M2UA - used for backhauling of SS7 MTP2-User signalling messages over IP using Stream Control Transmission Protocol (SCTP)

M3UA - supports transport of SS7 MTP3-User sugnalling over IP using Stream Control Transmission Protocol (SCTP)

MAPOS - Multiple Access Protocol over SONET / SDH

MARS - Multicast Address Resolution Server (TCP/IP)

Megaco - Media Gateway Control

MLP - Multilink Procedure, added upper sublayer of the LAPB, operating between the packet layer and a multiplicity of single data link protocol functions (SLPs) in the data link layer (X.25).

MOP - Maintenance Operation Protocol, utility services such as uploading and downloading system software, remote testing and problem diagnosis (DECnet).

MOUNT - protocol used to initiate client access to a server supporting NFS.

MPEG - Motion Picture Experts Group, ISO standards group dealing with video and audio compression.

MPLS - Multi Protocol Label Switching, set of procedures for augmenting network layer packets with "label stacks", thereby turning them into labeled packets. 

MPOA - Multi Protocol Over ATM, deals with efficient transfer of inner-subnet unicast data in a LAN emulation environment.

MPPC - Microsoft Point-to-Point Compression Protocol

MTP-2 - Message Transfer Part, Level 2, signalling link which together with MTP-3 provides reliable transfer of signalling messages between two directly connected signalling points (SS7).

MTP-3 - Message Transfer Part, Level 3, connects Q.SAAL to the users (SS7 suite).