Years ago the world of core network signalling of the 3GPP mobile and fixed networks was full of specialized, ever-expanding protocols from the SS7 family: ISUP, MAP, INAP, CAP… Each designed to support yet another novel service concept – digital voice calls, services of Intelligent Networks, handling of the mobility-related issues of mobile devices – they created a colourful multitude of various tools that all needed to be monitored, updated and optimized separately. As time went by, what was modern has quite quickly became outdated, and views of “SS7 will die out soon” started being voiced – only to be proven wrong over and over again. A few adaptation levels, a few tweaks here and there, and MAP or CAP could be reused for new services in the new networks – Packet Switched data, data transported over ATM or over IP – whatever changes came there was always a small extra that, added to the existing application protocols over SS7, kept them going.
Diameter, a creepy enemy
A few years ago a creeping enemy for MAP has appeared. Diameter – originally a newer-and-better RADIUS – was designed, intended to become a modern AAA protocol. As it turned out, it was also well suited for other tasks. We need to query a database in the mobile environment? Diameter suits that purpose – and replaces MAP once LTE/EPS standards have been released. The system needs a protocol to carry charging information? Diameter. We need QoS control of the IP-based User Plane transport for VoLTE? Diameter… Between that, and SIP taking over call- and service-related functions of ISUP, INAP and CAP it became clear that good old SS7 has really been relegated to the support of the ancient circuit-switched communication and is on verge of extinction. A longer and more detailed article on the “rise and fall of SS7” you can find here.
The triumphant march of Diameter continued – the list of the 3GPP Diameter Applications in R15 has 53 entries, with support for very varied services: good old SMS over PS, Non-IP Data Delivery in the IoT environment, support for Proximity Services (ProSe), for location services, for V2X…
The more of a surprise becomes therefore the sudden realization that in the 5G 3GPP networks the role of Diameter is reduced to… backwards compatibility! Which immediately brings up the obvious question – what has then been created to become the even newer, even better, more modern protocol? As we see Diameter abruptly leave the stage, here comes… HTTP. A bit anticlimactic, I would say. Okay, it’s really HTTP/2, but still…
The 5G core network solution is based on a service architecture concept, where various Network Functions, acting as Service Producers, enable Service Consumers access to a variety of supported services and capabilities. All that communication is realized over an interconnecting IP network, with HTTP/2 (RFC 7540) used between the NFs for signalling required in all of the 5G use cases. A uniform, flexible approach that will hopefully simplify running, monitoring and optimizing our networks.
If you would like to learn more about the 5G Core, look out for our new 5G Core Architecture course, coming out soon!
Go to our 5G courses here -> Learn: 5G training
Until next time,
The Apis IP-Solutions Team
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