The MPLS WG Archive

[Guangzhi Li <gli@research.att.com>]

Eric:

In GMPLS functional specification:
(1) Two uni-directional LSPs establishment with label suggestion will result contention. Downstream node
label assignment policy solves the contention.
(2) Two bi-directional LSPs establishment with I/O pair restriction will result contention. LSP with
master node label assignment wins the contention.
(3) How about the contention between a uni-directional LSP and bi-directional LSP in the same framework?
The application is not clear currently. But if you draw figures by yourself, you may find the issue.

-- Guangzhi

Eric Gray wrote:

> Guangzhi,
>
>     The thing I can't figure out, is where you're getting all of this from.
> I can't help you with your issues, because - from where I sit - it looks
> like you pulled them out of thin air.
>
>     Could you provide more specific information about where you see the
> these issues of contention being defined?
>
> --
> Eric Gray
>
> You wrote:
>
> > Dear GMPLS authors and all experts:
> >
> > During GMPLS last call, I posted the same question on the mailing list
> > without response. Please somebody spend a little time and check with the
> > following example? Something seems not clear when the current GMPLS
> > contention resution schemes are applied on a framework with both
> > bi-directional and uni-directional LSPs. Your clarification is very much
> > appreciated.
> >
> > Sincerely,
> >
> > Guangzhi
> >
> > --------------------------------------------------------------------------------------------------
> >
> > The issue arises because contention is resolved between bi-directional
> > LSPs by the node with the higher node index while for uni-directional
> > LSPs, contention is resolved by the downstream node. Consider the
> > following example of two nodes with paired, bi-directional interfaces
> > (i.e., a transmitter/receiver pair of ports).  Node 1 with ID=100 and
> > node 2 with ID = 50.  Node 1 uses label 1 for the transmitter port and
> > label 2 for the receiver port; node 2 uses label 4 for the transmitter
> > port and label 3 for the receiver port.   We assume that a
> > bi-directional LSP requires a single I/O interface.
> >
> > We consider two LSPs - a uni-directional LSP (LSP A) and a
> > bi-directional LSP (LSP B). Both LSPs are going from node 1 to node 2,
> > with the uni-directional LSP setup request arriving marginally before
> > the bi-directional LSP.  LSP A does not use a suggested label, and thus
> > is assigned a label (port) by node 2.  Label 3 is assigned,
> > corresponding to label 1 at node 1.  At the same time, for LSP B (the
> > bi-directional LSP) node 1 assigns label 2, with suggested label 1.
> > Because node 1 has the higher node ID, node 2 will assume (due to the
> > contention resolution rule for bi-directional LSPs) that LSP B wins the
> > contention and thus label 3 is assigned to LSP B.  Thus label 1 at node
> > 1 (label 3 at node 2) has been assigned to two different LSPs.  Both
> > LSPs have ?won? the contention.