[Users] how to refresh REGISTER state when restarting redundant proxy

Jiri Kuthan jiri at iptel.org
Mon Apr 23 04:20:26 CEST 2007

At 02:32 23/04/2007, Christian Schlatter wrote:
>Alan Crosswell wrote:
>>One option being discussed here is running mysql replicated.  This
>>brings up the concern that the independent proxies are not aware that
>>they are talking to a single database instance.  Will there be issues
>>involved such as:
>>- deadlocks
>>- inconsistency of in-memory and in-database data structures
>>  (e.g. usrloc, presence)
>>- collisions of per-proxy unique keys that are inserted into
>>  tables
>>Personally, I think mysql replication violates KISS if I am trying to
>>have my redundant servers as independent and survivable as possible.
>With mysql master-slave replication only one proxy could write to the database, so you'd need master-master replication which is possible but doesn't offer ACID as mysql cluster does.

I would not constrain oneself, for example one can do symmetric two-way client-server
replication. We have done that once with SER, other testimony can be found in 
(referring to a Columbia University technical report for even more details).

>I agree that using DB replication violates KISS as would also do the application layer state replication solutions you're describing below. 

I would say it depends on which type of data you are referring to. With SER (and I would
say this is 100% directly applicable to openser too) we have been using different replication
strategies to different types of data (tables).

>For me the best solution would be to have endpoints registering with all redundant proxies in parallel. This would also be in-line with SIP's redundancy in the previous hop. The newest firmware release for the Polycom SIP phones does support that, though I haven't tested it yet. Are there other endpoints implementing this feature?

The downside is that it does not work once you get a new SIP phone.


Jiri Kuthan            http://iptel.org/~jiri/

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