Another thing I forgot to ask: question about running public dccd

Vernon Schryver
Mon Sep 23 05:27:19 UTC 2002

> From: Adam Ierymenko <>

> ...
> We might be willing to run a public dccd and even have it listed as part of
>   How much bandwidth does this typically require?  I
> would also need a little help setting it up to work properly with the other
> servers.

There are serveral notions of "public DCC servers."  The first is running
your own DCC server for local DCC clients, and exchanging or flooding
reports of checksums with other more than 70 DCC servers in the global
network.  The numbers in the DCC FAQ at
about the loads imposed by that still look about right.

If you're interested in running your own server, please contact me
privately for an assigned DCC server-ID.  Having hacked on Exim,
I think you'll find running a DCC server easy.

A second notion is to answer DCC requests from anonymous DCC clients.
That can be done by having the IP address of your DCC added to one of
the names in or
having it listed separately there.  Of course, to answer anonymous,
requests you must be running your own server.

I only control the
list and the A RRs for  I can't speak about the
other public server names.  There are currently 6 RRs for, and so surely room for more.  (I guess I need to
discover that DNS/UDP/IP limit.  There is also a DCC client library
implementation limit of 8 IP addresses per server name.)

The bandwidth needed for that depends in part on the speed of your
connection.  If you have a slow link, fewer anonymous clients will
use your server.  The 6 current servers for are
receiving between 50,000 and 310,000 requests/day or about 1 to 4
requests per second, depending on how far they are from clients
and so how fast they seem.  Each DCC request is about the size of
a DNS request and needs between 1 and a dozen milliseconds for CPU
and disk processing on typical servers.

Judging from `cdcc clients` on a couple of the
systems, is just barely among the 1% of
anonymous clients of the servers that are offering
more than 50% of their load.  Thus, you seem like good a candidate
for at least running your own server.  The outfits that account for
bigger parts of that 50% seem even more compelling candidates.  Using
DCC servers that are 100's of milliseconds on the other sides of an
ocean and a continent is unlikely to matter if you are dealing with
a 1000 messages/day, but some of the other outfits are making 0.25 or
more anonymous DCC requests/second.  It seems stressful to make your
mail wait 300 or 400 ms for a long Internet round trip at those rates.

Vernon Schryver

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