Command Line Interface Reference Guide > The SLB Configuration Menu
/cfg/slb/virt <server number>/service/sip/sip
SIP Load Balancing Menu
From this menu, you can enable or disable Session Initiation Protocol (SIP) server load balancing. When enabled, you can configure a SIP service on the service port 5060 for a virtual server.
SIP is an application-level control protocol for creating, modifying, and terminating sessions with one or more participants (refer to RFC 3261). Alteon supports both TCP- and UDP-based SIP servers. Using SIP, you can load balance MCS (Multimedia Communication Server) proxy servers. MCS is a UDP-based SIP-enabled application Server. Microsoft LCS server is supported.
For non-standard ports, Alteon allows TCP and UDP services on the same virtual IP address.
 
 
Notes
*You need to activate Direct Access Mode (DAM) perform SIP load balancing.
*You can use only minmiss as the load-balancing metric, because load balancing is performed based on the Call-ID.
*When enabling sip flag in the SIP service, the size of acceptable SIP headers is limited to 512 chars. As an alternative Call ID persistency as well as advanced SIP-aware decisions or modifications can be achieved via AS++ script (in which case the sip flag must be disabled).
 
[SIP Load Balancing Menu]
sip - Enable/disable SIP load balancing
sdpnat - Enable/disable SIP SDP Media Portal NAT
hashlen - Set length for hashing (4- 256 bytes)
cur - Display current SIP configuration
Note: Layer 7 SIP load balancing is supported only in UDP and not in TCP. You must enable UDP for SIP service.
 
SIP Load Balancing Menu Options(/cfg/slb/virt/service/sip/sip) 
Command Syntax and Usage
sip <enable|disable>
 
Specifies whether to enable legacy SIP-aware load balancing.
*enable — SIP message persistence is maintained by performing hash on the Call-ID header.
The group SLB metric must be set to minmisses.
SIP headers over 512 characters are not accepted in this mode.
More advanced SIP-aware persistency and capabilities can be achieved using AppShape++ script. This parameter must be disabled when working in Force Proxy mode.
*disable — Alteon performs Layer 4 load balancing.
Default: disable
sdpnat <enable|disable>
 
Specifies whether to enable SIP media portal NAT.
This feature is useful if you have several media portal servers with private IP addresses. When the proxy servers respond to an INVITE request, the private IP address of the media portal is embedded in the SDP. Alteon translates this private IP address to a public IP address.
Default: disable
hashlen <4-256>
 
Specifies the number of bytes from the Call-ID that are used as input to the hash function performed when SIP load balancing is enabled.
Values: 4 – 256
Default: 256
cur
 
Displays the current SIP configuration.