RFC 3169 (rfc3169) - Page 2 of 17
Criteria for Evaluating Network Access Server Protocols
Alternative Format: Original Text Document
RFC 3169 Criteria for Evaluating NAS Protocols September 2001
carried over a telephony protocol. Second are broadband pseudo-
telephony access protocols, which are carried over xDSL or cable
modems, for example. These protocols typically support an
encapsulation method such as PPP over Ethernet [PPPOE]. Finally are
the virtual access protocols used by NAS's that terminate tunnels.
One example of this type of protocol is L2TP [L2TP].
It is a central assumption of the NAS model used here that a NAS
accepts multiple point-to-point links via one of the above access
protocols. Therefore, at a minimum, any NAS access protocol MUST be
able to carry PPP. The exception to this requirement is for NAS's
that support legacy text login methods such as telnet [TELNET],
rlogin, or LAT. Only these access protocols are exempt from the
requirement to support PPP.
4. Network Protocol Requirements
The network protocols supported by a NAS depend entirely on the kind
of network to which a NAS is providing access. This document does
not impose any additional requirements on network protocols beyond
the protocol specifications themselves. For example, if a NAS that
serves a routed network includes internet routing functionality, then
that NAS must adhere to [ROUTING-REQUIREMENTS], but there are no
additional protocol requirements imposed by virtue of the device
being a NAS.
5. AAA Protocol Requirements
5.1. General protocol characteristics
There are certain general characteristics that any AAA protocol used
by NAS's must meet. Note that the transport requirements for
authentication/authorization are not necessarily the same as those
for accounting/auditing. An AAA protocol suite MAY use the same
transport and protocol for both functions, but this is not strictly
required.
5.1.1. Transport requirements
5.1.1.1. Transport independence
The design of the AAA protocol MUST be transport independent.
Existing infrastructures use UDP-based protocols [RADIUS], gateways
to new protocols must be practical to encourage migration. The
design MUST comply with congestion control recommendations in RFC
2914 [CONGEST].
Beadles & Mitton Informational