The MPLS WG Archive

[Rohit Dube <rohit@xebeo.com>]

Hello,

At the MPLS WG meeting, the question came up that GMPLS already
supports bi-directional LSPs. As Rahul pointed out, this only
works for generalized labels and not for "classical" labels.
Here is some further clarification on the topic.

For classical mpls networks there are two ways of supporting
bidirectional lsps. One method is to make the UPSTREAM_LABEL
objects applicable to classic MPLS labels. The other is to 
exchange "generalized" labels between nodes that want to 
support bidirectional LSPs while continuing with classical 
labels for uni-directional ones. The draft presented uses 
the former approach. 

While both approaches are valid, for nodes that run classical 
MPLS already and which need to support uni-directional as well 
as bi-directional LSPs, this seems to be the easier approach as 
the operator and the implementor need to deal with just one 
type of label.

The -01 version of the draft proposes an UPSTREAM_FLOWSPEC 
object which allows for asymmetric bandwidth reservation
by carrying the required information for the reverse path 
in the PATH message. The updated draft is available at 
http://members.tripod.com/~rohit_dube/papers/draft-dube-bidirectional-lsp-01.txt

The updated version of the draft should appear on ietf's
web-site when the draft queue starts getting processed again.

Regards,
--rohit.