Bill and keep – agreement to interconnect and to exchange traffic without payment, ie settlement-free.

Best effort

Service type offered by a packet-switched network such as the public internet. With best-effort service, all packets are treated the same way with respect to forwarding priority and drop preference. If a packet does not make it to the final destination, it is then retransmitted from the source.

Bilateral interconnect

A commercial and technical agreement negotiated directly between two service providers.

Bit pipe

The transport medium, wired or wireless, for carrying voice and data traffic.

Carrier ENUM

A private “service providers-only” ENUM system.

Cascading payments

A commercial and technical agreement under which each party involved in the transport of traffic is compensated for its efforts in providing services to the end user. Specified within GSMA’s IPX.


A means of creating PSTN connections by setting up an end-to-end circuit.


Domain name system – hierarchical naming system for devices, resources or services connected to the internet.


Electronic numbering – a specific service within DNS that automatically translates a telephone number (E.164 number) into an IPbased address known as universal resource identifier (URI) as part of service discovery.

Ex ante regulation 

Anticipatory intervention via government-specified controls, to prevent socially undesirable actions or outcomes in markets or to direct market activity towards socially desirable ends.


GPRS roaming exchange – GSMA model for transporting GPRS data from roaming subscribers back to the home mobile network.


ITU standard for providing audiovisual communication sessions such as VoIP on any packet network.

HD voice 

High-definition voice, also known as wideband audio, uses wideband codecs to more accurately reproduce the human voice with a wider range of frequency coverage.


IP multimedia subsystem – the de facto standard architectural framework for delivering IP multimedia services.


IPX provider – a business (such as an IP carrier) offering IP interconnect capability for one or many IPX services compliant with GSMA’s IPX requirements.

IPX Proxy 

Effectively an SBC (see below), it enables the secure exchange of IP-based traffic between fixed and mobile carriers, application service providers and enterprises over private IP networks, enabling differentiated service quality and charging methods for bilateral and multilateral traffic exchange.

Jitter – Variability of delay.

Latency – Delay.


Long-term evolution – project name for a high-performance (3.5-4G) air interface for cellular mobile telephony.

Media gateway 

Enables transport inter-working between TDM and packet-switched networks.

Media servers 

Process, manage and deliver media requests made by voice application servers and softswitches in a wireline packet-based network.

Multilateral interconnect 

Allows for an intermediary/wholesale operator to provide one commercial and technical interconnect that gives reach to multiple destination networks.


Next generation network – defined by the ITU as a packet-based network able to provide services including telecommunications services and able to make use of multiple broadband and QoS-enabled transport technologies, and in which service-related functions are independent from underlying transport-related technologies.

Number resolution 

Number registries and look-up technologies that enable an originating service provider or international carrier to discover routable destination information and service platform information about a dialled number.


Over-the-top services carried by the network, delivering value to customers, without any involvement of the carrying network provider.


Arrangement whereby ISPs exchange traffic for their respective customers (and for customers of their respective customers), but not for third parties.


Point of interconnection – a point at which networks meet for interconnection purposes.


Packet voice interworking – the GSMA’s specification for SIP-I voice interconnect.


Session border controller – stand-alone network elements that control and manage real-time multimedia traffic flows between IP networks, handling signalling and media, performing native IP interconnection functions, and providing the border between IP networks for inter-service providers (peering borders) and service provider-customer borders (access borders).


Session initiation protocol – IETF standard signalling protocol used for creating and controlling session-oriented connections between two or more end-points in an IP network for multimedia elements such as voice, video and instant messaging.


Delivers software-based call control capabilities in service provider packet voice communication networks. This may also be referred to as a media gateway controller or a call agent.


Spam over internet telephony – the telephony equivalent of spam.


Signalling System No 7 – ITU standard set of signalling protocols used to set up and tear down PSTN telephone calls.


Time-division multiplexing – used in circuit-switched networks such as the PSTN, to enable transmission of multiple calls along the same transport medium.


Uniform resource identifier – a string of characters used to identify a name or a resource on the internet.

Voice application server 

Software platform that resides in the application layer of the three logical layers (application/ control/transport) and provides IP voice and multimedia services, communicates with softswitches using a SIP interface, and does not have media gateway control functions.


Voice over internet protocol – the delivery of voice communications over IP networks.


Voice over long-term evolution – an initiative led by a group of MNOs, operators, infrastructure vendors and handset vendors to define a profile for voice services using IMS in an LTE environment.

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