Brocade Virtual ADX Server Load Balancing Guide (Supporting ADX v03.1.00) - Manual (Page 349)

Brocade Virtual ADX Server Load Balancing Guide 333
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Configuring SIP SLB
7
SIP server health monitoring
There are two types of SIP servers of particular importance: SIP proxy servers and SIP registrar
servers. The Virtual ADX supports advanced UDP Layer-7 application health checks for both server
types.
Virtual ADX switches can be enabled to send REGISTER or OPTION messages to SIP servers to track
their health. When an error-free response status (default is 200 OK) is received, then the Virtual
ADX marks the SIP server as being available, and starts assigning new SIP sessions to the available
servers.
The switches can also be configured to send health-monitoring messages at user-defined
frequency and retrial attempts. By default, 200 OK is considered a valid response code. Optionally,
you can configure the switch to accept other response codes that indicate a healthy and available
server.
SIP messages with specific SIP methods are switched to the appropriate SIP server. As an example,
REGISTER messages are forwarded only to the SIP registrar server; whereas INVITE messages are
distributed among SIP proxy servers.
Configuring SIP SLB
SIP server load balancing over UDP is available in stateless SLB mode and stateful SLB mode.
SIP SLB over UDP features the following elements in both stateless and stateful modes:
• Persistence parameter can be extended: The persistence parameter can be extended to other
key header fields, such as the VIA header. This applies to both SIP stateful and SIP stateless
modes.
• Support for fragmented UDP support: Applies to both SIP stateful and SIP stateless modes.
The following elements are supported in stateful SLB mode only:
• SIP stateful support: Server selection is based on round-robin persistence on a user-configured
key header, such as Call-ID, and corresponding SIP sessions are created for this purpose.
• Server initiated SIP requests handling: Sessions are created so that subsequent transactions
with the same persistence parameter are directed to the same real server. This applies to SIP
stateful mode only. This enables the Virtual ADX to load balance the back-to-back user agent
(B2BUA) SIP servers.
• A SIP session created in Virtual ADX with multiple barrel processors are synchronized to all
barrel processors (BPs).
• Redundancy support: SIP stateful supports both hot standby HA and symmetric active-standby
HA configuration by synchronizing SIP sessions to peer box. Symmetric Active-Active HA
configuration is not recommended.
SIP SLB over UDP (Stateless SLB mode)
The following sections discuss SIP over UDP.