HP-UX C SIP Stack Programmer's Guide (Novembery 2007)

Advanced Features 363
19
ADVANCED FEATURES
EXTENSION
S
UPPORT
SIP provides a mechanism for allowing a client to request that a particular
protocol extension be used to process a request. The client uses either the
Require or Proxy-Require headers to indicate the requested extensions.
Extensions are identified using “option-tags,” which are unique string names
defined in the extension specifications.
The server declines the request with a 420 (Bad Extension) response message, if
the server does not support the requested extension, and includes the set of
unsupported option-tags in an Unsupported header. Clients and servers advertise
their extension support using the Supported header (which also contains
option-tags).
The SIP Stack provides an easy way to use this mechanism using the following
configuration parameters found in the configuration structure, RvSipStackCfg:
 supportedExtensionList
Specifies the SIP Stack supporting ability. It is a list of
supported option-tags, separated by commas, which are
supported by the SIP Stack.
 addSupportedListToMsg
Indicates whether or not the SIP Stack should add the supported
header with the list in the supportedExtensioinList to every
request and response except ACK.
 rejectUnsupportedExtensions
Indicates whether or not the call-legs should reject requests that
include a Require header with an option-tag not supported by
the SIP Stack. When configured to RV_TRUE, if the server