Technical data

ServerIron ADX Advanced Server Load Balancing Guide 19

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Configuring SIP SLB

FIGURE 7 Reuse of TCP connection

Server-side connection: With source NAT

If source NAT is enabled, then the ServerIron ADX uses source NAT IP addresses and ports for

establishing connections with proxy servers.

Server-side connection: Without source NAT

A ServerIron ADX may be configured with a maximum number of TCP connections to a specific

proxy server.

If source NAT is disabled on the ServerIron ADX, then the ServerIron ADX establishes new TCP

connections based on the connection reuse setting:

• Connection reuse disabled: If a new SIP request is received and the configured maximum

number of server connections has been reached, then ServerIron ADX drops any new request.

This is the default behavior.

• Connection reuse enabled: If a new SIP request is received and the configured maximum

number of server connections has been reached, then ServerIron ADX reuses an established

connection to process the client request.

NOTE

With either setting, the client identity (IP address and port) is preserved because source NAT is not

enabled.

Connection handling with SIP requests initiated by proxy server

Topologies involving back-to-back user agent (B2BUA) are also supported.

SIP Proxy Server

Call-ID1...

Call-ID3...

Call-ID2

ServerIron

Call-ID1...Call-ID2...Call-ID3

Mega-proxy

Several SIP messages

using one TCP Connection