Cell Relay Archive

["Dominic Richens" <dominicr@nospamnortelnetworks.com>]

Ken Agress <kagress@linkline.com> wrote in message
e1kuos0j9rkqhao2jb6c953mbqhsj0c5s4@4ax.com">news:e1kuos0j9rkqhao2jb6c953mbqhsj0c5s4@4ax.com...
> Is this really an accurate description?  I'd have said "both an SPVC
> and a PVC are established on a permanent basis, but an SPVC is capable
> of re-routing through the ATM network due to congestion, outages, or
> the creation of a more efficient path."  I suppose that from a network
> management of view, this shares many of the characteristics of an SVC,
> but it's still a PVC - just one with "intelligence" controlling the
> path it traverses through the network.

To expand on this, from a customer point of view, they like SPVCs because
you only have to do one provisioning step on the originating switch
(essentially src and dst tc/vpi/vci and dst AESA).  The SVC and routing
function of the switches takes care of the rest - and yes, if there is a
like/node failure somewhere along the path, the originating ATM switch will
attempt to re-establish the SPVC.

With PVCs, you have two provisioning steps (src and dst) at every single hop
along the path.  You can use VPTs to simplify this, but it quickly become a
network traffic engineering headache.  Most vendors have some kind of
network management platform that can automate the transit hop provisioning.

One advantage to PVCs is that you have full control of the path - customers
might be using ATM VCs as frame trunks or something, and want to diversely
routed VCs for redundancy.  Two SPVCs provisioned with the same dst AESA
will more than likely take the exact path (part engineering, part Murphies
law!).

I've also been hearing of something called PSVCs, which I think is just like
an SPVC, except that you can also provision the DTL so to takes the path you
want it to.  Anyone have more info on this?

dominic (too lazy to look at the ATM Forum web site) richens :-)