Much Ado about Registration

Registration is something what was missing in the times of wires. Ok, not completely but it was done more or less once when an MSISDN was assigned to some line.

IMS Registration

IMS Registration

In contrast to the previous types of the networks the 4G network is ‘user-centric’. It means the user can use multiple devices and identities and we have to deal with it. The main purpose of the registration is to create a binding between user (her public identity) and IP address of the device, so we know where we can send the data to. That’s why there is a Contact header in the SIP REGISTER message. The Contact header contains an address which identifies the current location of the user (Point-of-Presence – e.g. IP/FQDN of a particular client). During the registration is the Contact Address is linked to a Public Identity (IMPU, AOR in SIP terminology). The IMPU is an equivalent to MSISDN in GSM and has to be present in the To header of the SIP REGISTER. One identity can by used by more terminals and as each terminal can have different capabilities this has to be also taken into account. This information is part of the Contact header.

Contact: <sip:119560022547@152.67.235.234:49635;transport=tcp>;
   expires=3200;
   +g.oma.sip-im;
   language="en,fr";
   +u.asmc.apn="6a6044869e2aba3d23d4cfc0ef1384d00da28854c2408ddbbf";
   +sip.instance="<urn:uuid:D4196919-ED8A-4E00-9436-B9CDD1E76813>"

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RCS – Rich Communication Services

As this is a blog, I’m not going to recap all the stuff you can find in wikipedia about RCS. Wikipedia is a great source of information but sometimes you can’t see the forest for the trees. The RCS is really a big theme so I guess it would be better to write several posts than to try put all the relevant information in one. I’ll probably use some simplifications, the details and exceptions will be described later.

 

So what is the RCS?

Update: For the information about RCS Universal profile read the post GSMA Advanced Messaging – RCS Universal Profile.

RCS is an attempt of mobile operators and their vendors to be more than just connectivity providers. With the 3rd generation of mobile networks many people started to believe that they’ll not need the operators soon – as long as they can connect to the Internet they have VoIP, Instant messaging, Emails, Facebook, etc (Over-the-top  applications OTT). Why should anyone pay for roaming or use SMS anymore? But for the operators Voice services and SMS were/are the main sources of income. VoLTE and RCS should give their customers the user experience they know from Skype, Whatsapp, Viber or Line and enable them to stay relevant.

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