The MPLS WG Archive

[rpapneja@gmu.edu]

Please see the inline:
 -Rajiv

----- Original Message -----
From: Ramyanshu Datta <romidatta@yahoo.com>
Date: Friday, September 28, 2001 8:50 am
Subject: Downstream on Demand Label Distribution

> Hi,
> 
> Is Downstream on Demand mode for Label distribution
> practically possible.
 
 Yes, when any LSR in a MPLS network distributes a FEC label binding in 
response to a request from another LSR, it is termed as Downstream On 
Demand label distribution.
 
> 
> If it is possible how efficient is it to use
> Downstream on Demand mode for Label distribution,
> instead of actually using BGP or LDP for distribution
> of label information.


 LDP defines use of Downstream-on-Demand and Downstream Unsolicited 
Label Adverstisement once the LDP sessions have been established 
between the two peers. So, you cannot say that either use DoD for label 
distribution or LDP and it is a part of LDP operation. There is a 
difference between a label distribution Protocol (which is a general 
term and refers to MPLS-BGP, MPLS-LDP and MPLS-RSVP) and LDP (defined 
by the RFC 3036).

 BGP is used for distributing a particular route and can also be used 
to distribute MPLS label that is mapped to that route. The BGP can be 
used to distribute labels if two adjacent LSRs are also BGP peers. In 
this scenario the label distribution can be piggybacked in the BGP 
(using MP-BGP extensions) 
update message. 
 
> Is this mode of Label distribution any different from
> the other two I mentioned. And does this create a
> scenario for Dynamic LSP setup

 Please refer above. It does create a scenario for Dynamic LSP setup.

> Thanks in advance
> Ramyanshu
> 
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