Understanding Send-Q and Recv-Q by netstat
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From: Rick Jones on 7 Dec 2009 14:13 David Schwartz <davids(a)webmaster.com> wrote: > On Dec 4, 12:48?pm, Rick Jones <rick.jon...(a)hp.com> wrote: > > perhaps it is out of date, but the netstat manpage on my linux system > > has this to say about the Q's: > > > > ? ?Recv-Q > > ? ? ? ?The ?count ?of ?bytes ?not copied by the user program connected > > ? ? ? ?to this socket. > > > > ? ?Send-Q > > ? ? ? ?The count of bytes not acknowledged by the remote host. > > > > Which certainly sounds like application-level bytes to me. > I was talking about how the queue sizes are set, not how they are > measured. This description is TCP-specific, but the SO_SNDBUF/ > SO_RCVBUF socket options are protocol-neutral. > Think about UDP. Where do you think the source IP and port are stored > if not in the receive queue? Off to the side, with the rest of the meta-data :) However, that may not be the case under Linux, which relates to how it likes to effectively double (up to a limit) what one requests in a setsockopt() call. rick jones -- A: Because it fouls the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing on usenet and in e-mail?
From: Christophe Lohr on 8 Dec 2009 05:36 Christophe Lohr a �crit : > ... sorry, I don't understand what are socket receive/send buffers :-( > > This is another level of buffer? > What is in it? > Is it after or before Recv-Q (along data flow within the socket) According to "A User's Guide to TCP Windows", there is a direct relationship between TCP window and SO_RCVBUF http://www.ncsa.illinois.edu/People/vwelch/net_perf/tcp_windows.html so... I'm lost... What are socket buffers? Regards.
From: David Schwartz on 8 Dec 2009 09:33 On Dec 8, 2:36 am, Christophe Lohr <christophe.l...(a)enst-bretagne.fr> wrote: > What are socket buffers? It's implementation-defined, and you will have to get into the horribly gory details of the implementation to understand it. Why do you care? Is this for curiosity? Because if you think you need to know it to do something at application level, you're doing it wrong. An application should never try to "teach TCP" its protocol. DS
From: Christophe Lohr on 8 Dec 2009 09:42 David Schwartz a �crit : > >> What are socket buffers? > > It's implementation-defined, and you will have to get into the > horribly gory details of the implementation to understand it. > > Why do you care? Is this for curiosity? Yes, that's it. I'm just looking for a high-level information Regards
From: David Schwartz on 8 Dec 2009 10:26
On Dec 8, 6:42 am, Christophe Lohr <christophe.l...(a)enst-bretagne.fr> wrote: > > Why do you care? Is this for curiosity? > > Yes, that's it. > I'm just looking for a high-level information Unfortunately, the high-level information is that the underlying network protocol provides you an ability to set something it calls a "send buffer" and something it calls a "receive buffer" in units of bytes. And that's it. DS |