[p2p-hackers] Re: Silly question about UDP

Matthew Kaufman matthew at matthew.at
Wed Jan 31 14:26:20 EST 2007


Alexander Pevzner wrote:
> For ADSL I believe the constant C is noticeably smaller that for Ethernet
The unusable per-packet overhead is, for obvious reasons, engineered to 
be lower on expensive long-haul link technologies than it is on cheap 
high-bandwidth LAN technologies. ADSL, for instance, usually puts your 
packets into ATM cells, so there's no more than 47 wasted bytes of 
padding per packet, though there is extra overhead for each 48-byte cell 
that is transmitted. From your local CO, the same ATM framing stays in 
effect until IP aggregation. At peering points and for long-haul 
transport, ATM is often used, or POS (packet-over-SONET, which is simply 
PPP over SONET). And PPP, whether on a low-speed modem line or over 
SONET adds just a few bytes of framing overhead for each packet.

Matthew Kaufman
matthew at matthew.at


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