# in the sip URI

Asterisk Asterisk SIP
#1

I’m looking for clarity on the RFC interpretation around the use of the # in the user part of a sip uri. eg: sip:12345678#123@asterisk.org

sip.js say it should be encoded to its url friendly counterpart %23. However this means that the Asterisk dial plan must match %23. Other clients and phones allow sending # in the user part of the uri, so now Asterisk dial plan must look out for both.

I believe Asterisk doesn’t have the limitation on Dial() command. Correct?

The SIP RFC doesn’t make specific mention to the # character, but mentions that characters out of range of the reserved characters - _ . ! ~ * ’ ( ) should encoded, but, the only place that I saw # being specified with and example is the tel URL RFC, this says that the # is a pause character, and it just says that it could be copied to the sip url as-is. It does not mention encoding. It also mentions the it shouldn’t be the first character.

What is the correct handing of the # character in the user portion of a SIP URI?

#2

According to the sip-implementors list[1] it should be escaped. Dial() itself doesn’t care about any of it. It’s the responsibility of the underlying channel driver, such as chan_sip or chan_pjsip. The PJSIP stack is more strict on things and automatically escapes it. It also unescapes it on ingress back to ‘#’ so you don’t have to care about it.

[1] https://lists.cs.columbia.edu/pipermail/sip-implementors/2006-May/012770.html

#3

Yes, this is exactly what I read too.

Great to know that PJSIP :

#4

You are using an obsolete TEL: URI RFC. RFC 3966 does not define pause characters, but, even in RFC 2806, it is a dtmf-digit. RFC 3966 only allows it in local numbers and has a SHOULD NOT constraint on their use.

The relevant SIP URI productions are:

user             =  1*( unreserved / escaped / user-unreserved )
user-unreserved  =  "&" / "=" / "+" / "$" / "," / ";" / "?" / "/"
unreserved  =  alphanum / mark
mark        =  "-" / "_" / "." / "!" / "~" / "*" / "'"
                     / "(" / ")"
#5

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