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sip
Harish Yadav
Harish Yadav

Reputation: 39

Third party registration in sip protocol

I am new to the sip protocol.I Understand the sip normal registration process where from and to header fields are same.however i didn't understand the third party registration where from and to header fields are different.My questions are

1) what is the third party registration.

2) when this third party registrations are used.

Any help would be great.

Thank you

Upvotes: 1

Views: 2947

Answers (1)

Andriy Makukha
Andriy Makukha

Reputation: 8304

1) What is the third party registration?

Under SIP protocol a REGISTER request can be sent by either a user agent client (UAC) associated with some address itself or by some other entity - a third-party. Third-party registration is just a fancy term for the latter situation, when a REGISTER request is sent not by a UAC itself.

Particularly, RFC 3261 mentions:

Registration on behalf of a particular address-of-record (AOR) can be performed by a suitably authorized third party.

While these two fields [To and From header fields] are frequently the same, there are many valid deployments in which a third-party may register contacts on a user's behalf.

In architectures that support third-party registration, one entity may be responsible for updating the registrations associated with multiple addresses-of-record.

2) When this third party registrations are used?

Third-party registration is frequently used in architectures with many different servers and (particularly) multiple registrars.

For example, there could be three hypothetical servers in your architecture:

  • hyderabad.proxy.sip.in - proxy server which acts like a registrar for customers in Hyderabad
  • mumbai.proxy.sip.in - proxy server which acts like a registrar for customers in Mumbai
  • voicemail.sip.in - central telephony application server which particularly records voicemail when clients are out of reach.

When your UAC registers at hyderabad.proxy.sip.in, there might be a need to notify the voicemail server to stop recording voicemail and start to forward the calls directly to the current client's location. Therefore hyderabad.proxy.sip.in server would send a REGISTER request to voicemail.sip.in on your behalf, playing the role of third-party in this third-party registration. If there were more different specialized servers, your original registrar might need to send multiple REGISTER requests on your behalf.

In this scenario, you can think of third-party registration as of a kind of forwarding: you send a single REGISTER request and it gets forwarded to all relevant servers by your proxy server.

For a more real life example of third-party registration, you could take a look at this article regarding the Voice over LTE (VoLTE) architecture.

Upvotes: 2

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