All, To be precise, the only reason I have manipulated these parameters is to be able to render the 19.2 Mbps mpeg2 stream from Seattle (233.0.73.26) with VLC and similar higher throughput streams. I never had a problem with vic streams, so my experiments and observations reflected the need to optimize at higher bitrates.
However, I also played around with these settings at home with my wireless connection via Airport to roadrunner cable modem internet access, so I was interested in optimizing both tcp and udp. I also seem to recall something about the maxsockbuf being large enough to accommodate the tcp send/recv space settings, but perhaps that was inaccurate. Fyi, -gurcharan Piers O'Hanlon wrote: > Hi, > > I think the key sysctl here is this one: kern.ipc.maxsockbuf=8000000 > which determines the max UDP buffer sizes (the others, as Chris points > out, are only relevant to TCP). > > What would be useful to check is to run netstat -s on your system with > and without the ker.ipc.maxsocketbuf setting - and look at the UDP > section on "dropped due to full socket buffers" and see how this > changes. > > However this is odd as vic does set the socket buffer sizes in the > application. One explanation maybe that the application provided > buffer sizes are a guide and if they're overrun then it can use more > memory but if the default max (on my MacBook they're set to 262144) is > too low then they will run out and hence you'll get bad video. > > The other thing that is strange is that this doesn't appear to happen > on Linux (maybe it is and we haven't noticed it) but after a quick > look at the Linux kernel it seems that the SO_RCVBUF setsocketopt() > kernel implementation doubles the supplied value which may makes > things ok on Linux? However the max buffer size in Linux (Ubuntu 7.10 > anyway) is /proc/sys/net/core/wmem_max 131071 (which is lower than > OSX)... > > If we find that vic's default's are too low then we can tweak them, > though it may only be fixed on some systems but increasing the system > maximum..... > > It maybe worth keeping an eye on UDP buffer overruns (use netstat -s) > to see if this a more general problem. > > There's a good guide on UDP buffer sizing here: > http://www.29west.com/docs/THPM/udp-buffer-sizing.html > > Piers. > > > On 10/11/2007, gurcharan khanna <[email protected]> wrote: > >> Christoph Willing wrote: >> >>> On 10/11/2007, at 7:56 AM, gurcharan khanna wrote: >>> >>> >>>> Mark, >>>> >>>> my link to the source for this seems to be broken but here's what i >>>> have personally on my mac. >>>> >>>> in /etc/sysctl.conf, add these lines: >>>> >>>> >>>> net.inet.tcp.recvspace=4000000 >>>> net.inet.tcp.sendspace=4000000 >>>> kern.ipc.maxsockbuf=8000000 >>>> >>> Those settings look like they may have come from: >>> http://www.psc.edu/networking/projects/tcptune/ >>> >> You're right about the URL. However, the link doesn't work anymore.... >> >>> However, note that TCP tuning is the subject there, not UDP (which is >>> what multicast uses). >>> >> Understood. However, changing these settings DOES in fact improve things >> considerably, predictably, >> and repeatedly. I don't quite understand it, but it does work. >> >> -gurcharan >> >>> chris >>> >>> >>> >>> >>>> you probably have to restart to activate them. you can set these from >>>> the command line as well but they won't "stick", but you can try out >>>> different >>>> settings that way. >>>> >>>> use: sysctl -w net.inet.tcp.recvspace=4000000 (for example) >>>> >>>> to set these values interactively. >>>> >>>> -gurcharan >>>> >>>> >>>> >>>> Leonard, Mark wrote: >>>> >>>>> Listers-- >>>>> >>>>> It was probably a year ago that a setting change for Mac OS that >>>>> improved video quality of big video multicast streams (Gurcharan?) >>>>> but I >>>>> can't seem to find it any where... >>>>> >>>>> Can someone repost or point me towards a troubleshooting page for >>>>> tweaks >>>>> like this? >>>>> >>>>> Thanks >>>>> Mark >>>>> >>>>> >>>>> Mark Leonard >>>>> DL Studios, UNH >>>>> 603-862-0192 >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>> -- >>>> ------------------------- >>>> Gurcharan S. Khanna, Ph.D. >>>> Director of Research Computing >>>> Office of the Vice President for Research >>>> >>>> Director, Interactive Collaboration Environments Laboratory, >>>> Center for the Advancing the Study of Cyberinfrastructure >>>> --- >>>> Rochester Institute of Technology >>>> 1 Lomb Memorial Drive >>>> Rochester, New York 14623-5603 >>>> Phone: 585-475-7504 ~ Cell: 585-451-8370 >>>> Email: [email protected] >>>> Http: people.rit.edu/gskpop >>>> >>>> >>> Christoph Willing +61 7 3365 8350 >>> QCIF Access Grid Manager >>> University of Queensland >>> >>> >>> >>> >> -- >> ------------------------- >> Gurcharan S. Khanna, Ph.D. >> Director of Research Computing >> Office of the Vice President for Research >> >> Director, Interactive Collaboration Environments Laboratory, >> Center for the Advancing the Study of Cyberinfrastructure >> --- >> Rochester Institute of Technology >> 1 Lomb Memorial Drive >> Rochester, New York 14623-5603 >> Phone: 585-475-7504 ~ Cell: 585-451-8370 >> Email: [email protected] >> Http: www.rit.edu/~gskpop >> >> >> -- ------------------------- Gurcharan S. Khanna, Ph.D. Director of Research Computing Office of the Vice President for Research Director, Interactive Collaboration Environments Laboratory, Center for the Advancing the Study of Cyberinfrastructure --- Rochester Institute of Technology 1 Lomb Memorial Drive Rochester, New York 14623-5603 Phone: 585-475-7504 ~ Cell: 585-451-8370 Email: [email protected] Http: www.rit.edu/~gskpop
