I am curious, what exactly is the purpose and philosophy of the various
hash algorithms in the dispatcher module?  I am referring to the ones
that allow the gateway in the route set to be determined through a hash
of various SIP headers, such as the From URI, the To URI, the Call-ID
GUID, etc.

No guarantee of fair distribution - or in fact, any distribution that
can be characterised by any describable pattern whatsoever - is implied
by these algorithms.

Additionally, it seems that without knowing

(1) The exact hash algorithm in use;

(2) The distribution that this hash algorithm would yield for a given
set of possible values of these header fields, which in many cases are
specifically intended to be pseudorandom (e.g. Call-ID),

there is absolutely no way to determine, from any meaningfully
deterministic perspective, which numerical entry in the route set these
algorithms would computationally yield.

So, I guess my question is:  With no implied uniformity or weighting in
the distribution whatsoever based on the incidental character of such
values, what practical use does it serve to use any algorithms except
round-robin or random?  Is it expected that the user will plot the hash
values against a log of given input strings to determine how the
distribution will shape up?  Is there some reason why the sort of
profoundly lopsided distribution that may create might be desirable?

Thanks,

--
Alex Balashov
Evariste Systems
Web    : http://www.evaristesys.com/
Tel    : (+1) (678) 954-0670
Direct : (+1) (678) 954-0671
Mobile : (+1) (706) 338-8599

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