Re: [bess] bess: draft-zzhang-bess-mvpn-msdp-sa-interoperation

Toerless Eckert <> Fri, 24 November 2017 06:30 UTC

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Date: Fri, 24 Nov 2017 07:30:41 +0100
From: Toerless Eckert <>
To: Leonard Giuliano <>
Cc: Toerless Eckert <>,, MBONED WG <>
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Subject: Re: [bess] bess: draft-zzhang-bess-mvpn-msdp-sa-interoperation
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Hi Lenny,

a) I was asking Jeffrey in the WG meeting if he saw any difference
   between MSDP and 4610 wrt. to the applicability of your draft, and
   he also said no (as i think too), thats where this originated.

b) Wrt to your contentions below:

   1) I agree, #1 is covered - for both MVPN SA and rfc4610 register
   messages according to rfc6514, 14.1.

   2) Let first make the argument where MSDP and rfc4610 operate equally:
   when you configure an MSDP mesh group. If all the non-PE RPs in an
   MVPN C domain are either an MSDP mesh group or an rfc4610 RP-set
   (same function, different names), then you could just add some PE
   as members of the MSDP mesh group or the RFC4610 RP-set and that
   would work "fine" without extending rfc6514 14.1, aka: those PEs
   would learn active C (S,G) and distribute it to all other PE, and
   they would not need to send any (S,G) SA/register messages back to the
   non-PE mesh group/rp-set because those RPs already have all state
   they need. And, as your draft says, as soon as you add more than
   one PE this way, you have multiple PEs that will send to all other
   PEs all active C (S,G) state info. And its kinda difficult to figure
   out how much redundancy one wants to set up that way.

   So, the model that i thought your draft meant to establish is one
   where you would avoid having to build a mesh-group/RP-set across all
   non-PE RPs in a large network:

   You would logically have a per-MVPN-site mesh-group/RP-set between
   the PEs of that site (one or more) and one or more non-PE RP. 
   Whenenver a PE receives an MVPN SA that comes from another site,
   it would forward it to the other non-PE members of this mesh-group/RP-set,
   and your new draft section 3 would permit this type of source check
   (i am not completeley through understanding that part of your draft).

   So, that would be a very scaleable setup as soon as you have
   non-PE RPs in the MVPN.

   3) MSDP of course has setup options not shared with rfc6410, aka:
   any setup that is more than a mesh-group. If you intended for the
   draft to also apply to such cases, it would be great to give
   examples of the so tht one can check if/how the proposed spec in your
   draft would work in the fce of those cases existing MSDP RPF rules
   (which can of course be quite complex).

3) Btw: It would be good if you would add some picture to your draft
   starting from section 2 to illustrate your text example PE1, PE2
   and so on.

   Also, your draft says:

     [RFC6514] only specifies that a PE receiving the MVPN SA routes, say
     PE2, will advertise (C-S,C-G) C-multicast routes if it has
     corresponding (C-*,C-G) state learnt from its CE

   can you point me to the text in 6514 that says that ?


On Wed, Nov 22, 2017 at 02:38:09PM -0800, Leonard Giuliano wrote:
> Toerless,
> Thanks for the comments.  After thinking about your feedback on RFC4610 a 
> bit, I'm not sure that case is applicable here.  Consider the 2 directions 
> of interworking:
> 1) MSDP SA/AnycastRP_PIM_Register -> MVPN SA
> 2) MVPN SA -> MSDP SA/AnycastRP_PIM_Register
> As I understand, #1 is already covered by RFC6513/6514.  #2 is the missing 
> piece that this draft attempts to address.  I don't believe #2 will be 
> applicable for RFC4610, as these registers only go to members of the RP 
> set.  And the RP set should be configured on all the C-RPs.  It wouldn't 
> make much sense to have these registers transit the MVPN domain to go to 
> an AnycastRP not in the configured RP set.
> Hope this is clear, and let me know if I'm missing anything.
> -Lenny
> | -----Original Message-----
> | From: BESS [] On Behalf Of Toerless Eckert
> | Sent: Monday, November 13, 2017 9:43 PM
> | To:
> | Cc:
> | Subject: [bess] bess: draft-zzhang-bess-mvpn-msdp-sa-interoperation
> | 
> | Jeffrey presented subject draft in mboned. Given how i am
> | not usually tracking BESS WG mailing list and may not be around:
> | 
> | I would like to see subject draft to be adopted as a WG document in BESS
> | and become an update to RFC6514 (not to say bugfix ;-).
> | 
> | Feeedback detail: The draft should be amended to fix the same problem not only for
> | MSDP SA but also RFC4610 and probably accordingly change the draft name.
> | 
> | Cross-posted to mboned (sorry) because there where a couple of MBoned
> | participants expressing support for the draft in BESS and may like me not
> | be BESS regulars.
> | 
> | Cheers
> |     Toerless