ADTRAN AOS Version R10.1.0 Command Reference Manual page 1078

Command Reference Guide Global Configuration Mode Command Set
Functional Notes
Session Initiation Protocol (SIP) uses the SDP to format the SIP message body in order to negotiate a
Realtime Transport Protocol (RTP)/Realtime Transport Control Protocol (RTCP) connection between two
or more user agents (UAs). The ports used for this will always be selected in a pair, with the even port used
for RTP and the odd port for RTCP.
You can also specify which range of NAT UDP ports are reserved for use only for SIP RTP packets using
the <start udp port> <end udp port> parameters of this command.
The SIP application-level gateway (ALG) (enabled using the ip firewall alg sip command) configures the
firewall to examine the ALL SIP packets it identifies and maintain knowledge of SIP transmissions on the
network. Since SIP packet headers include port information for the call setup, the ALG must intelligently
read the packets and remember the information.
For a full SIP implementation, dynamic firewall traversal for RTP traffic must also be enabled using the ip
rtp firewall-traversal command. This allows the firewall to open the proper ports for the RTP traffic
between UAs. For more details on SIP functionality in AOS, refer to the Functional Notes and Technology
Review sections of the command ip firewall alg on page 1004.
Usage Examples
The following example enables dynamic firewall traversal, and sets the policy timeout period at 60
seconds:
(config)#ip rtp firewall-traversal policy-timeout 60
60000CRG0-35E Copyright © 2012 ADTRAN, Inc. 1078