Inter-exchange media types
jerry at fc.net
Sat May 4 05:58:35 UTC 1996
>A new stdaddr draft is forthcoming shortly. This other conversation is of
>interest, though. We're arguing about 100Mb/s interconnect technology as
>if we all planned to keep using it for some significant period. That's not
>so. Two years from now it'll be 622Mb/s or it'll be a dead concept. PMTUD
>matters, and TCP MSS (therefore IP MTU) matters because it will dictate the
>frame rate to the routers and the end hosts. Bytes are cheap, frames cost.
Paul, with all due respect, there is a lot of apparent need and
demand for 100mbps interconnects, one could argue
that 100 100mbps interconnects are better than 3 or 4 622mbps
interconnects. I think 100 interconnects are at least as likely
in 2 years as 4 622mbps interconnects.
Since most of the customers connecting up to these interconnects
will be by devices with MTUs of 1500 (frame, T-1, switched 10 and
100mbps interconnects), and all of the network below these interconnected
sites are 1500 MTU and smaller. I know of maybe 100 sites
around the globle that can currently send FDDI MTUs in the 4000
range.a By contrast good esitmates show about 10 million
dialup users connected via termial servers which have
In terms of total users FDDI users would be well below .001%.
In terms of total revenues FDDI users would be well below 1%.
Basied on these numbers, my recommendations to NAP/MAE builders
would be to build based on 100mbps switched ethernet, with
the option to interconnect FDDI. To make the FDDI worth
while there would have to be at least two networks attached
that had routers co-located (or virtually co-located), with
DS-3 rate connections, and those two networks would each
need at least one DS-3 rate customer each. Assuming
this is the case the upgrade to FDDI is a relatively
Comparing the cost of 100mbps switched ethernet, to
the 100 mbps switched FDDI, there is about 30% to 50%
difference per port on the switch, and greater than that
on the router. Prices on switched ethernet are dropping
much faster than those of FDDI, because the price point
is below the level at which a technology is only used where
speed is the only factor.
Speaking of interfaces and speed, I see Cisco now has a OC-3
packet interface that will do raw packets via HDLC or PPP
at OC-3 rates via SONET. That seems much nicer than
the ATM AIP card. You could build a fairly nice backbone
with a dual attached mesh of OC-3 routers.
Jeremy Porter, Freeside Communications, Inc. jerry at fc.net
PO BOX 80315 Austin, Tx 78708 | 1-800-968-8750 | 512-339-6094
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