Systemy sygnalizacji i zarządzania TI

Size: px

Start display at page:

Download "Systemy sygnalizacji i zarządzania TI"

Wilfred Simon
6 years ago
Views:

1 Systemy sygnalizacji i zarządzania TI SS7: warstwa sieciowa Krzysztof Wajda Katedra Telekomunikacji AGH Listopad, 2016

2 Outline Network management Message handling processes Message routing Traffic management Flow control Failure recovery

3 Signalling network functions (level 3) Correspond to the lower sublayer of the OSI s network layer provide procedures for the transfer of messages between signalling points two basic categories: signalling message handling signalling network management

4 Message structure inside SIF MTP F CK F B SIF SIO LI I FSN I BSN F B B CK F LI SF SIF SIO FSN BSN FIB BIB First Bit Transmitted Check Bitsg Flag Length Indicator Status Field Signaling Information Field Service Information Field Forward Sequence Number Backward Sequence Number Forward Indicator Bit Backward Indicator Bit SIF field will be revisited when describing User Parts (UP) TUP TUP Message Information Elements H1 Message Type H0 Message Group Label B ISUP ISUP Message Information Elements Message Type Label C SCCP E O P User Message/Data SCCP Message Header Message Type Label D Includes Called And Calling Party Adresses And Local References* (*CO Only) TCAP Component Portion Component n Component 2 Component 1 Transaction Portion TUP = Telephone User Part ISUP = ISDN User Part SCCP = Signaling Connection User Part TCAP = Transaction Capabilities Application Part

5 Signalling network functions Level 4 Level 3 User Parts MTP Signaling Network Functions Signaling Message Handling Level 2 Message Transfer Part Message Distribution Message Routing Message Discrimination message/packet management Signalling Route Management Signaling Network Management Signalling Traffic Management network/route management Signalling Link Management Testing and Maintenance (MTP) Signalling Message Flow Indications and Controls

6 Signalling message handling Consists of message routing, discrimination and distribution performed at each signalling point based on the content of Routing Label and Service Information Octet Routing Label: Destination Point Code (DPC) Origination Point Code (OPC) Signalling Link Selection (SLS) these fields have different length in ITU-T and ANSI specifications

7 Message routing Based on DPC and SLS fields, sometimes on SIO Usually more than one signalling link can be used to send message to DPC Selection is made on SLS-field basis - implementation of load sharing Link set it is set of links between two signalling points

8 Routing label Length (bit) n 8 SLS OPC DPC 0/3 4/5 14/24 14/24 Routing label Label First Bit Transmitted k/l: k is value for CCITT l is value for ANSI OPC - Origination Point Code DPC - Destination Point Code SLS - Signalling Link Selection

9 Load sharing chooses among links belonging to link set theobjective of load sharing is to spread the load, to keep it balanced can be done over links in the same link set or over links not belonging to the same link set collection of link sets used by load sharing is called a combined link set load sharing do not preserve sequence of messages, so when this is necessary, the SLS field should be kept the same

10 How SLS field works? A SLS= xxx1 xxx0 B D G xx11 xx10 xx01 C xx00 E H I

11 General structure of signalling system functions Level 4 Level 3 Level 2 Level 1 User Parts TUP D Signalling network functions Signalling message handling Message Transfer Part C Signalling link Signalling link functions B Signalling data link A DUP Signalling network management Other type Testing and maintenance TUP DUP Signalling message flow Controls and indications Telephone User Part Data User Part

12 Detailed structure of signalling system functions Level 4 User Parts TUP D Level 3 Level 2 Level 1 Message Transfer Part Signalling network functions Signalling message handling Message distribution C B Signalling link Signalling link functions Signalling data link Switching functions Message discrimination Transmission channels A DUP Message routing SCCP Other type Signalling Network Management Signalling traffic managemnet Signalling route management Signalling link management Testing and maintenance Signalling message flow Controls and indications

13 Signalling Connection Control Part (SCCP) Relation of SCCP to MTP Connection-oriented and connectionless services SCCP routing SCCP management

14 Relation of SCCP to MTP SCCP enhances services accomplished by MTP to provide the functional equivalent of OSI s network layer SCCP has enhanced addressing ability: DPC plus Subsystem Numbers (SSN) to identify local users at the node SCCP has ability to use global addresses, such as dialed digits (using global addresses needs their translation to DPC+SSN)

15 SCCP - service classes Class 0: Basic connectionless class Class 1: Sequenced connectionless class Class 2: Basic connection-oriented class Class 3: Flow control connectionoriented class

16 Class 0 of SCCP User-to-user information block is called Network Service Data Unit (NSDU) and is transported independently, possibly out of sequence (pure connectionless class)

17 Class 1 of SCCP Particular stream of NSDUs is supposed to be delivered in sequence There is association (by SCCP) between stream units and sequence control parameter All messages in one stream unit have the same SLS code

18 Class 2 of SCCP Bidirectional transfer of NSDUs is done through virtual circuit Messages belonging to the same signalling connection have the same SLS field Segmentation and reassembly capability is provided (when NSDU is longer than 255 octets)

19 Class 3 of SCCP Capabilities of class 2 are supported with addition of flow control Detection of message loss and missequencing is provided There is notification of higher layers about message loss and missequencing

20 SCCP functions SCCP Users SCCP MTP N-Connect Request N-Connect Response N-Data Request N-Exped. Data Request N-Data Acknowledgment Request N-Disconnect Request N-Reset Request N-Reset Response N-Inform Request SCCP N-Connect Indication N-Connect Confirmation N-Data Indication N-Exped. Data Indication N-Data Acknowledgment Indication N-Disconnected Indication N-Reset Indication N-Reset Confirmation N-Inform Indication Request Type 1 Request Type 2 Reply SCCP Connection-Oriented Control (SCOC) CO Message Routing Failure SCCP Routing Control (SCRC) MTP - Transfer Indication MTP - Transfer Request N-Unitdate Request N-Unitdate Indication N-Notice Indication SCCP Connectionless Control (SCLC) CL Message Routing Failure S O R S O G S S A S S P S S T Message Received for Unavailable Local SS N-Coordination Request N-Coordination Response N-State Request N-Coordination Indication N-Coordination Confirmation N-State Indication N-PC State Indication SCCP Management (SCMG) MTP - Pause Indication MTP - Resume Indication MTP - Status Indication

21 Signalling network structures

22 Basic SS7 network structure STP STP SP SP STP STP SP - Signalling Point STP - Signalling Transfer Point

23 Basic structure - mesh-type Mesh type or quad-type The STPs are combined ( mated ) on a pairwise basis Mesh-type network has 100% redundacy (any single failure causes traffic to be diverted to alternative paths) Each component should be engineered in such way to allow twice its peak load There is necessity to fulfil diversity criterion: split of quad pairs into different physical transmission paths

24 Alternate signalling network structure A Associated STP 2 STP 1 C Associated B Mix of associated and quasi-associated signalling modes Associated signalling mode can be used as first choice route Quasi-associated signalling mode can be used as backup in case the associated path fails

25 Generalization of mesh-network Cluster (1,3) Cluster (1,2) STP 2 Cluster (2,3) Cluster (2,6) STP 1 STP 3 Cluster (2,4) Cluster (1,6) Cluster (3,4) STP 6 STP 4 Cluster (1,5) Cluster (3,5) Cluster (5,6) STP 5 Cluster (4,6) Cluster (4,5)

26 Generalization of meshnetwork (2) Backbone network of fully connected STPs Clusters of offices (SPs) are connected to different pairs of STPs When STP fails - its load is split to number of STPs When signalling link fails - also split of traffic

27 SS7 node codes

28 Signalling Area Network Code (SANC) Country designations were decided before wide deployment of IP networks ITU Point Code Format is different than the ANSI (North American) 14 bits allow for adressing SPs Zone ID Network ID Signalling Point ID 3 bits 8 bits 3 bits

29 ITU Zone IDs Zone ID Geographical Region 2 Europe 3 North America, Mexico, the Caribean, Greenland 4 Middle East and Asia 5 South Asia, Australia, New Zealand 6 Africa 7 South America

30 Country Codes Code Network Poland Poland Liechtenstein

31 Inside Poland National-level arrangements are different In Poland 7+7 bits Zone ID Signalling Point ID 7 bits 7 bits

32 Summary MTP3 creates reliable packet network (common channel signalling network) + additionally SCCP High level of redundancy introduced, done by overdimensioning Routing based on quasi-static SLS field SCCP module and functions introduce connection-oriented service

33 References G. Danilewicz, W. Kabaciński, System Sygnalizacji nr 7, WKŁ, 2005 D. Minoli, G. Dobrowski, Principles of signaling for Cell Relay and Frame Relay, Artech House, 1995 Q ,706, 707, MTP Signalling Network Structure,Q.705 Lectures available at:

34 Literatura Strony WWW

35 Dziękuję za uwagę!

Systemy sygnalizacji

Systemy sygnalizacji i Zarządzania Sieciami System sygnalizacji nr 7-wprowadzenie Krzysztof Wajda Katedra Telekomunikacji AGH Październik, 2016 Goals of the course introduction of main problems and definitions