Uma –
One item I forgot…there are no meaningful nits.
Idnits reports:
-- Looks like a reference, but probably isn't: '100' on line 1009
'SRGB = [100, 199]...'
-- Looks like a reference, but probably isn't: '199' on line 1009
'SRGB = [100, 199]...'
-- Looks like a reference, but probably isn't: '1000' on line 1010
'[1000, 1099]...'
-- Looks like a reference, but probably isn't: '1099' on line 1010
'[1000, 1099]...'
-- Looks like a reference, but probably isn't: '500' on line 1011
'[500, 599]...'
-- Looks like a reference, but probably isn't: '599' on line 1011
'[500, 599]...'
-- Possible downref: Non-RFC (?) normative reference: ref. 'ISO10589'
The fact that idnits looks at everything enclosed in [] as a reference does not
mean the text requires revision.
Idnits also does not allow that a non-RFC document can be a normative reference
– but clearly ISO 10589 is a normative reference.
Thanx.
Les
From: Les Ginsberg (ginsberg)
Sent: Monday, June 11, 2018 10:00 PM
To: Uma Chunduri <umac.i...@gmail.com>; lsr@ietf.org
Cc: draft-ietf-isis-segment-routing-extensi...@ietf.org; lsr-cha...@ietf.org;
lsr-...@ietf.org
Subject: RE: draft-ietf-isis-segment-routing-extensions-16 - Shepherd review
comments
Uma –
Thanx for the prompt review.
I have attached proposed diffs to address some of your comments.
Additional responses inline.
From: Uma Chunduri <umac.i...@gmail.com<mailto:umac.i...@gmail.com>>
Sent: Monday, June 11, 2018 6:27 PM
To: lsr@ietf.org<mailto:lsr@ietf.org>
Cc:
draft-ietf-isis-segment-routing-extensi...@ietf.org<mailto:draft-ietf-isis-segment-routing-extensi...@ietf.org>;
lsr-cha...@ietf.org<mailto:lsr-cha...@ietf.org>;
lsr-...@ietf.org<mailto:lsr-...@ietf.org>
Subject: draft-ietf-isis-segment-routing-extensions-16 - Shepherd review
comments
Dear Authors,
I have done shepherd review of draft-ietf-isis-segment-routing-extensions-16
document as requested by LSR chairs. First, I would like to thank all the the
authors and contributors on this document.
I have few minor comments below and would be great if authors take a look at
these.
=====
A. I see few ID nits (comments and warnings). Please fix those.
B. For the record: (as this would come up soon) : Currently there are 8 front
page authors and please indicate why this document should be given exception
w.r.t 5 co-authors norm, that is being followed in general.
[Les:] This will be addressed after discussion among the authors – thanx for
the reminder. ☺
1. Abstract & Section 1
a.
"These segments are advertised by the link-state routing protocols (IS-IS
and OSPF)."
I see more than LSR protocols e.g.
https://tools.ietf.org/html/draft-ietf-idr-bgp-prefix-sid-07
Also not sure if this statement is necessary. Please either correct or
remove this.
[Les:] The abstract and introduction state “within IGP topologies”. In that
context I believe limiting the protocols mentioned to IGPs is appropriate.
b.
"Two types of segments are defined, Prefix segments and Adjacency
segments."
This document defines more than these two if you include Section 2.4
(SID/Label Binding TLV). Section 2 is much better
where all types in this document are described as well as
[I-D.ietf-spring-segment-routing] is referred for other types.
In that sense the above statement looks incomplete/repetitive.
[Les:] I have revised the text in this section – see attached diffs.
2. Section 2.1
a. "The 'Prefix SID' MUST be unique within a given IGP domain (when the
L-flag is not set)."
I see this is conflicting with what's been defined in
https://tools.ietf.org/html/draft-ietf-spring-segment-routing-14,
section 3.3 -
"Within an anycast group, all routers in an SR domain MUST advertise the
same prefix with the same SID value."
If you see otherwise please explain why?
[Les:] This is a misunderstanding on your part.
An anycast prefix may be advertised by multiple nodes, but the Prefix SID
associated with the prefix is the same regardless of which node advertises it.
So there is no contradiction/conflict here.
b. "A 4 octet index defining.."
What happens to the computed label value if the index is of 4 octets value? I
am asking this as index can have 4 octets but the eventual label (SRGB offset +
index) would be only 20 bits.
Can you point (if any) references to
https://tools.ietf.org/html/draft-ietf-spring-segment-routing-mpls appropriate
sections - is this is addressed there?
[Les:] See
https://tools.ietf.org/html/draft-ietf-spring-segment-routing-mpls-14#section-2.4
(emphasis added):
“ 0 =< I < size. If the index "I" does not satisfy the previous
inequality, then the label cannot be calculated.”
c. "A Prefix-SID sub-TLV is associated to a prefix advertised by a node and
MAY be present in any of the following TLVs:"
Nit: Perhaps the list should include Section 2.5 too.
[Les:] Added a reference to 2.5 as well. See attached diffs. Thanx.
3. Section 2.2.1
a. "F-Flag: Address-Family flag..."
Not sure why this has to do with encapsulation? What happens if native
IPv4/IPv6 data packet is using this SID with out any encapsulation? Could you
please clarify.
[Les:] When the packet is forwarded over the specified outgoing interface it
will either have an IPv4 encapsulation or an IPv6 encapsulation i.e., the
payload is encapsulated in the afi specific L3 protocol.
This does not mean that a new AFI specific header is imposed.
4. Section 2.2.2
a. Nit: V and L flags: Content is duplicated and perhaps it can instead refer
to section 2.2.1
[Les:] The text says:
“ where F, B, V, L, S and P flags are defined in Section 2.2.1.”
???
5. Section 3.2 and Section 2.1
Could you please clarify what is preferred if multiple prefix-sids with
different algorithm values are advertised for the same SID value?
[Les:] There is no “preference” here. In order to have algorithm specific
forwarding entries we MUST have different SIDs for each algorithm. A router
will use the SID which matches the algorithm associated with the forwarding
entry.
Les
--
Uma C.
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