Signaling Fifth Meeting

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Telephone Network transport data The data supplied by customers signaling data. supervisory and management data signaling channels channels carrying signaling transport channels channels carrying transport data Source:

Channel-Signaling Channel-Associated signaling data is always associated with a specific transport channel Two means of data signaling The signaling data and the transport data share a single communication channel The signaling data and transport data use different channels

Common-Channel A single channel carries signaling data of several transport channels. The transmission capacity is shared by statistical multiplexing The signaling data is sent in the form of messages ach message must carry an identification of the transport channel to which it refer Channel-Signaling

Protocol Reference Models Source:

Dual-tone Multi-frequency Signaling, 16 possible tone combinations The minimum signal duration 68 ms, Total duration at least 136 to be sent by a telephone

Features of Communication Networks Capable of evolution. Evolve to include new requirements without any major disruptions. Flexible. It should be possible to change one part of a network without affecting other parts. Able to support a range of applications. There may be problems of quality of service. Robust. A network should be able to tolerate a certain degree of failure of its components,

Different Views of Telephone Network

Signaling System 7 (SS7) 1. Physical, electrical and functional characteristics of a signaling link. 2. Transfer of signaling messages 3. Routing signaling messages through the signaling network 4. Has several user parts, each of which provides the services required by a particular application of SS7.

SS7 With Respect to OSI Application Entity breaks down into smaller functions, called application service elements (ASEs). The transaction capabilities application part (TCAP): One system request another system to perform an operation; remote procedure call RPC.

Message Transfer Part Each message must contain addressing information It is the forwarded to signaling point. It is located in a routing label It is contained in each signaling message signaling message

Routing Label point codes 14-bit numbers signaling network has a maximum of 2 14 = signaling points. signaling link selection 4-bit It distribute the traffic over the available routes between two signaling points. Hi mom Hi mo m

MTP Message MTP messages have variable lengths. A complete MTP message (user data + routing label) is placed in the signaling information field

MTP Flag The pattern chosen is the octet ‘ ’. A receiver examines all the bits it receives, Five consecutive bits with the value ‘1’ followed by a bit with the value ‘0’ it removes the ‘0’, thereby restoring the bit-sequence to its original value. Exactly six consecutive bits with the value ‘1’, A boundary flag is received Seven consecutive bits with the value ‘1’ An error has occurred

SS7

signaling connection control part (SCCP) The SCCP provides four general classes of service to the level above: 0 Connectionless service sequence of messages is not guaranteed, 1 Basic connectionless service sequence of messages is guaranteed. (under normal conditions) 2 Basic connection-oriented service a virtual connection is set up, no flow control nor out-of-sequence detection is provided. 3 connection-oriented service virtual connection is set up, flow control and message sequence are guaranteed.

SCCP messages format

Example of a ‘Connection request’ message

Parameters for ‘Connection Request’

Flow Control for SCCP Service Class 3 ‘Data form 2’ message type ‘Data acknowledgement’ message (piggybacking)

Integrated Services Digital Network User Part (ISDN) control the signaling of any circuit-switched network setting up 64 kbit/s circuit clearing of a 64 kbit/s circuit, calling line identification, and call forwarding It employs the services provided by the MTP (message transfer part) and the SCCP (signaling connection control part).

Public Land Mobile Networks (PLMNs)

Mobile Application Part (MAP) Support transactions that occur in mobile telephony. Supports ground-based mobile networks, which are commonly referred to as public land mobile networks (plmns). Customers are linked dynamically to the switching center nearest to their current location. Therefore, distributed databases are used in a plmn