Running dcc server cluster

Vernon Schryver
Mon Jun 1 20:16:10 UTC 2009

> From: Ross West <>

> That's what I thought after going through everything.  But the man page
> for dccd does talk about a "close cluster of DCC servers" being
> identified by a single serverID.  Hence my confusion - thought I was
> missing something.

I've fixed the man page for the next release.   thanks.

> VS>   - Define DNS CNAMES for each server, such as and
> VS>
> VS>   - Define DNS A RRs containing IP addresses for all servers, such
> VS>       as
> VS>   - Teach each DCC client about all servers by running
> VS>         cdcc "add RTT-1000 ms  32768 SECRET"
> VS>       where SECRET is the password for client-ID 32768 in /var/dcc/ids on
> VS>       all servers.  That will let the clients balance their loads among
> VS>       the servers named by
> Already done, 

Unless I'm confused about who is, that sounds like a
violation of the license on the free version of the DCC software.
These words:

 * security solution sold to other entities, or to a private network
 * which employs the DCC or uses data provided by operation of the DCC
 * but does not provide corresponding data to other users.

are intended to require that all DCC servers participate in the
global network of DCC servers to share checksums of bulk mail.  That
involves contact me server-IDs and flooding peers.

Peering with the DCC network costs radically improves the effectiveness
of DCC filtering, at least for sites without extensive spam traps or
fewer than millions of mail messages per dai.  Connecting to the DCC
network costs only bandwidth and system administration hassles for
organizations that qualify to use the free DCC client software.

If I am not confused, please either stop using the DCC server software
or contact me privately for server-IDs and peers.

Note that only about two dozen of the hundreds of DCC servers in the
global network of DCC servers are "public."  The rest are quite private
except for TCP connections to 3 or 4 peers and answering UDP status
requests for the server status monitor.

Note also that I'm assuming that meets the other restrictions
in the free license included in the tarball or at
If I am wrong about that, please stop using the free client DCC software.
Feel free to contact me about terms for a license for the commercial

> Already done, although I'm curious if there's a better 'way' of the
> two types:
> Does defining 2 servers for the dcc client (ie: add dcc1, add dcc2) or
> defining 1 server with multiple IP addresses make any difference?
> In my testing, I've got 2 servers defined, with 1 having a RTT+500ms
> to make a rough 'primary/secondary' kind of setup.

One name with multiple IP addresses is best.  Without compelling special
needs, fine tuning the RTT adjustments is a bad idea.  In this case,
500 ms is more than the 400 ms that a DCC server adjusts its announced
queue delays when it is too busy, has no peers or is otherwise not
entirely healthy.  As a result, DCC clients will not automatically switch
servers as quickly or at all.

Vernon Schryver

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