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Re: [rdiff-backup-users] Throttling

From: dean gaudet
Subject: Re: [rdiff-backup-users] Throttling
Date: Mon, 23 Jun 2003 10:14:32 -0700 (PDT)

On Mon, 23 Jun 2003, Nicholas Lee wrote:

> Personally I think its best is bwlimit control options where provided at
> all levels: OS, application layer transport, application.

the application does not have enough information to control bandwidth.
it especially has no global view of whatever else is going on, and no
ability to prioritize everything which is going on.  nor does it know what
other overheads are going to be added to the packets on the wire... or if
the data is going to run through a long series of pipes before reaching
the wire(*).  putting "bandwidth control" into application(s)  duplicates
the same, essentially useless, code everywhere.

about the only thing the application should do is use DIFFSERV or IPTOS to
identify its streams for the traffic shaper.  fwiw, ssh does this --
interactive sessions are marked IPTOS_LOWDELAY, and non-interactive
sessions are marked IPTOS_THROUGHPUT.  this gives a traffic shaper
something to filter on.


(*) not even ssh knows if it's the last application before the wire --
think about running ssh through a bastion host using ssh's ProxyCommand.

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