM router within a PIM domain MUST be
every PIM router within a PIM domain MUST be able to map a particular able to map a particular multicast group address to the same RP when
multicast group address to the same RP (see Section 4.7 of the source address is set to wildcard value (see Section 4.7 of
[RFC7761]), when the upstream AFBR checks the "source address" field [RFC7761]), when the upstream AFBR checks the "source address" field
of the message, it finds the IPv4 address of the RP, and ascertains of the message, it finds the IPv4 address of the RP, and ascertains
that this is originally a (*,G) message. This is then translated that this is originally a (*,G) message. This is then translated
back to the (*,G) message and processed. back to the (*,G) message and processed.
6. Control Plane Functions of AFBR 6. Control Plane Functions of AFBR
AFBRs are responsible for the following functions: AFBRs are responsible for the following functions:
6.1. E-IP (*,G) and (S,G) State Maintenance 6.1. E-IP (*,G) and (S,G) State Maintenance
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6.3. E-IP (S,G,rpt) State Maintenance 6.3. E-IP (S,G,rpt) State Maintenance
When an AFBR wishes to propagate a Join/Prune(S,G,rpt)[RFC7761] When an AFBR wishes to propagate a Join/Prune(S,G,rpt)[RFC7761]
message to an I-IP upstream router, the AFBR MUST operate as message to an I-IP upstream router, the AFBR MUST operate as
specified in Section 6.5 and Section 6.6. specified in Section 6.5 and Section 6.6.
6.4. Inter-AFBR Signaling 6.4. Inter-AFBR Signaling
Assume that one downstream AFBR has joined an RPT of (*,G) and an SPT Assume that one downstream AFBR has joined an RPT of (*,G) and an SPT
of (S,G), and decided to perform an SPT switchover. According to of (S,G), and decided to perform an SPT switchover (see Section 4.2.1
[RFC7761], it SHOULD propagate a Prune(S,G,rpt) message along with of [RFC7761]). According to [RFC7761], it should propagate a
the periodical Join(*,G) message upstream towards the RP. However, Prune(S,G,rpt) message along with the periodical Join(*,G) message
routers in the I-IP transit core do not process (S,G,rpt) messages upstream towards the RP. However, routers in the I-IP transit core
since the I-IP transit core is treated as SSM-only. As a result, the do not process (S,G,rpt) messages since the I-IP transit core is
downstream AFBR is unable to prune S from this RPT, so it will treated as SSM-only. As a result, the downstream AFBR is unable to
receive two copies of the same data for (S,G). In order to solve prune S from this RPT, so it will receive two copies of the same data
this problem, we introduce a new mechanism for downstream AFBRs to for (S,G). In order to solve this problem, we introduce a new
inform upstream AFBRs of pruning any given S from an RPT. mechanism for downstream AFBRs to inform upstream AFBRs of pruning
any given S from an RPT.
When a downstream AFBR wishes to propagate an (S,G,rpt) message When a downstream AFBR wishes to propagate an (S,G,rpt) message
upstream, it SHOULD encapsulate the (S,G,rpt) message, then send the upstream, it SHOULD encapsulate the (S,G,rpt) message, then send the
encapsulated unicast message to the corresponding upstream AFBR, encapsulated unicast message to the corresponding upstream AFBR,
which we call "RP'". which we call "RP'".
When RP' receives this encapsulated message, it SHOULD decapsulate When RP' receives this encapsulated message, it MUST decapsulate the
the message as in the unicast scenario, and retrieve the original message as in the unicast scenario, and retrieve the original
(S,G,rpt) message. The incoming interface of this message may be (S,G,rpt) message. The incoming interface of this message may be
different to the outgoing interface which propagates multicast data different to the outgoing interface which propagates multicast data
to the corresponding downstream AFBR, and there may be other to the corresponding downstream AFBR, and there may be other
downstream AFBRs that need to receive multicast data of (S,G) from downstream AFBRs that need to receive multicast data of (S,G) from
this incoming interface, so RP' SHOULD NOT simply process this this incoming interface, so RP' should not simply process this
message as specified in [RFC7761] on the incoming interface. message as specified in [RFC7761] on the incoming interface.
To solve this problem, we introduce an "interface agent" to process To solve this problem, we introduce an "interface agent" to process
all the encapsulated (S,G,rpt) messages the upstream AFBR receives. all the encapsulated (S,G,rpt) messages the upstream AFBR receives.
The interface agent's RP' SHOULD prune S from the RPT of group G when The interface agent's RP' should prune S from the RPT of group G when
no downstream AFBR is subscribed to receive multicast data of (S,G) no downstream AFBR is subscribed to receive multicast data of (S,G)
along the RPT. along the RPT.
In this way, we ensure that downstream AFBRs will not miss any In this way, we ensure that downstream AFBRs will not miss any
multicast data that they need. The cost of this is that multicast multicast data that they need. The cost of this is that multicast
data for (S,G) will be duplicated along the RPT received by AFBRs data for (S,G) will be duplicated along the RPT received by AFBRs
affected by the SPT switch over, if at least one downstream AFBR affected by the SPT switch over, if at least one downstream AFBR
exists that has not yet sent Prune(S,G,rpt) messages to the upstream exists that has not yet sent Prune(S,G,rpt) messages to the upstream
AFBR. AFBR.
skipping to change at page 12, line 37 skipping to change at page 12, line 42
| +----------+ +----------+ | | +----------+ +----------+ |
| ^ | ^ | | | ^ | ^ | |
| | | | | | | | | | | |
+--------|-----|----------|-----|--------+ +--------|-----|----------|-----|--------+
| v | v | v | v
Figure 4: Interface Agent Implementation Example Figure 4: Interface Agent Implementation Example
Figure 4 shows an example of an interface agent implementation using Figure 4 shows an example of an interface agent implementation using
UDP encapsulation. The interface agent has two responsibilities: In UDP encapsulation. The interface agent has two responsibilities: In
the control plane, it SHOULD work as a real interface that has joined the control plane, it should work as a real interface that has joined
(*,G), representing of all the I-IP interfaces which are outgoing (*,G), representing of all the I-IP interfaces which are outgoing
interfaces of the (*,G) state machine, and process the (S,G,rpt) interfaces of the (*,G) state machine, and process the (S,G,rpt)
messages received from all the I-IP interfaces. messages received from all the I-IP interfaces.
The interface agent maintains downstream (S,G,rpt) state machines for The interface agent maintains downstream (S,G,rpt) state machines for
every downstream AFBR, and submits Prune (S,G,rpt) messages to the every downstream AFBR, and submits Prune (S,G,rpt) messages to the
PIM-SM module only when every (S,G,rpt) state machine is in the PIM-SM module only when every (S,G,rpt) state machine is in the
Prune(P) or PruneTmp(P') state, which means that no downstream AFBR Prune(P) or PruneTmp(P') state, which means that no downstream AFBR
is subscribed to receive multicast data for (S,G) along the RPT of G. is subscribed to receive multicast data for (S,G) along the RPT of G.
Once a (S,G,rpt) state machine changes to NoInfo(NI) state, which Once a (S,G,rpt) state machine changes to NoInfo(NI) state, which
means that the corresponding downstream AFBR has switched to receive means that the corresponding downstream AFBR has switched to receive
multicast data of (S,G) along the RPT again, the interface agent multicast data of (S,G) along the RPT again, the interface agent MUST
SHOULD send a Join (S,G,rpt) to the PIM-SM module immediately. send a Join (S,G,rpt) to the PIM-SM module immediately.
In the data plane, upon receiving a multicast data packet, the In the data plane, upon receiving a multicast data packet, the
interface agent SHOULD encapsulate it at first, then propagate the interface agent MUST encapsulate it at first, then propagate the
encapsulated packet from every I-IP interface. encapsulated packet from every I-IP interface.
NOTICE: It is possible that an E-IP neighbor of RP' has joined the NOTICE: It is possible that an E-IP neighbor of RP' has joined the
RPT of G, so the per-interface state machine for receiving E-IP Join/ RPT of G, so the per-interface state machine for receiving E-IP Join/
Prune (S,G,rpt) messages SHOULD be preserved. Prune (S,G,rpt) messages should be preserved.
6.5. SPT Switchover 6.5. SPT Switchover
After a new AFBR requests the receipt of traffic destined for a After a new AFBR requests the receipt of traffic destined for a
multicast group, it will receive all the data from the RPT at first. multicast group, it will receive all the data from the RPT at first.
At this time, every downstream AFBR will receive multicast data from At this time, every downstream AFBR will receive multicast data from
any source from this RPT, in spite of whether they have switched over any source from this RPT, in spite of whether they have switched over
to an SPT or not. to an SPT or not.
To minimize this redundancy, it is recommended that every AFBR's To minimize this redundancy, it is recommended that every AFBR's
skipping to change at page 14, line 4 skipping to change at page 14, line 6
the processing of these messages is out of scope for this document. the processing of these messages is out of scope for this document.
6.7. Other PIM States Maintenance 6.7. Other PIM States Maintenance
In addition to states mentioned above, other states exist, including In addition to states mentioned above, other states exist, including
(*,*,RP) and I-IP (*,G') state. Since we treat the I-IP core as SSM- (*,*,RP) and I-IP (*,G') state. Since we treat the I-IP core as SSM-
only, the maintenance of these states is out of scope for this only, the maintenance of these states is out of scope for this
document. document.
7. Data Plane Functions of the AFBR 7. Data Plane Functions of the AFBR
7.1. Process and Forward Multicast Data 7.1. Process and Forward Multicast Data
Refer to Section 7.4 of [RFC8114]. If there is at least one outgoing Refer to Section 7.4 of [RFC8114]. If there is at least one outgoing
interface whose IP address family is different from the incoming interface whose IP address family is different from the incoming
interface, the AFBR MUST encapsulate this packet with interface, the AFBR MUST encapsulate this packet with
mPrefix46-derived and uPrefix46-derived IPv6 address to form an IPv6 mPrefix46-derived and uPrefix46-derived IPv6 address to form an IPv6
multicast packet. multicast packet.
7.2. TTL 7.2. TTL or Hop Count
Processing of TTL information in protocol headers depends on the Upon encapsulation, the TTL and hop account in the outer header
tunneling technology [I-D.ietf-intarea-tunnels], and it is out of SHOULD be set by policy. Upon decapsulation, the TTL and hop count
scope of this document. in the inner header SHOULD be modified by policy, it MUST NOT be
incremented and it MAY be decremented to reflect the cost of tunnel
forwarding. Besides, processing of TTL and hop count information in
protocol headers depends on the tunneling technology
[I-D.ietf-intarea-tunnels], which is out of scope of this document.
7.3. Fragmentation 7.3. Fragmentation
The encapsulation performed by an upstream AFBR will increase the The encapsulation performed by an upstream AFBR will increase the
size of packets. As a result, the outgoing I-IP link MTU may not size of packets. As a result, the outgoing I-IP link MTU may not
accommodate the larger packet size. It is not always possible for accommodate the larger packet size. It is not always possible for
core operators to increase the MTU of every link, thus fragmentation core operators to increase the MTU of every link, thus fragmentation
after encapsulation and reassembling of encapsulated packets MUST be after encapsulation and reassembling of encapsulated packets MUST be
supported by AFBRs [RFC5565]. The specific requirements for supported by AFBRs [RFC5565]. PMTUD [RFC8201] SHOULD be enabled and
fragmentation and tunnel configuration COULD be referred to in that ICMPv6 packets must not be filtered in the I-IP network. Using
[I-D.ietf-intarea-tunnels], which is under revision currently. tunnel will reduce the effective MTU of the datagram. When the
original packet size exceeds the effective MTU, fragmentation MUST
happen after encapsulation on the upstream AFBR, and reassembly MUST
happen before decapsulation on the downstream AFBR. Fragmentation
and tunnel configuration considerations are provided in [RFC5565] and
[I-D.ietf-intarea-tunnels]. The detailed procedure can be referred
in Section 7.2 of [RFC2473].
8. Packet Format and Translation 8. Packet Format and Translation
Because the PIM-SM Specification is independent of the underlying Because the PIM-SM Specification is independent of the underlying
unicast routing protocol, the packet format in Section 4.9 of unicast routing protocol, the packet format in Section 4.9 of
[RFC7761] remains the same, except that the group address and source [RFC7761] remains the same, except that the group address and source
address MUST be translated when traversing an AFBR. address MUST be translated when traversing an AFBR.
For example, Figure 5 shows the register-stop message format in the For example, Figure 5 shows the register-stop message format in the
IPv4 and IPv6 address families. IPv4 and IPv6 address families.
skipping to change at page 15, line 33 skipping to change at page 15, line 33
| IPv6 Source Address (Encoded-Unicast format) | | IPv6 Source Address (Encoded-Unicast format) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(2). IPv6 Register-Stop Message Format (2). IPv6 Register-Stop Message Format
Figure 5: Register-Stop Message Format Figure 5: Register-Stop Message Format
In Figure 5, the semantics of fields "PIM Ver", "Type", "Reserved", In Figure 5, the semantics of fields "PIM Ver", "Type", "Reserved",
and "Checksum" can be referred in Section 4.9 of [RFC7761]. and "Checksum" can be referred in Section 4.9 of [RFC7761].
IPv4 Group Address (Encoded-Group format): The encoded-group format IPv4 Group Address (Encoded-Group format): The encoded-group format
of the IPv4 group address described in Section 4.2. of the IPv4 group address described in Section 4.9.1 of [RFC7761]
IPv4 Source Address (Encoded-Group format): The encoded-unicast IPv4 Source Address (Encoded-Group format): The encoded-unicast
format of the IPv4 source address described in Section 4.3. format of the IPv4 source address described in Section 4.9.1 of
[RFC7761]
IPv6 Group Address (Encoded-Group format): The encoded-group format IPv6 Group Address (Encoded-Group format): The encoded-group format
of the IPv6 group address described in Section 4.2. of the IPv6 group address described in Section 5.2.
IPv6 Source Address (Encoded-Group format): The encoded-unicast IPv6 Source Address (Encoded-Group format): The encoded-unicast
format of the IPv6 source address described in Section 4.3. format of the IPv6 source address described in Section 5.3.
9. Softwire Mesh Multicast Encapsulation 9. Softwire Mesh Multicast Encapsulation
Softwire mesh multicast encapsulation does not require the use of any Softwire mesh multicast encapsulation does not require the use of any
one particular encapsulation mechanism. Rather, it MUST accommodate one particular encapsulation mechanism. Rather, it MUST accommodate
a variety of different encapsulation mechanisms, and allow the use of a variety of different encapsulation mechanisms, and allow the use of
encapsulation mechanisms mentioned in [RFC4925]. Additionally, all encapsulation mechanisms mentioned in [RFC4925]. Additionally, all
of the AFBRs attached to the I-IP network MUST implement the same of the AFBRs attached to the I-IP network MUST implement the same
encapsulation mechanism, and follow the requirements mentioned in encapsulation mechanism, and follow the requirements mentioned in
[I-D.ietf-intarea-tunnels]. [I-D.ietf-intarea-tunnels].
10. Security Considerations 10. Security Considerations
The security concerns raised in [RFC4925] and [RFC7761] are The security concerns raised in [RFC4925] and [RFC7761] are
applicable here. applicable here.
The additional workload associated with some schemes could be The additional workload associated with some schemes, such as
exploited by an attacker to perform a DDoS attack. interface agents, could be exploited by an attacker to perform a DDoS
attack.
Compared with [RFC4925], the security concerns SHOULD be considered Compared with [RFC4925], the security concerns should be considered
more carefully: an attacker could potentially set up many multicast more carefully: an attacker could potentially set up many multicast
trees in the edge networks, causing too many multicast states in the trees in the edge networks, causing too many multicast states in the
core network. To defend against these attacks, BGP policies SHOULD core network. To defend against these attacks, BGP policies SHOULD
be carefully configured, e.g., AFBRs only accept Well-Known prefix be carefully configured, e.g., AFBRs only accept Well-Known prefix
advertisements from trusted peers. advertisements from trusted peers. Besides, cryptographic methods
for authenticating BGP sessions [RFC7454] could be used.
11. IANA Considerations 11. IANA Considerations
This document includes no request to IANA. This document includes no request to IANA.
12. References 12. Normative References
12.1. Normative References [I-D.ietf-intarea-tunnels]
Touch, J. and M. Townsley, "IP Tunnels in the Internet
Architecture", draft-ietf-intarea-tunnels-09 (work in
progress), July 2018.
[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,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in
IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473,
December 1998, <https://www.rfc-editor.org/info/rfc2473>.
[RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter, [RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
"Multiprotocol Extensions for BGP-4", RFC 4760, "Multiprotocol Extensions for BGP-4", RFC 4760,
DOI 10.17487/RFC4760, January 2007, DOI 10.17487/RFC4760, January 2007,
<https://www.rfc-editor.org/info/rfc4760>. <https://www.rfc-editor.org/info/rfc4760>.
[RFC4925] Li, X., Ed., Dawkins, S., Ed., Ward, D., Ed., and A.
Durand, Ed., "Softwire Problem Statement", RFC 4925,
DOI 10.17487/RFC4925, July 2007,
<https://www.rfc-editor.org/info/rfc4925>.
[RFC5565] Wu, J., Cui, Y., Metz, C., and E. Rosen, "Softwire Mesh [RFC5565] Wu, J., Cui, Y., Metz, C., and E. Rosen, "Softwire Mesh
Framework", RFC 5565, DOI 10.17487/RFC5565, June 2009, Framework", RFC 5565, DOI 10.17487/RFC5565, June 2009,
<https://www.rfc-editor.org/info/rfc5565>. <https://www.rfc-editor.org/info/rfc5565>.
[RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X. [RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052, Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
DOI 10.17487/RFC6052, October 2010, DOI 10.17487/RFC6052, October 2010,
<https://www.rfc-editor.org/info/rfc6052>. <https://www.rfc-editor.org/info/rfc6052>.
[RFC6333] Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual- [RFC6333] Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
Stack Lite Broadband Deployments Following IPv4 Stack Lite Broadband Deployments Following IPv4
Exhaustion", RFC 6333, DOI 10.17487/RFC6333, August 2011, Exhaustion", RFC 6333, DOI 10.17487/RFC6333, August 2011,
<https://www.rfc-editor.org/info/rfc6333>. <https://www.rfc-editor.org/info/rfc6333>.
[RFC6513] Rosen, E., Ed. and R. Aggarwal, Ed., "Multicast in MPLS/ [RFC6513] Rosen, E., Ed. and R. Aggarwal, Ed., "Multicast in MPLS/
BGP IP VPNs", RFC 6513, DOI 10.17487/RFC6513, February BGP IP VPNs", RFC 6513, DOI 10.17487/RFC6513, February
2012, <https://www.rfc-editor.org/info/rfc6513>. 2012, <https://www.rfc-editor.org/info/rfc6513>.
[RFC7454] Durand, J., Pepelnjak, I., and G. Doering, "BGP Operations
and Security", BCP 194, RFC 7454, DOI 10.17487/RFC7454,
February 2015, <https://www.rfc-editor.org/info/rfc7454>.
[RFC7761] Fenner, B., Handley, M., Holbrook, H., Kouvelas, I., [RFC7761] Fenner, B., Handley, M., Holbrook, H., Kouvelas, I.,
Parekh, R., Zhang, Z., and L. Zheng, "Protocol Independent Parekh, R., Zhang, Z., and L. Zheng, "Protocol Independent
Multicast - Sparse Mode (PIM-SM): Protocol Specification Multicast - Sparse Mode (PIM-SM): Protocol Specification
(Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March (Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March
2016, <https://www.rfc-editor.org/info/rfc7761>. 2016, <https://www.rfc-editor.org/info/rfc7761>.
[RFC7899] Morin, T., Ed., Litkowski, S., Patel, K., Zhang, Z., [RFC7899] Morin, T., Ed., Litkowski, S., Patel, K., Zhang, Z.,
Kebler, R., and J. Haas, "Multicast VPN State Damping", Kebler, R., and J. Haas, "Multicast VPN State Damping",
RFC 7899, DOI 10.17487/RFC7899, June 2016, RFC 7899, DOI 10.17487/RFC7899, June 2016,
<https://www.rfc-editor.org/info/rfc7899>. <https://www.rfc-editor.org/info/rfc7899>.
[RFC8114] Boucadair, M., Qin, C., Jacquenet, C., Lee, Y., and Q. [RFC8114] Boucadair, M., Qin, C., Jacquenet, C., Lee, Y., and Q.
Wang, "Delivery of IPv4 Multicast Services to IPv4 Clients Wang, "Delivery of IPv4 Multicast Services to IPv4 Clients
over an IPv6 Multicast Network", RFC 8114, over an IPv6 Multicast Network", RFC 8114,
DOI 10.17487/RFC8114, March 2017, DOI 10.17487/RFC8114, March 2017,
<https://www.rfc-editor.org/info/rfc8114>. <https://www.rfc-editor.org/info/rfc8114>.
12.2. Informative References [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
[I-D.ietf-intarea-tunnels] May 2017, <https://www.rfc-editor.org/info/rfc8174>.
Touch, J. and M. Townsley, "IP Tunnels in the Internet
Architecture", draft-ietf-intarea-tunnels-09 (work in
progress), July 2018.
[RFC4925] Li, X., Ed., Dawkins, S., Ed., Ward, D., Ed., and A. [RFC8201] McCann, J., Deering, S., Mogul, J., and R. Hinden, Ed.,
Durand, Ed., "Softwire Problem Statement", RFC 4925, "Path MTU Discovery for IP version 6", STD 87, RFC 8201,
DOI 10.17487/RFC4925, July 2007, DOI 10.17487/RFC8201, July 2017,
<https://www.rfc-editor.org/info/rfc4925>. <https://www.rfc-editor.org/info/rfc8201>.
Appendix A. Acknowledgements Appendix A. Acknowledgements
Wenlong Chen, Xuan Chen, Alain Durand, Yiu Lee, Jacni Qin and Stig Wenlong Chen, Xuan Chen, Alain Durand, Yiu Lee, Jacni Qin and Stig
Venaas provided useful input into this document. Venaas provided useful input into this document.
Authors' Addresses Authors' Addresses
Mingwei Xu Mingwei Xu
Tsinghua University Tsinghua University
Department of Computer Science, Tsinghua University Department of Computer Science, Tsinghua University
Beijing 100084 Beijing 100084
P.R. China P.R. China
Phone: +86-10-6278-5822 Phone: +86-10-6278-5822
Email: xumw@tsinghua.edu.cn Email: xumw@tsinghua.edu.cn
Yong Cui Yong Cui
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