I think the Atlas 550 is rather expensive, an easier (and cheaper) way is to just purchase a 2500 router and e.g. one or two 1600 routers and connect them with a DTE/DCE cable or back to back. You can configure the 2500 as a frame-relay switch, and you can simulate PPP/HDLC WAN connections as well. The Atlas is, as far as I know, a rather heavy classroom tool. I wouldn´t spend the money unless you have a strong use for it afterwards.
If you can get a router with a minimum of two serial interfaces, then, you can use that as a frame-relay switch. Two routers can be connected to this unit as DTE equipment. If you can get a 2522 which has 9 serial interfaces, thats good enough to be used as a frame-relay switch. Check this link for setting up a router as frame-relay switch.
for ISDN I am using two 1603 routers (which I think you can get on Ebay, for example - which country are you from, by the way?) and as an ISDN simulator I am using the Elmeg DAVOS-44.net, which runs at about 250 Euros. I am not sure about the orice of the Atlas, but as far as I know it runs into the thousands of dollars.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...