Re: [spring] The SPRING WG has placed draft-voyer-spring-sr-replication-segment in state "Candidate for WG Adoption"

[John E Drake <[e-mail]>]

Hi,

I think Sasha has a valid point.  Further, ingress replication has been part of MVPN since forever.

Yours Irrespectively,

John



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From: spring <[e-mail]> On Behalf Of Alexander Vainshtein
Sent: Wednesday, November 13, 2019 9:26 AM
To: Robert Raszuk <[e-mail]>
Cc: [e-mail]; [e-mail]; <[e-mail]> ([e-mail]) <[e-mail]>
Subject: Re: [spring] The SPRING WG has placed draft-voyer-spring-sr-replication-segment in state "Candidate for WG Adoption"

Robert,
Lots of thanks for a prompt response.

You seem to imply that a multicast distribution tree that is built, say, by an SDN controller and used, say, to act as a PMSI in the mVPN application, is not really a multicast.  Personally I disagree, but this is a matter of taste and terminology.

What looks unambiguous to me is that:

  *   The WG charter explicitly mentions ingress replication as one of "new types of segments mapping to forwarding behavior" that "may require architectural extensions"
  *   The current architecture document does not cover any such segment type (whether because such segments have been considered as related to multicast by the authors, or for some other reason is not all that important. )
Therefore my concern remains unresolved regardless of whether ingress replication is or is not formally considered as multicast.

Regards,
Sasha

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From: Robert Raszuk <[e-mail]<mailto:[e-mail]>>
Sent: Wednesday, November 13, 2019 4:15 PM
To: Alexander Vainshtein <[e-mail]<mailto:[e-mail]>>
Cc: <[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]>
Subject: Re: [spring] The SPRING WG has placed draft-voyer-spring-sr-replication-segment in state "Candidate for WG Adoption"

Sasha,

If I have some content and I send it to you and your neighbour as two unicast streams am I suddenly doing multicast ?

IMHO N number of replicated unicasts is still not a multicast.

Multicast in my definition requires  multicast groups, receiver joins, tree building protocols etc ... and this draft does not suggest any of this. IN contrast it just describes how can we have p2mp unicast distribution ... call it fan out node.

Thx,
R.





On Wed, Nov 13, 2019 at 12:42 PM Alexander Vainshtein <[e-mail]<mailto:[e-mail]>> wrote:

Hi all,

I have a question regarding adoption of draft-voyer-sr-spring-replication-segment as a SPRING WG document.



These concerns are based on the following:

1.       This draft (both based on its title and on its content) deals with local (in the Root node) ingress replication which, in its turn, is one of the issues that could be used for delivery of multicast.

2.       Local ingress replication is mentioned in the SPRING WG Charter as one of the "New types of segments mapping to forwarding behavior". The charter further says that "Any of the above <Sasha: New types of segments> may require architectural extensions"

3.       The current (and, AFAIK, the only existing) Segment Routing Architecture document (RFC 8402<https://urldefense.com/v3/__https:/clicktime.symantec.com/34qM9QogJnh1eY5nZPXYAkA6H2?u=https*3A*2F*2Ftools.ietf.org*2Fhtml*2Frfc8402__;JSUlJSU!8WoA6RjC81c!TeDGZsCZsxVU3U1A-_hQaYhZsmLZFF4oF-lGSpNnOmTa-zUl6jfGkGEUOvwkLSU$>) explicitly states in Section 6 that "Segment Routing is defined for unicast. The application of the source-route concept to Multicast is not in the scope of this document".

The combinations of observations above strongly suggests to me that a document defining multicast-related extensions of segment routing architecture should be very useful (if not mandatory) for progressing the Replication Segment draft. From my POV the Replication Segment draft is not (and is not intended to be) such a document.



I wonder if there is an intention to produce such a document in the timeframe that could be relevant for discussion of the Replication Segment draft.



Nothing in this message should be interpreted as my objection to (or support of) adoption of the Replication Segment draft as a WG document per se.

Bit I find it difficult to take a position any which way without a clear and commonly agreed upon framework for multicast in segment routing.



Regards,

Sasha



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-----Original Message-----
From: spring <[e-mail]<mailto:[e-mail]>> On Behalf Of IETF Secretariat
Sent: Tuesday, November 12, 2019 7:06 PM
To: [e-mail]<mailto:[e-mail]>; spring-chairs@ietf..org<mailto:spring-chairs@ietf..org>; [e-mail]<mailto:[e-mail]>
Subject: [spring] The SPRING WG has placed draft-voyer-spring-sr-replication-segment in state "Candidate for WG Adoption"





The SPRING WG has placed draft-voyer-spring-sr-replication-segment in state Candidate for WG Adoption (entered by Bruno Decraene)



The document is available at

https://clicktime.symantec.com/3EMJRgfTdX6UyWKGnMPiVwZ6H2?u=https%3A%2F%2Fdatatracker.ietf.org%2Fdoc%2Fdraft-voyer-spring-sr-replication-segment%2F<https://urldefense.com/v3/__https:/clicktime.symantec.com/3EMJRgfTdX6UyWKGnMPiVwZ6H2?u=https*3A*2F*2Fdatatracker.ietf.org*2Fdoc*2Fdraft-voyer-spring-sr-replication-segment*2F__;JSUlJSUl!8WoA6RjC81c!TeDGZsCZsxVU3U1A-_hQaYhZsmLZFF4oF-lGSpNnOmTa-zUl6jfGkGEUHVCWfyU$>



Comment:

IPR call:

https://clicktime.symantec.com/3KG7A2qM3Xf2eqDctGju1e66H2?u=https%3A%2F%2Fmailarchive.ietf.org%2Farch%2Fmsg%2Fspring%2F_stJjBM5K6vr7QYw0HRKf-z0_us<https://urldefense.com/v3/__https:/clicktime.symantec.com/3KG7A2qM3Xf2eqDctGju1e66H2?u=https*3A*2F*2Fmailarchive.ietf.org*2Farch*2Fmsg*2Fspring*2F_stJjBM5K6vr7QYw0HRKf-z0_us__;JSUlJSUlJQ!8WoA6RjC81c!TeDGZsCZsxVU3U1A-_hQaYhZsmLZFF4oF-lGSpNnOmTa-zUl6jfGkGEUfVccUWU$>



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