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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: ATM vs. DS3
>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 >Because an ATM cell is 53 bytes, but 5 bytes of that is header. Thus we >pay for 4 Mb/s and get 3.62 Mb/s. >Now, the question is, what is the overhead of the serial (ppp?) protocol >running over the T3? Since it is point to point, and not addressed, it >should be less, or is this not the case? <24 bytes per MTU. If your MTU is 4000, your large frames buy you 3976/4K, which conveniently multiplies by 4M to give you 3.9+M. Also, don't forget that ATM switching introduces a latency that a p2p connection doesn't. If you're truly having a point-to-point application, and you have a choice of a non-switched/routed protocol vs a p2p protocol... um... go with b :) E >Any input would be appreciated! >Josh Beck [email protected] >------------------------------------------------------------------------ >CONNECTNet INS, Inc. Phone: (619)450-0254 Fax: (619)450-3216 >6370 Lusk Blvd., Suite F-208 San Diego, CA 92121 >------------------------------------------------------------------------
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