Heico Salfeld wrote:
>
> Hi there!
>
> I have a question about the -s option. In the manual of revision 2.1 it
> says that this will set the local send and receive buffer sizes to the
> value specified. The -S option will do the same for the remote system.
>
> What kind of buffer is actually meant...:
> 1) Is this just a buffer of the system's input and output functions?
> 2) Or does this parameter set the maximum window size of TCP, and can
> reach up to the max. CWND of 64 kBytes which is defined in the OS?
I guess it depends on the transport implementation. The -S and -s
options specify the values passed in setsockopt(SO_SNDBUF|SO_RCVBUF)
calls. On BSDish stacks, the SO_RCVBUF setting, controls the TCP window.
SO_SNDBUF tends to control how much the sender can have outstanding at
one time.
CWND can be more than 64KB if the window is more - though there are some
stacks which place a configurable limit on cwnd.
The maximum data outstanding at any one time on a TCP connection will
(more or less) be the minimum of the sender's SO_SNDBUF, the receiver's
window/SORCVBUF and the senders cwnd.
> In both cases: is it correct that it is counted in bytes?
Yes.
> BTW: I am sending TCP over a satellite link with a RTT of 560 msec. Any
> suggestions with which params it's mostly worth to play around?
The -s and -S are good ones.
rick jones
-- these opinions are mine, all mine; HP might not want them anyway... :) feel free to email, or post, but please do not do both... my email address is raj in the cup.hp.com domain...