when speaking of internet connections to ISPs we need to consider two aspects:
forwarding plane: traffic volume expected
control plane: amount of routing information
the first aspect is not a problem for a multilayer switch like 3560-E.
control plane: if the switch 3560-E receives only BGP default routes and advertises your ip prefixes you are fine
If you need to handle a BGP full table that are nowdays 270,000 BGP routes the C3560-E is not the right device: it hasn't enough memory to deal with BGP and to build CEF tables for all this routes.
If this is the case you should consider to use a router like C7206VXR with NPE-G1 or NPE-G2: it provides you a brain and memory powerful enough and can handle up to 1GBps of traffic between two GE ports
thanks for your input. We are expecting full utilization of the bw as they are isp and they distribute the raw bw to customers including home users as well on cable.
thinking of ip traffic above 64 bytes practically, does 3560-e can handle traffics like video, voice etc?which will definitely have bigger packet sizes.
since the isp have uplink isp peering with two different tier 1 isps, they should be able to download the full bgp routes so that they can do a routing based on customized policy for destination level routing. Your suggestion on 7200 series with NPE-G1/G2 is appreciated, however seeing that this device will be a very critical one with 300Mbps Internet link i suppose we can also propose 7600 with dual SUP at least. Additionally they are also looking for FIrewalling for some internal servers like Web and Email and some application servers as well.
Besides Giuseppe's suggestions on both the 7200 and ASR series, you might want to also look at the 7304. I understand it supports both redundant power and processors. Performance wise, using the NSE-150, it would be between the 7200 with NPE-G2 and the low end of the ASRs. It should easily handle dual OC-3 bandwidths.
If the application is a critical as you note, you might want to consider two boxes rather than one with redundant components.