[2663] in North American Network Operators' Group
Re: Inter-exchange media types
daemon@ATHENA.MIT.EDU (Erik Sherk)
Thu Apr 25 09:49:17 1996
To: Jeremy Porter <jerry@fc.net>
cc: nanog@merit.edu
In-reply-to: Your message of "Thu, 25 Apr 1996 01:21:34 CDT."
<199604250621.BAA09394@freeside.fc.net>
Date: Thu, 25 Apr 1996 09:45:18 -0400
From: Erik Sherk <sherk@uunet.uu.net>
>
> I know of plans for at least 2 exchanges that will use 100baseTx
> as a connection option. The only real problem is
> the backplane limit of boxes that switch 100baseTX,
> (Cisco Cat 5000, 1.2gbps). This is only slightly
> better than the Dec Gigaswitch limit of 800mbps.
>
> Certainly the hardware to do switched ethernet is much cheaper
> than FDDI, and with full duplex 100mbps there is very little
> advantage to FDDI. (FDDI does do full duplex now, but I don't
> know who offers interfaces that support this.) FDDI
> does offer larger frame sizes, assuming you have FDDI each
> end with no "MTU 1500"'s in between.
Don't gloss over the MTU issue. Fragmenting packets is a serious
performance hit. Also, DS3 customers want a hssi mtu end-to-end.
> To me it seems like a big cost win to drop in a C5000
> with 4 slots at 24 switched ethernet/slot, or 12 switched fast
> ethernet/slot. Particularlly since the router interfaces are
> about 1/2 to 1/4 as much.
Compared to the other costs in running an ISP it is just noise...
> The exchanges with the most traffic are the ones
> based on the oldest technology, because there are always bugs.
??!! Exchanges with the most traffic are the ones with the new technology
because they have no choice.
Erik
