The MPLS WG Archive

["David Allan" <dallan@nortelnetworks.com>]

Title: RE: [IP-Optical] RE: Optical link bundling. Was Re: DraftMinutes >From Pittsburgh

Mark:

I would agree that this is true if we are looking at a relatively invariant network topology and the entity in the network performing the "design" of the protection scheme for the new paths and SLA has a comprehensive view of network state. I also think that the optical space has a lot of complexity (consideration for amplifiers, regen etc.) which would suggest that we are going to have a relatively invariant topology for a while (although we are all working hard to eliminate much of this complexity or at least the need for its visibility to higher layers).

At some point though, when it is common that a fiber carries 80 OC192s so I have a capacity to configure some 15000 STS-1s on a given span in varying degress of concatenation, and we are trying to get STS provisioning down to LSP setup times, then we need to acknowledge that some central entity doing all of this is eventually going to break. At that point we need distributed algorithms and possibly hierarchical routing, with all the issues that entails (including the possiblity of "no-solution"). At the risk of inflamming the audience, as far as SLAs are concerned, what is an ATM SVC, and PNNI, other than a distributed means of establishing paths with a given SLA?

If the expectation is that we are only going to do "gross tweaking" and the granulatity of the managed paths is always going to track technology at some fixed fraction of what is capable (e.g. if STSn is the biggest path, then STSn/x (where 'x' is fixed), will be the smallest granularity manipulated regardless of the value of 'n'.), then we are doing a lot of work simply to preserve the status quo and probably assuming that there is only going to be one type of payload (e.g. IP packets). We are limiting ourselves to traffic engineering. Given all the points brought up on this thread so far, that is not a good assumption. It is probably more reasonable to say that the core of the network needs to scale faster that the requirements for bandwidth of individual clients and centralized path establishment will be inadequate at some point.

regards
Dave

-----Original Message-----
From:   Mark Stewart [SMTP:Mstewart@nexen.com]
Sent:   Thursday, October 26, 2000 9:41 AM
To:     Allan, David [CAR:NS00:EXCH]
Cc:     alchiu; 'Yakov Rekhter'; ip-optical; mpls; sc; xuyg; yxue
Subject:        Re: [IP-Optical] RE: Optical link bundling. Was Re: DraftMinutes From  Pittsburgh

Hi Dave

The concept of jointly routing primary and protection paths has been
well accepted by Bell heads looking at optimizing their networks for a
long time. Part of the reason for this is the assumption that protection
path(s) must also be conformant to the same SLA as the primary path, and
joint routing is the most likely to achieve this.

This does not of course address your concerns about race conditions at
connection establishment. But joint routing is guaranteed to produce a
solution not worse than independent routing, and results in a lower
commitment of network resources.

ciao

mark
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