SIP MESSAGE Delivered

 

 

 

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Some people misconstrue SIP MESSAGE to be SIP counterpart of existing SMS. But it is not. SMS works on store-n-forward mechanism i.e. even if destination is not available the SMS will be stored in SMSC for prescribed time. It will get delivered when the user gets available. Some services use delivery receipts as trigger for presence related services. On the other hand, SIP MESSAGE is real time and equivalent to instant message.

SIP MESSAGE is after all a SIP request only so it inherits all the routing capabilities of it.

MESSAGE sip:[e-mail] SIP/2.0
Via: SIP/2.0/TCP zz.yy.com;branch=z9hG4bK776sgdkse
Max-Forwards: 70
From: sip:[e-mail];tag=49584
To: sip:[e-mail]
Call-ID: asd88as54545345545@1.2.3.4
CSeq: 1 MESSAGE
Content-Type: text/plain
Content-Length: 10

Hi there !

First line of MESSAGE represents the request-uri i.e. the destination user. The payload of MESSAGE could be any format agreed upon by end-points. However, this agreement is outside the scope of MESSAGE and done out of band. Another MESSAGE to same request-uri will not be send until 200 OK of the previous request has been received.

 

Generally, plain text is used for sending the MESSAGE. For encrypted message S/MIME type body will be used.

SIP/2.0 200 OK
Via: SIP/2.0/TCP Via: SIP/2.0/TCP zz.yy.com;branch=z9hG4bK776sgdkse; received=1.2.3.4
From: sip:[e-mail];tag=49584
To: sip:[e-mail]
Call-ID: asd88as54545345545@1.2.3.4
CSeq: 1 MESSAGE
Content-Length: 0

The successful delivery of the SIP MESSAGE will result in 200 OK response from the remote user. Remember, 200 OK only represents that message have been delivered to the end-user it has no information of whether user has seen it or not.

Generally for secure MESSAGE, message/cpim format is used for the content. It contains payload along with encrypted metadata. Encrypted meta data is usually some of fields from the SIP header itself used for cross checking.

SIP MESSAGE has been further investigated by SIMPLE WG for various enhancements that we will cover later.