[Serusers] SER service: registration problem (load balancing quirk?)

Tom van der Geer tom.vandergeer at xs4all.nl
Tue Jan 22 09:49:43 CET 2008


Dear SER users,

I'm experiencing occasional problems with my SIP clients registration to 
the (free) iptel.org SER service. I'm not sure if this is the place to 
ask questions regarding this service. If not, please give me a pointer 
who/what I should contact.

I've made 2 tcpdumps. 1 from a failing registration request and  from a 
successful registration request. The setup for both situations is the 
same. These captures were made within 40 minutes from each other.

In both cases the first registration attempt is replied with a 401 
Unauthorized (obviously) which request for authentication. In both cases 
my SIP client (SJPhone) replies correctly (I assume) with a new 
registration and the requested account credentials. In the case of a 
successful registration the SER replies with a 200 OK. In the case of a 
failing registration my SIP client receives another 401 Unauthorized 
message. What struck me is that this second 401 is sent from another SER 
system. (The "Server:" header from the first registration attempt is 
different from the second registration attempt.)
The first header has "Server: Sip EXpress router (2.1.0-dev16-tcp 
(i386/linux))" while the second 401 has "Server: Sip EXpress router 
(2.0.0-rc5 (i386/linux))". (note the difference in SER versions)
I've verified that in the case of a successful registration the Server 
header in the first (401) and second (200) response are the same: 
"Server: Sip EXpress router (2.1.0-dev16-tcp (i386/linux))"

Is this some kind of weird load balancing quirk?

 From a security point of view I don't want to send my TCP Dumps (with 
my authentication) to the mailing list, but I can send it to a personal 
email address when required.
Thanks,

Tom







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