In this redundancy option, several (N) Media servers provide local support for branches. In addition to a central backup Media server, some branches have dedicated backup Media servers. The number of backup Media servers assigned to a primary Media server is represented by K.
In case of an N+K redundancy, N and K represent the following:
N – Number of primary Media servers
K – Number of backup Media servers for a specific primary Media server. This number may differ for various primary Media server.
The following two figures show the N + K redundancy for Media servers:
If the Telephony Control Server cluster nodes share the same branchFigure 1. N+K redundancy – Telephony Control Server cluster nodes at the same branch
Figure 2. N+K redundancy – Telephony Control Server cluster nodes geographically separated
If the Telephony Control Server cluster nodes are geographically separated
Both figures contain the following elements:
Each branch has its own Media server for altogether three primary Media servers.
On each of the Telephony Control Server cluster nodes you find a central backup Media server.
Branches A and C have their own backup Media servers, too. These two branches may represent bigger field offices, while branch B may be a smaller field office that does not require a local redundancy.
As a result, branches A and C have two backup Media servers; branch B has one.
In this scenario the Media servers in the large branches are locally redundant, and the smaller branches use a backup Media server located on one of the Telephony Control Server cluster nodes. In normal operation, the Media servers are operable in all branches and process the entire Media server data traffic of Telephony Control Server. Load balancing is achieved for a branch by assigning it an additional Media server and configuring all Media servers of the branch for load balancing.
In case of a failure and depending on the failure type, the following happens:
If an Telephony Control Server node fails, the partner node adopts its function. The MGCP signaling manager on the partner node still uses the Media servers like it did before the failure.
Media Server Failure
If one of the three active Media servers fails, Telephony Control Server registers this event. If the branch has its own backup, Telephony Control Server uses this Media server from then on. If the branch does not have its own backup or the backup server fails as well, Telephony Control Server uses the central backup Media server. Existing connections to the failed Media server are not switched over and drop away.
Failure of a Branch
If a branch fails completely, the other branches carry on using their own Media servers and are not affected by the failure.
If the WAN connection to a specific branch collapses, the branch concerned cannot receive tones and system announcements. The subscribers isolated in the branch can still use the Media server inasmuch as they are registered with an Telephony Control Server edge system anew.
The other branches are not affected by the failure.
Support of Several Languages
Each local backup Media server must be configured for all languages required by the different associated Media servers of the branches. The central backup Media server must be configured for all languages required by the different Media servers of the branches.
Parent topic: Media Server Redundancy on Telephony Control Server