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Question about LMp.21 in RFC3036

  • From: "James R. Leu" <jleu@mindspring.com>
  • Date: Wed, 23 Jan 2002 11:49:31 -0600
  • Cc: mpls@UU.NET
  • Organization: none

On Tue, Jan 22, 2002 at 08:25:22PM -0800, Zhun Jonathan Qiu wrote:
> Hi, there, I guess this may have been discussed before and if that's case please direct me
> to the thread.
> 
> In RFC3036, A.1.2 (Receive Label Mapping), when we reach LMp.21, we should have failed the
> check in LMp.18, i.e. LSR has NOT previously sent a label mapping for FEC to the peer. So
> at this point "PrevAdvLabel" should be undefined. Then how can LMp.21 uses it as a
> parameter to "Send_Message"?
> 
> Do we need to allocate a new label and advertise at this point?
> 
> I think I must be missing something obvious. Please help me out then. Thanks a lot!
> 

My interpretation is:

An LSR may have advertised a label for this FEC to another peer.  In which 
case the LSR can advertise the same label or advertise another label and 
merge the two.

In other words the check in LMp.18 has nothing to do with 'PrevAdvLabel'.

Jim

> Regards,
> Jonathan Zhun Qiu

-- 
James R. Leu