From: rpw3@rigden.wpd.sgi.com (Rob Warnock)
Newsgroups: comp.dcom.cell-relay
Subject: Re: Computers dont like ATM?
Date: 17 Dec 92 04:27:23 GMT
Organization: Silicon Graphics, Inc.  Mountain View, CA

finn@dalek.isi.edu (Greg Finn) writes:
+---------------
| rpw3@rigden.wpd.sgi.com (Rob Warnock) writes:
| 
| >Currently the big holdup is the ODL prices, but when those plummet ("soon"),
| >the prices for the gigabit encoder/decoder chips will be the bottleneck.
| >*That's* what needs work (e.g., price reduction).
| 
| 	Ahh.  I see now your misunderstanding or my lack of clarity.
| I worry about building gigabit NETWORK links.
+---------------

So was I, only short-haul ones (less than, say, 500 meters or so).

+---------------
| That includes the framing, encoder/decoder, and for 1300nm fiber, the OFC 
| logic needed to meet Class I compliance.
+---------------

For short [see above] links with pigtailed transmitters [*not* connectorized],
you can hold your power low enough to not worry about Class I compliance.
But that's a detail, since link control is (or will be) built in to many of
the serializers.

+---------------
| A typical gigabit fiber link for a network needs a framer, an encoder, a
| decoder, an optical transmitter, a detector and an OFC circuit. If you are
| point-to-point you need two sets to be duplex.
+---------------

Yes, of course. But the frame/encoder/decoder is already a single chip (and
some even have or will have the OFC stuff in them).

+---------------
| 	I can't get there from here today unless I spend circa $1500
| for parts alone.  But I can get the parts.  What you call the ODL is
| not the majority of the cost.
+---------------

Well, until the "new" ODLs ("Optical Data Link", a transmitter/receiver pair)
come out, the best I have seen for a gigabit is *$3000* the pair, *plus* your
$1500 for other chips. (The new ODLs will drop the ~$3000 to $500 or less...)

+---------------
| >Ironically, it is the LAN applications that are now pushing the deployment
| >schedule for ATM, so the components won't see volume production by the time
| >the first ATM LANs start being installed... so prices will be high at first.
| 
| 	I do not see 655 Mb/s OC-12 being pushed commercially for LANs
| for quite some time.  Some major computer manufacturers are moving
| toward 155 Mb/s and decommitting from their originally rosy prediction
| of OC-12.  I guessed publicly that it was because OC-12 rates require
| costly gigabit links ... meaning gigabit network links.  I still think
| that it is a good guess.
+---------------

Well, the HIPPI market is looking quite eagerly at 622 Mb/s ATM (or so
we've been told), because HIPPI fiber-optic extenders are so expensive
(over $10K per end). [HIPPI only goes 25m in copper.] And most HIPPI
users would be willing to settle for 622 instead of 800, given that
few systems can drive at the full 800 Mb/s anyway...

+---------------
| 	155 Mb/s with ATM's encoding overhead gets me somewhere in the
| neighborhood of 80 Mb/s of TCP/IP payload in today's Internet.  Hardly
| exciting.
+---------------

Well, as somebody pointed out to me, with SONET coding the actual cell
payload data rate is 135.63 Mb/s, substantially *above* FDDI, especially
when you consider it's full-duplex continuously.

+---------------
| It won't get you the headroom that you need for studio NTSC.
+---------------

The people I know who do that sort of stuff think so, with within-frame
JPEG compression.

+---------------
| 	For bandwidth in the gigabit domain for LANs, it looks to me
| as if Fibre Channel may have a commercial leg-up on ATM in the gigabit
| LAN arena.  My problem with Fibre Channel is that it makes the
| overhead of ATM carrying Internet packets look quite small by
| comparison.
+---------------

And I see the opposite. Oh well...

+---------------
| 	It will be an interesting next two years.
+---------------

*Exactly* because it's not clear what will win.


-Rob
Newsgroups: comp.dcom.cell-relay