DCC server or Client suite to us?

Vernon Schryver vjs@calcite.rhyolite.com
Wed Jul 5 13:25:27 UTC 2006


> From: "Mathew Thomas" 

> We have got four mail gateways - Total mail per day on four gateways
> together is 400,000 to 450,000 (50,000 -100,000 outbound, 300,000 -
> 350,000 inbound)
>
> Should I set up our own DCC server or can I use the public dcc servers?

400K mail messages/day is above the 100,000 threshold at which a local
DCC server is justified.
It is high enough that it will trigger some of the DoS defenses
in the public DCC servers.  Those start with delaying responses and
then ignoring requests entirely.  At 400K/day, some of your requests
should be ignored.

> Can I do it on one of the gateway? 

The DCC server process, dccd, uses needs trivial CPU cycles but at
least 3 GByte of RAM.  4 GByte is not too much.  If one of your gateways
has that much RAM to spare, it could run dccd.
A DCC server also needs as much as 12 GByte of disk space, but that is
also trivial today.


>                                    If I needed to set it up on one of
> the gateway, how can I set it up so that all four mail gateways can use
> it?

/var/dcc/map contains the names and IP addresses of the DCC servers
known to a DCC client such as one of your gateways.  It is best to
teach a DCC client about a local server with a command like:

   cdcc "add host.example.com  RTT-1000 ms  32768  secret"

where secret is the password for client-ID 32768 in /var/dcc/ids on the
DCC servers.


A DCC server needs a server-ID and 3-4 flooding peers to receive
checksums of recently seen bulk mail.  I can provide those.


Vernon Schryver    vjs@rhyolite.com



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