Re: [Pals] [bess] All-Active Multi-homing and Virtual Ethernet Segments: A Question

[Alexander Vainshtein <[e-mail]>]

Luc,
Lots of thanks for a prompt and highly informative response.

I am adding the PALS WG to the CC list since, from my POV, your proposal goes beyond the PW network reference model as shown in Figure 2 of RFC 3985<https://tools.ietf.org/html/rfc3985>.
While this model has been extended to cover multi-segment PWs (RFC 6073<https://tools.ietf.org/html/rfc6073>), PW redundancy (RFC 6718<https://tools.ietf.org/html/rfc6718>) and ICCP (RFC 7275<https://tools.ietf.org/html/rfc7275>)  none of these extensions seem to be directly applicable to the proposed scheme.

My 2c,
Sasha

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Cell:      [phone]
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From: Luc Andre Burdet (lburdet) [mailto:[e-mail]]
Sent: Tuesday, September 25, 2018 5:46 PM
To: Alexander Vainshtein <[e-mail]>; [e-mail]
Cc: Michael Gorokhovsky <[e-mail]>; Alexander Ferdman <[e-mail]>; Shell Nakash <[e-mail]>; [e-mail]
Subject: Re: [bess] All-Active Multi-homing and Virtual Ethernet Segments: A Question

Hi Sasha,

I agree the vES draft does not go in great detail about A/A PWs.

For A/A PWs terminating at peering PEs, the concept is similar to LAG, using static label at peering PEs:
-          The CE sets up a single PW to remote endpoint to anycast IP1, Label1.
-          PE1, PE2 set up a PW each to CE, using local static label Label1.
-          PE1,PE2 adv IP1 as anycast IP towards CE-side
There will not be excessive MAC-moves since the CE sees only one pseudowire to a single remote—very similar to what is done for LAG on “real” links.

We can update the draft to be more descriptive—that draft needs a re-read anyways, the header on each page still reads “PBB-EVPN” ☺

HTH,
Luc André

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Luc André Burdet
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From: BESS <[e-mail]<mailto:[e-mail]>> on behalf of Alexander Vainshtein <[e-mail]<mailto:[e-mail]>>
Date: Tuesday, September 25, 2018 at 06:25
To: "[e-mail]<mailto:[e-mail]>" <[e-mail]<mailto:[e-mail]>>
Cc: Michael Gorokhovsky <[e-mail]<mailto:[e-mail]>>, Alexander Ferdman <[e-mail]<mailto:[e-mail]>>, Shell Nakash <[e-mail]<mailto:[e-mail]>>, "[e-mail]<mailto:[e-mail]>" <[e-mail]<mailto:[e-mail]>>
Subject: [bess] All-Active Multi-homing and Virtual Ethernet Segments: A Question

Dear authors of the EVPN Virtual Ethernet Segment<https://tools.ietf.org/html/draft-sajassi-bess-evpn-virtual-eth-segment-03> draft,
My colleagues and I have a question pertaining to support of All-Active redundancy mode in EVPN that uses virtual Ethernet Segments.

Section 8.5 of RFC 7432<https://tools.ietf.org/html/rfc7432#section-8.5> says:

   If a bridged network is multihomed to more than one PE in an EVPN
   network via switches, then the support of All-Active redundancy mode
   requires the bridged network to be connected to two or more PEs using
   a LAG.

   If a bridged network does not connect to the PEs using a LAG, then
   only one of the links between the bridged network and the PEs must be
   the active link for a given <ES, VLAN> or <ES, VLAN bundle>.  In this
   case, the set of Ethernet A-D per ES routes advertised by each PE
   MUST have the "Single-Active" bit in the flags of the ESI Label
   extended community set to 1.

This restriction is easy to understand, since, with the All-Active multi-homing mode of an Ethernet Segment, a CE attached to such a segment potentially would receive traffic from all the PEs attached to this  segment. Since A CE that is part of a bridged network must learn MAC addresses of the received traffic, it would potentially experience continuous MAC Move events – with undesirable consequences.

The EVPN Virtual Ethernet Segment draft replaces Ethernet links (forming a “real” ES) with Ethernet PWs, and claims support of both Single-homed and multi-homed multi-homing modes. When I compare these claims with the quoted above statement from RFC 7432, I see two possibilities:

  *   Either a CE that is connected to an All-Active vES cannot be part of a bridged network (and thus would not do any MAC learning)
  *   Or  an extension of LAG that deals with Ethernet PWs instead of Ethernet links is required.

Could you please clarify which of these two options is correct?

Note: The draft includes Informative references to the two drafts that have been published as RFC 7432 and RFC 7623.

Regards,
Sasha

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Cell:      [phone]
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