[mpls] draft-ietf-idr-eag-distribution-05.txt

[Robert Raszuk <[e-mail]>]

/* While the draft is in IDR I am adding MPLS WG here as the discussion is
really about MPLS-TE and not BGP */

Hi,

I looked at draft-ietf-idr-eag-distribution-05.txt and would like to share
few comments on it.

The draft defines extension to BGP-LS in order for the node to signal
extended admin groups of a links in the TE domain relaxing the current
limit of 32 bits.

Observations:

1. Is the draft only applicable to MPLS-TE or also to SR networks ? If the
latter the title needs to be changed.

2. While it is usually considered good to have more then less of anything
let's look at the bigger picture and the consequences of this proposal in
respect to its current applicability of MPLS-TE:

Signalling of 32 affinity bits of the link is just a tiny piece of the full
picture. In MPLS-TE networks those bits are signaled in SESSION_ATTRIBUTE
of RSVP-PATH msg as defined in RFC3209 section 4.7

Signalling more then 32 bits will just not fit the current space hence
fundamental set of RSVP-TE (aka MPLS-TE) operation are broken.

Likewise most of the CSPF implementations would also need to modified to
accomodate for BGP signalled extened affinity bits.

IMO if there is real need to have more then 32 admin groups per link in a
TE domain the right process would be to extend IGP as well as RSVP-TE RFCs
for it.

Moreover as we know RSVP-TE or SR-TE while can steer packets via
constrained paths do not guarantee any interface level reservations or
packet prioritization. Those are control plane driven features.

As such one could also notice that with the extened set of link affinity
classes there is real need to also extend QoS of each network element to
offer more then 32 diffserv classes. Otherwise in the event of congestion
it is likely that packets assumed to be classified into one admin group
will likely compete for bandwith in the same queue with packets classified
into different group.

So while I do not have concerns to define such TLV in BGP-LS I do have
bigger picture observations which I believe need to be addressed and need
to become formal references in this document before we proceed on it in IDR
any further.

Cheers,
Robert.