[From RFC 3588] "The Diameter base protocol is intended to provide an Authentication, Authorization and Accounting (AAA) framework for applications such as network access or IP mobility. Diameter is also intended to work in both local Authentication, Authorization & Accounting and roaming situations. This document specifies the message format, transport, error reporting, accounting and security services to be used by all Diameter applications. The Diameter base application needs to be supported by all Diameter implementations".
This is the successor of the RADIUS protocol.
TCP or SCTP: Typically DIAMETER uses TCP or SCTP as its transport protocol. Its well-known port is 3868. Its well-known SCTP Payload Protocol Identifier is 46 (47 when encrypted with DTLS).
The DIAMETER dissector is fully functional. The dissection of AVPs is specified in .xml files in the diameter directory. You can add AVP dissection of vendor-specific or missing AVPs by editing those files. If you add publicly available AVPs please send us the updates.
Currently there is a problem with application Id: if two AVPs have the same vendor Id but different Application ID WS can't distinguish between them (Bug 1494).
A known problem is 3GPP vendor specific AVPs in the range 1 - 26 in TGPPGmb.xml and imscxdx.xml which are mutually exclusive; depending on which 3GPP interface you are tracing one set will have to be commented out. (In the Wireshark distribution, the set in imscxdx.xml is commented out).
TCP Port(s)/range. TCP packets on this port(s)/range will be dissected as Diameter.
SCTP port(s)/range. SCTP packets on this port will be dissected as Diameter.
Reassemble Diameter messages spanning multiple TCP segments. Default on.
You cannot directly filter DIAMETER protocols while capturing. However, if you know the TCP or SCTP port used (see above), you can filter on that one.