Network-based Call Signaling

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Network-based Call Signaling (NCS) is a profile of the Media Gateway Control Protocol (MGCP) for use in PacketCable applications for voice-over-IP.

The Media Gateway Control Protocol (MGCP) is a signaling and call control communications protocol used in voice over IP (VoIP) telecommunication systems. It implements the media gateway control protocol architecture for controlling media gateways on Internet Protocol (IP) networks connected to the public switched telephone network (PSTN). The protocol is a successor to the Simple Gateway Control Protocol (SGCP), which was developed by Bellcore and Cisco, and the Internet Protocol Device Control (IPDC).

PacketCable network is a technology specification defined by the industry consortium CableLabs for using Internet Protocol (IP) networks to deliver multimedia services, such as IP telephony, conferencing, and interactive gaming on a cable television infrastructure.

A network implementing NCS is designed according to the media gateway control protocol architecture for interconnecting a packet network with the traditional public switched telephone network (PSTN). This architecture physically decomposes the functionality of providing complete end-to-end multimedia telecommunication sessions into several discrete components, notably a media gateway (MG) located at the customer premises that performs the physical translation between analog voice or video streams to packetized digital data, and a media gateway controller (MGC) which is a centralized server that controls typically many media gateways and manages the complexity of call setup, resource negotiation, call routing, and tear-down. In addition, the architecture also uses signaling gateways to the traditional telecommunication channels, such as SS7-based networks.

Media gateway control protocol architecture

The media gateway control protocol architecture is a methodology of providing telecommunication services using decomposed multimedia gateways for transmitting telephone calls between an Internet Protocol network and traditional analog facilities of the public switched telephone network (PSTN). The architecture was originally defined in RFC 2805 and has been used in several prominent voice over IP (VoIP) protocol implementations, such as the Media Gateway Control Protocol (MGCP) and Megaco (H.248), both successors to the obsolete Simple Gateway Control Protocol (SGCP).

The public switched telephone network (PSTN) is the aggregate of the world's circuit-switched telephone networks that are operated by national, regional, or local telephony operators, providing infrastructure and services for public telecommunication. The PSTN consists of telephone lines, fiber optic cables, microwave transmission links, cellular networks, communications satellites, and undersea telephone cables, all interconnected by switching centers, thus allowing most telephones to communicate with each other. Originally a network of fixed-line analog telephone systems, the PSTN is now almost entirely digital in its core network and includes mobile and other networks, as well as fixed telephones.

Signaling System No. 7 (SS7) is a set of telephony signaling protocols developed in 1975, which is used to set up and tear down telephone calls in most parts of the world-wide public switched telephone network (PSTN). The protocol also performs number translation, local number portability, prepaid billing, Short Message Service (SMS), and other services.

Like MGCP, NCP is a device control protocol defining the interaction between the MGC, also called a call agent, and its media gateways. It is one layer of the PacketCable suite of specifications and relies upon companion protocol specifications to provide complete end-to-end telecommunication functionality.

Network-based Call Signaling is a modification of the Media Gateway Control Protocol (MGCP). [1]

NCS provides a PacketCable profile of an application programming interface (MGCI), [2] and a corresponding protocol (MGCP) for controlling voice-over-IP (VoIP) embedded clients from external call control elements. An embedded client is a network element that provides:

MGCI functions provide for connection control, endpoint control, auditing, and status reporting. They each use the same system model and the same naming conventions.

The modification of MGCP in the NCS profile include the following: NCS only aims at supporting PacketCable-embedded clients. Functionality present in the MGCP 1.0 protocol, which was superfluous to NCS, has been removed. It contains extensions and modifications to MGCP. However, the MGCP architecture, and all of the MGCP constructs relevant to embedded clients, are preserved in NCS. The NCS protocol contains minor simplifications of MGCP 1.0.

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The Session Initiation Protocol (SIP) is a signaling protocol used for initiating, maintaining, and terminating real-time sessions that include voice, video and messaging applications. SIP is used for signaling and controlling multimedia communication sessions in applications of Internet telephony for voice and video calls, in private IP telephone systems, in instant messaging over Internet Protocol (IP) networks as well as mobile phone calling over LTE (VoLTE).

Voice over Internet Protocol (VoIP), also called IP telephony, is a methodology and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the Internet. The terms Internet telephony, broadband telephony, and broadband phone service specifically refer to the provisioning of communications services over the public Internet, rather than via the public switched telephone network (PSTN).

The Skinny Client Control Protocol (SCCP) is a proprietary network terminal control protocol originally developed by Selsius Systems, which was acquired by Cisco Systems in 1998.

Inter-Asterisk eXchange (IAX) is a communications protocol native to the Asterisk private branch exchange (PBX) software, and is supported by a few other softswitches, PBX systems, and softphones. It is used for transporting VoIP telephony sessions between servers and to terminal devices.

A signaling gateway is a network component responsible for transferring signaling messages between Common Channel Signaling (CCS) nodes that communicate using different protocols and transports. Transport conversion is often from SS7 to IP.

A softswitch is a central device in a telecommunications network which connects telephone calls from one phone line to another, across a telecommunication network or the public Internet, entirely by means of software running on a general-purpose computer system. Most landline calls are routed by purpose-built electronic hardware; however, soft switches using general purpose servers and VoIP technology are becoming more popular.

The IP Multimedia Subsystem or IP Multimedia Core Network Subsystem (IMS) is an architectural framework for delivering IP multimedia services. Historically, mobile phones have provided voice call services over a circuit-switched-style network, rather than strictly over an IP packet-switched network. Alternative methods of delivering voice (VoIP) or other multimedia services have become available on smartphones, but they have not become standardized across the industry. IMS is an architectural framework to provide such standardization.

H.248 computer network protocol

The Gateway Control Protocol is an implementation of the media gateway control protocol architecture for providing telecommunication services across a converged internetwork consisting of the traditional public switched telephone network (PSTN) and modern packet networks, such as the Internet. H.248 is the designation of the recommendations developed by the ITU Telecommunication Standardization Sector (ITU-T) and Megaco is a contraction of media gateway control protocol used by the earliest specifications by the Internet Engineering Task Force (IETF). The standard published in March 2013 by ITU-T is entitled H.248.1: Gateway control protocol: Version 3.

A Session Border Controller (SBC) is a network element deployed to protect SIP based Voice over Internet Protocol (VoIP) networks.

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An Internet telephony service provider (ITSP) offers digital telecommunications services based on Voice over Internet Protocol (VoIP) that are provisioned via the Internet.

VoIP phone phone using one or more VoIP technologies

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The Simple Gateway Control Protocol (SGCP) is a communications protocol used within a voice over Internet Protocol (VoIP) system. It has been superseded by the Media Gateway Control Protocol (MGCP), another implementation of the media gateway control protocol architecture.

H.323 is a recommendation from the ITU Telecommunication Standardization Sector (ITU-T) that defines the protocols to provide audio-visual communication sessions on any packet network. The H.323 standard addresses call signaling and control, multimedia transport and control, and bandwidth control for point-to-point and multi-point conferences.

T.38 is an ITU recommendation for allowing transmission of fax over IP networks (FoIP) in real time.

Internet Protocol Device Control (IPDC) is a 1998 specification of a communications protocol for voice over Internet Protocol (VoIP) telephony, developed by Level 3 Communications.

References

  1. ↑ "PacketCable™ Network-Based Call Signaling Protocol Specification" (PDF). Cable Television Laboratories, Inc. 2007. p. 59.
  2. ↑ "PacketCable™ Network-Based Call Signaling Protocol Specification" (PDF). Cable Television Laboratories, Inc. 2007. p. 7.


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