| The Require header field is used by UACs to tell UASs about options that
the UAC expects the UAS to support in order to process the request.
Although an optional header field, the Require MUST NOT be ignored if it
is present.
The Require header field contains a list of option tags. Each option tag
defines a SIP extension that MUST be understood to process the request.
Frequently, this is used to indicate that a specific set of extension
header fields need to be understood. A UAC compliant to this specification
MUST only include option tags corresponding to standards-track RFCs.
If a server does not understand the option, it must respond by returning a
BAD_EXTENSION Response and list those options it does not understand in
the UnsupportedHeader.
Proxy and redirect servers must ignore features that are not understood. If
a particular extension requires that intermediate devices support it, the
extension must be tagged in the ProxyRequireHeader as well.
For Example:
Require: 100rel
See Also: ProxyRequireHeader
See Also: OptionTag
author:
BEA Systems, NIST
version:
1.2 |