DCC server high latency

Vernon Schryver vjs@calcite.rhyolite.com
Thu Jan 24 16:45:57 UTC 2008


> From: Mark v Herpen <markvh@office.cambrium.nl>
> To: dcc@rhyolite.com

> I've installed the dcc daemon, but the latency to this server on 
> localhost is higher than the latency to the public servers.
>
> When I do a cdcc info on the same machine as where the dcc daemon runs, 
> I get '400 ms queue wait' as response.
>
> I think it is typical that it alway exact 400 ms, so perhaps I forgot a 
> some configuration option.
>
> The version of DCC is 1.3.80 and it doesn't matter if i connect to 
> 127.0.0.1 or the public IP address.
>
> Can someone give me some advice?


DCC stands for "distributed checksum clearinghouses."   The basic
idea is to pool information about incoming mail with clearinghouses
to recognize bulk mail.  That idea makes no sense unless that
information is from more than one mail system.

Each sane DCC server exchanges or "floods" information with 3-4 peers.
If network problems or maintenance disconnect a DCC server from all of
its peers, it artificially delays its responses to encourage its DCC
clients to switch automatically to another DCC server.


Please note that running DCC servers not connected to the global
network of DCC servers violates the license on the code.  By running
a private DCC server that is not exchanging checksums with other
DCC servers or "flooding," you are violating this paragraph of the
license on the free version of the code that is in all of the files:

 * This agreement is not applicable to any entity which sells anti-spam
 * solutions to others or provides an anti-spam solution as part of a
 * 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.
   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
You need to buy a license for the commercial version of the code
to run a private network of DCC servers.  I think there are good
reasons for some organizations to buy the commercial code, but I
doubt it makes sense to run a private, disconnected DCC network
even with the commercial code.

That restriction in the license exists only to add a handle on
certain appliance and filter service vendors that do not qualify
for the free version of the DCC code but that use it regardless.


Vernon Schryver    vjs@rhyolite.com



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