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3.4.1.5.1 Construction of User-Agent header

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The UAC includes a User-Agent header when it sends a REGISTER request. The User-Agent header, as specified in [RFC3261] section 20.41, is constructed per the ABNF, as defined in [RFC5234], specified in [RFC3261] section 24.1. The ABNF is as follows:

User-Agent  =  "User-Agent" HCOLON server-val *(LWS server-val)
server-val       =  product / comment
product          =  token [SLASH product-version]
product-version  =  token

The UAC constructs the product-version using the following ABNF:

product-version = Major-version "." Minor-version "." Build-number "." Qfe-number
Major-version = 1*DIGIT
Minor-version = 1*DIGIT
Build-number = 4*DIGIT
QfeNumber = 1*DIGIT

Following is an example of a User-Agent header as constructed by a UAC:

 User-Agent: UCCAPI/3.5.6889.0 OC/3.5.6889.0