RFC 3588:Diameter Base Protocol
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capability negotiation


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... provides support for the following: Capability negotiation RADIUS does not support error messages ...
... RADIUS does not support error messages, capability negotiation, or a mandatory/non-mandatory flag for attributes. Since RADIUS clients and servers are not aware of each other's capabilities, ...
... service has been implemented. Diameter includes support for error handling (Section 7), capability negotiation (Section 5.3), and mandatory/non-mandatory attribute-value pairs (AVPs ...



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