[1454] in North American Network Operators' Group
Re: value of co-location
daemon@ATHENA.MIT.EDU (Dorian Kim)
Fri Jan 19 15:34:31 1996
Date: Fri, 19 Jan 1996 14:58:14 -0500 (EST)
From: Dorian Kim <dorian@CIC.Net>
To: Jim Forster <forster@cisco.com>
cc: Dennis Ferguson <dennis@Ipsilon.COM>,
"George H. Clapp" <clapp@bellcore.com>, nanog@merit.edu
In-Reply-To: <199601191917.LAA02246@stilton.cisco.com>
On Fri, 19 Jan 1996, Jim Forster wrote:
> > Not using either of the last two fast packet services, in particular, will
> > also yield 30% more useful bandwidth from a T3 circuit. This all by itself
> > may make up for the co-location costs and the cost of a router.
>
> What's the average packet size now? I think the overhead on DS-3 ATM/SMDS
> is worse than on OC-3, if I recall correctly, because the DS-3 PLCP is so
> wasteful as well. Someone should redo these calculations more accurately.
With PLCP, maximum bit rate available for ATM cells =
53 cells * 12 rows * 8bits / 125us = 40.704 mpbs.
So, 40.704 * 48/53 = 36.864 mpbs = data rate.
Now if you use AAL5, then it's another 2 bytes for SAR, and 2 bytes for
CS, so, 40.704 * (48-4)/53 = 33.792 mpbs.
Now, that's the theorectical maximum, and you go down from there.
-dorian
______________________________________________________________________________
Dorian Kim Email: dorian@cic.net 2901 Hubbard Drive
Network Engineer Phone: (313)998-6976 Ann Arbor MI 48105
CICNet Network Systems Fax: (313)998-6105 http://www.cic.net/~dorian
