Re: [bess] WG adoption and IPR poll for draft-zzhang-bess-bgp-multicast-03

[Gyan Mishra <[e-mail]>]

In-line comment

On Wed, Jan 8, 2020 at 5:15 PM Leonard Giuliano <[e-mail]> 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: [phone]

Email: [e-mail]