Re: [Idr] AD Review: draft-ietf-idr-ls-distribution

"Adrian Farrel" <> Tue, 29 September 2015 16:49 UTC

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From: "Adrian Farrel" <>
To: "Alia Atlas" <>
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Date: Tue, 29 Sep 2015 17:48:59 +0100
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Subject: Re: [Idr] AD Review: draft-ietf-idr-ls-distribution
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Hi Alia,
Since the thing that triggered you to send this mail was me investigating the
status and promising to pick up the comments, I think you can rely on the emails
getting answered soon.

From: Alia Atlas
Sent: 29 September 2015 15:35:24 (UTC) Dublin, Edinburgh, Lisbon, London
To:; idr@ietf. org
Subject: Re: AD Review: draft-ietf-idr-ls-distribution
It has been about 6 months since I did my review of
and I don't see the comments addressed in draft-ietf-ls-distribution-11.
Of course, Alvaro is now the responsible AD for IDR - and may have his own
comments as well.
It's very sad when a draft is held up for this long due to editors' not
None of my comments were blocking issues, which is why I was willing to run
the IETF Last Call in parallel, but I did and do expect a response.
On Wed, Mar 18, 2015 at 12:43 PM, Alia Atlas <> wrote:
As is customary upon receiving a publication request, I have done my AD review
of draft-ietf-idr-ls-distribution.  First, thanks for the hard work on this very
useful and non-trivial specification.  Second, I have found a number of
clarifications and issues that I would like to see resolved in the draft.
I will start an IETF Last Call so that you can get additional comments in
parallel.  Because of the upcoming IETF, I expect this to run longer - ending
April 8.  
1) In Sec 3.2, 3rd paragraph last sentence, it says:
"This is done as specified in [RFC4760], by using capability code 1
(multi-protocol BGP), with an AFI 16388 / SAFI 71 and AFI 16388 / SAFI TBD for
the VPN flavor."   Could you please turn this into non-colloquial language with
clear requirements language?  Can one support "the VPN flavor" but not the
2) On p. 9, the Route Distinguisher is introduced and its length is included -
but no reference is given nor length specified.  Could you please provide both?
3) In Sec 3.2.1, second paragraph, it says "We use Autonomous System (AS) Number
and BGP-LS Identifier (Paragraph 2) in order to disambiguate the Router-IDs, as
described in Section"
I suspect that "Paragraph 2" is intended to refer to the last paragraph on p. 11
- but that isn't a clear way to reference it; also the Identifier is not
referred to as a "BGP-LS Identifier" but merely an Identifier.  Also, instead of
"we" perhaps "BGP-LS".
4) In Sec 3.2.2, I see that link descriptors are actually only a unidirectional
representation.  Could you please mention this when the link NLRI is introduced?
5) In the NLRI format, I see a 64 bit identifier. From the discussion (last
paragraph in p. 11), it looks like this 64-bit identifier is intended to be the
5-bit "Routing Universe Identifier" which is supposed to indicate the protocol
plus routing instance???
5) In Sec I see the OSPF Area-ID listed.  How are IS-IS levels handled?
I see the Node Attribute TLV (1027) but this seems to require that a link would
have to have its remote and local nodes looked up to find the associated IS-IS
Area Identifier.  What would be actually really useful is to describe, in the
introduction, the different handling for IS-IS and OSPF in the encapsulations
and why they differ.  
6) In Sec 3.2.2  3rd from last paragraph:  Can both IPv4 AND IPv6 addresses both
be included in the link descriptor?  Presumably the same logic that prevents the
link local/remote identifiers from being included would apply?  Also, why are
the neighbor addresses included for the Link Descriptor when the remote node's
descriptor should already be in the Remote Node Descriptor?  
7) In Sec  It says "The OSPF Route Type field values are defined in the
OSPF protocol, and can be one of the following".  Could you please add a
reference to which version of OSPF and what field you are describing?  I suspect
it is the LSA types and they are different values between OSPFv2 and OSPFv3.
This section could benefit from some clarity.
8) In Sec  Please add a reference and describe what an "Area Identifier
(variable)" is.  
9) Sec  I like the idea of this - but an example or two in terms of
encoding/parsing would be useful.  You have a couple pointers - but it could use
another level of explanation.
10) Sec  I am not clear what the rationale for deciding what protocols
to include here is.  For instance, is mLDP considered a different protocol or a
subset of LDP?  I would like to see a short paragraph discussing how this
information might be used or what criteria would be applied to decide if another
protocol should be added.  8 bits is a pretty small space...
11) Sec  " If a source protocol (e.g. IS-IS) does not support a Metric
width of 32 bits then the high order octet MUST be set to zero."   Surely you
mean that if the source protocol supports a metric width shorter than 32 bits,
then the metric is placed in the bottom of the word and the high order bits from
the supported metric width to 32 MUST be set to 0.  As written, it assumes that
any source protocol that doesn't support 32 bits of metric must support exactly
24 bits.
12) Sec  Please correct the sentence that claims "Note that there is no
SRLG TLV in OSPF-TE".  A simple browsing in the IANA registry
ml#subtlv2 ) clearly shows it defined:

Shared Risk Link Group (variable)
[RFC4203 <> ]
13) Sec  How large are the bit fields that are mashed together from
IS-IS and OSPF to form the IGP Flags TLV?  Can you please add some guidance on
when new flags should be allocated?
14) Sec and Sec  Please add a reference for OSPF TAGs.
draft-acee-ospf-admin-tags-01 seems to be the corresponding one.  I think that
the reference can be Informational.
15) Sec  The reference to RFC5305 is, I presume to Section 4.  That
would be useful to clarify since it isn't easy to find.  Similarly, where does
the information come from in OSPF?  Could you please add a reference?
16) Sec 3.5:  Can you please provide more guidance here around what Protocol-ID
to use for inter-AS links - particularly if they are not in the IGP?  Are there
any issues around the Protocol-ID implying the format for data that an inter-AS
link might have? 
17) Sec 5 IANA Considerations:  There are several fields (i.e. MPLS protocols,
IGP Flags, etc) that are not included in the IANA Considerations.  The authors
and document shepherd should go through and describe how each field that is not
managed by IANA would have additional values added - or whether that isn't
expected and why.
18) Sec 6.2.1:  I assume that by "does not mandate", the authors mean "we're not
doing it now"?  It's clearly absurd and ludicrous to think that BGP-LS wouldn't
need some type of extensions - whether that is topology-related YANG models or
something else.  Please figure out what you want to say other than "someone
else's problem" and put it in here.
Thanks again for the hard work so far,