Issues In Multicast Transition For presentation to the Multrans BOF Tom Taylor Cathy Zhou

Issues In Multicast Transition2 Contents 3.Technical Issues 4.Address Acquisition 5.Multicast Signalling 6.Transition Techniques 7.Translation 8.Encapsulation 9.Dual Stack Source Operation 10.Dual Stack Network Operation

Issues In Multicast Transition3 Technical Issues Multicast distribution of a given stream enabled in three stages: 1)Address acquisition by the receiver  Multicast group address and, for SSM, unicast source address for the desired multicast stream  Could be other unicast addresses involved (e.g., RTCP feedback target) 2)Multicast signalling from the receiver toward the source to set up the multicast tree 3)Transporting multicast content from a source to the receivers through the tree that has been set up Multicast transition presents issues at each stage.

Issues In Multicast Transition4 Address Acquisition Various ways to do address acquisition: Configuration, session signalling (SIP), announcements (SAP), proprietary program guide (HTML),... Issue: if the receiver just supports one IP version, it has to receive the addresses in that version May need translation, either off-line or in some node along the acquisition stage messaging path.

Issues In Multicast Transition5 Multicast Signalling Three protocols -- IGMP (IPv4, three versions), MLD (IPv6, two versions), and PIM-SM (IPv4 and IPv6) Establish paths between sources, multicast routers, and receivers Objective: minimize total bandwidth required to distribute multicast content Outcome: tree structures set up with multicast routers as the intermediate nodes Issue: IPv6 transition creates new protocol interworking combinations IGMP  PIM v6, MLD  PIM v4, PIM v4  PIM v6, IGMP  MLD

Issues In Multicast Transition6 Transition Techniques Three basic transition techniques: Translation Encapsulation Dual stack

Issues In Multicast Transition7 Translation Stateless translation may be an option (true in higher- priority scenarios). Issue: need the multicast equivalent of RFC 6052 for stateless translation. draft-boucadair-behave-64-multicast-address-format is a candidate. Translation of a given address happens at multiple nodes, different stages within the same node. Issue: for stateful mapping, need coordination to ensure the same mapping or its inverse, as applicable, is used each time a given address is translated.

Issues In Multicast Transition8 Encapsulation Unicast encapsulation solutions such as 6rd or DS-lite do not apply to multicast. Unicast solutions carry packets from edge to edge. Multicast signalling and content distribution has to pass from one multicast router to the next within the network interior. Issue: at the architectural level, interaction with unicast solutions in terms of potential collocation/reuse of functions May use tunneling between multicast routers for content distribution. IP-in-IP encapsulation: multicast routers can route based on the outer header. IP-in-non-IP encapsulation: multicast routing may use the inner header, which then may need translation to make it usable.

Issues In Multicast Transition9 Dual Stack Source Operation Issue: need to avoid carrying the same content in parallel IPv4 and IPv6 streams through the network. Hence operating source in dual stack mode is undesirable. Translate at receiver end instead. S MR RRR IPv6 IPv4 IPv6 IPv4 S MR RRR IPv4 IPv6 IPv4 T

Issues In Multicast Transition10 Dual Stack Network Operation Two basic strategies (applicable both to ASM and SSM): SS T IPv6 IPv4 R R T IPv6 IPv4 Common Core Double translation for some streams Dual stack network operating as (e.g.) IPv4 network for multicast Source version through network S S T IPv6 IPv4 R R T IPv6 IPv4 Operational complexity Dual stack network Source-IPv6: PIMv6 to set up multicast tree, some v4 receivers can receive the content by v6->v4 translation Source-IPv4: PIMv4 to set up multicast tree, some v6 receivers can receive the content by v4->v6 translation

Acknowledgement The authors would like to thank Joel M. Halpern, Dan Wing, Jacni Qin and Yiu Lee for their valuable comments.

Issues In Multicast Transition12 Questions for clarification?