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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: MCI [ATM overhead]
Jim Forster <[email protected]> wrote: >He's talking about the overhead due to carrying variable length IP packets >in fixed length ATM cells. ... >There's beginning to be some expectation that there will be a transmission >capacity crunch in the carrier's Sonet nets, and this ~25% ATM cell tax may >be looked at carefully as packet over Sonet solutions emerge. Given the bimodailty of IP traffic size distribution (about 40% of packets are small, like TCP ACKs or telnet/rlogin keystrokes) the ATM "cell tax" is closer to 32%. I.e. a dual clearline DS-3 actually carries as much user data as OC-3c ATM. Which, incidentally, was why SprintLink backbone design is easily expandable to dual links (that includes carefully considering implications for routing). Sean presented that design on NANOG a year ago, BTW. Funny thing, the design is expandable beyond that, too, so OC-3 ATM is already obsolete. --vadim
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