Subject: [mpls] AD review of draft-ietf-mpls-in-udp-09

From: Alia Atlas <[email-masked]>
Date: Mon, 22 Dec 2014 14:07:53 -0500

As usual, I have done my AD review of this draft before progressing it to
IETF Last Call.  I have a few minor comments, as given below, but nothing
that prevents my requesting an IETF Last Call now.  Due to the holidays, I
will ask for that to end about Jan 12.

Thanks very much for the hard work on this draft - finding a good way
forward that clearly articulates the trade-offs and considerations wasn't
easy.

Please address my comments along with IETF Last Call concerns.

Minor comments:

1) In the abstract, "MPLS-in-UDP is primarily applicable to service
provider networks"  but when this was first discussed, at least, I believe
it was targeting data center networks also.  Has that changed?

Similarly in Sec 1.3, it says "The MPLS-in-UDP encapsulation technology
MUST only be deployed within a Service Provider (SP) network..."  I
certainly agree that it shouldn't escape into the open Internet, but am
concerned that the applicability doesn't also apply to data-center
networks.

Sec 3.1 is also focused on service provider networks, though at least
corporate networks are mentioned.

2) In Sec 3.1, it says "This check will often be part of the MPLS LSR
forwarding logic, but MUST be scoped to the specific tunnel."  I do not
understand what this scoping means?  The MPLS labels are frequently
per-platform, though of course context-labels and per-interface labels are
also used.  For the per-platform labels, is new behavior expected???

3) In Sec 4, it says:
"That is to say, if the destination IP address is a multicast address, the
top label SHOULD be upstream-assigned, otherwise if the destination IP
address is a ..."   This seems to require that the IP network is capable of
supporting multicast where one can easily see using MPLS-in-UDP tunnels to
provide point-to-point tunnels.  Is there a reason that the negotiation
mechanism to set up the MPLS-in-UDP tunnel wouldn't also be able to specify
alternate destination IP addresses for upstrteam-assigned?  How much
discussion and agreement has this limitation had??

4) I notice a difference in the applicability statement and Sec 5.  In the
former, no use of MPLS-in-UDP on the general Internet is allowed, but in
the latter, if the MPLS has only congestion-controlled traffic, then it is
permitted.  Given the current agreed text in Sec 5, perhaps an additional
sentence in Sec 5 along the lines of

"Despite this discussion of which MPLS traffic may be congestion-controlled
for network deployment considerations, as previously specified in Sec 1.3,
the MPLS-in-UDP encapsulation technology MUST NOT be used across the open
Internet."

Thanks,
Alia