Diameter protocol is a corner stone of all-IP telco networks. There are two main signalling protocols in IMS. Session Initiation Protocol (SIP) and right, the Diameter.
The main purpose of the SIP protocol is to establish a real-time multimedia session. This session goes end-to-end between the phones (or other devices) of the originator and recipient.
Internally – within the operator’s network – during the session establishment, we have to trigger many network functions. That can be because of the authentication of users, charging, allocation of resources, application of services, etc. 3GPP mandates for this purpose the Diameter protocol. The Diameter is used by both ePC and IMS for requesting/triggering additional information. These requests are sent in a form of transactions. During one IMS session setup or one IMS registration procedure we have to perform several Diameter transactions.
Diameter triggering during VoLTE session setup
Over and over again I can hear:
Why we need VoLTE, when I can use Skype or Whatsapp (for free)?
What is the difference between native (volte) and non-native client?
Of course, everyone likes applications for free. And it’s a great thing we can use our facebook, skype or google accounts practically on any device and from anywhere. Maybe it’s a bit annoying that in order to communicate using such an Over-The-Top (OTT) application, we have to install the same applications as all our buddies.
By OTT we understand an application for a real-time communication using audio, video, and other media over the Internet without the involvement of a mobile operators’ IMS network. But when it comes to mobility we can’t get along without the operators’ infrastructure completely, we still need them to provide us with the internet connectivity.
OTT and LTE
Skype and other icons are used only for illustration.
There are many aspects and technical details which can’t be covered in this short article. Please, take this post as a brief introduction into the matter.