[Samba] Re: Unusable performance over WAN (part 2)

[James Lamanna]

On 10/8/07, James Lamanna <jlamanna at gmail.com> wrote:
> On 10/7/07, James Lamanna <jlamanna at gmail.com> wrote:
> > On 10/7/07, James Lamanna <jlamanna at gmail.com> wrote:
> > > On 10/7/07, Volker Lendecke <Volker.Lendecke at sernet.de> wrote:
> > > > On Sun, Oct 07, 2007 at 09:31:23AM -0700, James Lamanna wrote:
> > > >
> > > > > Server sends 1500 byte packet
> > > > > Client sends 52 bye ACK
> > > > > Server sends 1500 byte packet
> > > > > Client sends 52 byte ACK
> > > > > etc..
> > > > >
> > > > > Can anyone think of a reason for this?
> > > >
> > > > I did not find a link spontaneously, but Windows sometimes
> > > > falls back to something that we call "rabbit pellet"
> > > > mode. Maybe google shows up something for you.
> > > >
> > > > Volker
> > > >
> > > >
> > >
> > > I actually see that behavior using smbclient from a linux machine, so
> > > its not necessarily Windows related.
> > >
> > > -- James
> > >
> >
> > I've put some tcpdump logs from my macbook up at:
> > http://emagiccards.com/james/tcpdump-vpn-logs.tar.bz2.
> > It contains 2 files:
> >
> > vpn-wan.log - Transferring a file from my macbook over the WAN (logged
> > in through VPN)
> > vpn-nowan2.log - Transferring a file from my macbook not over the WAN
> > (logging through VPN)
> > (I have separate VPN servers on each size of the WAN).
> >
> > Here are the smbclient outputs:
> >
> > No WAN:
> > getting file \Jun07.xls of size 2321920 as Jun07.xls (23.8 kb/s)
> > (average 23.8 kb/s)
> >
> > Using WAN:
> > getting file \Jun07.xls of size 2321920 as Jun07.xls Short read when
> > getting file \Jun07.xls. Only got 1032192 bytes.
> > Error Call timed out: server did not respond after 20000 milliseconds
> > closing remote file
> > (3.9 kb/s) (average 3.9 kb/s)
> >
> > -- James
> >
>
> I've put up more logs this morning sans VPN.
> They are in:
> http://emagiccards.com/james/tcpdump-novpn-logs.tar.bz2
>
> Both of these logs are from being directly plugged in on either side of the WAN.
> The 'nowan' log is the normal, fast transfer, whereas the 'wan' log is
> over the WAN and has the unusable throughput.
>
> -- James
>

Another point of information:

Samba (and only Samba, other protocols work fine) seems to drop a lot
of packets.
Looking at simultaneous tcpdump traces from both the server and client
side, I see that lots of packets are dropped that are going from the
samba server to the client.
The sequence numbers look like this in some cases:

Client Recv                        Server Send
1150                                      1150
1152                                      1152
                                             1154
                                             1156
                                             1158
                                             1160
                                             1162
1164                                      1164
1166                                      1166
1168                                      1168
1170                                      1170

So in that case, a whole 5 packets were missed.
I'm going to assume this isn't normal behavior, and other protocols
(scp / ftp) don't seem to suffer from this problem.

-- James