Here is the senario I was thinking about Case 1 R1 --- R2 --- R3 Case 2 R1 --- SW --- R3 | | R2 Assume that the wide area segments are the same in both cases and that SW and R2 are collocated. In case 1 there are 2 router hops between R1 and R3. In case 2, given a full mesh of PVCs, R1 and R2 are only one hop apart. This does not imply that the traffic flows any differently relative to the physical paths taken, but if I do a traceroute I think it will look different. Am I missing the point here? Jim
If you have full use of the fiber across which you move your packets you can create a mesh of PVCs directly connecting each router thus decreasing the hop count. The same can be done when using an existing cell-relay cloud, but you pay on a per pvc basis so the benefit needs to be weighed against the cost. Of course the packets still flow along the same physical path and in a wide area network the time in transit will be more significant than the time to get through the routers.
Jim
Nope, remember - there is no magic. Any mesh of PVCs that one makes over a switched network must reflect the toplogy of that network, and one can set up a matching set of active routing sessions and route weights which will cause traffic to flow the same way.
Yes, the switches are a bit faster and have less to do. Data moves through them in a few ms less per point. But as you said (and as I said in our discussion in NYC), relative to any distance, the speed of light guarantees that you won't notice the difference.
The question is: Will there be routers available that can make IP routing decisions based on 40-60kroutes and move 2-3 OC3s worth of bidirectional traffic? The building of the configs to have a routed network work the same as a switched ATM one can be automated, but it's true that it *can be* easier to see what's going on in a large-scale switched network.
Avi