4 May
2007
4 May
'07
8:39 p.m.
Hi Klaus, Alex et al.
I was thinking about the same problem.
My setup has two redundant SIP Proxy/Registrar (OpenSER 1.1) Servers (P1
and P2), no additonal edge proxies. It uses either MySQL cluster or
Master-Master Replication to exchange the state of the location table.
For NAT Processing of REGISTER I use the Nathelper module, which writes
the original (inside NAT) address to the 'contact' column and the
information, where the REGISTER request was received from (outside NAT
socket) goes to 'received' column of the location table.
e.g.:
contact column: sip:behoe@192.168.1.56:2051
received column: sip:130.56.88.20:5432
When an INVITE arrives at P1 (or P2), the 'contact' column will go to the
R-URI and the 'received' value will be used as the next target of the
INVITE request.
INVITE requests that do not arrive at the proxy, where the UA
has registered, have (depending on the NAT type) some likelihood to fail.
Appart from that and as long as there is no path value saved in the
location table, this work fine. If there is a path value, its content will
go to the Route header field and the the request is sent to the topmost
Route entry. Therefore it looses the information that was stored in the
'received' column....:-(
The preserve this information and to make sure that LL requests are
routed via the proxy, the UA has registered to, I have some idea, that uses
path. (Unfortunately not all of my UAs support 'outbound'...:-( ):
When the REGISTER arrives at the Proxy P1, I would insert a Path header
field with the address of P1 (i.e. the IP address and port of the proxy
processing the request)
Furthermore I would add a new header field parameter to the contact header
field (let's call it "extsock" for the time being) containing the external
NAT socket (i.e. the same information that also goes to 'received' column)
e.g.
Path: <sip:136.59.10.85:5060;lr>,
Contact: <sip:behoe@192.168.1.56:2051;extsock=sip:130.56.88.20:5432;lr>
This will then be stored in the 'path' / 'contact' columns of the
location table at save().
When the INVITE arrives e.g. at P2, it does the location lookup: The
Route header field will be populated with the content of the 'path'
column and the R-URI will be rewritten with the 'contact' column. This
means the request will be normally forwarded to P1 (topmost Route).
The SIP INVITE looks e.g. as follows:
INVITE sip:behoe@192.168.1.56:2051;extsock=sip:130.56.88.20:5432 SIP/2.0
Route:<sip:136.59.10.85:5060;lr>
[...]
After the request arrives at P1, it checks, whether there is an extsock
parameter in the R-URI, and if yes, it uses its values as the next target
of the request i.e. sip:130.56.88.20:5432
(Maybe P1 could even remove the extsock parameter from the
R-URI at this stage to make some Nokia E-Series' phones happier...)
My questions:
- Is this idea feasible? Does it work in any case? Any issues with
forking?
- Could it easily be configured to OpenSER, or is there a change in the
source code necessairy?
- How much does it break SIP standards? ;-)
Looking forward to your feedback.
Have a nice weekend!
cheers,
Bernie
On Wednesday 02 May 2007 08:33, Klaus Darilion wrote:
Hi Alex!
Without having done this: You can configure the SIP proxies as load
balancers too which distribute the load over all the proxy/registrars
(including itself).
I thought of that, but then every REGISTER needs to be forwarded to another
proxy to get the path info right. This result in a great amount of traffic
between the proxies and extra processing power. I want the REGISTER request
to be handled on the first host it arrives on. Then only some INVITE's need
to create inter-proxy traffic.