Subject: RE: Queries regarding LMP.

From: "Martin Dubuc" <[email-masked]>
Date: Wed, 25 Jul 2001 11:58:31 -0400

Q1) a) & b) LMP is useful for auto-discovery of links and monitoring of
control and data link health. To determine whether LMP is useful or not,
one has to look at the operational aspect of product deployment and
maintenance, i.e. what tools the vendor wants to implement to facilitate
provisioning and maintenance of their customers network. In a small
network, a vendor may be able to get away with manual configuration of
links. In an opaque network, it is also easy to pinpoint link failures.
However, in a truly optical network, there needs to be mechanisms to
isolate faults (which LMP provides).

Usefulness of LMP is not directly tied to use of link bundles. Link
bundles are mostly used to reduce the flooding of link information
generated by the routing protocol.

Q3) Destination address can be multicast or any valid IP address of
destination node (most likely the NodeID of the destination node).

-----Original Message-----
From: rajesh [mailto:[email-masked]]
Sent: Wednesday, July 25, 2001 1:59 AM
To: [email-masked]; [email-masked]; [email-masked];
[email-masked]
Subject: Queries regarding LMP.

Hi,

     Have a few queries regd LMP.

Q1)  Regd the applicability of LMP...

draft-many-gmpls-architecture-00.txt states that

"   For instance, the traditional IP routing model assumes the
   establishment of a routing adjacency over each link connecting two
   adjacent nodes. Having such a large number of adjacencies is not
   scalable at all. Each node needs to maintain each of its adjacencies
   one by one, and link state routing information must be flooded in
   the topology for each link.

   To solve this issue the concept of bundling was introduced.
   Moreover, the manual configuration and control of these links, even
   if they are unnumbered, becomes totally impractical. The Link
   Management Protocol (LMP) was specified to solve these problems. "

a) Can one assume that LMP makes sense ONLY in the case of a large
     number of parallel links and link bundling...

      and an implementation of GMPLS neednot have LMP if no link
      bundling is used ??

      The above maybe the case when using lower end SONET ADM,
       DXCs...

b) Under what other conditions would one require LMP (ie other than
      link bundling) ?

Q2) Suppose one does NOT need to use LMP but then one needs to use
         OSPF extensions to support TE
(draft-kompella-ospf-gmpls-extensions-01.txt) ,

        then one may need to do a  correlation of Link Ids between 2
TE nodes.

       a) Is there a standard recommended way to do this correlation ??

             E.g OSPF - Link Local Signaling
                    or OSPF - link scope LSA ?

Q3) Section 9 of draft-ietf-mpls-lmp-02.txt   says that LMP messages
         are encoded as IP packets and also suggests protocol number
140.

          What would be the destination IP address of an LMP packet ??

           A multicast or is it got from an IGP ??

Q4) In LMP, if a Link Id correlation has been done,  and If the link ids

         on one of the ends or both change... How is this change taken
into
         account ??

         Eg for i = 1,2
                          Port i, Node 1 connected to Port i, Node 2

          If one interchanges the connection then one has to recorrelate

           the Link Id mappings..

Thanks in advance,
Rajesh

---

From: Zhi-Wei Lin <[email-masked]>
Date: Wed, 25 Jul 2001 12:34:38 -0400

Hi Martin, comments in-line

> isolate faults (which LMP provides).

When you say "truly optical network", do you mean a network that has no
O/E/O (no 3R) at all? or is there some 3R at the edge?

As for mechanisms to isolate faults, I think this capability is already
part of networks. For example, SONET has mechanisms such as trace
identifiers, AIS/RDI signals, and tandem connection points for doing
this. OTN (G.709) also has these defined. In addition, OTN has defined 6
flexible layers for TCM and 2 fixed layer for TCM (section and path). 

I think LMP is not necessary for fault isolation, but it could be
another mechanism that may be used (if one so chooses).

---

From: Suresh Katukam <[email-masked]>
Date: Thu, 26 Jul 2001 10:53:58 -0700

Rajesh,

> If it is the Node ID of the neighbour then how does one find it
> without manual configuration ?? Is it with the help of an IGP
> such as OSPF ? We would like to automate things as much as
> possible.

Initial Config message will go out on a multicast address. 
This makes it easy for initial communication.

All other messages will be addressed to Node ID. 
Section 9 of OIF2000.125.5. clairifies this issues. 

This may change again if Node ID is
not be a routable IP address. It should be really the source
IP address of the Config message to whom you should send
your LMP messages.

Thanks,
Suresh

> 
> If LMP is designed as an independent protocol then IMHO
> we should use a multicast address.
> 
> Regds,
> - Rajesh

---

From: rajesh <[email-masked]>
Date: Thu, 26 Jul 2001 16:13:45 +0530

Regds,
- Rajesh