Re: [Pce] Is there any activity related to PCE graceful restart?

[Alexander Vainshtein <[e-mail]>]

Dhruv,
Lots of thanks for a prompt response and valuable inputs.
My colleagues and I will look at the documents you’ve pointed.

I have already responded to Adrian’s questions in an earlier email (attached for your convenience). Hopefully my answers clarify the context of our questions.

Regards,
Sasha

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From: [e-mail] [mailto:[e-mail]] On Behalf Of Dhruv Dhody
Sent: Monday, June 19, 2017 9:26 AM
To: Alexander Vainshtein <[e-mail]>
Cc: [e-mail]; [e-mail]; [e-mail]; Marina Fizgeer <[e-mail]>; Michael Gorokhovsky <[e-mail]>; [e-mail]; Alexander Ferdman <[e-mail]>
Subject: Re: [Pce] Is there any activity related to PCE graceful restart?

Hi Sasha,

Since you pointed stateful PCE specifically, the draft talks about what to do during a session restart. [https://tools.ietf.org/html/draft-ietf-pce-stateful-pce-19#section-5.6]

There is another draft that talks about optimizing it - https://datatracker.ietf.org/doc/draft-ietf-pce-stateful-sync-optimizations/

Note that we also have re-delagation, which would try to find another active stateful PCE to take over control -
[https://tools.ietf.org/html/draft-ietf-pce-stateful-pce-19#section-5.7.5]

As Adrian asked, do you have something else in mind when you say GR?

Regards,
Dhruv


On Sun, Jun 18, 2017 at 9:12 PM, Alexander Vainshtein <[e-mail]<mailto:[e-mail]>> wrote:
Re-sending with the correct WG mailing list address…

Regards,
Sasha

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From: Alexander Vainshtein
Sent: Sunday, June 18, 2017 6:41 PM
To: '[e-mail]<mailto:[e-mail]>' <[e-mail]<mailto:[e-mail]>>; '[e-mail]<mailto:[e-mail]>' <[e-mail]<mailto:[e-mail]>>; '[e-mail]<mailto:[e-mail]>' <[e-mail]<mailto:[e-mail]>>
Cc: '[e-mail]' <[e-mail]<mailto:[e-mail]>>; Michael Gorokhovsky <[e-mail]<mailto:[e-mail]>>; Marina Fizgeer <[e-mail]<mailto:[e-mail]>>; Alexander Ferdman <[e-mail]<mailto:[e-mail]>>
Subject: Is there any activity related to PCE graceful restart?

Hi all,
My colleagues and I tried to find any work in the PCE WG related to PCEP graceful restart.
So far, we did not succeed. This could mean one of the following:

-          Our search did not go deep enough. In this case pointers to any specific documents would be highly appreciated

-          Such work does not exist because (for some reason) it is not required. This looks problematic to me, especially if we deal with a stateful  active PCE and the path computed by the PCE was implemented using Segment Routing (so that only the head end of the computed path is aware of the path). However, I could have missed something obvious, and any clarifications would be highly appreciated

-          Such work is required but, so far, nobody has taken care of it. The implications are obvious:-(.

Your feedback would be highly appreciated.

Regards, and lots of thanks in advance,
Sasha

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Cell:      [phone]
Email:   [e-mail]<mailto:[e-mail]>


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--- Begin Message ---

Adrian,

Lots of thanks for a prompt response.



However, our primary interest is the control plane (including PCC) restart in a network element with separated  control and forwarding planes.



Specifically, my colleagues and I try to understand, how to make such a restart non-traffic affecting while:

-          The network uses Segment Routing for setting up paths computed by the PCE. This means that these paths are only known to their respective head-end nodes. This situation is different from the scenario where RSVP-TE is used to signal these paths, since they cannot be re-learned from the neighbors as part of the RSVP-TE graceful restart procedures

-          The protocols used for distributing SR-related information (i.e., IGP and BGP SR extensions) are GR-capable, and GR for them is enabled in the network

-          The PCE is an active stateful PCE, i.e., it instructs the head-end node, which paths should be set up without any requests coming from the nodes.



Hopefully this clarifies the context for our question.



It may well be that the requirement for non-traffic affecting control plane restart can be addressed without any changed to the existing protocols. Alternatively, it  is possible that some minor changes (like making the PCE aware of separation between the control and forwarding planes, negotiation of GR capabilities and grace periods etc.) are required.



Any inputs would be highly appreciated.



Regards, and lots fo thanks in advance,

Sasha



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From: Adrian Farrel [mailto:[e-mail]]
Sent: Sunday, June 18, 2017 8:34 PM
To: Alexander Vainshtein <[e-mail]>; [e-mail]; [e-mail]; [e-mail]
Cc: Marina Fizgeer <[e-mail]>; Michael Gorokhovsky <[e-mail]>; [e-mail]; Alexander Ferdman <[e-mail]>
Subject: RE: [Pce] Is there any activity related to PCE graceful restart?



Sasha,



What are you hoping to achieve?



That a restarting PCE can retain its TED and LSP-DB?

That a restarting PCE can synch state with the network?

That a restarting PCE with outstanding (unanswered) messages in either direction can not need to resend them?

That a restarting PCE can resend outstanding (unanswered) messages without problems caused by duplication?



I think you may want to read around the definition of the request-id. Although 5440 doesn't make it explicit, a lot comes from how you process the request-id. That "a lot" arose from consideration of parallel sessions and distilled to not needing to write about restart.



Cheers,

Adrian (resurrecting old memories, possibly not entirely accurately)



From: Pce [mailto:[e-mail]] On Behalf Of Alexander Vainshtein
Sent: 18 June 2017 16:43
To: [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>
Cc: Marina Fizgeer; Michael Gorokhovsky; [e-mail]<mailto:[e-mail]>; Alexander Ferdman
Subject: Re: [Pce] Is there any activity related to PCE graceful restart?



Re-sending with the correct WG mailing list address...



Regards,

Sasha



Office: [phone]

Cell:      [phone]

Email:   [e-mail]<mailto:[e-mail]>



From: Alexander Vainshtein
Sent: Sunday, June 18, 2017 6:41 PM
To: '[e-mail]' <[e-mail]<mailto:[e-mail]>>; '[e-mail]' <[e-mail]<mailto:[e-mail]>>; '[e-mail]' <[e-mail]<mailto:[e-mail]>>
Cc: '[e-mail]' <[e-mail]<mailto:[e-mail]>>; Michael Gorokhovsky <[e-mail]<mailto:[e-mail]>>; Marina Fizgeer <[e-mail]<mailto:[e-mail]>>; Alexander Ferdman <[e-mail]<mailto:[e-mail]>>
Subject: Is there any activity related to PCE graceful restart?



Hi all,

My colleagues and I tried to find any work in the PCE WG related to PCEP graceful restart.

So far, we did not succeed. This could mean one of the following:

-          Our search did not go deep enough. In this case pointers to any specific documents would be highly appreciated

-          Such work does not exist because (for some reason) it is not required. This looks problematic to me, especially if we deal with a stateful  active PCE and the path computed by the PCE was implemented using Segment Routing (so that only the head end of the computed path is aware of the path). However, I could have missed something obvious, and any clarifications would be highly appreciated

-          Such work is required but, so far, nobody has taken care of it. The implications are obvious:-(.



Your feedback would be highly appreciated.



Regards, and lots of thanks in advance,

Sasha



Office: [phone]

Cell:      [phone]

Email:   [e-mail]<mailto:[e-mail]>




___________________________________________________________________________

This e-mail message is intended for the recipient only and contains information which is
CONFIDENTIAL and which may be proprietary to ECI Telecom. If you have received this
transmission in error, please inform us by e-mail, phone or fax, and then delete the original
and all copies thereof.
___________________________________________________________________________

--- End Message ---