IMS

  

 

 

 

SIP Header : Contact

 

In conventional SIP signaling, the main purpose of Contact header is tocarries the direct address information of the message sender as shown in the following example.

 

 

But in IMS, Contact header takes another very important functionality. It is to carry the information about UA capability as shown in the following example.

 

[ Line  1 ] REGISTER sip:test.3gpp.com SIP/2.0

[ Line  2 ] From: <sip:+11234567890@test.3gpp.com>;tag=3671736275

[ Line  3 ] To: <sip:+11234567890@test.3gpp.com>

[ Line  4 ] CSeq: 450510774 REGISTER

[ Line  5 ] Call-ID: 3671736255_186872264@2001:0:0:1::3

[ Line  6 ] Via: SIP/2.0/UDP [2001:0:0:1::3]:5060;branch=z9hG4bK74372383

[ Line  7 ] Max-Forwards: 70

[ Line  8 ] Contact: <sip:+11234567890@[2001:0:0:1::3]:5060>;

                           reg-id=1;

                           +g.3gpp.csi.smsip;

                           +g.3gpp.icsi-ref="urn%3Aurn-7%3A3gpp-service.ims.icsi.mmtel"

[ Line  9 ] Route: <sip:[2001:0:0:1::2]:5060;lr>

[ Line  10] P-Access-Network-Info: 3GPP-E-UTRAN-FDD; utran-cell-id-3gpp=0010100010000000

[ Line  11] Content-Length: 0

[ Line  12] Authorization: Digest

[ Line  13] uri="sip:test.3gpp.com",

              username="001010123456789@test.3gpp.com",

              response="",realm="test.3gpp.com",

              nonce=""

[ Line  14] Expires: 7200

[ Line  15] Supported: path

[ Line  16] Allow: INVITE,BYE,CANCEL,ACK,NOTIFY,UPDATE,REFER,PRACK,INFO,MESSAGE,OPTIONS

 

[Line 8] According to GSMA IR92,

  • The UE must include an IMEI URN (see 3GPP TS 23.003 section 13.8) in the "+sip.instance" header field parameter (Instance ID) of the Contact address.
  • The UE must include IMS Communication Service Identifier (ICSI) value used to indicate the IMS Multimedia Telephony service, that being urn:urn-7:3gpp-service.ims.icsi.mmtel per 3GPP TS 24.173, using procedures as defined in section 5.1.1.2.1 of 3GPP TS 24.229. If the UE supports SMS over IP (see section 2.5 and A.7), it must include feature tag used to indicate SMS over IP service, that being +g.3gpp.smsip as defined in section 5.3.2.2 of 3GPP TS 24.341

 

In detail, the contents of the Contact message may vary depending the SIP method.

 

 

According to 3GPP 34 229-1 V10.2.0 (2013-07) A.1

REGISTER

Header/param

Value/remark

Ref

Contact

     

     

     

    Feature Param

     

     

 
  • SIP URI with IP address or FQDN and indicating either an unprotected port selected by the UE or no port at all. When A7 the SIP URI shall contain the sos URI parameter.
  • SIP URI with IP address or FQDN and protected server port of UE. When A7 the SIP URI shall contain the sos URI parameter.
  • +g.3gpp.icsi-ref="urn%3Aurn-7%3A3gppservice.ims.icsi.mmtel"
  • +g.3gpp.smsip
  • video
  • +sip.instance media feature tag with the instance ID of the UE
  

 

According to 3GPP 34 229-1 V10.2.0 (2013-07) A.2.9

INVITE (MT)

Header/param

Value/remark

Ref

Contact

 
  • SIP URI with IP address or FQDN and protected server port of the calling UE, for example 'sip:caller@3gpp.org:6543'.
  • SIP URI with IP address or FQDN and unprotected server port of the calling UE.