SIP-Based Load Balancing/Virtual IP Address

This feature allows you to distribute SIP traffic between IMG's configured as “SIP Servers” using Virtual IP Addresses and a SIP load balancer. The IMG allows you to configure a Virtual IP address (VIP) in addition to the existing Real IP address. The IP address set allows SIP calls to be terminated concurrently on any of the IP addresses, real or virtual. The deployment of multiple IMG products sharing Virtual IP addresses creates in effect a set of redundant SIP signaling paths.


Note: Accounting for capacity and the balancing algorithm are configured on the Load Balancer, not the IMG.


Diagram - SIP-Based Load Balancing

Load balancers can create pools of IMG gateways, all sharing the same Virtual IP addresses. The diagram below shows the relationship between these network endpoints







Load Balancers

Load Balancers automatically detect when a server is unavailable using “heartbeats”, either through ICMP Ping or SIP OPTIONS. Load balancing takes place between a set of IMG's reachable through such heartbeats. This provides increased VoIP network availability by routing traffic through “healthy” signaling paths. It also reduces the number of re-transmitted SIP INVITEs and consequently increases the overall call completion rate.


This activity is commonly described using one of the following terms:


The use of Virtual IP addresses on the IMG enables seamless integration of load Balancers in a Dialogic solution. Load Balancers are not SIP-specific, however they are SIP-aware in order to route subsequent transactions for an existing call to the correct gateway/IMG. Load Balancers have redundant features and can be geographically distributed.


Note: A SIP proxy could also be used to load balance SIP traffic, however it would use the actual IMG IP address and not the MAC address; therefore, the Virtual IP Address could not be used.


Related Topics

Configuring SIP-Based Load Balancing

SIP Virtual Address

IP Address