Scaling PPTP

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Scaling PPTP

by Steve Pearson-2 :: Rate this Message:

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Hi,

I would like to scale PPTPD to 2048 maximum simultaneous clients by re-compiling the kernel (2.6.18) as is referred to in Jeff Blaize’s How-to (see below for exerpt). I am having trouble determining exactly which parameters need changing in the kernel source. Would someone please be able to provide me more specifics on what needs changing to increase per-process file descriptors, ttys and max processes etc as indicated below. Also he refers to code changes that need to be made in libc/kernel, any info on this would be appreciated if that is still necessary.

thanks!

Steve

See Jeff Blaize’s How-to Below

The limits under Linux are:

per-process filedescriptors

one per client (would limit clients to 256 by default, or 1024 with kernel recompile, or more with major libc/kernel hackery)
no relevant limit

ttys

currently, with a standard kernel, 256 clients
with Unix98 ptys and a small amount of coding, 2048

ppp devices

no limit in kernel source for ppp

processes

2 per client plus system processes
standard kernel max = 512 processes, ie 256 clients
i386 max = 4096 processes, ie 2048 clients

So it seems that 2048 will be the limit, if you fix a few things and with a minor kernel mod (I could do all of these pretty easily and send you a trivial kernel patch). To go above 2048 the easiest approach would be to combine pptpctrl and pppd in one process, which would get you to 4096. Beyond there, you need to go for a select() based model, which would be significant coding effort and require large fd-set sizes and so on. So 4096 is the practical limit, and 2048 the easy limit.

Steve Pearson

Network Integration

Prodea Systems

214.278.1805
www.prodeasystems.com


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