Re: [Idr] 2 Week WG LC for draft-ietf-idr-bgp-prefix-sid-04.txt - 3/6 to 3/20/2017 - extending to 3/31
"Stefano Previdi (sprevidi)" <sprevidi@cisco.com> Tue, 04 April 2017 13:08 UTC
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From: "Stefano Previdi (sprevidi)" <sprevidi@cisco.com>
To: "adrian@olddog.co.uk" <adrian@olddog.co.uk>
CC: Susan Hares <shares@ndzh.com>, idr wg <idr@ietf.org>
Thread-Topic: [Idr] 2 Week WG LC for draft-ietf-idr-bgp-prefix-sid-04.txt - 3/6 to 3/20/2017 - extending to 3/31
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Date: Tue, 04 Apr 2017 13:08:34 +0000
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Subject: Re: [Idr] 2 Week WG LC for draft-ietf-idr-bgp-prefix-sid-04.txt - 3/6 to 3/20/2017 - extending to 3/31
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Thanks Adrian, I’ll go through them asap. s. > On Apr 3, 2017, at 10:13 PM, Adrian Farrel <adrian@olddog.co.uk> wrote: > > Hi Sue, WG, > > Yes, sorry for not getting to this the first time around. > > It's a good piece of work that needs to be standardised, and this document is ready modulo the relatively small comments below. > > Thanks, > Adrian > > > === Code point stuff === > > I thought we had some fairly good clue in IDR about not "suggesting" > code point values, but in section 4 I found... > > The BGP Prefix SID attribute is an optional, transitive BGP path > attribute. The attribute type code is to be assigned by IANA > (suggested value: 40). > > As it turns out, an early allocation has been done and is recorded in > section 8. So this text should read... > > The BGP Prefix SID attribute is an optional, transitive BGP path > attribute. The attribute type code 40 has been assigned by IANA > (see Section 8). > > > === Rambling Thoughts === > > Section 4.2 > > * S flag: if set then it means that the BGP speaker attaching the > Prefix-SID Attribute to a prefix is capable of processing the > IPv6 Segment Routing Header (SRH, > [I-D.ietf-6man-segment-routing-header]) for the segment > corresponding to the originated IPv6 prefix. The use case > leveraging the S flag is described in > [I-D.ietf-spring-segment-routing-msdc]. > > Suppose that sometime in the future a third type of SID processing is > defined. Well, you'd burn a new bit, say the X bit, to indicate the > support of that method. But how would you set the S bit in that case? > So, perhaps you need two bits already. > > > === Minor === > > Odd to reference draft-ietf-6man-segment-routing-header but not > draft-ietf-spring-segment-routing-mpls. > > --- > > I think draft-ietf-spring-segment-routing and draft-ietf-spring-segment- > routing-msdc are normative references based both on the importance as > background material and the text in the first paragraph of the document. > > The material in Section 1 suggests that draft-ietf-spring-segment- > routing-central-epe and draft-ietf-idr-bgpls-segment-routing-epe might > also be normative references. > > --- > > The RFC Editor will require that the first section of the document is > the "Introduction". I think you fix this by moving the current Section > 1 to be a sub-section of the current Section 2. > > --- > > I wish we (or the SPRING WG) would nail down the terminology of a > "segment" and a "segment identifier." This muddiness is just not > necessary, but is perpetrated by this document saying that > The ingress node of the SR domain prepends a (sic) SR > header containing "segments" to an incoming packet. > but then saying that > Each segment is identified by a Segment Identifier (SID). > So, in fact, the SR header contains SIDs not segments. > > This confusions is continued by > Each segment represents a topological instruction > Do segments *represent* topological instructions or are they > topological instruction? > > --- > > Section 2 has... > A BGP-Prefix-SID is always global within the SR/BGP domain > While this language is clear from the referenced documents, it is not > very clear in this document. I think you need to say ... > A BGP-Prefix-SID is always a global SID [I-D.ietf-spring-segment- > routing] within the SR/BGP domain > ...although (of course) draft-ietf-spring-segment-routing talks about > global segments but not global SIDs except in 3.1.3 where the mention > is a little without context. > > --- > > Section 3.1 has... > While it is recommended to use the same SRGB across > all the nodes within the SR domain, the SRGB of a node is a local > property and could be different on different speakers. > I *think* that this recommendation comes from the referenced document > [I-D.ietf-spring-segment-routing] and not from this current document. > This would be clearer by writing... > While [I-D.ietf-spring-segment-routing] recommends to use the same > SRGB across all the nodes within the SR domain, the SRGB of a node > is a local property and could be different on different speakers. > Doing this will stop questions about whether "recommended" is supposed > to be in 2119 upper case. > > --- > > In 3.1... > > The index L_I is a 32 bit offset in the SRGB. Each BGP speaker > derives its local MPLS label, L, by adding L_I to the start value > of its own SRGB, and programs L in its MPLS dataplane as its > incoming/local label for the prefix. > > Is this right or is L_I, as defined in draft-ietf-spring-segment- > routing-mpls, a 20 bit offset into a reduced 20-bit space out of the 32- > bit SID space? > > FWIW, this section is another place I would have expected to see a > reference to draft-ietf-spring-segment-routing-mpls. > > --- > > First para of section 4 ends... > > The value field of the BGP-Prefix-SID > attribute has the following format: > > Is there supposed to be a figure here? The next paragraph doesn't seem > to flow. Maybe this sentence can be deleted. > > --- > > 4.2 > Are you sure you don't want a registry for flags? > > --- > > 5.1 > A BGP speaker may be locally configured with an SRGB=[GB_S, GB_E]. > Probably "MAY"? > I think that the notation needs some small explanation. > > --- > > 5.1 > The Label Index gives a hint to the receiving node on which > local/incoming label the BGP speaker SHOULD use. > > This is like a double SHOULD: "hint" and "SHOULD use". > It might be helpful to describe the potential variance. > > --- > > 6. > In order to > prevent distribution of the BGP Prefix-SID attribute beyond its > intended scope of applicability, attribute filtering MAY be deployed. > > Yeah. That's OK, but the language implies there are other ways to prevent > distribution beyond the intended scope. > > --- > > 7. > all the occurrences of > the attribute other than the first one SHALL be discarded and the BGP > Update message shall continue to be processed. > > I think the second "shall" is a "SHALL" as well. > > > > === Nits === > > The authors need to sort out their affiliations and email addresses. > > --- > > The AD will probably not be happy with 7 names on the front page. > > --- > > 3.1 > s/This informations/This information/ > > --- > > 4.1 and 4.3 > s/None are/None is/ > > --- > > 5.2 > When a SR IPv6 BGP speaker receives a IPv6 Unicast BGP Update with > s/a/an/ x2 > > --- > > 6. > s/[RFC3107]or/[RFC3107] or/ > > --- > > 6.1 > s/([RFC3107])The/([RFC3107]). The/ > > --- > > Section 11 might possibly be of no value. > > From: Idr [mailto:idr-bounces@ietf.org] On Behalf Of Susan Hares > Sent: 21 March 2017 16:53 > To: 'idr wg' > Subject: Re: [Idr] 2 Week WG LC for draft-ietf-idr-bgp-prefix-sid-04.txt - 3/6 to 3/20/2017 - extending to 3/31 > > IDR WG: > > Perhaps the WG LC came at a bad time since have received only 1 response. We will length the call to 3/31. Unless with have substantial input, this WG LC will not indicate consensus. > > Sue Hares > _______________________________________________ > Idr mailing list > Idr@ietf.org > https://www.ietf.org/mailman/listinfo/idr
- Re: [Idr] 2 Week WG LC for draft-ietf-idr-bgp-pre… Susan Hares
- Re: [Idr] 2 Week WG LC for draft-ietf-idr-bgp-pre… Acee Lindem (acee)
- Re: [Idr] 2 Week WG LC for draft-ietf-idr-bgp-pre… Stefano Previdi (sprevidi)
- Re: [Idr] 2 Week WG LC for draft-ietf-idr-bgp-pre… Satya Mohanty (satyamoh)
- Re: [Idr] 2 Week WG LC for draft-ietf-idr-bgp-pre… Arjun Sreekantiah (asreekan)
- Re: [Idr] 2 Week WG LC for draft-ietf-idr-bgp-pre… Keyur Patel
- Re: [Idr] 2 Week WG LC for draft-ietf-idr-bgp-pre… John G. Scudder
- Re: [Idr] 2 Week WG LC for draft-ietf-idr-bgp-pre… Stefano Previdi (sprevidi)
- Re: [Idr] 2 Week WG LC for draft-ietf-idr-bgp-pre… Ahmed Bashandy (bashandy)
- Re: [Idr] 2 Week WG LC for draft-ietf-idr-bgp-pre… Adrian Farrel
- Re: [Idr] 2 Week WG LC for draft-ietf-idr-bgp-pre… Susan Hares
- Re: [Idr] 2 Week WG LC for draft-ietf-idr-bgp-pre… Martin Horneffer
- Re: [Idr] 2 Week WG LC for draft-ietf-idr-bgp-pre… Adrian Farrel
- Re: [Idr] 2 Week WG LC for draft-ietf-idr-bgp-pre… Stefano Previdi (sprevidi)