01-10-2012, 11:56 AM
Common Channel Signalling System No. 7 (SS7)
[attachment=34892]
Introduction
• Common Channel Signalling System No. 7 (SS7)
is data communications network standard
• SS7 is intended to be used as a control and
management network for telecommunication
networks
• SS7 provides call management, data base query,
routing, flow and congestion control functionality
for telecommunication networks
• SS7 is specifically designed to support the
functions of an Integrated Services Digital
Network
Signalling Transmission
• DC Signalling
– On-Off type digital signals
• Tone Signalling
– In-band or out-of-band signalling
• Digital Control Signals
– similar to on-off signals but represent bit sequences
• Common Channel Signalling
– digital signalling scheme between switches in the
network
Common Channel Signalling
As public network become more complex and provide a richer set of
services, the drawbacks of in-channel signalling become more apparent. The
information transfer rate is quite limited and with inband signalling only
available if there are no voice signals on the circuit. Out-of-band signalling
provides only a very limited bandwidth. With these limitations it is difficult
to provide more complex control messages in order to manage the increasing
complexity of evolving network technology. A more powerful approach is
required. This approach is based on common channel signalling. In this
approach the signalling path is physically distinct from the path for voice and
other subscriber signals. The common channel can be configured with the
bandwidth required to carry control signals for a rich variety of functions.
With dropping costs for hardware this concept has become so attractive that
it is being introduced in all public telecommunication networks. The control
signals are messages passed between switches as wells as between a switch
and the network management centre. Thus, the control-signalling portion of
the network is a distributed computer network carrying short messages.
Common Channel Signalling System #7
• Internationally standardised common-channel
signalling system with primary characteristics
– Optimised for use in digital telecommunication networks in
conjunction with digital switches, utilising 64kbps digital
channels
– Designed to meet present and future information transfer
requirements for call control, remote control, management,
and maintenance
– Provides a reliable means for the transfer of information
– Suitable for operation over analogue channels and at speeds
below 64kbps
– Suitable for use on point-to-point terrestrial and satellite
links
Intelligent Network Concept
• Goal of intelligent network is to allow a wide
range of information to pass through telephone
network without special provision
• IN will provide a backbone for implementation of
wide range of information transfer services
• SS7 will provide infrastructure for IN
• Example IN services
– Find Me Service
– Follow Me Service
– Call Routing Service
– Call Pick-up Service
Service Switching Point
• Local exchange in the telecommunication network
• SSP can be
– a combined voice and SS7 switch
– an adjunct computer connected to a local exchange’s voice switch
• SSP communicates with the voice switch via primitives
and creates signal units for communication over SS7
network
• SSP converts signalling from voice switch into SS7 format
• SSP may send messages for data base queries through SS7
network
• SS7 traffic has been mainly circuit-related but is now
becoming more non-circuit-related
Service Switching Point
• Voice connection is established through look-up
of routing tables and sending SS7 messages to
adjacent switches to request circuit connection.
• SSPs are in most cases adjunct computers to
switches as this allows upgrading the network
without replacing expensive switches
• Few features are required by an SSP, in particular
the implementation of the TUP, ISUP and/or
TCAP protocols
[attachment=34892]
Introduction
• Common Channel Signalling System No. 7 (SS7)
is data communications network standard
• SS7 is intended to be used as a control and
management network for telecommunication
networks
• SS7 provides call management, data base query,
routing, flow and congestion control functionality
for telecommunication networks
• SS7 is specifically designed to support the
functions of an Integrated Services Digital
Network
Signalling Transmission
• DC Signalling
– On-Off type digital signals
• Tone Signalling
– In-band or out-of-band signalling
• Digital Control Signals
– similar to on-off signals but represent bit sequences
• Common Channel Signalling
– digital signalling scheme between switches in the
network
Common Channel Signalling
As public network become more complex and provide a richer set of
services, the drawbacks of in-channel signalling become more apparent. The
information transfer rate is quite limited and with inband signalling only
available if there are no voice signals on the circuit. Out-of-band signalling
provides only a very limited bandwidth. With these limitations it is difficult
to provide more complex control messages in order to manage the increasing
complexity of evolving network technology. A more powerful approach is
required. This approach is based on common channel signalling. In this
approach the signalling path is physically distinct from the path for voice and
other subscriber signals. The common channel can be configured with the
bandwidth required to carry control signals for a rich variety of functions.
With dropping costs for hardware this concept has become so attractive that
it is being introduced in all public telecommunication networks. The control
signals are messages passed between switches as wells as between a switch
and the network management centre. Thus, the control-signalling portion of
the network is a distributed computer network carrying short messages.
Common Channel Signalling System #7
• Internationally standardised common-channel
signalling system with primary characteristics
– Optimised for use in digital telecommunication networks in
conjunction with digital switches, utilising 64kbps digital
channels
– Designed to meet present and future information transfer
requirements for call control, remote control, management,
and maintenance
– Provides a reliable means for the transfer of information
– Suitable for operation over analogue channels and at speeds
below 64kbps
– Suitable for use on point-to-point terrestrial and satellite
links
Intelligent Network Concept
• Goal of intelligent network is to allow a wide
range of information to pass through telephone
network without special provision
• IN will provide a backbone for implementation of
wide range of information transfer services
• SS7 will provide infrastructure for IN
• Example IN services
– Find Me Service
– Follow Me Service
– Call Routing Service
– Call Pick-up Service
Service Switching Point
• Local exchange in the telecommunication network
• SSP can be
– a combined voice and SS7 switch
– an adjunct computer connected to a local exchange’s voice switch
• SSP communicates with the voice switch via primitives
and creates signal units for communication over SS7
network
• SSP converts signalling from voice switch into SS7 format
• SSP may send messages for data base queries through SS7
network
• SS7 traffic has been mainly circuit-related but is now
becoming more non-circuit-related
Service Switching Point
• Voice connection is established through look-up
of routing tables and sending SS7 messages to
adjacent switches to request circuit connection.
• SSPs are in most cases adjunct computers to
switches as this allows upgrading the network
without replacing expensive switches
• Few features are required by an SSP, in particular
the implementation of the TUP, ISUP and/or
TCAP protocols