> What kinds of routers can route at near wire speeds a bunch of ports at > 155Mb ATM?
None right now. Gigarouter can handle it theoretically, but...
I'm being picky, but it's a moot question since doing wirespeed OC3c using ATM is impossible in of itself. Hell, mapping of SONET framings to ATM cells take off about 6 mbps right there.
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By the way, I did not post the above..
Oops. Replied to the right thread but wrong author.
bajaj@bellcore.com (Shikhar Bajaj) wrote:
A couple of minor corrections here. ATM cells are mapped into SONET frames and not the reverse. Also, I presume that the 6 Mbps that you are talking about is that the ATM bit rate over an OC-3 is 149 Mbps as opposed to the OC-3 pipe rate of 155 Mbps. Those 6 Mbps are taken up by the SONET management overhead (section, line, and path) in the frame. This is independent of whatever goes in the SONET payload envelope and has nothing to do with ATM.
It seems to me that Sonet OC-3 is often taken as transport for 3 DS3s, which would reduce 155.530 Mbps to 134.208 Mbps (3 x 44.736 Mbps), less than the 149 Mbps you cite above.
The 149 Mbps assumes that you have a native ATM/OC-3 interface where the SONET transport is STS-3c ('c' for concatenated). Here, a single connection can use the full bandwidth of the pipe. In your example, a DS-3 gets mapped into an STS-1 and then 3 STS-1s get muliplexed into an STS-3. The multiplexing is for trunking purposes and there is no relation between any of the STS-1's (other than they are byte multiplexed). Thus, the maximum bandwidth available for any single connection is 51 Mbps (or DS-3 in this case). Routers with ATM/OC-3 interfaces do STS-3c framing.
Do you have a good recommendation for Gordon Cook, TCP/IP direct over Sonet?
I've heard rumblings about such work going on but I am not personally familiar with any of it. The only thing I can think of is some work that the IETF did for PPP over SONET (RFC 1619). I *think* it became an Internet Standard. Shikhar