The MPLS WG Archive

["Choudhury, Sanjaya" <Sanjaya.Choudhury@marconi.com>]

Hi Tom! This is a follow-up question based on your reply.
In your reply, you pointed-out "the XCindex notes the 
"group" of LSPs used for the tunnel". 

If this was the main reason for having the mplsXCIndex in
the mplsXCTable, then I might have mis-interpreted the MIB
definitions related to the mplsXCTable. I will appreciate,
if you can clarify the following.

Given the following context:
---------------------------
(1) mplsLspId is not a part of the index into the mplsXCTable
and is optional for implementation [LSR-MIB mplsXCTable 
definition and conformance statements]

(1) "It supports point-to-point, point-to-multipoint and
multipoint-to-point connections" [mplsXCTable description,
in LSR-MIB]

(2) "mplsTunnelTable does not define the in and out segments
   forming the tunnel.  Instead, these are defined by creating
   rows in the in-segment and out-segment tables, defining
   relationships in the cross-connect table and referring to
   these rows in the mplsTunnelTable using a cross-connect
   index, mplsTunnelXCIndex. These segment and cross-connect
   related objects are defined in LSRMIB." [MPLS-TE-MIB Section
   6.1]

(3)"Uniquely identifies an instance of a tunnel. It is
    useful to identify multiple instances of tunnels
    for the purposes of backup and parallel tunnels." [Description
    of mplsTunnelInstance in MPLS-TE-MIB]

I interpreted the following statement:
-------------------------------------
"-cross-connect index mplsXCIndex that uniquely identifies
  a group of cross-connect entries" [Description in the   
  mplsXCEntry]

as:
---
(a) cross-connect index mplsXCINdex uniquely identifies a group of 
    cross-connects entries, that belong to the __same LSP___.
    [NOT a group of independent LSPs, as you pointed out in your
    reply.] 

(b) The main (and only) reason for having the mplsXCIndex, is to 
    represent a LSP (inside the switch)with different cast types: 
    point-to-point point-to-multipoint and multipoint-to-point.
   
(c) mplsTunnelXCPointer is used to associated a particular LSP 
    with the mpls tunnel defined in the mplsTunnelTable.

(d) Parallel tunnels are abstracted in mplsTunnelTable using the
    mplsTunnelIndex and mplsTunnelInstance.

Please correct me, if I mis-interpreted the MIB. 

Thanks,
sanjay	



-----Original Message-----
From: Thomas D. Nadeau [mailto:tnadeau@cisco.com]
Sent: Friday, February 09, 2001 10:41 PM
To: Filipe Miguel Sousa; mpls@UU.NET
Subject: Re: Draft IETF MPLS TE MIB 05 usage question: Tunnel Table



>Question about the mplsTunnelXcPointer Object.
>
>Can someone clarify me on this issue?
>
>In the MPLS TE MIB the mplsTunnelTable as the
>mplsTunnelXcpointer. This object points to a row in the mplsXCTable
>in the MPLS LSR MIB. My question is how the MPLS TE MIB as all
>the XCsegments used by this tunnel if this pointer only points to
>one row in a specif mib?

         I think that you could be asking two things above, so
I will try to answer both questions. First, the XCindex is
the major index for associated cross-connects on that
particular LSR in the LSR MIB. If there are parallel links
for example, then the XCindex notes the "group" of
LSPs used for the tunnel. If you are asking why the totality
of cross-connects (i.e.: throughout the network) is not
available at the head-end LSR, then this is simple: because
you need to go hop-by-hop checking the LSR MIB along the
way.

         --Tom