Technical data

Brocade ServerIron ADX Advanced Server Load Balancing Guide 27
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SIP SLB for a SIP media session
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Stateful SIP session handling in the event of a proxy server failure
ServerIron ADX can seamlessly handle failure of proxy servers while running in stateful mode. The
ServerIron ADX can be enabled to reroute subsequent SIP packets on an existing flow for a failed
proxy server to an available healthy proxy server. However, note that the back-end SIP proxy server
should have the capability of handling such SIP calls that were originally serviced by a different
proxy server.
This feature is generally useful when back-end proxy servers are configured in cluster
configuration.
ServerIronADX(config)#server sip enable-session-failover-on-server-failure
Syntax: [no] server sip enable-session-failover-on-server-failure
NOTE
This command is not required when ServerIron ADX is configured in SIP stateless mode. With
stateless mode, ServerIron ADX automatically assigns a new proxy server when packets arrive on an
existing flow to failed server.
SIP SLB for a SIP media session
The ServerIron ADX performs load balancing of SIP control traffic. However, it does not perform any
processing of the SIP media (data) session created after an SDP “200 OK” message. Typically, this
works because the media session is independent of SIP and is established directly between the
participants, bypassing the ServerIron ADX.
Occasionally, the media session goes through the ServerIron ADX and requires to be forwarded to
the same SIP proxy server that previously forwarded the SDP “200 OK” message. In this case, the
ServerIron ADX does not parse SDP header and is unable to transport the media session.
To resolve this issue, you can partition the media ports among the proxy servers behind a VIP. In
the SDP “200 OK” response packet from a proxy server, the media server IP should be the VIP, and
the media port should be within the range of ports that is allocated to the proxy server. The
ServerIron ADX creates tracking sessions to ensure appropriate packet translation and forwarded it
to the proxy server.
You can configure a media range setting on the SIP server that excludes well-known ports for this
purpose. The ServerIron ADX identifies the UDP packet through the port within media range and
uses a persisted session to create both forward and reverse flow sessions instead of a server
selection.
NOTE
The feature is also supported with IPv6 SIP servers.
Configure range of media ports
To create, update or delete a media-range settings on the SIP server, use the port sip media-range
command under real server configuration mode.
ServerIronADX(config)# real-server rs1
ServerIronADX(config-real-server-rs1)# port sip media-range 10000 to 100001
Syntax: [no] port sip media-range start_port_number to end_port_number