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Re: [PWE3] WG Last Call for draft-ietf-pwe3-endpoint-fast-protection-01

"Stewart Bryant (stbryant)" <stbryant@cisco.com> Sun, 10 August 2014 13:38 UTC

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From: "Stewart Bryant (stbryant)" <stbryant@cisco.com>
To: Alexander Vainshtein <Alexander.Vainshtein@ecitele.com>
Thread-Topic: [PWE3] WG Last Call for draft-ietf-pwe3-endpoint-fast-protection-01
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Date: Sun, 10 Aug 2014 13:38:26 +0000
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References: <201407251524.s6PFOPn92012@magenta.juniper.net> <53D79504.4050904@cisco.com> <a8d070daae424ec0b9f338edfd0cde7c@AM3PR03MB612.eurprd03.prod.outlook.com> <04f15bedf2be4c7480d3e9ca01bdfd7f@BY2PR05MB728.namprd05.prod.outlook.com> <2597291f7b074922b690e4b06999cf1a@AM3PR03MB612.eurprd03.prod.outlook.com>, <30e13900814f41a681151971cbe9ebef@BY2PR05MB728.namprd05.prod.outlook.com> <1407215578702.64387@ecitele.com>, <2280b8e0d5f94a60badab91a2237181b@BY2PR05MB728.namprd05.prod.outlook.com> <1407304503657.72312@ecitele.com> <f8c4d4382dda4f7d94ce61b4b421fe4f@AM3PR03MB612.eurprd03.prod.outlook.com> <046050cb2d254a139b4650b2d7f93075@BY2PR05MB728.namprd05.prod.outlook.com> <09ab595ab24a46a0a4e87ebeb2cd185a@AM3PR03MB612.eurprd03.prod.outlook.com>, <2afb5c963e054aef929f38dcb3defa07@BY2PR05MB728.namprd05.prod.outlook.com>, <1407647722694.18724@ecitele.com> <004289D0-C473-4C1D-8A76-B42757F599A2@cisco.com>, <ee672591563c40fda0cd2debd238db26@AM3PR03MB612.eurprd03.prod.outlook.com>
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Cc: Yakov Rekhter <yakov@juniper.net>, "pwe3@ietf.org" <pwe3@ietf.org>, "Eric Rosen (erosen)" <erosen@cisco.com>
Subject: Re: [PWE3] WG Last Call for draft-ietf-pwe3-endpoint-fast-protection-01
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That is my interpretation.

Now they could specify no PW ecmp but that restricts the scope of the draft and must be both stated and tested against the requirements.

Stewart



On 10 Aug 2014, at 11:23, "Alexander Vainshtein" <Alexander.Vainshtein@ecitele.com<mailto:Alexander.Vainshtein@ecitele.com>> wrote:

Stewart,

My reading of your email is like following:

1.       Within the scope of the draft the PLR is always the penultimate P LSR on the LSP terminated by the Primary PE. I believe that the draft states that explicitly

2.       The PLR cannot differentiate between the failure of the link connecting it to the Primary PE and failure of the Primary PE in a timely manner; hence every time such a link fails, the PLR assumes failure of the Primary PE to be on the safe side. T

3.       With ECMP in the PSN, there typically would be several LSPs terminated by the Primary PE, each with its own PLR. So if the link between one of these PLRs and the Primary PE fails, it would apply the mechanisms defined in the draft, while the rest of the PLRs would not do anything.

4.       As a consequence, the dual-homed PE would receive some flows of the traffic crossing a flow-aware pw from one AC and some – from the other AC.  The draft does not specify that this is possible and that the CE should be able to cope with this situation.

Is my interpretation correct?

Regards,
       Sasha
Email: Alexander.Vainshtein@ecitele.com<mailto:Alexander.Vainshtein@ecitele.com>
Mobile: 054-9266302

From: Stewart Bryant (stbryant) [mailto:stbryant@cisco.com]
Sent: Sunday, August 10, 2014 12:24 PM
To: Alexander Vainshtein
Cc: Yimin Shen; Yakov Rekhter; pwe3@ietf.org<mailto:pwe3@ietf.org>; Eric Rosen (erosen)
Subject: Re: [PWE3] WG Last Call for draft-ietf-pwe3-endpoint-fast-protection-01


ECMP paths to xPEs naturally form and disappear in LDP PSNs (they are a fundamental property of that PSN type) and it is entirely normal  to find an ECMP to an xPE.

So, if you have a PW that is load balancing (again quite normal) and one of the attachments to the xPE fails, you can legitimately end  up with some traffic on one egress AC and some on another.

please you confirm that this design works correctly when a PE gets its traffic from both ACs?

Stewart

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