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Signaling is used in the PSTN (public-switched telephone network) and in various Internet protocols to set up and terminate circuits, virtual circuits, sessions, and so on. Signals may be included in packets that travel the same network as data, or in a separate network. Some example signaling protocols are listed here:

• SS7 (Signaling System 7)    The signaling protocol for the PSTN.


• Q.933    Frame Relay signaling protocol.


• PNNI (Private Network-to-Network Interface)    A signaling protocol for ATM networks used to signal routing topology information and SVC setup.


• RSVP (Resource Reservation Protocol)    An Internet protocol that network devices use to request a particular level of QoS across a network of routers.


• SCTP (Stream Control Transmission Protocol)    SCTP is designed to transport PSTN signaling messages over IP networks and is used to support VoIP (Voice over IP).


• SIP (Session Initiation Protocol)    A simple application layer protocol used to set up, maintain, and terminate multimedia sessions such as voice calls and videoconferences.

MPLS has several signaling protocols that were still being developed at the time of this writing. The protocols set up label switched paths across a network of switches. See "MPLS (Multiprotocol Label Switching)."

Technologies such as voice/data networks, IP telephony, and VoIP (Voice over IP) involve the use of signaling protocols that allow Internet users to send call setup signals into the PSTN, or vice versa. These are outlined under "Voice over IP (VoIP)" and at the Web sites listed on the related entries page.

An interesting Internet document is RFC 2719 (Framework Architecture for Signaling Transport, October 1999), which defines an architecture framework for transport of message-based signaling protocols over IP networks. The scope of this work includes definition of encapsulation methods, end-to-end protocol mechanisms, and use of existing IP capabilities to support the functional and performance requirements for signaling transport. RFC 2960 (Stream Control Transmission Protocol, October 2000) defines the actual signaling protocol.

The IETF Signaling Transport (sigtran) Working Group developed RFC 2719 and is working on other aspects of signaling. The working group has additional documents that describe SS7 signaling and the Internet. Also refer to the PINT and SPIRITS related entries listed next.

Copyright (c) 2001 Tom Sheldon and Big Sur Multimedia.
All rights reserved under Pan American and International copyright conventions.