29 Sep
2008
29 Sep
'08
7:36 a.m.
On 09/29/08 14:22, Alex Balashov wrote:
samuel wrote:
There are use cases even when doing stateful processing. So:
- hash over call id - it is fast, good distribution, can be used for
calls to be sent to gateways, etc, works for stateless processing as well
- hash over from uri - caller is sent to same server, good for cdr
collection, authentication, etc
- hash over to uri - good to send registrations for a user to same
location server
- hash over r-uri - good to send calls to same location server as the
registration server for that user
Using a farm of servers, grouped by users, by combining the last three
you can route the sip messages inside your network to get auth, acc and
location services ok, and the first one to send to gateways :-)
Cheers,
Daniel
--
Daniel-Constantin Mierla
http://www.asipto.com
The Call-ID hash is used to send all requests of
the same dialog to the
same endpoint (proxy,application server,gateway,whatever...). The
reason after this behaviour is not to have these SIP endpoints sharing
the status of all the dialogs (not many applications out there share
this status and therefore you are required to send all within-dialog
messages to the same SIP instance).
simple: to send the BYE to the same gateway you sent the INVITE...
This does not guarantee fare load distribution....that's why depending
on what you are dispatching you can hash on several headers (if you
don't have to keep dialog state,...)
Yes, but is that not a relatively minor use case that applies to
situations in which stateful transaction forwarding (TM module) is not
used?
Meaning, if I t_relay() an INVITE to a gateway selected by dispatcher,
subsequent provisional responses and in-dialog requests will be passed
between the original endpoints without further intervention.
If it didn't work that way, round-robin and random wouldn't work as
algorithms because the next message would be sent to another server.
So, stateless forwarding aside (why would you want to do that in a
dispatcher load balancing or failover scenario?), why do these hash
algorithms make any sense to use?