MTP Signaling Analysis and Process

Chapter 1 Overview of SS7

       Basic Concept

Direct Connection Networking

Quasi- direct connection networking

Difference between Tandem Exchange & STP

A and B have no signaling relation. The destination of A is a tandem exchange and it does not know where is B. Only tandem exchange knows the location of A and B.

A and B are in the same signaling network and they know location of each other. STP is just signaling transfer channel. The connection mode is quasi-direct connection.

  SS7 Overall Organization Structure

Three Kinds of Basic Signaling Unit Format

Service Information Octet SIO

SI: Service indication

D   C  B  A

0   0   0  0    Signaling network management SNM

0   0   0  1    Signaling network test SNT

0   0   1  0    spare

0   0   1  1    Signaling connection control part SCCP

0   1   0  0    Telephone user part TUP

0   1   0  1    ISDN user part ISUP

0   1   1  0    data user part which is related to calling and circuit DUP

0   1   1  1    data user part capability registration and withdraw DUP

1    0  0  0

……        spare

1   1   1  1

SSF: Sub-service field

D    C   B  A

0   0    0   0   International network

0   1    0   0   International spare network

1   0    0   0   National network

1   1    0   0   National Spare network

Universal message assignment flag format

.There are four important type of flags：

  -Class A, For MTP to manage message；

  -Class B, For TUP；

  -Class C, For ISUP (circuit related) message；

  -Class D, For SCCP message.

  Signaling information field SIF

MTP Structure

  .64Kbit/s bi-directional transparent channel

  .Exchange function, It connects SS7 signaling terminal with trunk equipment by semi-permanent connection mode

Signaling Link Layer – MTP Layer 2

 .SU delimiting & alignment

 .Error detection

 .Error correction

 .Initial alignment

 .Signaling link error ratio monitor

 .Flow control

Signaling Link Layer – MTP Layer 2

Signaling Link Layer – MTP Layer 2

     .Signaling link assignment procedure

Signaling network function – MTP3

 .Two functions

    -Signaling Message Handling

    -Signaling Network Management

 .Main MTP3 message

    -Link test message SLTM/SLTA

    -Transfer inhibit and transfer permission TFP/TFA

    -Changeover and changed-back message  COO/COA，    CBD/CBA，ECO/ECA

    -Management inhibit and release inhibit  LIN/LIA、LUN/LUA

Signaling network function – MTP3

.Signaling link test Message

  -When link is normal, signaling link will send SLTM message every minute. After SLTM is received, the destination SP will send back SLTA message. The value and number of test codes in SLTA should be equal to that in SLTM

  -If SLTA can not be received within 6s, it can not enter service activation state.

Signaling network function – MTP3

  .Link change over

  .Time control changeover

      -In event of failure as shown, SP1 will start up time control changeover timer. When time out, link 2 will transfer service of link 1.

Signaling network function – MTP3

 .Link change back

  -When failure is recovered, SP1 and SP2 starts change-back procedure

  -SP1 starts time control change-back timer. When time out, change-back is over

Signaling network function – MTP3

.Signaling link management inhibit

.Under following conditions management inhibition cannot be carried out:

  -inhibition will make destination SP unreachable;

  -link congestion.

Signaling network function – MTP3

  .Signaling link inhibition release


  

Signaling network function – MTP3

 .Transfer prohibited procedure

     -When link 1 failure induces failure from STP1 to SP2, STP1 sends TFP to SP1

Signaling network function – MTP3

  
.Transfer Allowed procedure

     -When link1 failure recovery makes route from STP1 to SP2 available, STP1 sends TFA to SP1

Signaling network function – MTP3

  .Forced Routing

 Signaling network function – MTP3

 SP1 receives TFA and recovers former routing
.Controlled rerouting

  -When link1 failure recovery makes route from STP1 to SP2 available, STP1 sends TFA to SP1

Load Sharing Algorithms

  

      .Link Selection Method

     SLS =1 0  1 1
     Mask=0 0 1 0
Link number=1

Chapter 2 Maintenance Commands

    .SS7 signaling link management

    .SS7 signaling correlative state inquiry

    .MTP message tracing concept and process instruction

    .MTP traffic measurement

SS7 signaling link management

 .ACT N7LNK：Activate MTP link

 .DEA N7LNK：Deactivate MTP link

 .INH N7LNK：Management prohibit MTP link

 .UIH N7LNK：MTP link management prohibit release

SS7 signaling correlative state inquiry

    .DSP N7DPC：Inquire MTP destination state

    .DSP N7RT：Inquire MTP routing state

    .DSP N7LNK：Inquire MTP link

    Link tracing setting of graphical interface

Link tracing message explanation frame 

Chapter 3 MTP Alarm

 MTP Alarm
  .MTP alarm overview
  .MTP state alarm
  .MTP event alarm

        MTP Alarm Overview
 .There are three kinds of MTP alarm:
   -failure alarm
   -recovery alarm
   -event alarm
 .The failure alarm and recovery alarm can be called a general name, state alarm, and state alarms are bi-directional.
 .According to the relationship of MTP tables, MTP alarms often appear as following sequence:
   -Link alarm<＝> link set alarm <＝> routing alarm <＝> destination SP alarm
 
         MTP State Alarm
  .State alarm refers to the alarms generated when there are state changes in signaling link and signaling network of MTP module.
    For example：
      -Signaling link available-unavailable
      -Destination signaling point available-unavailable

       MTP Event Alarm
  .Event alarm refers to report between independent events and they have no certain relation.
     -Since an event is always followed with some state changes, so an event alarm is always followed with one or some state alarms.

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