Subject: Re: MPLS and fast reroute.

From: Danny McPherson <[email-masked]>
Date: Fri, 09 Jun 2000 09:06:23 -0600

> The protection infrastructure in SONET is usable (I'm not sure what was
> meant by "traditionally") for some SONET protection schemes. BLSR and linear
> 1:1 SONET APS protection protocols/networks allow for preemptable traffic to
> be carried over the protection channels. It's been defined in the SONET
> standards, and the SONET products that I have worked on, supported this
> capability.

I was referring more to the router<->ADM section, I guess I should 
have been more clear in my message.  However, the granularity provided
by an MPLS protection scheme is clearly more flexible than that of SONET
APS, especially when designing networks expressly for packet switching 
services. 

-danny

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From: Yangguang Xu <[email-masked]>
Date: Fri, 09 Jun 2000 11:45:34 -0400

> APS, especially when designing networks expressly for packet switching

One way to use take advantage of both SONET APS and MPLS flexibility is to have
LSR aggregate LSPs with similar requirements onto SONET tribs, which are
provisioned with certain protection scheme. 

Yangguang

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From: Curtis Villamizar <[email-masked]>
Date: Fri, 09 Jun 2000 22:30:39 -0400

> provisioned with certain protection scheme. 

Except for the fact that that would be grossly inefficient from a
traffic engineering standpoint, this is a fine idea.  

For example, if 10% of your traffic required the type of restoration
offerred by APS or MPLS local-protect, then you'd spend a lot less
accommodating your backup need with MPLS local-protect on the 10% of
the LSPs than carving out separate lambdas for those SONET paths that
were carrying traffic needing protection.

Curtis

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From: Yangguang Xu <[email-masked]>
Date: Sun, 11 Jun 2000 09:11:52 -0400

First, we don't do double protection, which means we'd better use only one
protection mechanism closed to SLA.

Second, as SONET APS and MPLS local-protect each has its own strongness and
weakness, the router/switch should be the decision maker as to which protection
mechanism to use. Extra intelligence should be added to router/switch to
aggregate traffic and choose the best way. This may require router/switch to
control the SONET/DWDM, which shouldn't be a problem in integrated
IP/ATM/SONET/DWDM products.

Third, SONET APS can go all the way down to VT1.5 level. 

Yangguang

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From: Jennifer Yates <[email-masked]>
Date: Sun, 11 Jun 2000 15:22:31 -0400

A description of an integrated IP/WDM architecture that incorporates all network
intelligence in a single layer (i.e. the IP layer) can be found at
http://www.research.att.com/~jyates/srso.html.  This architecture is similar to
that described here, in that all restoration decisions will be made at a single
layer, with lower layer failure indications being passed up to the higher decision
making layer.

An OFC publication titled "Smart Routers - Simple Optics: A Network Architecture
for IP over WDM" further describes this architecture, and can be found on the above
web site.

Jennnifer

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From: Curtis Villamizar <[email-masked]>
Date: Mon, 12 Jun 2000 10:35:02 -0400

> Third, SONET APS can go all the way down to VT1.5 level. 

In order to make use of that capability the OC48c and OC192c router
interfaces that currently use SONET only as an encapsulation and feed
directly into the DWDM would have to be channelized and feed into an
ADM and break out the LSP (or set of LSP) that needed protection into
separate SONET channels.  It is worth noting that this prevents
sharing of bandwidth such that one class of service can use more than
its allocation if the other is underutilizing its allocation which is
one of the main reasons SONET is losing favor to IP.

I don't know anyone that is doing or planning to do this on the
backbone side.  I'm quite sure this is done on the access side (and is
one motivation for administrative colors in MPLS).  So perhaps we are
both right but I am concentrating on the backbone and you are
concentrationg on the access side.

Curtis