The Simple Authentication and Security Layer (SASL) is a framework
for providing authentication and data security services in
connection-oriented protocols via replaceable mechanisms. It
provides a structured interface between protocols and mechanisms.
The resulting framework allows new protocols to reuse existing
mechanisms and allows old protocols to make use of new mechanisms.
The framework also provides a protocol for securing subsequent
protocol exchanges within a data security layer.

This document describes how a SASL mechanism is structured, describes
how protocols include support for SASL, and defines the protocol for
carrying a data security layer over a connection. In addition, this
document defines one SASL mechanism, the EXTERNAL mechanism.

This document obsoletes RFC 2222.