The MPLS WG Archive

[darren.freeland@bt.com]

Hi Kireeti,

>> However, the point of GMPLS is NOT a peer model.  It is an IP-based
>> control plane, leveraging existing work, and the flexibility of a
>> peer or overlay or hybrid model.

Perhaps you missed my point.  I didn't say the point of GMPLS is a peer
model (I have read the draft) - I questioned the assumption that IP-centric
control protocols will be appropriate for an optical (or indeed any) control
plane.  As far as I can see (having read the IPO framework, the MPLambdaS,
and the Generalised MPLS drafts I hasten to add), this assumption has been
made without giving full consideration to the requirements of the particular
networks the protocols will be applied to.  My interest is the OTN, so
that's what I've been focussing on.

The IPO framework document starts out in the introduction by saying that
"there is wide consensus in the industry that the optical control plane
should be IP-centric".  I would question this 'wide consensus'.  There is a
few (very basic) requirements set out in the introduction, but nothing that
justifies thoroughly the choice of IP-centric control protocols for the OTN.

The MPL(ambda)S document does the same - we're told in the intro that the
optical control plane will be based on the MPLS TE control plane model.  The
only justification that is given for this is the reuse of existing
protocols.  Cool - why not reuse PNNI then?  I'm not advocating one or the
other yet - what I am saying is that the requirements of the OTN (or any
other network in the case of GMPLS) should be fully considered in the first
place.  The choice (and extensions) of control plane protocols should then
be made to fit these requirements.

The other problem I have with the MPL(ambda)S philosophy is its clear bias
towards the 'peer' option.  Sure, the 'overlay' option is described, but it
is not fully discussed - we are simply told that "to understand the
drawbacks of this approach ... one need look no further than the experience
with IP over ATM".  This is a whole discussion in itself which Neil Harrison
has touched on in his reply to you.  ATM is not the OTN.  This aside, my
point is that the peer model is clearly advocated over the overlay model -
but there is no mention to the effect the peer model would have on an
operator who has a multi-client environment.  There is also a clear
reluctance on this list to recognise the problems the peer model may bring.

I think a new draft is in order, but I get the feeling many won't like it.

Regards,
Darren.