Subject: loop detection and label mapping procedures

From: Jhilmil Kochar <[email-masked]>
Date: Thu, 09 Mar 2000 14:53:20 +0530

Hi,

    I am facing a small issue in the LDP draft. The LDP -06 draft talks
about  loop detection in label mapping message in DoD mode in the
following possible ways -
1. sec 2.8.2 says that if R has detected a loop in a label mapping
message it should respond to the downstream with a notification with
loop detected status code and drop the label mapping message.
2. Appendix A.1.2 receive label mapping procedures indicate that the
loop detected notification must be sent (LMp.3, check received
attributes procedure) followed by label release message (LMp.8).
3. The notes following the same Appendix points out that the LSR "should
simply release the label".

What is being tried to achieve here is that the downstream LSR must
realize that the mapping message it sent across created a loop and also
it needs a label release message so that it can free up the resources
acquired by the cross connect. The draft also does not talk about how a
downstream LSR should behave on receiving a loop detected notification
after having sent a mapping.

Instead of sending multiple messages/ or sending one message that does
not give the complete indication; the same thing can be achieved in a
different way. The upstream LSR on detecting a loop in label mapping
message must send a label release message only which must also carry a
status tlv indicating loop detection. This serves both purpose in a
single message and the downstream LSR realizes that it created a loop
and it must release the resources.

This approch is already followed in CRLDP draft (sec 4.3.2.2) when a
release is sent with an indicative status code.

regards
Jhilmil

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Jhilmil Kochar
Ficon Technology
E-mail:[email-masked]
Web: www.ficon-tech.com