SIP high availability

SIP uses the high availability features included in the product to offer a comprehensive high availability solution.

The following topics describe how high availability is implemented for this product.

• High availability manager
• Replicating SIP sessions
• SIP session affinity and failover
• SIP cluster routing
• Upgrading SIP applications
• SIP IP sprayer
• Set up a high availability environment

SIP high availability architectural considerations

• Each container is able to handle state replication and SIP traffic.
• UDP (User Datagram Protocol), Transmission Control Protocol (TCP), and TLS (Transport Layer Security) are used for state replication and SIP protocol.
• Complete session state is replicated between all servers in the replication domain.
• Each replication domain is optimal at two servers. Three servers per replication domain does not perform as well because each server must maintain a copy of all session data in the replication domain, but on a failure only half the server's replicated data is activated on any of the remaining servers.

• The number of SIP proxy servers per blade is dependent on the number of cluster addresses configured at the IP sprayer.

SIP proxy configuration considerations

• No call state information is stored at the SIP proxy server.

• If the IP sprayer is configured for MAC forwarding:

  • The SIP proxy must listen on the loopback address that corresponds to a cluster address configured at the IP sprayer.

  • The IP sprayer configuration dictates the number of SIP proxy servers per node (or blade).
  • Each configured cluster address can have at most one corresponding SIP proxy instance per node.

Core groups and Distribution and Consistency Services (DCS)

A core group is a set of processes that handles high availability activities. Each core group has a coordinator function that manages all the singleton services running in the core group. Typical SIP deployments require only a single core group. For extremely large-scale deployments, such as 50 or more cell members, multiple core groups may be required.

The core group coordinator does the following:

• Maintains all group information - group name, group members, the policy of the group, and the state of each group member

• Assigns singleton service to group members and handles failover of singleton services.

For more information on core groups, read about high availability domain core groups.

DCS failure detection

For details on the core group failure detection mechanisms and algorithms, see the information on core group discovery and failure detection protocols.

DCS failure detection includes:

• Active failure detection using a tunable heartbeat mechanism that monitors:
  • Time interval between heartbeats
  • Number of heartbeats lost before declaring failure

• TCP KEEP_ALIVE / Sockets closing

Subtopics

• SIP session affinity and failover
  SIP in WebSphere provides session affinity and failover.
• SIP cluster routing
  Cluster routing rules is the method used to define how the SIP proxy routes messages to specific clusters in the cell.
• SIP IP sprayer
  SIP in WebSphere provides an IP sprayer.

Related:

Core groups (high availability domains)

Core group discovery and failure detection protocols

Browse all SIP topics

Replicating SIP sessions

Upgrading SIP applications