5143 Synchronous Optical Network/Synchronous Digital Hierarchy (SONET/SDH) Circuit Emulation Service over MPLS (CEM) Encapsulation

4906 Transport of Layer 2 Frames Over MPLS

4905 Encapsulation Methods for Transport of Layer 2 Frames over MPLS Networks

4870 Domain-Based Email Authentication Using Public Keys Advertised in the DNS (DomainKeys)

4612 Real-Time Facsimile (T.38) - audio/t38 MIME Sub-type Registration

4351 Real-Time Transport Protocol (RTP) Payload for Text Conversation Interleaved in an Audio Stream

4157 The prospero URI Scheme

4156 The wais URI Scheme

2841 IP Authentication using Keyed SHA1 with Interleaved Padding (IP-MAC)

2341 Cisco Layer Two Forwarding (Protocol) "L2F"