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Common-channel signaling

January 01, 1970

In telecommunication, common-channel signaling (CCS), or common-channel interoffice signaling (CCIS), is the transmission of control information (signaling) via a separate channel than that used for the messages,[1][2] The signaling channel usually controls multiple message channels.[3]

In the public switched telephone network (PSTN) one channel of a communications link is typically used for the sole purpose of carrying signaling for establishment and tear down of telephone calls. The remaining channels are used entirely for the transmission of voice messages. In most cases, a single 64 kbit/s channel is sufficient to handle the call setup and call clear-down traffic for numerous bearer (voice and data) channels.[4]

The technical alternative to CCS is channel-associated signaling (CAS), in which each bearer channel has a dedicated signaling channel.

CCS offers the following advantages over CAS, in the context of the PSTN:[5]

  • Faster call set-up time
  • Greater trunking efficiency due to the quicker set up and clearing, thereby reducing traffic on the network
  • Can transfer additional information along with the signaling traffic, providing features such as caller ID
  • Signaling can be performed mid-call

The most common CCS signaling methods in use are Integrated Services Digital Network (ISDN) and Signalling System No. 7 (SS7).

ISDN signaling is used primarily on trunks connecting end-user private branch exchange (PBX) systems to a central office. SS7 is primarily used within the PSTN. The two signaling methods are very similar since they share a common heritage and in some cases, the same signaling messages are transmitted in both ISDN and SS7.

Common channel signaling networks edit

A CCS network provides signaling message transfer for participating Common Channel Signaling Switching Offices (CCSSOs), databases, and operator systems. It is a packet-switched communication network that allows call control and transaction messages from the voice and data networks to be transferred on communications paths that are separate from the voice and data connections.

CCS messages provide for transaction-based services and for call control signaling between network nodes. The architecture for a CCS network is generally based on the geographical location of signaling points, the number and sizes of signaling points, the expected traffic load, and the services to be provided by the network.

Regardless of the type of architecture selected, the CCS network will consist of a combination of the following components:

  • Signaling Link - A communication path between two adjacent Signaling Points (SPs) in the CCS network.
  • Link Set - A set of signaling links that connects the same pair of adjacent signaling points.
  • Combined Link Set - A collection of link sets from a signaling node over which message traffic to a given destination is shared.
  • Signaling Point (SP) - An SP transmits, receives, and processes CCS(SS7) messages. An SP can be a Signaling End Point (SEP) or a Signaling Transfer Point (STP).
  • Signaling Transfer Point (STP) - An SP that performs message routing functions and provides switching of messages between SEPs.
  • Signaling End Point (SEP) - An SP, other than an STP, with the ability to serve as a source or a sink for CCS messages.
  • Service Control Point (SCP) - An SEP that acts as a database to provide information to another SEP, e.g., a Service Switching Point (SSP) or another SCP, for processing and/or routing certain types of network calls.
  • Signaling Gateway - Responsible for exchanging SS7 messages over a set of links from an SS7 node in a Voice Over Packet (VOP) network to a traditional PSTN network and encapsulating the user information (either ISUP for call setup or SCCP/TCAP for service related signaling) contained in the message for distribution to the Call Control Agent (CCA).
  • Internet Call Router (ICR) - Also called the Internet Offload, the ICR is a new network element used in the “post-switch" off-load architecture.
  • Switch - An SEP that is equipped to switch end user voice or data calls.
  • Combined Node (CN) – An SP that combines the functions of two or more types of SPs.
  • A-Link Concentrator (ALC) - An SP that has the Message Transfer Part (MTP) functionality of an STP and also serves as a CCSSO.

Interconnecting CCS networks edit

As CCS networks have continued to evolve, and network interconnection architectures and the services they support have grown more complex, it has become necessary to identify the type of behavior all network providers are expected to exhibit when specific requirements do not exist.

Providers of Interconnecting CCS networks and other interconnecting networks need information about the processes and interfaces that need to be supported to ensure that call originations routed via other interconnecting networks receive at least the same quality of service as intranetwork calls.

Telcordia GR-905, Common Channel Signaling Network Interface Specification (CCSNIS) Supporting Network Interconnection, Message Transfer Part (MTP), and Integrated Services Digital Network User Part (ISDNU),[6] contains this important information and includes information for providers of Legacy Network Gateway and Legacy Selective Router Gateway systems to support the delivery of emergency calls between legacy origination networks and IP-enabled PSAPs, as well as emergency calls routed via Emergency Services IP Networks (ESInets) and legacy PSAPs that are served by Selective Routers. It provides explicit references to ANSI and ATIS Standards and ITU-T Recommendations.

Notes edit

  1. ^ John G. Van Bosse and Fabrizio U. Devetak (2007). Signaling in telecommunication networks (2nd ed.). John Wiley and Sons. p. 111. ISBN 978-0-471-66288-4.
  2. ^ Martin H. Weik (2000). Computer science and communications dictionary. Vol. 2. Springer. p. 245. ISBN 978-0-7923-8425-0.
  3. ^ (Ronayne 1986, p. 141).
  4. ^ (Ronayne 1986, p. 145).
  5. ^ (Ronayne 1986, p. 142).
  6. ^ GR-905, Common Channel Signaling Network Interface Specification (CCSNIS) Supporting Network Interconnection, Message Transfer Part (MTP) and Integrated Services Digital Network User Part (ISDNU)

References edit

  • Ronayne, John P. (1986). "The Digital Network". Introduction to Digital Communications Switching (1st ed.). Indianapolis: Howard W. Sams & Co., Inc. ISBN 0-672-22498-4.

January 01, 1970
common, channel, signaling, this, article, needs, additional, citations, verification, please, help, improve, this, article, adding, citations, reliable, sources, unsourced, material, challenged, removed, find, sources, news, newspapers, books, scholar, jstor,. This article needs additional citations for verification Please help improve this article by adding citations to reliable sources Unsourced material may be challenged and removed Find sources Common channel signaling news newspapers books scholar JSTOR March 2019 Learn how and when to remove this message In telecommunication common channel signaling CCS or common channel interoffice signaling CCIS is the transmission of control information signaling via a separate channel than that used for the messages 1 2 The signaling channel usually controls multiple message channels 3 In the public switched telephone network PSTN one channel of a communications link is typically used for the sole purpose of carrying signaling for establishment and tear down of telephone calls The remaining channels are used entirely for the transmission of voice messages In most cases a single 64 kbit s channel is sufficient to handle the call setup and call clear down traffic for numerous bearer voice and data channels 4 The technical alternative to CCS is channel associated signaling CAS in which each bearer channel has a dedicated signaling channel CCS offers the following advantages over CAS in the context of the PSTN 5 Faster call set up time Greater trunking efficiency due to the quicker set up and clearing thereby reducing traffic on the network Can transfer additional information along with the signaling traffic providing features such as caller ID Signaling can be performed mid call The most common CCS signaling methods in use are Integrated Services Digital Network ISDN and Signalling System No 7 SS7 ISDN signaling is used primarily on trunks connecting end user private branch exchange PBX systems to a central office SS7 is primarily used within the PSTN The two signaling methods are very similar since they share a common heritage and in some cases the same signaling messages are transmitted in both ISDN and SS7 Contents 1 Common channel signaling networks 1 1 Interconnecting CCS networks 2 Notes 3 ReferencesCommon channel signaling networks editA CCS network provides signaling message transfer for participating Common Channel Signaling Switching Offices CCSSOs databases and operator systems It is a packet switched communication network that allows call control and transaction messages from the voice and data networks to be transferred on communications paths that are separate from the voice and data connections CCS messages provide for transaction based services and for call control signaling between network nodes The architecture for a CCS network is generally based on the geographical location of signaling points the number and sizes of signaling points the expected traffic load and the services to be provided by the network Regardless of the type of architecture selected the CCS network will consist of a combination of the following components Signaling Link A communication path between two adjacent Signaling Points SPs in the CCS network Link Set A set of signaling links that connects the same pair of adjacent signaling points Combined Link Set A collection of link sets from a signaling node over which message traffic to a given destination is shared Signaling Point SP An SP transmits receives and processes CCS SS7 messages An SP can be a Signaling End Point SEP or a Signaling Transfer Point STP Signaling Transfer Point STP An SP that performs message routing functions and provides switching of messages between SEPs Signaling End Point SEP An SP other than an STP with the ability to serve as a source or a sink for CCS messages Service Control Point SCP An SEP that acts as a database to provide information to another SEP e g a Service Switching Point SSP or another SCP for processing and or routing certain types of network calls Signaling Gateway Responsible for exchanging SS7 messages over a set of links from an SS7 node in a Voice Over Packet VOP network to a traditional PSTN network and encapsulating the user information either ISUP for call setup or SCCP TCAP for service related signaling contained in the message for distribution to the Call Control Agent CCA Internet Call Router ICR Also called the Internet Offload the ICR is a new network element used in the post switch off load architecture Switch An SEP that is equipped to switch end user voice or data calls Combined Node CN An SP that combines the functions of two or more types of SPs A Link Concentrator ALC An SP that has the Message Transfer Part MTP functionality of an STP and also serves as a CCSSO Interconnecting CCS networks edit As CCS networks have continued to evolve and network interconnection architectures and the services they support have grown more complex it has become necessary to identify the type of behavior all network providers are expected to exhibit when specific requirements do not exist Providers of Interconnecting CCS networks and other interconnecting networks need information about the processes and interfaces that need to be supported to ensure that call originations routed via other interconnecting networks receive at least the same quality of service as intranetwork calls Telcordia GR 905 Common Channel Signaling Network Interface Specification CCSNIS Supporting Network Interconnection Message Transfer Part MTP and Integrated Services Digital Network User Part ISDNU 6 contains this important information and includes information for providers of Legacy Network Gateway and Legacy Selective Router Gateway systems to support the delivery of emergency calls between legacy origination networks and IP enabled PSAPs as well as emergency calls routed via Emergency Services IP Networks ESInets and legacy PSAPs that are served by Selective Routers It provides explicit references to ANSI and ATIS Standards and ITU T Recommendations Notes edit John G Van Bosse and Fabrizio U Devetak 2007 Signaling in telecommunication networks 2nd ed John Wiley and Sons p 111 ISBN 978 0 471 66288 4 Martin H Weik 2000 Computer science and communications dictionary Vol 2 Springer p 245 ISBN 978 0 7923 8425 0 Ronayne 1986 p 141 Ronayne 1986 p 145 Ronayne 1986 p 142 GR 905 Common Channel Signaling Network Interface Specification CCSNIS Supporting Network Interconnection Message Transfer Part MTP and Integrated Services Digital Network User Part ISDNU References editRonayne John P 1986 The Digital Network Introduction to Digital Communications Switching 1st ed Indianapolis Howard W Sams amp Co Inc ISBN 0 672 22498 4 Retrieved from https en wikipedia org w index php title Common channel signaling amp oldid 1034925068, wikipedia, wiki, book, books, library,

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