Subject: [mpls] wg last call for "LDP extension for Inter-Area LSP"

From: Loa Andersson <[email-masked]>
Date: Wed, 06 Feb 2008 18:07:51 +0100

Working Group,

this is to initiate a working group last call on

"LDP extension for Inter-Area LSP"
http://www.ietf.org/internet-drafts/draft-ietf-mpls-ldp-interarea-02.txt

The working group last call will end on eob February 21st. Please send
your comments to the working group mailing list.

Loa and George

-- 
Loa Andersson

Principal Networking Architect
Acreo AB                           phone:  +46 8 632 77 14
Isafjordsgatan 22                  mobile: +46 739 81 21 64
Kista, Sweden                      email:  [email-masked]
                                            [email-masked]
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From: Yakov Rekhter <[email-masked]>
Date: Thu, 07 Feb 2008 05:58:50 -0800

Loa,

> your comments to the working group mailing list.

Support.

Yakov.

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From: <[email-masked]>
Date: Thu, 7 Feb 2008 15:19:39 +0100

Support.

Christian.

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From: Kireeti Kompella <[email-masked]>
Date: Sat, 9 Feb 2008 14:42:05 -0800 (PST)

> your comments to the working group mailing list.

support.

> Loa and George

Kireeti.
-------

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From: "Vishwas Manral" <[email-masked]>
Date: Sun, 10 Feb 2008 12:17:17 -0800

Hi,

I just looked at the document. I find a few issues.

The document in the introduction section still talks about Host
Address FEC element, even though the same has been removed from
RFC5036.

The introduction quote seems to be from RFC3036 and not RFC5036.

The whole document seems to be written with IPv4 in mind. We talk
about /32 prefix etc in the whole document. Check the "Problem
Statement" section.

The document talks about IGP route leaking and the problems associated
with it. However even now in OSPF we already inject all ASBR Router
ID's Inter Area (loopback IP address as the Router ID) and the summary
information is injected Inter Area(though as summary ASBR LSA and not
Summary type-3 LSA) so it is not as much overload as it might seem
from the document. We could have used Host Address FEC element in this
case, however that has been deprecated.

Some typos

s/MPLS connectivity (ie an LSP) / MPLS connectivity (i.e. an LSP) /
s/reduces the Linkstate database / reduces the link state database /
s/distributed in an ordered way.. / distributed in an ordered way./

Thanks,
Vishwas

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From: "Vishwas Manral" <[email-masked]>
Date: Tue, 12 Feb 2008 17:48:09 -0800

Reforwarding to the authors of the document as I have not got a reply for 3 days

Hi,

Some typos

Thanks,
Vishwas

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From: <[email-masked]>
Date: Wed, 13 Feb 2008 09:39:44 +0100

Hi Vishwas,

Thanks for your review of the draft and your comments.

> The introduction quote seems to be from RFC3036 and not RFC5036.

Agreed. Correction done.

> about /32 prefix etc in the whole document. Check the "Problem

OK.

First occurrence is changed 
from: "the exact (/32 for IPv4) loopback addresses" 
into: "the specific (e.g. /32 for IPv4) loopback addresses"

Others occurrences are changed from "/32" into "specific"

Except in the examples section (§6.1) where the use case is IPv4 only.

Is this fine for you or would you prefer an additional sentence stating that the document is also applicable to IPv6?

> case, however that has been deprecated.

From a general standpoint, OSPF can perform route summarization. Detailed OSPF machinery is network design specific (e.g. the kind of area used such as standard/stub/totally stubby...). 
In addition, from an IP RIB/FIB perspective, general considerations as to whether redistributing specific routes or performing route summarization is not specific to a routing protocol. The draft reference RFC 2966 which adequately discusses the pros and cons of distributing specific addresses versus aggregate ones. 

> s/distributed in an ordered way.. / distributed in an ordered way./

Done.

Thanks,
Bruno

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From: "Raveendra Torvi" <[email-masked]>
Date: Wed, 13 Feb 2008 11:19:58 -0500

Hi,

I have couple of points on the section below
7.2. Impact on routing convergence time
"The solution documented in this draft reduces the Linkstate database

   size and the number of FIB entries. However, it does not decrease the

   number of LFIB entries."
[...]

Imo, the solution documented in this draft by itself does not reduce the
linkstate database and FIB entries, it is reduced by route summarization
procedures of IGP, so above text needs rewording.

I also want to know author's opinion regarding combining LDP Fec Aggregation
idea, so that all the inter-area scalability concerns are addressed
comprehensively in one draft, reducing LFIB entries is also very important
for MPLS convergence.

Ravi.

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From: "Vishwas Manral" <[email-masked]>
Date: Wed, 13 Feb 2008 19:28:51 -0800

Hi Bruno,

Thanks for making all the changes.

Instead of specific you could use the term "more specific".
> document is also applicable to IPv6?
I would say you could actually specify in the beginning that the same
mechanism will work for both IPv4 as well as IPv6.

The draft looks good otherwise (it does save a few routing entries).
However in the case of PE to PE communication like we talk about, we
could do things more intelligently by using the summary ASBR route
which is anyway propagated in OSPF - (so a direct OSPF to LDP checking
instead of the LDP to RIB mapping). This however will work only in
case of PE routers (ASBR's) and not general aggregation case.

Thanks,
Vishwas

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From: <[email-masked]>
Date: Thu, 14 Feb 2008 15:42:56 +0100

Hi Vishwas,

> > Is this fine for you or would you prefer an additional sentence
stating that the
> > document is also applicable to IPv6?

Done.

Added: "It is applicable to IPv4 and IPv6 prefix FEC elements (addresses
families 1 and 2 as per [ASSIGNED_AF])."

(In section 5 "Label Mapping Procedure", following "This document
defines a new label mapping procedure for [LDP].")

> case of PE routers (ASBR's) and not general aggregation case.

Besides, this would be specific to OSPF whereas currently LDP is not.

Thanks,
Bruno

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From: <[email-masked]>
Date: Thu, 14 Feb 2008 16:16:51 +0100

Hi,

> De Raveendra Torvi
> Imo, the solution documented in this draft by itself does not reduce the linkstate database and FIB
> entries, it is reduced by route summarization procedures of IGP,

Agreed.

> so above text needs rewording.

Well, full wording would be something like: "The solution document in this draft, allows the (re)use of route summarization in the IGP. As a result this reduces the link state database size and the number of FIB entries."

Agreed the sentence is a short cut, but this point has been discussed in the sections 3 and 4 of the draft. So IMO, it doesn't need to be explained again at the end of this short draft. Yet, if you have a strong opinion on this, I can make the above change.

> I also want to know author's opinion regarding combining LDP Fec Aggregation idea, so that all the
> inter-area scalability concerns are addressed comprehensively in one draft reducing LFIB entries is also very important for MPLS convergence.

I'm not in favor of combining the two drafts:
First, both drafts are in different stages. This draft is a straightforward protocol extension which has been discussed in the MPLS WG for nearly three years. We believe it is ready and I don't see what we would gain in delaying the work any further.
Second, these are two different solution space: flat versus hierarchy. We can't really combine both. Combining would mean that a document would actually specify two solutions. As a (negative) consequence, two routers complying with such document could in fact be non-interoperable.

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From: "Vishwas Manral" <[email-masked]>
Date: Thu, 14 Feb 2008 08:44:18 -0800

Hi Bruno,

>  Besides, this would be specific to OSPF whereas currently LDP is not.
I agree the solution you give works for more use cases. However for
the MPLS-VPN case the solution I am talking about would make an easier
change (treat ASBR addresses - got through Summary ASBR LSA's - just
like we treat routes),

Thanks,
Vishwas

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From: Loa Andersson <[email-masked]>
Date: Sat, 23 Feb 2008 09:03:02 +0100

All,

this working group last call has ended. There have been comments,
could the authors review and respond to the comments, when the new
ID is submitted please also make sure it passes the ID-nits tool
cleanly.

/Loa

-- 
Loa Andersson

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From: <[email-masked]>
Date: Tue, 26 Feb 2008 11:03:34 +0100

Loa, George, all,

The draft has been updated to address the comments received, as per the discussions on the mailing list:

http://www.ietf.org/internet-drafts/draft-ietf-mpls-ldp-interarea-03.txt

Bruno

> -----Message d'origine-----
> De : Loa Andersson [mailto:[email-masked]]
> Envoyé : samedi 23 février 2008 09:03
> À : [email-masked]; George Swallow; Ross Callon; David Ward; DECRAENE Bruno RD-
> CORE-ISS; LE ROUX Jean-Louis RD-SIRP-LAN; Ina Minei
> Objet : wg last call ended:Re: [mpls] wg last call for "LDP extension forInter-
> Area LSP"
> 
> All,
>