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

[Greg Mirsky <[e-mail]>]

Hi Ketan,
thank you for your thoughtful consideration of my comment. In
the draft-voyer-spring-sr-replication-segment I find the following
statement:
   A Replication segment at ingress node of Multi-point
   service replicates packets directly to each egress node of the
   service, without need for any state in the core of SR domain.
   Multiple Replication segments can be stitched together to build a
   tree in SR domain for Multi-point service; this is outside the scope
   of this document.
confusing. Firstly, what is the definition of  "core of SR domain"?
Secondly, isn't the suggestion of the potential stitching of Replication
segments, an acknowledgment that the Replication Segment introduces the
state to internal nodes of a single SR domain in order to realize a
scalable Multi-point service within an SR domain?

Regards,
Greg

On Sun, Nov 17, 2019 at 5:21 PM Ketan Talaulikar (ketant) <[e-mail]>
wrote:

> Hi Greg,
>
>
>
> Please check inline.
>
>
>
> *From:* Greg Mirsky <[e-mail]>
> *Sent:* 17 November 2019 13:14
> *To:* Ketan Talaulikar (ketant) <[e-mail]>
> *Cc:* John E Drake <jdrake=[e-mail]>; [e-mail];
> Alexander Vainshtein <[e-mail]>;
> [e-mail]; Robert Raszuk
> <[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"
>
>
>
> Hi Ketan,
>
> thank you for your suggestion. As you've pointed out, the draft in
> discussion introduces a new segment type, Replication Segment, to realize
> p2mp behavior in an SR domain. Looking into RFC 8402, I find the following
> statement regarding multicast:
>
> 6.  Multicast
>
>    Segment Routing is defined for unicast.  The application of the
>    source-route concept to Multicast is not in the scope of this
>    document.
>
>
>
> Hence, I believe, is the valid question to where the possible impact of
> multicast on the architecture of segment routing should be discussed,
> described.
>
> *[KT] Sure and I think I understand your point. Multicast in SR networks
> is for the WG to discuss and the chairs/AD to guide. However, I believe
> this is not related or blocking for the document in the subject line (as
> also echoed by Sasha). Just wanted to clarify this part.*
>
>
>
> *Thanks,*
>
> *Ketan*
>
>
>
> I hope that clarifies what has been the topic of discussion on this thread.
>
>
>
> Regards,
>
> Greg
>
>
>
> On Sun, Nov 17, 2019 at 12:09 PM Ketan Talaulikar (ketant) <
> [e-mail]> wrote:
>
> Hi Greg/Sasha/All,
>
>
>
> I really wonder whether we are talking about the same document anymore.
> The subject of this thread is
> https://tools.ietf.org/html/draft-voyer-spring-sr-replication-segment-00
>
>
>
> It is indeed possible that you and others are referring to some other
> document(s)?
>
>
>
> From reading of the draft, one can see that :
>
>    - It does not deal with multicast group joins/receivers or senders
>    - It does not build multicast trees
>    - It does not talk about multicast flows
>    - It simply introduces a new type of segment called Replication
>    Segment (p2mp) for a specific local node forwarding behaviour that is in
>    line with the Spring Charter (see below)
>
>
>
> o New types of segments mapping to forwarding behaviour (e.g., local
> ingress replication, local forwarding resources, a pre-existing
> replication structure) if needed for new usages.
>
>
>
> Can you please take another quick read over the draft with the above
> context in mind? I am positive that you will see that this is not getting
> multicast work in Spring – that is being worked on in other WGs.
>
>
>
> Thanks,
>
> Ketan
>
>
>
> *From:* spring <[e-mail]> *On Behalf Of *Greg Mirsky
> *Sent:* 17 November 2019 11:39
> *To:* John E Drake <jdrake=[e-mail]>
> *Cc:* [e-mail]; Alexander Vainshtein <
> [e-mail]>;
> [e-mail]; Robert Raszuk
> <[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"
>
>
>
> Dear All,
>
> I concur with Sasha and John. Intended ingress replication of a particular
> flow, though using a unicast destination address, is still a multicast.
>
>
>
> Regards,
>
> Greg
>
>
>
> On Thu, Nov 14, 2019 at 5:36 AM John E Drake <jdrake=
> [e-mail]> wrote:
>
> Robert,
>
>
>
> As Sasha and I have indicated, your position is your own and is not
> consistent with the majority of work on this topic.  I’m fine w/ agreeing
> to disagree.
>
>
>
> John
>
> Sent from my iPhone
>
>
>
> On Nov 14, 2019, at 2:57 AM, Robert Raszuk <[e-mail]> wrote:
>
> 
>
> John,
>
>
>
> > Your claim that ingress replication is not multicast is, at best, a
> stretch.
>
>
>
> I use a very basic and simple rule of thumb ... if address of my packet is
> a multicast address then it is multicast if not it is unicast.
>
>
>
> Ref:
> https://www.iana.org/assignments/multicast-addresses/multicast-addresses.xhtml
> <https://urldefense.com/v3/__https:/www.iana.org/assignments/multicast-addresses/multicast-addresses.xhtml__;!8WoA6RjC81c!QFbPjRVo7hB9622FCxHnivS8PVicSm5TCW9kaF-KRqhC3G7uLL0tCrGUUxL2sAQ$>
>
>
>
>
> Solution as described in draft-voyer-spring-sr-replication-segment does
> not seems to be requiring multicast addresses hence it is applicable to
> pure unicast networks.
>
>
>
> Thx,
>
> Robert.
>
>
>
>
>
> On Wed, Nov 13, 2019 at 10:20 PM John E Drake <[e-mail]> wrote:
>
> Robert,
>
>
>
> I’m sorry for the confusion.  My only point was that MVPN provides the
> reference architecture for dealing w/ multicast using a multiplicity of
> tunnel types in a consistent manner, as Sasha alluded to in his mention of
> PMSI.  Your claim that ingress replication is not multicast is, at best, a
> stretch.
>
>
>
> Yours Irrespectively,
>
>
>
> John
>
>
>
>
>
> Juniper Business Use Only
>
> *From:* Robert Raszuk <[e-mail]>
> *Sent:* Wednesday, November 13, 2019 3:55 PM
> *To:* John E Drake <[e-mail]>
> *Cc:* Alexander Vainshtein <[e-mail]>;
> [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"
>
>
>
> Hi John,
>
>
>
> > Further, ingress replication has been part of MVPN since forever.
>
>
>
> Just curious how is this at all relevant for this discussion ?
>
>
>
> Do I have to roll out MVPN monster to split my unicast UDP stream to few
> receivers at selected network point ?
>
>
>
> And last but not least who said this is at all related to "ingress
> replication" ??? Ingress to p2mp segment can be at any SR midpoint in the
> network. Are you suggesting to run MVPN apparatus with manual tree building
> ? Whow :)
>
>
>
> Thx,
>
> R.
>
>
>
>
>
>
>
>
>
>
>
>
>
> On Wed, Nov 13, 2019 at 9:40 PM John E Drake <[e-mail]> wrote:
>
> Hi,
>
>
>
> I think Sasha has a valid point.  Further, ingress replication has been
> part of MVPN since forever.
>
>
>
> Yours Irrespectively,
>
>
>
> John
>
>
>
>
>
> Juniper Business Use Only
>
> *From:* spring <[e-mail]> *On Behalf Of *Alexander
> Vainshtein
> *Sent:* Wednesday, November 13, 2019 9:26 AM
> *To:* Robert Raszuk <[e-mail]>
> *Cc:* spring@ietf..org <[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
>
>
>
> Office: [phone]
>
> Cell:      [phone]
>
> Email:   [e-mail]
>
>
>
> *From:* Robert Raszuk <[e-mail]>
> *Sent:* Wednesday, November 13, 2019 4:15 PM
> *To:* Alexander Vainshtein <[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"
>
>
>
> 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]> 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
>
>
>
> Office: [phone]
>
> Cell:      [phone]
>
> Email:   [e-mail]
>
>
>
> -----Original Message-----
> From: spring <[e-mail]> On Behalf Of IETF Secretariat
> Sent: Tuesday, November 12, 2019 7:06 PM
> To: [e-mail];
> spring-chairs@ietf..org; [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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>
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