[2595] in Commercialization & Privatization of the Internet
Re: Network World article Raises New Questions on T-3 Network
daemon@ATHENA.MIT.EDU (Stan Hanks)
Thu Mar 19 02:30:51 1992
From: Stan Hanks <stan@casc.math.uh.edu>
To: fair@apple.com (Erik E. Fair)
Date: Thu, 19 Mar 92 1:27:05 CST
Cc: com-priv@psi.com
In-Reply-To: <15349.700983629@apple.com>; from "Erik E. Fair" at Mar 18, 92 9:40 pm
> The cisco AGS+ router has a proprietary 500Mbit/sec backplane called
> "cBus", into which you can plug up to four interface cards. The
> available interface cards include FDDI, a 6-port Ethernet, and High
> Speed Serial Interface (HSSI) for T3. Apple is using cisco AGS+ routers
> throughout the Apple Engineering Network, including one which is
> routing TCP/IP and AppleTalk traffic between two FDDI rings (our two
> backbones), so I would be surprised to hear that a cisco AGS+ couldn't
> handle T3.
>
> It is the case, as I understand it, that the CCITT V.35 interface is
> good for only a few megabits per second, which is why cisco Systems,
> in cooperation with some T3 comm gear vendors, spec'd and published
> HSSI. This is what you get when you buy cisco T3 interfaces. These
> interfaces will only go into cisco AGS+ routers, on the cBus. This
> also indicates that the reporter misunderstood ANS.
The problem isn't how fast you can jam bits around inside the router
(although I routinely do things where that *IS* the problem). In this
case it's how fast you can get them off the router and into the T3 CSU.
You have a head start on FDDI --there are chipsets casually available. But
have you tried to buy a T3 chipset lately? (hint: I know of one, and
you can't buy it. not that it doesn't exist, but that they won't sell it
to you. why it's listed is left as an exercise to the reader)
In evaluating T3 technologies, one of the more instructive things you
can do is talk to the guys at T3Plus (maker of CSUs and "bandwidth
managers") about who really can and can't pump the full ~45 Mbs to them.
As of my last review of this, around September, only Network Systems
could really get the full bandwidth out of their HSSI interface.
And, to quote the T3Plus guy, "they had to cheat". V.35 is known to lose
at high speeds, and apparently a strict "by-the-book" HSSI has similar
shortcomings. Anyway, T3Plus has a "standard" HSSI interface and a "NSC"
HSSI interface, which are different.
In talking to folks at cisco, they claimed to recognize this and be
working on a full solution. I have not had a chance to benchmark their
stuff, but expect to in the next month or so.
Note as well that this lack of industry standard chipsets will cripple
our ability to deliver *WORKING* ATM and SONET (either STS-x or OC-x)
routers. Not to mention jacking up the costs. Just imagine what FDDI
would be like if it was all one-off silicon or mondo-discrete logic...
Regards,
Stanley P. Hanks Principal Scientist, Technology Transfer Associates
U.S. Snail: P.O. Box 2087, Bellaire TX 77402-2087
FedEx/Shipping: 5303-F Glenmont, Houston TX 77081
e-mail: stan@karazm.math.uh.edu voice: (713) 661-2084 fax: (713) 661-0336
