Telephony Control Server supports various redundancy options for connecting Media servers. In this support, any combination of RadiSys and Media Server can be used.
Owing to this combinability, the Media server that complies with the respective performance requirements can be used anywhere in the Lotus Sametime Unified Telephony system.
Telephony Control Server supports the following redundancy options for connecting Media servers:
Local Media servers can be configured in branches for the redundancy options N+1 and N+K. In this configuration, tones and system announcements need not be transmitted via the WAN, but are available locally. This optimizes the bandwidth use for the WAN.
Redundancy Software Support
Software support of the redundancy mechanism refers to the following main functions:
Administration of the Media servers, so that they can provide security for each other. Depending on the type of redundancy used, the requirements differ slightly.
A heartbeat mechanism that interconnects Telephony Control Server and the Media servers via keep-alive messages. This mechanism detects failed connections between systems or their recovery. It also ensures that Telephony Control Server automatically switches over to the connection to another Media server if the connection to the preferred Media server fails.
The following is required for providing this feature:
The Telephony Control Server feature automatic Media server audit
must be active. This enables the automatic audit between Telephony Control Server and all Media servers. Furthermore, the following features must have been defined:
The number of failed audits before the Media server is locked
The number of successful audits before the Media server is put into operation again
The control signal interval, which indicates the interval for sending the audits
An audit circuit must be provided for each Media server. This circuit provides Telephony Control Server with a path for checking the statuses between the single Media servers. This audit circuit enables the control signal for the respective Media server.
The Multi Homing
flag must have been disabled for the single Media servers. This flag indicates that the Media server does not have an internal redundancy, and that an IP address is assigned to each fully qualified domain name.
The redundant Media servers must be administered in the same way. Example:
The announcements IDs of all provided Media servers should match, so that the user does not notice any functional difference when a Media server is taken out of operation.
The number of ports of the local backup Media server of a branch must correspond to the number of ports of the primary Media server.
The central backup Media server should contain all languages used by the Media servers it supports.
The use of redundant Media servers enables in the following way the administration of the bandwidth between the two Telephony Control Server nodes and between branches:
Parent topic: Media Services
Within Telephony Control Server, load balancing occurs between the MGCP signaling managers by even distribution of the subscribers among the two nodes. The MGCP signaling manager of the caller's node is selected.
For branches, bandwidth administration is achieved in the following way:
Installation of a local Media server in each branch
Assignment of a tariff zone to each branch
Creation of an origin destination for the tariff zone. This destination indicates that the local Media server of the branch is to be used
In case of geographically separated Telephony Control Server nodes, a Media server that is located at the same branch as the node or is integrated in this node can be configured as primary Media server for local subscribers through use of tariff zones. In this case, the Media server on the other node acts as backup Media server for local subscribers.
1 + 1 Redundancy for Media Servers
In this redundancy option, one Media server is assigned to each Telephony Control Server cluster node. Each of the two Media servers acts as backup for the other one.
N + 1 Redundancy for Media Servers
In this redundancy option, several (N) Media servers provide local support for branches, and a central Media server serves as backup for all other servers.
N + K Redundancy for Media Servers
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.