nanog mailing list archives
Re: value of co-location
From: bajaj () faline bellcore com (Shikhar Bajaj)
Date: Fri, 19 Jan 1996 17:21:07 -0500
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.
You are correct up til you get to the efficiency at the AAL level. AAL-5 does not have any SAR overhead but it does have 8 bytes of CS overhead. Now, this overhead is on a per PDU basis and NOT a per cell basis. Thus, you maximum efficiency will be 36.864 * [(x-8) / x] where x = PDU size in bytes. Thus, if you just send 64-byte packets, your min throughput will be 36.8 * (56 / 64) = 32.3 Mbps. Of course, larger PDUs are more efficient. Shikhar
Current thread:
- value of co-location George H. Clapp (Jan 19)
- Re: value of co-location Stephen Balbach (Jan 19)
- Re: value of co-location Dennis Ferguson (Jan 19)
- Re: value of co-location Jim Forster (Jan 19)
- Re: value of co-location Dorian Kim (Jan 19)
- Re: value of co-location Jim Forster (Jan 19)
- <Possible follow-ups>
- Re: value of co-location Kent W. England (Jan 19)
- Re: value of co-location Stephen Balbach (Jan 19)
- Re: value of co-location Paul A Vixie (Jan 19)
- Re: value of co-location Russ Pagenkopf (Jan 19)
- Re: value of co-location Stephen Balbach (Jan 19)
- Re: value of co-location Shikhar Bajaj (Jan 19)
- Re: value of co-location Dorian Kim (Jan 19)
- Re: value of co-location postel (Jan 19)
- Re: value of co-location Mike O'Dell (Jan 20)
- Re: value of co-location George H. Clapp (Jan 19)
- Re: value of co-location Andrew Partan (Jan 20)
- Re: value of co-location Warren K. Williams (Jan 20)
- Re: value of co-location Paul Ferguson (Jan 20)
- Re: value of co-location Dave Siegel (Jan 20)
- Re: value of co-location Nathan Stratton (Jan 20)
- Re: value of co-location Kent W. England (Jan 20)
(Thread continues...)