But now the Single Point of Failure is the SIP proxy. If our SIP proxy application crashes or the server drops dead then we're nowhere !
In this post we will create a High-Available cluster of SIP proxy. There will be minimum of two SIP proxy servers (Physically unique) in one cluster.
One of the node will be defined as the primary node and our set of applications will run on the primary server. If the application set fails on primary node then our HearBeat will first try to restart it. If the restarting retries fails then it migrates the group of applications to the secondary node or any other node in the cluster.
The Set/Group of services which run on the any node in cluster are as follows (Priority in the order written)
1- Floating/Virtual IP
This IP is basically the only Public IP assigned on the cluster node. SIP proxy Listens to this address.
2- Linux Default Route
This will use Virtual IP configurations and use it as only way In&Out of Server to Internet.
3- SIP proxy
kamailio or OpenSIPS - This is the primary application which will be monitored for any crashes.
4- Add on Applications
Any other applications which are required in combination with SIP proxy and need to be started along with the SIP proxy i.e RTPproxy or Media-Proxy or any other application.
What this setup requires is atleast two physically unique serverswith atleast two NICs. eth0 IP of each server will have a unique Private IP, eth1 of both will be unused. The most important thing to mention here is that we don't set default-gateway on these machines. We can only access these machine from anyother third machine on Private IPs.
The only way these machines connect to internet is that they become primary node. When they become primary node the Public IP is assigned on eth1 and then default-gateway is set by the heartbeat application.
Once the default-gateway is set on primary node only then internet is accessible.
|SIP proxy HA design|
We have a separate independent Database for SIP proxy servers to save the User-Location Records. In case of primary server failure the secondary servers connects to the same DB and have all the registered users and active calls record in DB already. This is the key for this setup to work.
Read on to this blog's Second part on creating such a setup.