Subject: Doubt in cr-ldp Release meaage

From: "gopinathg" <[email-masked]>
Date: Mon, 25 Jun 2001 23:05:51 +0530

Hi All

     What to do in cr-ldp If a release mesage contains a wild card FEC and
LSP-ID ? ie release message with no Label TLV.
Do we need to get the label using the LSP-ID and apply the same procedure as
for the wild card FEC & Label ?

Please Correct If I am wrong ....

Thanks In Advance

Gopinath.G.S
HCL Technologies
CHENNAI  600 006

http://www.hcltechnologies.com
Ph work: +91-44-8291735/36/37 ext-629
Ph Res  : +91-44-8292491

---

From: Eric Gray <[email-masked]>
Date: Mon, 25 Jun 2001 15:14:15 -0400

Gopinath,

    CR-LDP relies on Label Release processing as defined in RFC 3036.
Section 3.5.11.1 (of RFC 3036) says on this subject:

   "The FEC TLV may contain the Wildcard FEC Element; if so, it may
   contain no other FEC Elements.  In this case, if the Label Release
   message contains an optional Label TLV, then the label is to be
   released for all FECs to which it is bound.  If there is not an
   optional Label TLV in the Label Release message, then the sending LSR
   is releasing all label mappings previously learned from the receiving
   LSR."

Inclusion of the LSPID TLV was intended to be a potential optimization
that might be used by some LSRs to more quickly recover the state block
for the LSP.  This 'optimization' is not likely to be useful at any LSR
other than the one that assigned the LSPID (the LSP ingress).  It is
explicitly not intended to replace the Label and FEC in the standard LDP
Label Release message since an LSR that did not keep the LSPID as part
of its LSP state would be unable to recover information about the LSP to
be released.  The LSPID is only useful at LSRs with local repair capability
(i.e. - those 'terminating' a loose hop or those adjacent to an abstract
node).  Therefore, inclusion of an LSPID TLV with a wildcard FEC and no
Label TLV is likely to be an error; it can only be reliably handled using
basic LDP procedures.  In other words, considering only the FEC and Label
and releasing ALL labels distributed by the downstream LSR peer.

--
Eric Gray