[Csci551-talk] Re: [Cs551] Project b - Time out question
xiw at usc.edu
Tue Apr 26 12:08:19 PDT 2005
> (1)Now,,,in the termination codition of non-seed nodes,,,,they
> shouldn't make any progress in downloading for 4 rounds,,,the
> progress here does it mean recving some segments only or it could
> mean also recving request as well from other clients?
> if we are to consider recving a req as a progress , then we fall
> into an infinite situation in high loss rate,,,,assume i have one
> seed and 2 clients if the seed terminated because it didn't recv a
> req(because the req are lost), then the 2 clients will never end
> since they recv req from each other?
You can do some experiments with these. A good way is to consider a node is making progress if it is receiving a segment or sending out a segment. Swapping segment information is not considered as progress, so there won't be infinite loops.
> (2)Assume the following scenario, The delay is one second...and
> the timeout is 5 second,,,,now if client send to the seed seg req
> and assume the seed has 10 replies waiting,,,then the seed will
> send the client reply after 11 second....the problem here is the
> client will timeout assuming that the packet is lost where it
> didn't>,.....Do we have to consider such a scenario in our project
> or we can safely assume that if i sent a packet and then i
> timeout without recving a response then this packet is lost?
> In other words, can we assume that if the time out is always very
> large comparing to the delay
If nodes cannot complete downloading due to high delay and small timeout value, and they terminate gracefully, that's not an error. We will use higher timeouts for some testcases.
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