On Tue, Jul 09, 1996 at 10:38:57PM -0500, Chris A. Icide wrote:
On Wednesday, July 09, 1997 9:34 PM, Josh Beck [SMTP:jbeck@connectnet.com] wrote:
Hello, I just thought of something. We are in the process of purchasing a 4 Mb CIR from another backbone. Now, we have the choice of ATM or standard T3 delivery (over a DS3 either way). Now, if we get ATM, that 4 Mb CIR turns into:
[ (53-5)/53 ] * 4 Mb/s = 48/53 * 4 Mb/s = 3.62 Mb/s
Emperical data shows that we are currently losing about 20.5% of capacity to IP over ATM overhead on fairly aggregated traffic. This means that *IF* your new connection is being measured as 4Mbps of cell bandwisth, you will only be getting 3.18Mbps. You may want to verify from the company providing this link what exactly are they limiting you to?
btw, the extra overhead is lost in things like the last cell of a packet not being full, etc.
Chris A. Icide Sr. Engineer Nap.Net, L.L.C.
My God, someone admits it? I've used 20% as the general ATM overhead now for almost two years, and have been poo-pooed by lots of people claiming that it wasn't anywhere near that bad. Funny how it all comes out in the end. :-) -- -- Karl Denninger (karl@MCS.Net)| MCSNet - The Finest Internet Connectivity http://www.mcs.net/~karl | T1's from $600 monthly to FULL DS-3 Service | 99 Analog numbers, 77 ISDN, http://www.mcs.net/ Voice: [+1 312 803-MCS1 x219]| NOW Serving 56kbps DIGITAL on our analog lines! Fax: [+1 312 803-4929] | 2 FULL DS-3 Internet links; 400Mbps B/W Internal