Subject: Re: [mpls] I-D Action: draft-ietf-mpls-tp-te-mib-00.txt

From: venkatesan mahalingam <[email-masked]>
Date: Sun, 14 Aug 2011 22:49:23 -0400

Spike,

Thanks for reviewing the draft. Please find below the responses
inlined with the tag VM>>

Thanks,
Venkat.

From: Spike Curtis [[email-masked]]
Sent: Monday, August 08, 2011 2:55 PM
To: [email-masked]
Cc: [email-masked]
Subject: RE: [mpls] I-D Action: draft-ietf-mpls-tp-te-mib-00.txt

Hi Venkat & all,

I’ve read the draft and have a question and then some comments.  I’m
happy to be of assistance with any of what follows, and/or with
working on other MIB drafts that we need to fill out the gaps
identified in draft-ietf-mpls-tp-mib-management-overview.

MPLS-TP Identifiers:
I understand that one of the purposes of this draft is to allow
configuration using MPLS-TP identifiers.  Presumably, there are at
least three ways this could be accomplished:

1.     Define a brand new tunnel table for MPLS-TP, based on the
mplsTunnelTable, but with the MPLS-TP identifiers as indices.

2.     Redefine the existing mplsTunnelTable indexing, adding GlobalID
and ICC for ingress and egress nodes, and using 0 as “not used” values
to allow back-compatibility.

3.     Create a separate set of tables which maps the old identifiers
to the new MPLS-TP identifiers.
This draft takes the third strategy, but it’s not immediately clear to
me why this is preferable to the other two. (2) seems the least
complicated because it does away extra mapping and inverse mapping
tables.  It’s also difficult to guarantee that local identifiers
(which don’t have configuration or signalling significance) will not
change in the case of graceful restart or configuration replay.  Was
option (3) chosen to avoid back-compatibility issues, or for other
reasons?

VM>> As replied by Tom, we reuse the existing mplsTunnelTable for
bidirectional tunnel extensions also without affecting the backward
compatibility.

A comment on tunnels:
I’d like to clarify how unidirectional, associated bidirectional and
co-routed bidirectional paths are modelled in the MIB, and how exactly
the MPLS-TP identifiers for the Tunnel_IDs and LSP_IDs map onto MIB
fields.  My preference is as follows.

·         Unidirectional LSPs in MPLS-TP are very similar to “normal”
MPLS, but with different identifiers.  Tunnels of this type do not
have any entries in the mplsTunnelExtTable.

VM>> Yes, this is how the tables are designed in the draft.

·         In associated bidirectional LSPs, the transport directions
are set up and monitored independently, so each transport direction
should be a separate row in the mplsTunnelTable.

VM>> Yes, this is how the tables are designed in the draft.

·         In co-routed bidirectional LSPs, both transport directions
are set up and monitored together.  This means we should have only one
row in the mplsTunnelTable to represent a tunnel of this type.  This
is not how the draft is currently structured, where the example in
Section 9 creates two rows in the mplsTunnelTable.

VM>> Thanks for pointing out this issue. We will update the draft with
the required changes in the next version.

About gaps:
Lastly, I think the MIB is still missing some configuration that we’ll
need in order to satisfy MPLS-TP requirements.  These include

·         Bidirectional tunnels with asymmetric resource requirements
VM>> We will address this requirement in the next version.

·         OAM configuration.  Presumably this will be a reference to
yet-to-be-defined OAM MIBs so that tunnels can be easily assigned OAM
profiles.

VM>> Please refer the draft
http://tools.ietf.org/html/draft-vkst-mpls-tp-oam-id-mib-00 for more
information.

Let me know if I can be of further assistance.

VM>> Thanks for your help. If time permits, please review the TP OAM
identifier draft also and post the comments on MPLS WG mailing list.

Cheers,
Spike

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________________________________

A New Internet-Draft is available from the on-line Internet-Drafts
directories. This draft is a work item of the Multiprotocol Label
Switching Working Group of the IETF.

       Title           : MPLS-TP Traffic Engineering (TE) Management
Information Base (MIB)

       Author(s)       : Venkatesan Mahalingam

                         Kannan KV Sampath

                         Huawei Technologies

                         Thomas D. Nadeau

       Filename        : draft-ietf-mpls-tp-te-mib-00.txt

       Pages           : 39

       Date            : 2011-06-17

  This memo defines a portion of the Management Information Base (MIB)

  for use with network management protocols in the Internet community.

  In particular, it describes managed objects of Tunnels, Identifiers,

  Label Switch Router and Textual conventions for Multiprotocol Label

  Switching (MPLS) based Transport Profile (TP).

A URL for this Internet-Draft is:

http://www.ietf.org/internet-drafts/draft-ietf-mpls-tp-te-mib-00.txt

Internet-Drafts are also available by anonymous FTP at:

ftp://ftp.ietf.org/internet-drafts/

This Internet-Draft can be retrieved at:

ftp://ftp.ietf.org/internet-drafts/draft-ietf-mpls-tp-te-mib-00.txt

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