[spring] Re: spring WG Adoption Call for draft-peng-spring-pmtu-sr-policy

["Pengshuping (Peng Shuping)" <[e-mail]>]

Hi Changwang, 

Thank you for your support and suggestions. 
We will consider them in the future version. Thank you! 

Best Regards, 
Shuping 

-----Original Message-----
From: linchangwang <[e-mail]> 
Sent: Thursday, June 20, 2024 10:32 PM
To: Alvaro Retana <[e-mail]>; SPRING WG <[e-mail]>
Cc: [e-mail]; spring Chairs <[e-mail]>
Subject: Re: [spring] spring WG Adoption Call for draft-peng-spring-pmtu-sr-policy


Hi WG,

I support the adoption of this draft.
MTU is crucial in the actual deployment of SR and requires comprehensive planning, taking into account various factors.

There are still some issues with the document, and I suggest further enhancement in the future.

 1. In addition to 5.2.5 TI-LFA, consideration should also be given to SR micro loop prevention or tail-end protection mechanisms, which can also result in packet length changes.

 2. SR-PMTU not only involves the minimum MTU along the path but also considers the reserved protection path or the potential increase in packet length due to binding SIDs.
  The final SR-PMTU issued should be the minimum interface MTU minus the potential increase.

 3. Path protection should also consider the length changes caused by compression or non-compression.

 4. When the primary path fails, and the backup path is activated, the MTU may change.
  If changes do occur, considerations for a smooth transition back to the original path are advised to be added.
  Example:
        SR Policy Policy_A
          Path path-1
             Pref 100
                Segment 1
                   Mtu 1800
          Path path-2
            Pref 50
               Segment 2
                   Mtu 1500
      When the primary path-1 has an MTU of 1800 and fails, the backup path-2 is activated, resulting in an MTU change to 1500.
      For subsequent reversion, considerations for a smooth transition back need to be made.

  5. When there are multiple segment lists under the same path, considerations should be made to keep the MTU as consistent as possible when segment list status changes.
    If changes occur, considerations for a smooth transition back to the original list should be added.
  Example:
         SR Policy Policy_A
            Path path-1
              Pref 100
               Segment 1
                  Mtu 2000
               Segment 2
                  Mtu 1800
               Segment 3
                  Mtu 1500
     Similar to the previous point, when multiple segment lists switch, MTU will fluctuate, requiring attention for a smooth transition.


Thanks,
Changwang

-----邮件原件-----
发件人: Alvaro Retana <[e-mail]>
发送时间: 2024年6月18日 23:42
收件人: SPRING WG <[e-mail]>
抄送: [e-mail]; spring Chairs <[e-mail]>
主题: [spring] spring WG Adoption Call for draft-peng-spring-pmtu-sr-policy

Dear WG:

This message starts a two-week adoption call for draft-peng-spring-pmtu-sr-policy, ending on July/2nd. From the
Abstract:

   This document defines the Path MTU (PMTU) for Segment Routing (SR)
   Policy (called SR-PMTU). It applies to both Segment Routing over IPv6
   (SRv6) and SR-MPLS. This document specifies the framework of SR-PMTU
   for SR Policy including the link MTU collection, the SR-PMTU
   computation, the SR-PMTU enforcement, and the handling behaviours on
   the headend.


   https://datatracker.ietf.org/doc/draft-peng-spring-pmtu-sr-policy/


Please review the draft and consider whether you support its adoption by the WG. Please share any thoughts with the list to indicate support or opposition -- this is not a vote.

If you are willing to provide a more in-depth review, please state it explicitly to give the chairs an indication of the energy level in the working group willing to work on the document.

WG adoption is the start of the process. The fundamental question is whether you agree the proposal is worth the WG's time to work on and whether this draft represents a good starting point. The chairs are particularly interested in hearing the opinions of people who are not authors of the document.

Note that draft-ietf-pce-pcep-pmtu ("Support for Path MTU (PMTU) in the Path Computation Element (PCE) Communication Protocol (PCEP)") Normatively references this document. It may be helpful to look at that document too.

Thanks!

Alvaro (for the Chairs)

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