Multilink PPP Download Speeds With Round-Robin Packets

[Julian Elischer]

Michael MacLeod wrote:
> Hello all,
> 
> I've got two DSL lines running to my house, and two WAN NIC's
> installed in my FreeBSD router. I've been trying to get multilink ppp
> working through my ISP (TekSavvy in Canada) for the last little while,
> with mixed results. Each of my DSL lines sync's at 6016 kbits down and
> 800 kbits up. I have traffic working through the bonded connection,
> and the upload speed is 1350 kb, which is about right for a 1.6
> megabit connection minus network overhead. The problem I'm running
> into is the download speed is only that of one of my downlinks (approx
> 5000kb, which is about right for 6 megabits minus network overhead).
> 
> TekSavvy enabled packet splitting on the upload side of my connection,
> but are being cautious and only doing round-robin packets for the
> download side. I assume they are worried about collateral damage to
> non-multilink ppp users. I've posted to the dslreports teksavvy forum
> about my problem, and another FreeBSD user posted parts of his config
> and some speedtests that show that he has his download running at the
> full bonded speed. I've also received still another ppp.conf file from
> another FreeBSD user from the dslreports forums who was also able to
> get full bonded download speeds. This leads me to believe that there's
> something specific to my setup that is causing the problem.
> 
> In discussions on the dslreports forums I've compared my sysctl output
> for net.inet.tcp with someone successfully getting full download
> speed, so it doesn't seem to be there, though it could certainly be
> elsewhere in sysctl. I'm already using ppp.conf files from someone
> who's successfully made their download go full speed. It could be a
> kernel option, but the other two users haven't reported changing
> anything special in the kernel. Unfortunately, I'm relatively new to
> FreeBSD, so I'm not sure where else to look.
> 
> I've documented large parts of the setup, and my problems, on a wiki page here:
> http://bsdtips.utcorp.net/mediawiki/index.php/Mersault/MultiLink_PPP
> 
> And here are the important threads from the dslreports forums:
> http://www.dslreports.com/forum/r19513042-MultiLink-PPP-Performance
> http://www.dslreports.com/forum/r19719787-Still-Having-Multilink-PPP-Problems
> 
> If anyone has any ideas of where to look next, I'd be very grateful.

a couple of things...

1/ when downloading, does the load on each incoming interface
(I assume you have one ethernet to each modem) match?

2/ do the IP stats show a lot of out-of order packets?
(netstat -s -ptcp I think)
in fact ip reassembly problems might be of interest.
(netstat -s -pip (?))

3/are there many retransmissions?
4/ what is the outgoing data bandwidth when you are downloading?


5/ have you tried mpd? (in ports (multilink ppp daemon).)
it may have different operating characteristics.. (it does it all
in the kernel using netgraph). Sounds like you need to fix it
at the other end but mpd might trigger different behaviour
in the router.



> 
> Mike
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