cdcc RTTs in FreeBSD Jails

Vernon Schryver
Tue Jun 1 16:09:41 UTC 2004

> From: Andy Hilker 

> What does determine, which server is queried when "cdcc load map.txt"
> or "cdcc RTT" ?

`cdcc "load map.txt"` or `cdcc RTT` does the following:

  1. resolve the IP addresses of all known hostnames of DCC servers

  2. retain as many as 12 of the IP addresses found in step #1. 
    Which 12 is a random or at least arbitrary function of the DCC client's
    own IP address and other bits likely to be unique and unchanging
    for the client.

  3. send DCC NOPs to all of the IP addresses from step #2.

  4. collect responses to the NOPs for the default RTT guess.

  5. if several DCC servers have been heard from or 4 or 5 batches
    of NOPs have been sent,, quit.  Otherwise double the default RTT guess
    and go to step #3.

If you see fewer than 12 NOPs and if you have dcc{1,2,3,4,5}
in your map.txt file, then I would check your DNS resolver.  Does
`nslookup` or `host` find 16 A RRs for,,,, and  Do you see 7 A RRs for

What happens if you try the command `cdcc "host x.y.z.w; stats"`
for various IP addresses x.y.z.w?

Vernon Schryver

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