On Fri, Nov 06, 1998 at 02:06:29PM +0000, Jamie Lokier wrote:
> On Thu, Nov 05, 1998 at 08:58:24PM -0800, Steve Shah wrote:
> > I'm fiddling with TCP options -- I'd like to have the system
> > add MSS announcements as part of each packet's stock list of options.
> > I found that the options are generated in tcp.h in the
> > tcp_build_and_update_options for all packets after the handshake.
>
> Why do you want to do this? It's not part of any TCP spec AFAIK.
#include "maniacal_laughter.h"
Earlier this week I asked about TCP window sizes causing the perfomance
to take a nose dive when the window went below 1448 bytes. (1 ethernet
frame - appropriate headers) Thanks to others, I was shown that
letting the TCP window drop below the MSS made things break big time.
(AKA Silly Window Syndrome) <sarcasim>So I got this bright idea</sarcasim>
to to see if I could reduce the MSS midstream to correspond with
situations when I want to bring the TCP window that low. (This is
for a experiment.)
Looking at tcpdump and ipgrab, I saw that no one explicitly diallowed
this. TCP/IP Illustrated never forbided it.
> > The addition of the MSS info appears to be on a nice 4 byte boundry
> > and with the possibility of being able to send any number of SACKs
> > in the options, adding one more entry shouldn't mean I need to change
> > anything else. Looking at the tcp_syn_build_options, I can't see
> > what I'm doing wrong.
>
> No, it's limited to 3 SACKs with a timestamp. When all 3 SACKs are
> sent, you're overrunning the options. To quote RFC2018:
[snip]
I brought up the SACK's because I wanted to show that I did have space
left in the options field because they weren't being sent.
So to summerize: I'm really talking out of my ass when say I'm trying to
change the MSS midstream?
Thanks,
-Steve
--
______________________________________________________________________________
Steve Shah ([EMAIL PROTECTED]) | SysAdmin/Coder/Gabbernaut/DJ/Writer/Minister
http://www.cs.ucr.edu/~sshah | We're not dropping out, we're infiltrating.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Dilbert: It's not a cartoon. It's a documentary.
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