[p2p-hackers] UDP file transfer protocol peer review

[coderman]

On 7/23/05, Saikat Guha <sg266 at cornell.edu> wrote:
> ...
> In a wireless scenario, [1] shows that a single packet loss (a) or even
> a threshold percent of packet loss within some period (b) are not good
> indicators of congestion/contention -- i.e. cannot differentiate among
> them. TCP uses a) and performs poorly in the wireless scenario. Instead,
> [1] proposes looking at the number of _consecutive_ losses since such
> losses are temporally correlated. FastTCP [2] more or less ignores
> isolated losses and moreover uses delay based congestion signals.

i've found the best results when the wireless transport layer takes
the following 802.11 specific peculiarities into account:
- if you are getting interference with other network / clients /
microwaves the retransmission in layer 2 (802.11MAC) will cause
intermittent single hop delays in excess of 1 or 2 seconds.

- packet loss without congestion is the norm and not the exception;
both intermittent latency and intermittent loss must be tolerated to a
greater degree.

a fun environment to tune a stack in.

Best regards,

[also, airhook is a nice example of how to optimize datagram transport
for wireless environments]