MCI

Tue Mar 19 18:36:57 UTC 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.
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 

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.

Shikhar