Re: [Lsr] AD Review of draft-ietf-lsr-isis-srv6-extensions-11

Peter Psenak <ppsenak@cisco.com> Fri, 09 April 2021 08:12 UTC

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To: Alvaro Retana <aretana.ietf@gmail.com>, draft-ietf-lsr-isis-srv6-extensions@ietf.org
Cc: John Scudder <jgs@juniper.net>, "lsr-chairs@ietf.org" <lsr-chairs@ietf.org>, lsr@ietf.org, Christian Hopps <chopps@chopps.org>
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From: Peter Psenak <ppsenak@cisco.com>
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Date: Fri, 9 Apr 2021 10:12:39 +0200
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Subject: Re: [Lsr] AD Review of draft-ietf-lsr-isis-srv6-extensions-11
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Hi Alvaro,

please see inline (##PP):

On 09/04/2021 00:17, Alvaro Retana wrote:
> Peter:
> 
> Hi!
> 
> I looked at -12.
> 
> I have a couple of nits/minor comments below.  There's only one
> significant one related to the information that must be shared between
> the Prefix Reachability TLV and the SRv6 Locator TLV: it is currently
> phrased as an example.
> 
> We're also waiting of the resolution of the registry thread.  If that
> results in not needed to add registries then you can address the
> comments below with any other IETF LC comments.  Otherwise I'll wait
> for an update.
> 
> Thanks!
> 
> Alvaro.
> 
> 
> [Line numbers from idnits.]
> 
> 
> ...
> 16	Abstract
> ...
> 25	   This documents updates [RFC7370] by modifying an existing registry.
> 
> [minor] s/[RFC7370]/RFC 7370
> No references in the Abstract.

##PP
done

> 
> 
> ...
> 102	1.  Introduction
> ...
> 137	   This documents updates [RFC7370] by modifying an existing registry
> 138	   Section 11.1.2.
> 
> [nit] s/Section 11.1.2/(Section 11.1.2)

##PP
done
> 
> 
> ...
> 192	4.1.  Maximum Segments Left MSD Type
> 
> 194	   The Maximum Segments Left MSD Type specifies the maximum value of the
> 195	   "Segments Left" field [RFC8754] in the SRH of a received packet
> 196	   before applying the Endpoint behavior associated with a SID.
> 
> [minor] s/specifies/signals

##PP
done
> 
> 
> ...
> 229	4.4.  Maximum End D MSD Type
> 
> 231	   The Maximum End D MSD Type specifies the maximum number of SIDs
> 232	   present in an SRH when performing decapsulation.  These includes, but
> 233	   not limited to, End.DX6, End.DT4, End.DT46, End with USD, End.X with
> 234	   USD as defined in [RFC8986]).
> 
> [nit] s/[RFC8986])/[RFC8986]
> 

##PP
done

> 
> ...
> 243	5.  SRv6 SIDs and Reachability
> ...
> 263	   Locators associated with algorithm 0 and 1 (for all supported
> 264	   topologies) SHOULD be advertised in a Prefix Reachability TLV (236 or
> 265	   237) so that legacy routers (i.e., routers which do NOT support SRv6)
> 266	   will install a forwarding entry for algorithm 0 and 1 SRv6 traffic.
> 
> [minor] s/NOT/not
> This is not an rfc2119 keyword -- and someone else will ask for the same thing.

##PP
done

> 
> 
> 268	   In cases where a locator advertisement is received in both a Prefix
> 269	   Reachability TLV and an SRv6 Locator TLV - (e.g. prefix, prefix-
> 270	   length, MTID all being equal and Algorithm being 0 in Locator TLV),
> 271	   the Prefix Reachability advertisement MUST be preferred when
> 272	   installing entries in the forwarding plane.  This is to prevent
> 273	   inconsistent forwarding entries between SRv6 capable and SRv6
> 274	   incapable routers.  Such preference of Prefix Reachability
> 275	   advertisement does not have any impact on the rest of the data
> 276	   advertised in the SRv6 Locator TLV.
> 
> [major] "e.g. prefix, prefix-length, MTID all being equal and
> Algorithm being 0 in Locator TLV"
> 
> This text should not be an example because those are the fields that
> should match.  Please make it clear: "The locator advertisement is
> both TLVs is considered the same when the following fliends match..."
> (or something like that with better words).

what about:

"In case where the same prefix, with the same prefix-length, MTID and 
algorithm is received  in both a Prefix Reachability TLV and an SRv6 
Locator TLV the Prefix Reachability advertisement MUST be preferred.."
> 
> 
> ...
> 866	11.5.  Sub-Sub-TLVs for SID Sub-TLVs
> 
> 868	   This document requests a new IANA registry be created under the IS-IS
> 869	   TLV Codepoints Registry to control the assignment of sub-TLV types
> 870	   for the SID Sub-TLVs specified in this document - Section 7.2,
> 871	   Section 8.1, Section 8.2.  The suggested name of the new registry is
> 872	   "sub-sub-TLVs for SRv6 End SID (5) (sub-TLV of TLVs 27, 135, 235, 236
> 873	   and 237) and SRv6 End.X SID (43)/SRv6 LAN End.X SID (44) (sub-TLVs of
> 874	   TLVs 27, 135, 235, 236 and 237)".  The registration procedure is
> 875	   "Expert Review" as defined in [RFC8126].  Guidance for the Designated
> 876	   Experts is provided in [RFC7370]The following assignments are made by
> 877	   this document:
> 
> [nit] s/[RFC7370]The/[RFC7370]. The

##PP
done

> 
> 
> 879	    Type   Description                          Encoding
> 880	                                                Reference
> 881	   ---------------------------------------------------------
> 882	    0      Reserved
> 883	    1      SRv6 SID Structure Sub-Sub-TLV       Section 9
> 884	    2-255  Unassigned
> 
> [major] The reference should be "[This Document]".

##PP
done

thanks,
Peter




> 
> [End]
> 
>