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Re: value of co-location

  • From: Dorian Kim
  • Date: Fri Jan 19 17:33:04 1996

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





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