In-line comment On Wed, Jan 8, 2020 at 5:15 PM Leonard Giuliano <[email protected]> wrote:
> > > On Wed, 8 Jan 2020, Gyan Mishra wrote: > > <trimmed> > > | Gyan> Source discovery is only necessary with ASM not SSM. With SSM > the receiver is "source" aware so does not require any discovery > mechanism. > | So with SSM which requires IGMPv3 enabled on the receiver last hop > router subnets and on the source first hop router subnet for the both to be > "source aware" ; for the receiver now to > | send the (S,G) join for the channel since it is now source aware. How > the receiver gets that source awareness is from the server URI that the > user connects to which has the S,G > | information ; server has to be also source aware and has S,G channel > available that can be joined. With IGMPv3 the packet accommodate the > Source information in the S,G join sent > | along the RPF path to the source. You mention that SSM deployment has > been limited but in fact the opposite and reason why ASM is being > officially deprecated by the IETF for inter > | domain multicast routing. IPv6 does not even have MSDP support since > with ASM MSDP source discovery and propagation is not necessary since no > RPs exist all disparate ASM multicast > | domains can now be collapsed into a single SSM domain. ASM MSDP/Anycast > has its complexities which is why IPv6 nixed the idea of integrating MSDP > into the architecture. Thus IPv6 only > | supports SSM for inter-domain multicast routing. I would keep the > comment about ASM complexity which is true but remove mention of SSM. I > would not mention any gains with less state > > Actually, Embedded RP provides interdomain ASM for IPv6 and is the reason > there is no need for MSDP in IPv6. Gyan> With embedded RP how is the “source” SA propagated as is done by MSDP with IPv4 accomplished with IPv6. The only alternative and is a way that SSM for both IPv4 and IPv6 can provide network discovery that I know of and not have to rely on app based discovery ; is via BGP multicast NLRI AFI 1 and 2 for v4 v6 with SAFI 2 to propagate the source information. This is also used when migration from ASM to SSM and want to maintain inter domain boundaries you can use SAFI 2 for multicast NLRI source propagation. > > > No one would disagree that SSM is simpler and the ideal way to go, hence > draft-ietf-mboned-deprecate-interdomain-asm recommends SSM-only for > interdomain deployments. Unfortunately, for various (and sometimes > somewhat valid) reasons, ASM lives on, at least in intradomain > deployments. Hence, BGP would still need to cover ASM scenarios, at > least for these intradomain deployments that still rely on ASM to work. Gyan> Agreed ASM must be supported for intra domain > > > -- Gyan Mishra Network Engineering & Technology Verizon Silver Spring, MD 20904 Phone: 301 502-1347 Email: [email protected]
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