server-ID path

Vernon Schryver
Wed Jan 16 20:15:15 UTC 2002

> From: John Payne <>

> Is there any documentation on the server-ID path?

not yet

>                                                    And is it 
> good/bad/indifferent if there are loops seen in the path?
> Just out of curiousity I had a look at the paths I'm seeing,
> and I see double digit counts of paths like 101<-1015<-101<-1016

A loop implies one of several things:
  - a duplicate server ID, which is a Bad Thing(tm)
  - server ID translating causing confusion, probably also a Bad Thing
  - a server that lost its database and was restored by its neighbors
  - broken or experimental software and/or "bad hands." 
    Last week I tried something with the authenticated client bit that
    didn't work out.

> Should we also be looking to exchange floods with as many people 
> as willing, or people we see lots of times in the path, or is it 
> better to have a couple of big exchangers and lots of leaf servers?

I think Usenet provides the right models (plural).
In that universe, 
  - there are both big exchangers and lots of leaves.
  - there are both full feeds and leaf-only upstream or partial feeds
  - every server needs at least 2 and possibly 3 full feeds links.
  - no server needs more than 3 or 4 full feeds.

The normal DCC bandwith is likely to remain small, but when servers
need to be reflooded, wires get hot.  The current flood is about 4
MByte/day and the 7-day database is about 30 MByte (with perhaps a
doubling within the next month).  Many 4 MByte/day streams are no
problem, even for a 56 Kbit/sec modem.  However, if you have a few
dozen flooding peers and you do something that causes refreshing of
the full 30-60 MByte (current) database, things get kind of slow.

The equivalent to a netnews "L1" upstream feed is something like this in
/var/dcc/flod:   1234 5678 self->self,all->reject

An L2 feed where server-IDs 4444 and 555 are downstream might be   1234 5678 self->self,4444->4444,5555->5555,all->reject

Vernon Schryver

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