Internet DRAFT - draft-sarikaya-softwire-dslitemulticast
draft-sarikaya-softwire-dslitemulticast
Network Working Group B. Sarikaya
Internet-Draft Huawei USA
Intended status: Standards Track June 21, 2012
Expires: December 23, 2012
Multicast Support for Dual Stack Lite
draft-sarikaya-softwire-dslitemulticast-01.txt
Abstract
This memo specifies modifications required to Dual-Stack Lite (DS-
Lite) so that both IPv4 hosts can receive multicast data from IPv4
servers.
The DS-Lite solution is based on DS-Lite Basic Bridging BroadBand
element (B4) proxying Internet Group Management Protocol (IGMP) and
then tunneling IGMP messages over IPv4-in-IPv6 softwire to DS-Lite
Address Family Transition Router element (AFTR). IPv4 multicast data
received at AFTR is tunneled over IPv4-in-IPv6 softwire to B4 and
then delivered to the hosts. This solution integrates well with DS-
Lite unicast solution by using IPv4-in-IPv6 softwire and works with
unicast IPv6 network connecting B4 with AFTR.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on December 23, 2012.
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document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Architecture . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. DS-Lite Multicast Operation . . . . . . . . . . . . . . . . . 4
5.1. Tunnel Interface Considerations . . . . . . . . . . . . . 6
6. Multicast Support for Host-Based Architecture . . . . . . . . 7
7. Avalanche Problem . . . . . . . . . . . . . . . . . . . . . . 7
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 8
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
10.1. Normative References . . . . . . . . . . . . . . . . . . . 8
10.2. Informative references . . . . . . . . . . . . . . . . . . 8
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 10
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1. Introduction
With IPv4 address depletion on the horizon, many techniques are being
standardized for IPv6 migration including DS-Lite [RFC6333] and 6rd
[RFC5969]. DS-Lite enables IPv4 hosts to communicate with external
hosts using IPv6 only network and moves the traditional NAT to the
network. B4 element's LAN side is dual stack and WAN side is IPv6
only. B4 tunnels IPv4 packets received from the LAN side to AFTR
element after encapsulating IPv4 packet in an IPv6 packet. AFTR
decapsulates the packet, does a NAT operation and then sends the
packet out to IPv4 public internet.
DS-Lite as defined in [RFC6333] is unicast only, it does not support
multicast. In this document we specify multicast extensions to DS-
Lite in order to provide IP multicast communication to home IPv4
users in DS-Lite.
2. Terminology
This document uses the terminology defined in [RFC6333] and
[RFC3376].
3. Requirements
This section states requirements on DS-Lite multicast support
protocol.
DS-Lite multicast solution MUST integrate with DS-Lite unicast
solution, it MUST not introduce additional mechanisms to the existing
B4 to AFTR communication.
DS-Lite multicast solution MUST not require additional capabilities
in IPv6 network connecting B4 to AFTR other than what unicast DS-Lite
solution requires.
DS-Lite B4 MUST support IGMP Proxy as defined in [RFC4605]. DS-Lite
B4 MAY support MLD Proxy.
DS-Lite AFTR MUST support IGMP Querrier. DS-Lite AFTR MAY support
MLD Querrier.
Both any source multicast (ASM) and source specific multicast (SSM)
MUST be supported.
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4. Architecture
In DS-Lite, there are hosts (possibly IPv4/ IPv6 dual stack) served
by B4 element. B4 is dual stack facing the hosts and IPv6 only
facing the network or WAN side. At the boundary of the network there
is AFTR. AFTR receives IPv4 packets tunneled in IPv6 from B4 and
decapsulates them and sends them out to IPv4 network.
In order to support multicast communication B4 implements IGMP Proxy
function [RFC4605]. IPv4 hosts send their join requests (IGMP
Membership Report messages) to B4. B4 as a proxy sends aggregated
Report messages upstream towards AFTR.
AFTR is the default multicast querier for B4. AFTR implements
multicast router function or it could be another IGMP proxy.
All the elements of DS-Lite multicast support system are shown in
Figure 1.
Dual Stack Hosts IPv4
+----+ Network
| H1 | IPv6
+----+ +-----+ only +-------+ +
+----+ | B4 | network -- | AFTR |
| H2 | ---| IGMP|--- IPv4-in- | IGMP | IPv6
+----+ |Proxy| IPv6 |Querier| Network
+----+ +-----+ tunnel +-------+
| H3 |
+----+
Figure 1: Architecture of DS-Lite Multicast Protocol
5. DS-Lite Multicast Operation
In this section we specify how the host can subscribe and receive
IPv4 multicast data from IPv4 content providers based on the
architecture defined in Section 4.
The hosts will send their subscription requests for IPv4 multicast
groups upstream to the default router, i.e. B4 Element. After
subscribing to the group, the host can receive multicast data from
the B4. The host implements IGMP protocol's host part.
In order to support SSM, IGMPv3 MUST be supported by the host, B4 and
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AFTR.
B4 Element is IGMP Proxy. After receiving the first IGMP Report
message requesting subscription to an IPv4 multicast group, B4
establishes a tunnel interface with a AFTR. The tunnel is IPv6 based
but it will carry IPv4 traffic, IGMP messages back and forth and IPv4
multicast data messages downstream. This is similar to [RFC6224]
Section 4.4 but the operation is much simpler. In DS-Lite
environment there is no requirement to handle host mobility. B4 does
not have to keep more than one tunnel interfaces, a single interface
is sufficient. IGMP Proxy at the B4 does not have to have more than
one proxy instances, a single instance is sufficient.
B4 is regular IGMP proxy and it keeps IGMP proxy membership database.
B4 inserts multicast forwarding state on the incoming interface, and
merges state updates into the IGMP proxy membership database. B4
updates or removes elements from the database as required. B4 will
then send an aggregated Report via the upstream tunnel to the AFTR
when the membership database changes.
B4 answers IGMP queries from AFTR based on the membership database.
B4's downstream link follows the traditional multipoint channel
forwarding and does not pose any specific problems.
B4 receives IPv4 multicast data from the AFTR tunneled over the
tunnel interface. B4 decapsulates the packet and then forwards it
downstream. Each member host receives the data packet based on Layer
2 multicast interface. No packet duplication is necessary.
AFTR acts as the as the default multicast querier for all B4s that
have established an IPv6 tunnel with it. In order to keep a
consistent multicast state between a B4 and AFTR, once a B4 is
connected it will stay connected until the state becomes empty.
After that point, the B4 may continue to use the tunnel for IPv4
unicast traffic.
According to aggregated IGMP reports received from a B4, AFTR
establishes group/source-specific multicast forwarding states at its
corresponding downstream tunnel interfaces. After that, AFTR
maintains or removes the state as required by the aggregated reports
received from B4.
At the upstream interface, AFTR procures for aggregated multicast
membership maintenance. Based on the multicast-transparent
operations of the B4s, the AFTR treats its tunnel interfaces as
multicast enabled downstream links, serving zero to many listening
nodes.
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Multicast traffic arriving at the AFTR is transparently forwarded
according to its multicast forwarding information base. Multicast
data is first replicated and then forwarded in IPv4-in-IPv6 tunnel
from AFTR to the corresponding B4.
5.1. Tunnel Interface Considerations
Legacy IPv4 in IPv6 tunneling is performed as in [RFC2473] and
[RFC4213]. Considerations specified in [RFC6333] apply. Packets
upstream from B4 carry only IGMP signaling messages and they are not
expected to fragmentation. However packets downstream, i.e.
multicast data to B4 may be subject to fragmentation.
Source and destination addresses of IGMP messages in IPv4-in-IPv6
softwire from B4 is as follows:
Source address of IPv6 header is B4 IPv6 address, e.g.
2001:db8:0:1::1, destination address is AFTR address, e.g. 2001:db8:
0:2::1.
Source address of IGMP messages is B4's IPv4 interface address, e.g.
192.0.0.2, destination address is the all-systems multicast address
of 224.0.0.1 for IGMP Query, all IGMPv3-capable multicast routers of
224.0.0.22 for IGMPv3 Report, the multicast group specified in the
Group Address field of the Report for IGMPv1 or IGMPv2 Report.
Source and destination addresses of IGMP messages in IPv4-in-IPv6
softwire from AFTR is as follows:
Source address of IPv6 header is AFTR address, e.g. 2001:db8:0:2::1,
destination address is B4 IPv6 address, e.g. 2001:db8:0:1::1.
Source address of IGMP messages is AFTR's IPv4 interface address,
e.g. 192.0.2.1, destination address is the all-systems multicast
address of 224.0.0.1 for IGMP Query, all IGMPv3-capable multicast
routers of 224.0.0.22 for IGMPv3 Report, the multicast group
specified in the Group Address field of the Report for IGMPv1 or
IGMPv2 Report.
Source and destination addresses of multicast data messages in IPv4-
in-IPv6 softwire is as follows:
Source address of IPv6 header is AFTR address, e.g. 2001:db8:0:2::1,
destination address is B4 IPv6 address, e.g. 2001:db8:0:1::1.
Source address of IPv4 multicast data is unicast IPv4 address of the
multicast source, e.g. the content provider, destination address is
IPv4 multicast group address.
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AFTR decapsulates datagrams carrying IGMP messages from B4's and then
IGMP router processing takes over. Network Address Translation (NAT)
is not applied on IGMP messages.
6. Multicast Support for Host-Based Architecture
In this section we specify multicast support for Host-Based DS-Lite
architecture described in Appendix B2 of [RFC6333].
In host-based DS-Lite, the host accesses the service provider network
directly with an IPv6 global address. Host sends its IPv4 datagrams
in IPv6 using an IPv4-in-IPv6 softwire tunnel to an AFTR, i.e. it
implements DS-Lite B4. Source address of all IPv4 datagrams is the
pre-configured well-known IPv4 non-routable address.
For multicast, there are two choices: the host could implement host
side of IGMP protocol or for mobile router type of hosts, the host
implements IGMP proxy as in Section 5.
Host encapsulates IGMP messages as described in Section 5.1 and sends
them to AFTR. AFTR does not perform IPv4-IPv4 NAT translations on
IGMP datagrams instead they are processed by IGMP router at the AFTR.
Multicast data received from AFTR for a multicast group that the host
has subscribed is decapsulated by the host, if the host is IGMP
client, it processes the data. If the host is IGMP proxy, it
consults multicast state for the group and forwards the data
downstream so that the members can receive the data.
7. Avalanche Problem
When multicast datagrams are received at the AFTR, AFTR consults its
memebership database and duplicates the packets for each member B4
interface and then these datagrams are forwarded in IPv4-in-IPv6
softwire downstream. This may cause an avalanche of downstream
packets if the number of member B4's is high.
Avalanche problem can be eased by network partitioning. AFTR can be
deployed closer to the users. For example in broadband networks,
AFTR can be deployed at the Broadband Network Gateway (BNG) nodes.
8. IANA Considerations
None.
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9. Acknowledgements
TBD.
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
June 1999.
[RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick,
"Internet Group Management Protocol (IGMP) / Multicast
Listener Discovery (MLD)-Based Multicast Forwarding
("IGMP/MLD Proxying")", RFC 4605, August 2006.
[RFC3376] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A.
Thyagarajan, "Internet Group Management Protocol, Version
3", RFC 3376, October 2002.
[RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in
IPv6 Specification", RFC 2473, December 1998.
[RFC4213] Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms
for IPv6 Hosts and Routers", RFC 4213, October 2005.
[RFC6224] Schmidt, T., Waehlisch, M., and S. Krishnan, "Base
Deployment for Multicast Listener Support in Proxy Mobile
IPv6 (PMIPv6) Domains", RFC 6224, April 2011.
[RFC6333] Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
Stack Lite Broadband Deployments Following IPv4
Exhaustion", RFC 6333, August 2011.
10.2. Informative references
[RFC5969] Townsley, W. and O. Troan, "IPv6 Rapid Deployment on IPv4
Infrastructures (6rd) -- Protocol Specification",
RFC 5969, August 2010.
[RFC4286] Haberman, B. and J. Martin, "Multicast Router Discovery",
RFC 4286, December 2005.
[RFC4541] Christensen, M., Kimball, K., and F. Solensky,
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"Considerations for Internet Group Management Protocol
(IGMP) and Multicast Listener Discovery (MLD) Snooping
Switches", RFC 4541, May 2006.
[RFC3810] Vida, R. and L. Costa, "Multicast Listener Discovery
Version 2 (MLDv2) for IPv6", RFC 3810, June 2004.
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Author's Address
Behcet Sarikaya
Huawei USA
5340 Legacy Drive Building 175
Plano, TX 75074
Phone:
Email: sarikaya@ieee.org
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