DCC server list

Vernon Schryver vjs@calcite.rhyolite.com
Mon Dec 29 16:05:16 UTC 2003

> From: "Earl A.Killian" <dcc@lists.killian.com>

> I have an old non-stateful router firewall.  Those are particularly
> problematic for allowing UDP packets, so my solution has been to
> explicitly list all UDP servers I use.
> ...

That sounds problematic.  I hope the IP addresses of the DCC servers
will continue to change.  Besides the usual IP address changes, DCC
servers come, go, and take vacations.

> ...
> Note that dcc2.dcc-servers.net are not in the dcc.rhyolite.com list.
> Should I instead use dcc*.dcc-servers.net?


Recall the familiar DNS/UDP/IP packet size limitation and notice that
there are more than 17 public DCC servers (but certainly not too many).

Each DCC client randomly selects 12 IP addresses from among those
available, while trying to pick evenly from all of the domain names.
The goals include spreading the work uniformly among all of the DCC
servers, while paying attention to any local servers.  The client code
picks the best server from among those 12 addresses.  There are minor
complications such as ensuring that a given DCC client picks the same
dozen IP addresses until the total set changes despite randomizing
efforts by DNS servers.

The map.txt//map file in the souce users the dcc{1,2,3,4,5}.dcc-servers.net
names.  For now, dcc.dcc-severs.net and dcc{1,3,4,5}.dcc-servers.net
are same, but that may be a mistake.  I've not figured out a tactic
that works well both for clients that use the dcc{1,3,4,5}.dcc-servers.net
names and clients that use the dcc.dcc-servers.net name, and without
making the lists too easy to get wrong.

Vernon Schryver    vjs@rhyolite.com

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