Fumble,
Routers are IP layer 3 devices that hold information of where a packet should be directed. An ATM switch is a cell based layer 2 device that passes cells to its next hop. Basic 'routing" is being added to layer 2 switches via MPOA or MPLS. However, this is to route amongst ATM switches and does not scale the same as say OSPF or BGP4, the internet's routing protocols. Therefore, the "intelligence" resides on the edge, within the routers.
Routers, being software based today, are much slower than ATM switches or layer 3 switches, which can both perform at 'wire speed', depending on who you believe (vbg).
QoS is superior today in ATM because you can actually carve out a portion of your connection and dedicate it to a customer or application. QoS on routers is developping, but not there yet. ATM QoS schemes tend to be proprietary, however.
I wasn't slamming ATM, just trying to answer your question.
Cheers,
Peppe |
