|
North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: IP over ATM overhead
> We are installing an ATM backbone connection and wondering what level > of overhead can be expected. Ive read from %10 to %50 - this will be a > LAN connection so we can assume almost no cell loss. Our provider has > said on average %12 bandwidth is overhead. It will be a Cisco->Cisco LAN > configuration. Thanks! > > Stephen Balbach > VP ClarkNet It probably depends on what you define as overhead. You might define it as that 16 bytes of AAL5/SNAP header & trailer per IP datagram, plus 5 bytes per cell, plus whatever trailing bytes are wasted in the last cell. Compare this with packet over sonet (1 byte of IFG, 4 bytes of ppp encapsulation, and 4 bytes of CRC). Peter Lothberg gathered some packet size distributions at various internet routers in January, and found that using the above definitions, atm overhead consumed 22% of bandwidth, vs. 3.1% for POS overhead. Looking at it another way, POS can move 24% more payload than ATM using the same packet size distribution. I've taken other snapshots at other routers since then, and the results come very close. /Darren - - - - - - - - - - - - - - - - -
|