Allow

An example of the header is shown below:

Allow: REGISTER,OPTIONS,INVITE,ACK,CANCEL,BYE,NOTIFY,PRACK,REFER,INFO,SUBSCRIBE

The header properties are shown in the following table:

Header Level Action	Add	Delete	Modify	List Entries
Operations Supported	Yes	Yes	No	N/A

Keyword	Sub Types	Attributes
N/A	N/A	Read/Write

Below is a header manipulation example:

Rule:	Add an Allow header to all INVITE messages: Message Type: Invite ■ Condition: header.supported != 'mm,100rel,timer,replaces' ■ Action Subject: header.allow ■ Action Type: Add ■ Action Value: 'REGISTER,OPTIONS,INVITE,ACK,CANCEL,BYE,NOTIFY,PRACK,REFER,INFO,SUBSCRIBE, XMESSAGE'
Result:	Allow: REGISTER,OPTIONS,INVITE,ACK,CANCEL,BYE,NOTIFY,PRACK,REFER,INFO,SUBSCRIBE, XMESSAGE