More than a clever pun on RADIUS, Diameter is an attempt to address some of its shortcomings (defined below). As of this writing, it is little more than a series of IETF drafts, with little (or no) vendor support.

As stated in its RFC, Diameter addresses:

  • Consistent failover
  • Transmission-Level Security (TLS or IPSec)
  • Reliable (TCP) Transport
  • Agent support (predefined roles for servers)
  • Server-Initiated Messages (notifications to edge devices and users)
  • Auditability (as in data security)
  • Transition support (migration from RADIUS, at some undefined point in the future)
  • Capability Negotiation (common set of known attributes between servers)
  • Peer discovery and configuration (oh boy)
  • Roaming support (as in end-to-end secure proxying)