4&5 Signaling2y

munchdrabNetworking and Communications

Oct 30, 2013 (3 years and 10 months ago)

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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 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

= 16384
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 ‘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