[Cerowrt-devel] rsync over ssh

Michael Richardson mcr at sandelman.ca
Wed Jan 29 16:27:58 EST 2014

I often run rsync over ssh to transfer files.
I suspect that they are being classified wrong, and are competing with my
interactive ssh sessions.  I experience classic bufferbloat issues with a
congested uplink when typing.  (But, DNS and web is unaffected, it seems)

I notice in ssh_config(5) man page that it says:

     IPQoS   Specifies the IPv4 type-of-service or DSCP class for connections.  Accepted values are ``af11'',
             ``af12'', ``af13'', ``af21'', ``af22'', ``af23'', ``af31'', ``af32'', ``af33'', ``af41'', ``af42'',
             ``af43'', ``cs0'', ``cs1'', ``cs2'', ``cs3'', ``cs4'', ``cs5'', ``cs6'', ``cs7'', ``ef'', ``lowdelay'',
             ``throughput'', ``reliability'', or a numeric value.  This option may take one or two arguments, sepa-
             rated by whitespace.  If one argument is specified, it is used as the packet class unconditionally.  If
             two values are specified, the first is automatically selected for interactive sessions and the second
             for non-interactive sessions.  The default is ``lowdelay'' for interactive sessions and ``throughput''
             for non-interactive sessions.

I can see no evidence that my IPv6 packets are being changed in anyway.
On IPv4, I see:

16:25:50.744290 IP (tos 0x8, ttl 64, id 62723, offset 0, flags [DF], proto TCP (6), length 52) > Flags [F.], cksum 0x5735 (correct), seq 623906, ack 3314, win 110, options [nop,nop,TS val 1178738167 ecr 2623900673], length 0

I'm not sure that "tos 0x8" is particularly useful. It's DSCP 1, and I think
it's actually being marked TOS-like.

Will any value here have any affect on default 3.10 qos.sh script?

]               Never tell me the odds!                 | ipv6 mesh networks [
]   Michael Richardson, Sandelman Software Works        | network architect  [
]     mcr at sandelman.ca  http://www.sandelman.ca/        |   ruby on rails    [

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