MTP2 User Peer-to-Peer Adaptation Layer is a sigtran protocol for transporting SS7 MTP Level 2 user part signaling messages (i.e. MTP Level 3) over IP using the Stream Control Transmission Protocol (SCTP). Unlike M2UA, M2PA is used to support full MTP Level 3 message handling and network management between any two SS7 nodes communicating over an IP network. IP signaling points function as traditional SS7 nodes using the IP network instead of the SS7 network. Each switched circuit or IP signaling point has an SS7 point code. The M2PA protocol layer provides the same set of services as MTP Level 2 provides to MTP Level 3.
M2PA can be used between a signaling gateway and a media gateway controller, between a signaling gateway and an IP signaling point, and between two IP signaling points. Signaling points may use M2PA over IP or MTP Level 2 over standard SS7 links to send and receive MTP Level 3 messages.

MTP2 User Adaptation Layer is a protocol defined by the IETF Sigtran Working Group for transporting SS7 MTP Level 2 user (i.e. MTP Level 3) signaling messages over IP using the Stream Control Transmission Protocol (SCTP). The M2UA protocol layer provides the equivalent set of services to its users as MTP Level 2 provides to MTP Level 3.
M2UA is used between the Signaling Gateway and Media Gateway Controller in VoIP networks. The signaling gateway receives SS7 messages over an MTP Level 1 and Level 2 interface from a signaling end point (SCP or SSP) or signal transfer point (STP) in the public switched telephone networks. The signaling gateway terminates the SS7 link at MTP Level 2 and transports MTP Level 3 and above to a Media Gateway Controller or other IP endpoint using M2UA over SCTP/IP. The signaling gateway maintains the Availability State of all media gateway controllers to manage signaling traffic flows across active SCTP associations.

The Stream Control Transmission Protocol is a reliable transport protocol operating on top of a connectionless packet network such as IP. SCTP is designed to transport PSTN signaling messages over IP networks, but is capable of broader applications.

It offers the following services to its users:

• Acknowledged error-free non-duplicated transfer of user data.
  
• Data fragmentation to conform to discovered path MTU size.
  
• Sequenced delivery of user messages within multiple streams, with an option for order-of-arrival delivery of individual user messages.
  
• Optional bundling of multiple-user messages into a single SCTP packet.
  
• Network-level fault tolerance through supporting of multi-homing at either or both ends of an association.

The Session Initiation Protocol (SIP) is an application-layer control protocol. A signaling protocol for Internet telephony that allows for creation of innovative new services for IP Telephony networks. It allows packet-based networks to carry voice, video, and data. SIP can establish sessions for features such as audio/videoconferencing, interactive gaming, and call forwarding to be deployed over IP networks thus enabling service providers to integrate basic IP telephony services with Web, email, and chat services.

In addition to user authentication, redirect and registration services, the SIP Server supports traditional telephony features such as personal mobility, time-of-day routing and call forwarding based on the geographical location of the person being called.

Signaling System No. 7 (SS7) is a global standard for telecommunications defined by the International Telecommunication Union (ITU) Telecommunication Standardization Sector (ITU-T). The standard defines the procedures and protocol by which network elements in the public switched telephone network (PSTN) exchange information over a digital signaling network to effect wireless (cellular) and wireline call setup, routing and control. It is an industry proven protocol stack for building telecom equipment, network components as well as SS7 based applications.

The SS7 network and protocol are used for:

• basic call setup, management, and tear down
• wireless services such as personal communications services (PCS), wireless roaming, and mobile subscriber authentication
• enhanced call features such as call forwarding, calling party name/number display, and three-way calling
• efficient and secure worldwide telecommunications

Message Transfer Part (MTP)

The Message Transfer Part (MTP) is divided into three levels. The lowest level, MTP Level 1, is equivalent to the OSI Physical Layer. MTP Level 1 defines the physical, electrical, and functional characteristics of the digital signaling link. Physical interfaces defined include E-1 (2048 kb/s; 32 64 kb/s channels), DS-1 (1544 kb/s; 24 64kb/s channels), V.35 (64 kb/s), DS-0 (64 kb/s), and DS-0A (56 kb/s).

MTP Level 2 ensures accurate end-to-end transmission of a message across a signaling link. Level 2 implements flow control, message sequence validation, and error checking. When an error occurs on a signaling link, the message (or set of messages) is retransmitted. MTP Level 2 is equivalent to the OSI Data Link Layer.

MTP Level 3 provides message routing between signaling points in the SS7 network. MTP Level 3 re-routes traffic away from failed links and signaling points and controls traffic when congestion occurs. MTP Level 3 is equivalent to the OSI Network Layer.

ISDN User Part (ISUP)

The ISDN User Part (ISUP) defines the protocol used to set-up, manage, and release trunk circuits that carry voice and data between terminating line exchanges (e.g., between a calling party and a called party). ISUP is used for both ISDN and non-ISDN calls. However, calls that originate and terminate at the same switch do not use ISUP signaling.

Telephone User Part (TUP)

In some parts of the world (e.g., China, Brazil), the Telephone User Part (TUP) is used to support basic call setup and tear-down. TUP handles analog circuits only. In many countries, ISUP has replaced TUP for call management.

Signaling Connection Control Part (SCCP)

SCCP provides connectionless and connection-oriented network services and global title translation (GTT) capabilities above MTP Level 3. The primary difference between MTP and SCCP is in the addressing scheme and routing. SCCP is used as the transport layer for TCAP-based services.

Transaction Capabilities Applications Part (TCAP)

TCAP supports the exchange of non-circuit related data between applications across the SS7 network using the SCCP connectionless service. Queries and responses sent between SSPs and SCPs are carried in TCAP messages. For example, an SSP sends a TCAP query to determine the routing number associated with a dialed 800/888 number and to to check the personal identification number (PIN) of a calling card user. In mobile networks (IS-41 and GSM), TCAP carries Mobile Application Part (MAP) messages sent between mobile switches and databases to support user authentication, equipment identification, and roaming. CAP and INAP also use TCAP as the underlying layer.

The totality of a mobile application system (sometimes also called a wireless application) is often referred to as a Mobile Application Platform, and consists of two or more Mobile Application Parts (MAP). It enables signaling between different network entities. Some MAPs have specific data definition, transaction definition, overall output and input definition, and processing rules. The MAP stack is built on top of the Transaction Capabilities Application Part (TCAP) layer, which is the top most layer of the Signaling System Number 7 (SS7) stack.

GGSN is a GPRS support node which acts as a gateway between the GPRS network and packet switched public data network (PSPDN).

GTP is a General Packet Radio Service (GPRS) protocol used in transmitting user data packets and signalling between GPRS support nodes (GSN) over the GPRS backbone network.

A Public Land Mobile Network is the full set of systems such as switches, transmission towers, etc. that enable a cellular network service to be provided over a given area.

SGSN is a General Packet Radio Service Support (GPRS) support node that serves GPRS mobile by sending or receiving packets via a base station (BS) subsystem.

Defined by the European Telecommunications Standards Institute (ETSI), the recently adopted ETS V5.1/V5.2 standards define a set of universal signaling and switching characteristics for communications between a telecom Access Network (AN) and a digital Local Exchange (LE). ETS V5.1/V5.2 identifies a full range of procedural and protocol interface requirements, allowing vendors to develop non-proprietary, standards-based local access and local exchange equipment. The ultimate goal of ETS V5.1/V5.2 is to ensure connectivity and compatibility between competing vendors, giving operators greater choice when purchasing AN and LE equipment.

VB5.x is a set of ETSI standards used to define the interconnection of local exchanges over broadband networks. This provides wireless, fiber, and copper access networks a common interface to the Access Node (AN) or Service Node (SN). VB5 Interface specifies the physical, procedural and protocol requirements for interfaces at the reference point between Access Network (AN) and Service Node (SN).

GR-303 is an ISDN protocol based protocol for communication between the core and access network. It defines a set of requirements for Next Generation Integrated Digital Loop Carrier (NG-IDLC) systems that includes open interfaces for mix-and-match of Local Digital Switches (LDS) with Remote Digital Terminals (RDT).

GR-303 unbundles the interface between access equipment and Local Digital Switch (LDS) providers allowing Service Providers to mix and match equipment and facilities to meet their needs. GR-303's flexible concentration of bandwidth into the LDS for analog and ISDN services enables Service Providers to service additional customers with existing analog and digital media. GR-303 runs on dedicated redundant control channels between the Integrated Digital Terminal (IDT) within the LDS and the access equipment (Remote Digital Terminal (RDT)).