[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]

Re: FC3 Torrents available? [Was: FC3 ISOs alerady online?]



On Mon, Nov 08, 2004 at 01:12:23PM -0500, Uday Kumar Reddy wrote:
> > So the aim of seperating trackers is not avoiding small bandwidth links,
> > but high RTT (delay) links, which directly affects TCP performance.
> 
> I understand what you are saying. But, isn't it that the link delay
> doesn't matter for large transfers? For large transfers, the link
> delay is just reflected as the startup time. So, an 'n' mbps link
> whether it is transatlantic or close-by would almost take the same
> time to transfer data for _large_ files/streams.

No, this is wrong, exactly the other way 'round.

TCP has a concept of "windowing" where it limits the amount of data
which can be in-flight without having received an ACKnowledgement of
receipt from the receiver. The window is initially very small and grows
larger over time. This is the so-called "slow start". The window
doesn't grow infinite though, so you you'll arrive at some maximum
size. Let it be 16K, 32K, 64K... depending on OS, version etc. Now
you can calculate how much unACKed data can be "on wire" on a given
latency link at once and thus calculate the maximum theoretically
possible throughput of that link which is characterized by the latency.

A good explanation with formula can be found here:
http://www.psc.edu/networking/projects/tcptune/

> So, I think its congestion that justifies having seperate trackers.

Nope.


Best regards,
Daniel

-- 
CLUE-RIPE -- Jabber: dr cluenet de -- dr IRCnet -- PGP: 0xA85C8AA0


[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]