On Thu, Jan 9, 2020 at 1:30 PM Jeffrey (Zhaohui) Zhang <[email protected]> wrote:
> Please see zzh> below. > > > > *From:* Gyan Mishra <[email protected]> > *Sent:* Thursday, January 9, 2020 1:25 PM > *To:* Jeffrey (Zhaohui) Zhang <[email protected]> > *Cc:* Lenny Giuliano <[email protected]>; [email protected]; > [email protected]; [email protected]; > [email protected] > *Subject:* Re: [bess] WG adoption and IPR poll for > draft-zzhang-bess-bgp-multicast-03 > > > > > > > > On Thu, Jan 9, 2020 at 12:41 PM Jeffrey (Zhaohui) Zhang < > [email protected]> wrote: > > Gyan, > > What embedded RP gives you is that you don't need to configure RP > addresses. Once the RP is known for a group (however it is done - static > config in case of IPv4/IPv6, dynamic learning via BSR/Auto-RP in case of > v4, or embedded RP in case of IPv6), the rest is all the same: source sends > register towards the RP and LHRs sends (*,g) join towards the RP. In case a > set of RPs are used for a single group, the RPs learn the sources from each > other either via MSDP (IPv4 only) or via PIM registers sent among > themselves. > > Once the traffic arrives at the LHR routers they learn the sources and can > send (s,g) joins. When we say network-based source discovery we refer to > the learning of sources by the LHRs (so that they can send (s,g) joins). > > > > Gyan> I understand the IPv4 scenario. I was referring to the IPv6 > scenario that the embedded RP provides the RP address to build the group RP > map which is fine but you still need a LHR mechanism to discover the source > which does not exist with SSM. There are reasons for that and I am > drafting reply to the other thread I will explain. > > > > Zzh> That’s why the draft has relevant text: 1) SSM needs source discovery > and will not totally succeed unless the source discovery problem is solved > 2) this draft provides a BGP based source discovery mechanism (in addition > to BGP based join/prune). > > > > > > via BGP multicast NLRI AFI 1 and 2 for v4 v6 with SAFI 2 to propagate > the source information > > That is not for source learning. It is for learning of the non-congruent > routes to the sources. In many cases you only need to originate a few > routes (in extreme cases a default route is enough), and it has no group > information. > > > > Gyan> I understand that non congruent routes is one use case for > multicast NLRI ; If the LHR was BGP connected and its RPF path to the > source was now via BGP multicast NLRI you could use this method to > discover all SSM sources via the network. Imagine if you decided you > wanted to augment you SSM infrastructure with a multicast NLRI for source > propagation you could do this on your source FHR and receiver LHR and with > all intermediate hops including the core now providing congruent reach > ability to the SSM multicast sources ; you now have solved the SSM gap > mentioned related to LHR network based source discovery. I don’t think > their is a draft on this but I think it’s a worthwhile I-D. > > > > Zzh> Source discovery is about (s,g), and SAFI 2 does not have group > information. > > Zzh> Jeffrey > > Gyan> Understood. > > Jeffrey > > -----Original Message----- > From: Lenny Giuliano <[email protected]> > Sent: Thursday, January 9, 2020 12:06 PM > To: Gyan Mishra <[email protected]> > Cc: Jeffrey (Zhaohui) Zhang <[email protected]>; [email protected]; > [email protected]; [email protected]; > [email protected] > Subject: Re: [bess] WG adoption and IPR poll for > draft-zzhang-bess-bgp-multicast-03 > > > On Thu, 9 Jan 2020, Gyan Mishra wrote: > > <trimmed> > > | > | 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. > > With Embedded RP, the address of the RP is "embedded" in the group > address, so just by looking at the group address, routers can derive the RP > address and know where to send their (*,g) joins. Hence there is no need > for RPs to "talk" to one another as they do in IPv4 with MSDP. See RFC > 3956 for more details. > > | > | > | 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 > > Then I suspect we are all in violent agreement. > > -- > > Gyan Mishra > > Network Engineering & Technology > > Verizon > > Silver Spring, MD 20904 > > Phone: 301 502-1347 > > Email: [email protected] > > > > > -- Gyan Mishra Network Engineering & Technology Verizon Silver Spring, MD 20904 Phone: 301 502-1347 Email: [email protected]
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