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  • From: Wolfgang Henke
  • Date: Tue Mar 19 17:05:33 1996

> >      > 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.
>        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 

By the way, I did not post the above.. (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. 
Do you have a good recommendation for Gordon Cook, TCP/IP direct over Sonet?

Thank you for posting,


Wolfgang Henke  .
WH Networks                        ... /pub/wolfgang
2672 Bayshore Parkway Suite 503  .......             +1 415 390 9316
Mountain View CA 94043     ...................   fax +1 415 390 9317

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