DIAMETER, The Next Mobile Telecommunication Data Network RADIUS Protocol

As we should already know Remote Authentication Dial-In User Service (RADIUS) is a network entity that widely used at mobile and fix telecommunication network to provide centralized Authentication, Authorization, and Accounting (AAA) function. However, these days, it seems that RADIUS can not meet the requirement of the mobile telecommunication standard – especially the mobile telecommunication data standard – which growth very fast at these 5 years. Therefore DIAMETER as successor AAA protocol for RADIUS is created.

Indeed, DIAMETER protocol is not fully as a replacement for RADIUS protocol. DIAMETER protocol is more like as an extended version of RADIUS protocol. DIAMETER adds some new commands and/or attributes at the base protocol. It can be said that DIAMETER protocol provides the upgrade path for RADIUS protocol which means that DIAMETER is the advance version of RADIUS. It means that the base function is the same but the additional function is different.

The main difference between RADIUS and DIAMTER protocol are as below:

Reliable transport protocols (TCP or SCTP, not UDP)
Network or transport layer security (IPsec or TLS)
Transition support for RADIUS, although Diameter is not fully compatible with RADIUS
Larger address space for attribute-value pairs (AVPs) and identifiers (32 bits instead of 8 bits)
Client–server protocol, with exception of supporting some server-initiated messages as well
Both stateful and stateless models can be used
Dynamic discovery of peers (using DNS SRV and NAPTR)
Capability negotiation
Supports application layer acknowledgements, defines failover methods and state machines (RFC 3539)
Error notification
Better roaming support
More easily extended; new commands and attributes can be defined
Aligned on 32-bit boundaries
Basic support for user-sessions and accounting

Please note that DIAMETER application is not a software application but protocol based on the RFC 3588. Indeed RFC 3588 only defines DIAMETER base protocol which is only the minimum requirement for AAA function. DIAMETER base protocol can be extended by adding new commands and/or attributes. DIAMETER protocol still uses the Attributes-Value Pairs (AVPs) based AAA packets.