What is Diameter

Diameter is a next-generation industry-standard protocol used to exchange authentication, authorization and accounting (AAA) information in Long-Term Evolution (LTE) and IP Multimedia Systems (IMS) networks. It is an extension of RADIUS protocol with the following features: 

• Uses TCP/SCTP instead of UDP to improve transport reliability and flexibility 

• Uses IPSec (mandatory) or TLS (optional) to secure communications between services 

• Uses a much larger 32-bit address space for AVPs 

• Supports both stateless and stateful modes 

• Supports dynamic discovery of entries using DNS, SRV and NAPTR records 

• Supports peer alignment by negotiation 

• Supports RFC 3539 for transport layer failover 

• Supports secure and scalable roaming 

• Extensible support for new commands and AVPs