Re: Switching technologies requiring bidirectional asymmetric LSPs?

["Adrian Farrel" <adrian@olddog.co.uk>]

Hi,

I'm a bit surprised that there was no follow-up to Lou's email.

Does silence indicate that this was put to bed in Prague and no-one is 
interested in these LSPs?

> So a few of us have been having been discussing the asymmetric work 
> presented in Prague and it seems to me we have an open question on 
> requirements.
>
> It's clear that at least one switching technology (i.e., ethernet/PBB-TE) 
> requires support for bidirectional asymmetric LSPs.

Is this clear? I continue to hear talk of service requirements, but not so 
much of how those services are required to be supported.

The benefits I have heard are:
1. Fewer control plane messages
2. Ease of enforecement of fate-sharing

These are significant, but not dramatic, requirements.

> The question is:
>
> Is the *requirement* for bidirectional asymmetric LSPs:
> (a) a technology specific requirement, or
> (b) one that is common (this is CCAMP after all!) to multiple switching 
> technologies?

CCAMP deals in transport networks. As far as I can see the service 
requirements would be pretty much the same all transport networks and would 
certainly be applicable to packet, L2, and TDM (the latter because TDM will 
be called on to support L2).

> Please keep in mind that service requirements are not the same thing as 
> switching technology requirements.  For example, we have long built 
> bidirectional asymmetric services on unidirectional MPLS LSPs.

Well, exactly!
Perhaps someone can explain why the Ethernet hardware is forced to require 
bidirectional asymmetric LSPs when MPLS is happy without?

> The answer to this question will help determine if we should have a 
> technology specific solution or a generic CCAMP solution (as well as the 
> complexity of the solution.)

We should not take any action that deliberately precludes or makes more 
complex the genericisation (is that an American word?) of the solution 
unless there is a significant difference in simplicity of solutions.

But we should take no action at all unless there is some more evidence of 
support for this work!

Adrian