Subject: One doubt about CR_LDP-02

From: Prosenjit Pal <[email-masked]>
Date: Wed, 15 Sep 1999 10:11:50 +0530

Hi,

   Can anyone please clarify this doubt?

1. cr-ldp-02 draft : section 3.2 (Label Request Message)
it is said that "if any of the CR-TLVs is included in the Label
Request Message", "only a single FEC-TLV may be included in the 
Label Request Message".

2. ldp-05 draft : section 3.4.1 (FEC TLV)

it is said that multiple FEC elements can be included in a single
FEC TLV only in case of label mapping messages.

Above two implies that only a single FEC element can be there in CR-LSP
Label Request Message.

3. cr-ldp-02 draft : section 3.2
"The CR-LSP FEC TLV should be used." This FEC TLV is defined in section
4.10
of the same draft as one with an CR-LSP FEC element.

=> In CR-LSP label request message, I can have only CR-LSP FEC TLV
element.

This is fine if I am having ER-TLV in the label request message. But
since
ER-TLV is optional in label request message, how do I carry information 
about the destination if ER-TLV is absent in CR-LDP label request
message?

WIth regards,
Prosenjit Pal
XYLAN Development Centre Pvt. Ltd.  
(An Alcatel Company)
Suryodaya Complex, 4th Floor        
7, Airport Road, Kodihalli, Bangalore 560008                    

voice : +91-80-5097607/8 Extn. 109
email : [email-masked]

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From: "Srinivasan.E.S" <[email-masked]>
Date: Wed, 15 Sep 1999 11:02:06 +0530

Prosenjit,

     In accordance with the current draft of LDP (Ldp-05), only a single
FEC element is allowed in the label request messsages. (Drafts upto Ldp-03
provisioned the use of multiple FEC elements in label request messages).
The case where multiple FEC elements may exist in the label mapping
messages is when a downstream peer support "DU" mode for label
advertisements and may try to include multiple FEC elements corresponding
to a FEC.

     For the case of CRLSP FEC element, it is recommended to use the NULL
FEC element in the CRLSP label request messsages. I think that's what
"Should" implies. In this case, the LSP will be established based solely on
the ER-HOP information. If the ER-HOPs are absent in the label requests
where the FEC is of CRLSP FEC type, then the message can be considered to
be error and notifications should be sent towards the upstream as the
packet doesn't have destination information and hence can't be routed.
CRLSP label requests can have other types of FEC element also such as
Prefix and Host-based.

Hope things are clear.

--Srini..