Signaling

Fifth Meeting

Sunday Monday Tuesday

Sixth meeting Sixth meeting Seventh meeting

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: http://www.windowsfordevices.com/files/misc/3cx_ippbx_diag.jpg

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: http://www.cs.wustl.edu/~jain/cis788-97/ftp/atm_security/figure1.gif

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 smallerfunctions, called application service elements (ASEs).

application entities (AEs) which represent the functions needed by

applications (such as the operations, maintenance and administration part)

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 214 = 16384 signaling points.

signaling link selection 4-bit It distribute the traffic over the

available routes between two signaling points.

Hi momHimom

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 ‘01111110’. 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.

111110111110111111011111110

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

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