8/2/2019 05 NO.7 Signaling System
1/34
www.univ.zte.com.cn
Part5
NO.7 Signaling System
8/2/2019 05 NO.7 Signaling System
2/34
www.univ.zte.com.cn
Agenda
NO.7 Signaling System overview
The Protocol stack
Message Transfer Part
Network architecture and elements
8/2/2019 05 NO.7 Signaling System
3/34
www.univ.zte.com.cn
Overview :
Signaling System SS7 is the predominant signaling
system for the Public Switched Telephone Network(PSTN) and also Public Land Mobile Networks (PLMN).
SS7 defines the procedures for setting-up, managing and
clearing down calls between users, as well as non-circuit
related signaling.
NO.7 Signaling System
8/2/2019 05 NO.7 Signaling System
4/34
www.univ.zte.com.cn
Voice group
Switch
net...
MPMP STB
signaling link
DT DT
Switch
net
STB
NO.7 Signaling System
8/2/2019 05 NO.7 Signaling System
5/34
www.univ.zte.com.cn
Basic concept:
Signaling link:
SS7 messages are exchanged between network elements over 64
kilobit per second (kbps) bidirectional channels called signaling
links.
Signaling linkset:
Links are usually organized into groups known as linksets. A
linkset is a collection of links that share the same destination .
When links are collected in linksets, the total load of messages istypically shared between the active links.
There can be up to 16 links in a linkset
8/2/2019 05 NO.7 Signaling System
6/34
www.univ.zte.com.cn
Route:
When one SP is in communication with another, there is said to be a
route between the two. A route is the path that exists between any
twoSPs. The route may include a single linkset, or multiplelinksets;
8/2/2019 05 NO.7 Signaling System
7/34
www.univ.zte.com.cn
BA
Signaling link
C
SP ASP B
SP C
A, B and C areconnected to each other via signaling links.
In each case, we see twolinks, united in a linkset. Each SP node can be said
to have a route toeach other. However, the arrangement also allows for the
possibilitythat any two points can be reached indirectly via a third, as well as
directly.
8/2/2019 05 NO.7 Signaling System
8/34
www.univ.zte.com.cn
Link
Link Set 1
ROUTE1
ROUTE2
ROUTE3
8/2/2019 05 NO.7 Signaling System
9/34
www.univ.zte.com.cn
In the signaling hierarchy, we can see that the most fundamental
unit is link. Links are grouped in linksets, which make up routes,
to the same office ,we can built several different routes.
In the same way that links within a linkset can work together to
ensure secure transmission of information, the possibility of
supporting alternative routes to the same destination serves to
promote network security.
8/2/2019 05 NO.7 Signaling System
10/34
www.univ.zte.com.cn
Agenda
NO.7 Signaling System overview
The Protocol stack
Message Transfer Part
Network architecture and elements
8/2/2019 05 NO.7 Signaling System
11/34
www.univ.zte.com.cn
The earliest structure of No.7 signaling protocol system
SCCPMTP3network layer
MTP2Data link layer
MTP1Physical layer
TUPISUP DUP
The earliest No.7 signaling technical specifications were based on
the circuit related phone control requirements.
NO.7 Signaling System
8/2/2019 05 NO.7 Signaling System
12/34
www.univ.zte.com.cn
OSI model
MTP1MTP2MTP3
TCAP
ISP
(Intermediate
service part)
SCCP
CCITT No.7 Signaling functional class
TUP DUPISUP
presentation layer
session layer
Transport layer
Application layer
network layerdata link layerPhysical layer
OSI 1,2,3
OSI 4,5,6
OSI 7
MAP INAP OAMP
NO.7 Signaling System
8/2/2019 05 NO.7 Signaling System
13/34
www.univ.zte.com.cn
Agenda
NO.7 Signaling System overview
The Protocol stack
Message Transfer Part
Network architecture and elements
8/2/2019 05 NO.7 Signaling System
14/34
www.univ.zte.com.cn
MTP is further divided into MTP 1, MTP 2 and MTP 3,respectively
corresponding to layers 1, 2 and 3 of the 7-layer protocol.
1. Function of MTP1:
MTP1 is at the data link level, corresponding to the physical
layer in OSI. The 1st level defines the physical, electrical, and
functional features of the signaling data link . Primarily serving
as a two-way data transmission channel, it contains digital
transmission channels with a basic rate of 64kb/s and signal
terminal equipment.
MTP (message transfer part)
8/2/2019 05 NO.7 Signaling System
15/34
www.univ.zte.com.cn
2. Function of MTP2:
MTP Level 2 ensures accurate end-to-end
transmission of a message cross a signaling link.
Level 2 implements flow control, messagesequence validation, and error checking. When
an error occurs on a signaling link, the message
is retransmitted.
8/2/2019 05 NO.7 Signaling System
16/34
www.univ.zte.com.cn
3. Function of MTP3:
MTP3 performs the functions of a signaling network.
It is combined with the SCCP to form the OSI L3 functional
level.
Major functions:
Signal message processing: involves message routing, message
identification and message distribution.Signal network management: involves management of signal
traffic, signal link and signal routing.
.
8/2/2019 05 NO.7 Signaling System
17/34
www.univ.zte.com.cn
3.1 signaling messages Processing
Message routing:
To select a signaling link for each signaling message to be sent out.
Message distribution:
The process in which the destination point decides, after receiving
messages, to send messages to which user part or to the third level.
The decision shall be made by the service analysis indication code.
8/2/2019 05 NO.7 Signaling System
18/34
www.univ.zte.com.cn
Message Discrimination:
The process in which the signaling point determines whether this point is the destination point
of that message after receiving the message. Such decisions are based on analyzing the
destination point codes in message channeling.
If the signaling point is the destination point, the message is then sent to the message
distribution function part.
If it is not, and if the signaling point has the signaling transfer capacity, then the message shall
be sent to the message channeling function part so that it is then sent out on another signalinglink.
8/2/2019 05 NO.7 Signaling System
19/34
www.univ.zte.com.cn
MDC
MRT
MDTDPC=own SPC
DPCown SPC
MTP2
SCCP,TUP,IS
UP,DUP SI
DPC&
SLS
MTP3
MDC: Message Discrimination
MDT: Message Distribution
MRT: Message Routing
8/2/2019 05 NO.7 Signaling System
20/34
www.univ.zte.com.cn
Service Indicator: MTP User
0000 signaling network management message0001 signaling network test and maintenance message
0010 reserved
0011 SCCP
0100 the telephone user part (TUP)
0101 the ISDN user part (ISUP)
0110 the data user part (messages related to call and circuit)0111 the DUT (performance registration and canceling message)
1000 reserved for MTP to test the user part
1001
1010
1011
1100 reserved1101
1110
1111
8/2/2019 05 NO.7 Signaling System
21/34
www.univ.zte.com.cn
The routing label:
The routing label is comprised of the destination point code (DPC),
originating point code (OPC), and signaling link selection (SLS) field.
The first transmitted bit
SLS OPC DPC
4 14/24 14/24
DPC is the destination signaling point code, indicating the signaling point the message
shall reach.OPC is the original signaling point code showing the original message signaling point.
8/2/2019 05 NO.7 Signaling System
22/34
www.univ.zte.com.cn
SLS is used for:
Ensure message sequencing. Any two messages sent with the same
SLS will always arrive at the destination in the same order in which
they were originally sent.
Allow equal load sharing of traffic among all available links. In
theory, if a user part sends messages at regular intervals and assigns
the SLS values in a round-robin mode, the traffic level should be
equal among all links (within the combined linkset) to thatdestination.
8/2/2019 05 NO.7 Signaling System
23/34
www.univ.zte.com.cn
ZXC10ZXC10
transmission system D TD T
2048kb/s
Level 1
Signaling link
Level 2
M PM P
Level 3
Message transfer partLevel 4
S T BS T B
semi-permanent connecting64kb/s
NET NET
C di l i b
8/2/2019 05 NO.7 Signaling System
24/34
www.univ.zte.com.cn
Corresponding relation about
ZXC10 and NO.7 system
No.7 DTI board MTP1
No.7 signaling board MTP2
MP board MTP3
MP board
UP
8/2/2019 05 NO.7 Signaling System
25/34
www.univ.zte.com.cn
AgendaNO.7 Signaling System overview
The Protocol stack
Message Transfer Part
Network architecture and elements
8/2/2019 05 NO.7 Signaling System
26/34
www.univ.zte.com.cn
1)Signaling point (local exchange)
It refers to the node in the signaling system that provides common
channel signaling.
SP can also be divided into 2 types:
Source points : OPC (Originating points code)
Destination points: DPC (Destination point code)
Actually, SP is part of a switching system.
8/2/2019 05 NO.7 Signaling System
27/34
www.univ.zte.com.cn
2)Signal transfer point (STP)
It refers to SP that transfer signaling messages from one signaling
link to another. They are the middle signaling points during signaling
transfer.
STPs are usually setted in pairs, as they are linked to ensure
redundancy and achieve routing reliability.
One key advantage of STP is that it enables a SP to signal to other
SPs without being directly connected to them.
8/2/2019 05 NO.7 Signaling System
28/34
www.univ.zte.com.cn
B
Voice channels
A
Signaling link
C
SP ASP B
STP
2_2_2 3_3_3
8_8_5
8/2/2019 05 NO.7 Signaling System
29/34
www.univ.zte.com.cn
Signaling code
OPC or DPC is 14-bit address for CCITT (24-bit for China)
International3bit-8bit-3bit
In CHINAthe frame is 8bit-8bit-8bit
8/2/2019 05 NO.7 Signaling System
30/34
www.univ.zte.com.cn
OPC and DPC is a opposite conception, but signaling point code (SPC) is absolute.
For example, the SP of switch A is 2_2_2, and SP of switch B is 3_3_3. If you work in
switch A then 2_2_2 is OPC for A, and 3_3_3 is DSP for A. If other work in switch B, then
3_3_3 is OPC for B, and 2_2_2 is DPC for B.
B
Voice channels
A
Signaling link
C
2_2_2 3_3_3
8/2/2019 05 NO.7 Signaling System
31/34
www.univ.zte.com.cn
1)The associated mode
In this mode, messages related to the voice channel connecting
two switches are sent on the signaling link that directly connects
two switches, as shown in the Figure.
B
Voice channels
A
Signaling link
Signaling Mode
8/2/2019 05 NO.7 Signaling System
32/34
www.univ.zte.com.cn
2)The quasi-associated modeThis can be called a special case of the non-associated mode.In this mode, signaling messages between switches A and B gothrough the several preset concatenated signaling links.
B
Voice channels
A
Signaling link
CSTP
SP SP
Th 3 l l i li k
8/2/2019 05 NO.7 Signaling System
33/34
www.univ.zte.com.cn
B2
A2
A1
LSTP
HSTP
HSTPHSTP
D DD
DDD
DD
B1
C1
C2
A B
C
A
C
B
B
BB
B
SPSP
SP
SP
A A A A
A areaC area
B area
The 3-level signaling network
8/2/2019 05 NO.7 Signaling System
34/34
www univ zte com cn
The End