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Issues In Multicast Transition For presentation to the Multrans BOF Tom Taylor <[email protected]> Cathy Zhou <[email protected]> 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 Transition 2 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 Transition 3 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 Transition 4 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 Transition 5 Transition Techniques Three basic transition techniques: Translation Encapsulation Dual stack Issues In Multicast Transition 6 Translation Stateless translation may be an option (true in higherpriority 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 Transition 7 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 Transition 8 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 IPv6 S IPv4 IPv4 MR MR IPv6 IPv4 IPv4 MR IPv6 IPv4 IPv4 MR IPv4 IPv4 T IPv6 R R R R Issues In Multicast Transition R R 9 Dual Stack Network Operation Two basic strategies (applicable both to ASM and SSM): Common Core S Pv6 S S IPv4 T Source version through network IPv6 IPv4 Dual stack network operating as (e.g.) IPv4 network for multicast Dual stack • Source-IPv6: PIMv6 to set up network multicast tree, some v4 T IPv4 S T T R R 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 IPv6 R R Double translation for some streams IPv4 IPv6 Operational complexity Issues In Multicast Transition 10 Acknowledgement The authors would like to thank Joel M. Halpern, Dan Wing, Jacni Qin and Yiu Lee for their valuable comments. Questions for clarification? Issues In Multicast Transition 12