Q3 Management of V5.1 - V5.2 Conversion

Transcription

1 HELSINKI UNIVERSITY OF TECHNOLOGY Department of Computer Science and Engineering Pradip Lamsal Q3 Management of V5.1 - V5.2 Conversion Thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Engineering. Espoo, 12 th of June, 2000 Advisor: Prof. Reijo Sulonen Supervisor: Stephen Day, M.A

2 HELSINKI UNIVERSITY ABSTRACT OF THE OF TECHNOLOGY MASTER'S THESIS Author: Pradip Lamsal Name of the Thesis: Q3 Management of V5.1 - V5.2 Conversion Date: Number of pages: 77 Faculty: Professorship: Code: Advisor: Supervisor: Computer Science and Engineering Information Processing Science Tik-76 Prof. Reijo Sulonen Stephen Day, M.A This thesis is a part of a larger project that involves designing and developing an access node, which conforms to the V5 standard. V5 is an ETSI standard and it defines a set of messages that allows communication between an access network and a local exchange. The management aspect of the access node is very important as it ensures proper operation of the equipment and helps predict any possible problems. This thesis tackles one management problem, which involves identifying a subscriber line throughout an access network. The problem arises due to the fact that the management system faces difficulties when one subscriber line is represented by two different network layer addresses. This problem must be solved and hidden inside the access node so that the management system does not have to worry about how to map those addresses. The main outcome of the thesis work is a piece of software that solves the problem by mapping the addresses properly. The thesis first reviews two approaches of solving the problem and then uses the most appropriate one to design and develop the software. The octopus process, developed at Nokia, was used and all the necessary aspects of the development process are described in this thesis. Keywords: Access Node, Access Network, Conversion, Design Pattern, EF Address, Interface, L3 Address, Network Management, Object, Octopus, OO, V5, V5.1, V5.2

3 PREFACE This thesis was written for Nokia Networks, Broadband Systems division during the period from September 1999 to May I would like to take this opportunity to express my gratitude to my supervisor Stephen Day for guiding me and reviewing the thesis several times. Without his suggestions and feedback it would have been very difficult to finish the thesis. I would also like to thank Dewi Jones and Pekka Aaltonen for their help and the rest of my colleagues in V5ASW team for their constant support. I also appreciate the help and feedback I received from Prof. Reijo Sulonen, my thesis advisor. Finally, I would like to thank my family and friends for their support and encouragement throughout the whole time. Espoo, 8 th of May, 2000 Pradip Lamsal

4 TABLE OF CONTENTS ABBREVIATIONS...6 GLOSSARY INTRODUCTION ACCESS NETWORKS & V TELECOMMUNICATIONS NETWORK Transmission Switching ACCESS NETWORK Concentration in the Access Network V5 Introduction Mbps Multiplexing Signaling in V V5 Protocols V5 Message Structure SUMMARY NETWORK MANAGEMENT WHAT IS NETWORK MANAGEMENT? WHY IS NETWORK MANAGEMENT IMPORTANT? NETWORK MANAGEMENT FUNCTIONAL AREAS Fault Management Configuration Management Accounting Management Performance Management Security Management NETWORK MANAGEMENT ARCHITECTURE Information model NETWORK MANAGEMENT PROTOCOLS SNMP CMIP TELECOMMUNICATIONS MANAGEMENT NETWORK (TMN) Network Management Layers TMN Architecture SUMMARY PROBLEM CONCEPTUAL PROBLEM CURRENT SCENARIO Limitations of current implementation Significance of V FUTURE SCENARIO FUTURE SCENARIO THESIS PROJECT SUMMARY SOLUTION AVAILABLE SOLUTION(S) POSSIBLE SOLUTION(S) GENERAL REQUIREMENTS ANALYSIS OF POSSIBLE SOLUTIONS OBJECT ORIENTED MODELING SUMMARY...50

5 6 SW DEVELOPMENT: BACKGROUND INFORMATION PROCESS MODEL AND LIFECYCLE EXISTING SOFTWARE IN BRIEF V5ASW ARCHITECTURE STATIC RELATIONSHIP OF SUBSYSTEMS SUMMARY SW DEVELOPMENT: PROCESS REQUIREMENTS SPECIFICATION & SYSTEM ARCHITECTURE ANALYSIS Structural Model Functional Model Dynamic Model DESIGN Structural Model Dynamic Model TESTING & VERIFICATION DISCUSSION SUMMARY & CONCLUSION REFERENCES APPENDICES APPENDIX 1: OSI MODEL APPENDIX 2: MANAGED OBJECT ASSOCIATION FOR CONVERSION...77

6 Abbreviations Page 6 of 77 ABBREVIATIONS ACH ASW ATM BCC CAS CMIP CMIS CMISE CCS C-Channel C-Path DCN EF Address ETSI FCAPS HDL ISDN ISO ITU ITU-T LAPD LAPV5 L3 Address MD MEH MF MIB MIT NE NEF Application Configuration Handler Application Software Asynchronous Transfer Mode Bearer Channel Control Channel Associated Signaling Common Management Information Protocol Common Management Information Service Common Management Information Service Element Common Channel Signaling Communication Channel Communication Path Data Communication Network Envelope Function Address European Telecommunication Standard Institute Fault, Configuration, Accounting, Performance, Security Hardware Driver Layer Integrated Services Digital Network International Standardization Organization International Telecommunication Union International Telecommunication Union Telecommunication Standardization Sector Link Access Protocol D Channel Link Access Protocol V5 Layer 3 Address Mediation Device Managed Element Handler Mediation Function Management Information Base Management Information Tree Network Element Network Element Function

7 Abbreviations Page 7 of 77 NMS Network Management System OMT Object Modeling Technique OO Object Oriented OS Operations Systems OSF Operations Systems Function OSI Open System Interconnection POTS Plain Old Telephone System PSTN Public Switch Telephone Network QA Q Adapter QAF Q Adapter Function SAH Subscriber Access Handler SNMP Simple Network Management Protocol SPLL Semi Permanent Leased Line SS7 Signaling System No. 7 SSW Support Software TCP/IP Transmission Control Protocol/ Internet Protocol TMN Telecommunication Management Network UML Unified Modeling Language V5ASWP V5ASW Platform V5H V5 Handler V5L V5 Layer V5TtpH V5 Trail Termination Point Handler VSAH Virtual Subscriber Access Handler WS Workstation WSF Workstation Function

8 Glossary Page 8 of 77 GLOSSARY Access network: The system implemented between a local exchange and user replacing part or the whole of the local line distribution network. Normally, it consists of two copper wires, which connect the phone to the local switch or the local exchange. Access node: An equipment implemented between a local exchange and subscribers' phone lines. It is connected to a local exchange via one or more high capacity links. Agent: A piece of software with which the manager communicates. The main role of an agent is to respond to the commands issued by the manager. Communication path (c-path): A communication path is an entity, which collects the messages generated in connection with a set of user ports or subscribers. Conversion: A term used to describe the conversion of a network address of one network to a network address of another network. Design pattern: A design pattern systematically names, motivates and explains a general design that addresses a recurring design problem in objectoriented systems. It describes the problem, the solution, when to apply the solution and its consequences. Direct user port: A user port managed object, which models the subscriber port that is associated to a V5.2 interface. Envelope function address (EF address): A network layer address, used to identify an ISDN subscriber port (or ISDN user port). It is a 13 bit number. Information model: The management information model presents an abstraction of the management aspects of network resources and the related support management activities. In simple terms, an information model describes how functions in a managed device are represented to the NMS. It contains physical and logical resources of the device and their mutual relationships. Integrated services digital network (ISDN): ISDN is a public digital telephone network, which is built to handle a variety of services such as voice, data and video. It can be either narrow band ISDN (N-ISDN) or broadband ISDN (B-ISDN). N-ISDN uses the existing PSTN infrastructure whereas B-ISDN is a complete redesign of the network. In this thesis ISDN simply refers to N-ISDN. ISDN Basic rate: Basic rate ISDN is characterized by 2B+D, where D indicates signaling channel and B indicates bearer channel. 2B+D means that basic

9 Glossary Page 9 of 77 rate ISDN has one channel for signaling and two channels for bearer data. ISDN Primary rate: Primary rate ISDN is characterized by 30B+D. 30B+D means is that primary rate ISDN has one channel for signaling and two channels for bearer data. Layer 3 address (L3 address): A network layer address, used to identify a PSTN subscriber port ( or PSTN user port). It is a 15 bit number. Local exchange (LE): A telecommunications equipment that switches telephone calls to the right destination. Local switch: See local exchange. Logical c-channel: A collection of communication paths (c-paths) Managed device: See managed element. Managed element: A managed element is a network element that needs to be managed. Managed object: The management view of a resource that may be managed through the use of a management protocol. Manager: See NMS Octopus: Octopus is a software development process, which provides a systematic approach for developing object-oriented software for embedded real-time systems. Network management system (NMS): An NMS is a network equipment which is responsible for managing a set of equipment in that network. Depending on the type of the NMS, it can manage only one equipment, a set of similar equipment or more than one type of equipment. The primary role of a manager is to issue management commands and receive notifications. Physical communication channel: A timeslot in a 2 mega bits per second link, which carries signaling information, not bearer data. 1 mega bits per second = 10 6 bits per second. Protocol: An agreement that governs the procedures used to exchange information between communicating entities. In other word, a protocol defines the messages that allow communication between two entities. Public switch telephone network (PSTN): PSTN refers to the analog public switched network. Plain Old Telephone Service (POTS) is one of the

10 Glossary Page 10 of 77 services provided by PSTN. Sometimes, these two terms are used interchangeably. Unified modeling language (UML): UML provides system architects working on object analysis and design with one consistent language for specifying, visualizing, constructing and documenting the artifacts of software systems as well as for business modeling. User port: Subscriber Virtual user port: A user port managed object, which models the subscriber port that is associated to a V5.1 interface

11 Introduction Page 11 of 77 1 INTRODUCTION The telecommunications industry has changed a lot over the last decade. Network operators now prefer to buy different equipment from different vendors for their networks and expect them to work together, as opposed to buying the whole network solution from a single vendor. When a network consists of several equipment types from different vendors, it is very likely that a proprietary solution does not work with all the equipment as the implementation of the same type of equipment is generally different. This situation can be avoided if all the vendors adhere to some standards or recommendations for that given equipment type so that the equipment can work together even if the implementation of each of them is different. This has forced the vendors to take advantage of the open standards proposed by the international standardization bodies. Network management is very important in any network. Network management involves monitoring and controlling the equipment in the network so that any possible problem in the network can be detected and fixed as soon as possible ( 3 contains a detailed explanation of network management). Telecommunications networks are very large, and competition in this industry is very stiff. Therefore, to be a successful operator it is very important to provide good services to the customers and at the same time respond to their problems promptly. To respond quickly, any problem or potential problem should be known as soon as it occurs and a possible solution should be available immediately. This is exactly when network management becomes important. With the help of a proper network management tool any equipment in a network can be monitored for any possible fault and if a fault occurs, it can be detected and fixed quickly. Modern telecommunications networks have experienced some changes in terms of efficiency as well. The customers are asking for better services at lower cost. One of the approaches taken by the network operators is to add new equipment (most probably employing a new technology) at different points in the network in order to increase its efficiency. Since the installation of telecommunications equipment is expensive and time consuming, it is uneconomical to replace the existing network every time a new technology evolves. Therefore, when a new equipment is added to a network it must work with the existing network. One of the new equipment types that has been added to an existing telecommunications networks is the access node. 'Access node' and related concepts are explained in 2.2, but in simple words an access node is a piece of equipment, to which the customers phone lines are connected. This is shown in Figure 1.

12 Introduction Page 12 of 77 Figure 1: Access node and local exchange The access node multiplexes these phone lines and transmits them to a local exchange via a high capacity link. A local exchange, also referred to as a local switch, is another piece of telecommunications equipment whose prime responsibility is to switch a call to the right destination. In a network, each phone line is identified by a network level address called layer3 address. This layer 3 address, also represented as L3 address, is unique in a network. This uniqueness means that each of the phone lines in the network can be identified if its L3 address is known. From network management s point of view, this L3 address is very important because it can be used to isolate a phone line and detect any faults and fix them if possible. A phone number is also unique but it does not have meaning everywhere in the network. For instance, an access node does not recognize a phone number. There can be a scenario where an access node is in between two networks. In this scenario, it is very likely that the same phone line is represented by two different L3 addresses in those two networks because an L3 address is unique only in one network. For network management, two L3 addresses representing the same phone line create a problem. This is due to the fact that two different L3 addresses generally mean two different phone lines. Therefore, there is an L3 address mismatch in the access node. If the Network Management System (NMS), the system which performs network management, takes these two L3 addresses as two different phone lines then it will not be able to associate the information from one network to the other. Without this, proper network management is not possible. For proper operation of the access node, the L3 address in one network has to be converted to or associated to the L3 address in the other network and must be hidden from the management. Throughout this document this problem is referred to as the conversion problem. The conversion problem becomes more complex if the two networks run different protocols. A protocol in this context refers to a set of messages, which allows communication between two pieces of equipment. The reason why two protocols can add extra complexity is because

13 Introduction Page 13 of 77 different protocols can have different requirements and the solution must adhere to both of them for proper operation of the access node. The thesis is about network management of an access node, which has a conversion problem. The conversion problem is slightly complicated because the two networks involved in conversion use slightly different standards V5.1 and V5.2. Both V5.1 and V5.2 are two different forms of V5 standard, which is a European Telecommunications Standards Institute (ETSI). Details of V5 standard are explained in 2.2. The thesis looks at different approaches of solving the conversion problem and develops software that solves the problem by using the most appropriate approach. The prime objective of the thesis work is design and development of network management software. The software is for a subsystem, which models the solution to the conversion problem so that it is no longer seen as a problem by the management system. In addition to the prime objective, the thesis also discusses whether the chosen approach can be used to solve similar address mismatch problem or not. This thesis is organized in the following order: Chapter 2 and chapter 3 contain some background information. Chapter 2 is an introduction to access networks and V5. Chapter 3 describes the basic concepts behind network management. Chapter 4 describes the problem. The problem at the conceptual level is described first and some scenarios are considered. The scope of the thesis is then defined by considering one of the scenarios. Chapter 5 concentrates on the solution. Chapters 6 and 7 describe the software development. Some background information is described first and the development process is illustrated in detail. Conclusions are presented in chapter 8. Chapter 9 lists the set of references and finally chapter 10 contains some relevant attachments as appendices. Throughout the document, technical terms are italicized when they are introduced and the terms in glossary index are written in bold for quick reference.

14 Access Networks & V5 Page 14 of 77 2 ACCESS NETWORKS & V5 Today, telecommunications network operators have been able to provide a lot of modern services to their customers. Modern services often require changes or upgrades in a lot of network equipment and sometimes changes in the network architecture itself. A network architecture shows how a network is constructed, which equipment is involved and how they are interconnected. One architectural change that can be done in order to increase the capacity, to make it more robust and ultimately to give better services to the customers, is to add new and more efficient equipment at different points of the network. One of the equipment, which is added in modern telecommunication network is access node. This chapter first introduces the basic telecommunications architecture and then describes access networks, access nodes and the protocols relevant to access networks. 2.1 Telecommunications Network A telecommunications network performs two major functions: transmission and switching. Transmission is used to convey signals from one place to another via some medium such as cables or radio. These cables or radio links make a transmission path. Switching, on the other hand, is used to switch signals from one transmission path to another Transmission The transmission part of the telecommunications networks consists of access networks and trunk networks [17].

15 Access Networks & V5 Page 15 of 77 Figure 2: A basic telecommunications network ETSI defines an access network as "The system implemented between a local exchange and user replacing part or the whole of the local line distribution network" [23]. Normally, it consists of two copper wires, which connect the phone to the local switch or the local exchange. This pair of copper wires can be replaced by an optical fiber cable or radio connection. In situations where the customers' telephones are directly connected to the local switch, the local switch has more functions than the switch, which is connected to those telephones via some intermediate network equipment. These extra functions include: Converting the 2-wire cable to a 4-wire cable transmission. In a 2-wire cable transmission, the two voice directions meet on the same cable pair whereas in a 4-wire cable transmission voice is carried separately in each direction. Converting the analog speech signal to a digital signal. Identifying the called number in order to determine the route. Connecting the called number in the same local area. Connecting the customer to the trunk switch for long distance calls.

16 Access Networks & V5 Page 16 of 77 Providing metering of the call for charging purpose. Local switches are connected to larger trunk switches, which are linked together to form a trunk network. The transmission in this trunk network is fully digital and of very high capacity. Signaling System No. 7 (SS7), which is an International Telecommunication Union Telecommunication Standardization Sector (ITU-T) standard, is the signaling protocol used in the trunk network. This signaling protocol defines the set of messages transmitted between two trunk switches in order to transmit signals Switching The ITU-T defines switching as: "The establishing, on demand, of an individual connection from a desired inlet to a desired outlet within a set of inlets and outlets for as long as is required for the transfer of information". In simple words, switching involves setting up a connection between two telephone subscribers so that they can talk to each other. Originally, switching meant a human operator interconnecting two subscribers with each other. But today, switching is viewed differently. There are switching equipment, which are capable of switching different kinds of information than just voice. These switching equipment employ different switching techniques. The switching techniques can be divided into two broad categories: circuit switching and packet switching. In circuit switching a transmission path is first reserved before any communication is performed and is used in more traditional technologies such as Public Switched Telephone Network (PSTN) and Integrated Services Digital Network (ISDN). In packet switching a transmission path does not have to be reserved. Instead, the messages are broken down into packets and these packets are sent through the network with proper destination address. Asynchronous Transfer Mode (ATM) is an example of packet switching technique. In ATM, a message is broken down into 53-octet packets and sent through the network. 2.2 Access Network Concentration in the Access Network It is unnecessary and uneconomical to connect all the customers from a certain geographical area to the local exchange directly. This is due to the fact that not everyone uses the phone at the same time, even in the busiest time of the day. In order to avoid this inefficiency a new kind of network equipment, called the concentrator, can be put between the customers' telephones and the local switch. The number of input channels in a concentrator is greater than the number of output channels. The concentrator connects only those customers, who have picked up their handsets, to the local switch for the duration of the call. For instance, a transmission path between a local switch and an access node, which

17 Access Networks & V5 Page 17 of 77 has a capacity of carrying 30 subscribers, can be used to connect 100 subscribers to an access node. This is illustrated in Figure 3. Figure 3: Use of a concentrator in an access network This concentrator is commonly referred to as Access Node. An access node does not necessarily have to be a concentrator but can be any other equipment in an access network such as a multiplexer. A simple multiplexer selects the correct subscriber line based on some other information provided externally and cannot support concentration, as described above. An access node can be situated in the same building as the local switch or it can be located remotely from the switch in roadside cabinets. Keeping an access node on the street reduces the length of the copper wire between a telephone handset and the point where the signal is digitized, and hence reduces signal degradation and infrastructure cost V5 Introduction V is the reference point between an access node and a local exchange as shown in Figure 4. A reference point defines the boundary between two entities in terms of functionality. V5 is defined as the interface between the access network and the local exchange. An interface defines a protocol suite and messages carried by that protocol. In simple terms V5 defines a set of messages that allows communication between the access network and the local exchange. V5 is designed to support both PSTN and ISDN services on 2*10 6 bits per second (2*10 6 bps or 2Mbps) capacity links. [8, 11, 23]

18 Access Networks & V5 Page 18 of 77 Figure 4: V reference point V5 has two forms: V5.1 and V5.2. V5.1 offers the advantage of standard signaling but has some limitations. One V5.1 interface supports only one 2Mbps link, it does not support concentration and its support of ISDN is limited to basic rate (2B+D) only. In basic rate ISDN there are two 64*10 3 bps (64Kbps; 1Kbps = 10 3 bps) bearer channels and one 64Kbps signaling channel. The signaling channel carries the signaling information whereas the bearer channel carries the data or the real information. These limitations of V5.1 are overcome by the introduction of V5.2. V5.2 supports concentration, primary rate (30B+D) ISDN, protection of V5 signaling information and up to 16 2Mbps links. Primary rate ISDN has 30 bearer channels and one signaling channel. One bearer channel (=64Kbps channel) is required for one standard telephone conversation. This means that with basic rate ISDN two conversations are possible and with primary rate ISDN 30 conversations are possible simultaneously Mbps Multiplexing ITU-T G.704 [24] standard defines several synchronous frame structure for digital transmission. One of the frames is 2.048Mbps (commonly written as 2Mbps) where the frame length is 256 bits, numbered from 1 to 256 and repeated 8000 times per second. There are eight bits per 64Kbps channel timeslot and they are numbered 1 to 8. The 256 bits in the frame carry 32-octet interleaved timeslots numbered 0 to 31. Timeslot 0 is used for frame alignment and the remaining timeslots 1 to 15 and 17 to 31 can accommodate a 64Kbps digital signal. Timeslot 16 may be used for signaling but if not needed for signaling then it may be used in the same way as timeslots 1 to 15 and 17 to 31.

19 Access Networks & V5 Page 19 of 77 Figure 5: Format of the 2Mbps link [11] V5 uses this 2Mbps structure to carry traffic between an access node and a local exchange. Here, timeslot 16 is generally used as a communication timeslot, i.e., it is used to carry signaling protocols. The remaining 30 timeslots can be used by the V5 interface to carry bearer data, which is routed across the network. If a timeslot carries bearer data then it is called a bearer timeslot. Thus, with 30 bearer timeslots, a 2Mbps link can carry 30 PSTN or 15 ISDN (basic rate) simultaneous calls and the signaling information. If more physical timeslots are required to carry the communication information then timeslots 15 and 31 are used for that purpose Signaling in V5 V5 uses Common Channel Signaling (CCS). In CCS one timeslot is used to carry signaling for many client timeslots. In older signaling systems Channel Associated Signaling (CAS) was used. In CAS one timeslot is used to carry signaling information for other client timeslots but two at a time. For instance, in one frame timeslot 16 would carry signaling for timeslot 1 and 17 and the following frame would carry signaling for timeslots 2 and 18 and so on. The signaling timeslots are also referred to as physical communication channels (c-channels). The allocation of signaling to time slots is arranged using two levels of logical entities: communication channels and communication paths (c-paths). A communication path is an entity, which collects the messages generated in connection with a set of user ports or subscribers. A logical c-channel is a collection of c-paths and is associated to a physical c-channel (a time slot on a 2Mbps link). This association is illustrated in Figure 6.

20 Access Networks & V5 Page 20 of 77 Figure 6: Signaling in V5 PSTN has only one type of signaling and therefore one c-path can carry all the signaling information. This c-path is assigned to one logical c-channel, which is further assigned to one physical c-channel. However, ISDN signaling can be of Ds, p or f type and they cannot be mixed together. Therefore, one c-path is required for each signaling type. Also, V5 allows for multiple ISDN c-paths of the same type V5 Protocols There are five protocols in the V5 standard. The first two are only for V5.1 whereas V5.2 has all five of them. These protocols are listed below. Control protocol: This is the most important protocol of the V5 interface and the software entities responsible for its operation must be present all the time. The messages in control protocol control user ports. Besides, these messages are responsible for checking V5 interface identification and configuration (how V5 is configured in the given equipment), restarting of other protocols after a failure and switch over between the current V5 configuration and a new V5 configuration. PSTN protocol: The messages in the PSTN signaling protocol are responsible for setting up and taking down of analog telephone calls. Link control protocol: The messages in the link control protocol are responsible for link identification and blocking and unblocking of 2Mbps

21 Access Networks & V5 Page 21 of 77 links. Blocking a link means disabling it temporarily. This might be required for some testing or fixing a fault. By unblocking a blocked link, the link can be made operational for normal use again. Bearer channel connection (BCC) protocol: The messages in the BCC protocol control the association between the 64Kbps channels at the user ports and the 64Kbps bearer timeslots on the 2Mbps link contained in the V5.2 interface. These messages allow bearer timeslots to be allocated to user ports when they are required and to be deallocated when service is no longer needed. By allocating the timeslots to the user ports according to demand, this protocol allows the V5.2 interface to concentrate traffic. [11] Traffic concentration in this context is what was described in Protection protocol: The main purpose of the protection protocol is to make sure that other protocols can still operate even if some of the equipment fail. This makes the operation of V5.2 protocol robust. Most importantly, the messages in this protocol safeguard the logical c-channels against the failure of a single link on a V5.2 interface. These messages are not responsible for protecting bearer channels. This means that if there is a phone call in progress on a link and the link fails then the call will be lost but the signaling information is protected by this protocol. The logical c- channels protected by the protection protocol are divided into two groups: protection group 1 and protection group 2. Protection group 1 is mandatory and it implements protection of the vital protocols whereas protection group 2 is optional and it implements protection of the subscriber signaling (PSTN & ISDN). PSTN protocol and control protocols are vital protocols for they are required all the time V5 Message Structure The V5 stack consists of the lowest three layers of the Open System Interconnection (OSI) stack: layer 1 - physical layer, layer2 - data link layer and layer 3 - network layer. A complete diagram of the seven-layer OSI stack can be found in Figure 7 shows the V5.1 protocol architecture. V5.2 protocol architecture is exactly the same as of V5.1 but it has extra three protocols (link control, BCC and protection) at the network layer. Here, all the rectangular boxes are software entities that perform the functions of the layer they belong to. The entities in the network layer are responsible for network to network communication. The entities in the data link layer are responsible for error detection, error recovery, sequence control and flow control. The entities in the physical layer are responsible for controlling the hardware in order to transmit the data along the physical medium.

22 Access Networks & V5 Page 22 of 77 Figure 7: V5.1 protocol architecture [23] All the V5 protocols mentioned in are network layer (layer 3) protocols. The network layer messages are encapsulated in data link layer messages. The general name for the data link layer protocol is link access protocol, however, it can have different names when different technologies are considered. For instance, in ISDN world data link layer protocol is called Link Access Protocol - D channel (LAPD) and in V5 world the protocol at the same layer is called Link Access Protocol -V5 (LAPV5). The V5 data link layer is divided into two sublayers: data link sublayer (LAPV5- DL) and envelope function sublayer (LAPV5-EF). This is due to the fact that ISDN message structure needs to conform to ISDN standards and V5 has to take that into consideration. LAPV5-DL is capable of carrying either standard ISDN messages or standard V5 messages. The mapping function adds an outer frame envelope to the LAPV5-DL sublayer messages and converts them into LAPV5- EF sublayer messages Envelope Function Address ETSI defines an Envelope Function (EF) address as "An address used in the LAPV5-EF frame to identify different V5 enveloping function sublayer connections, each of them used to support a relaying mechanism for the LAPD

23 Access Networks & V5 Page 23 of 77 frames of each of the ISDN user port or messages corresponding to the V5 layer 3 protocols (e.g., PSTN protocol, control protocol)" [23]. In simple terms, an EF address provides a common envelope to both the LAPV5-DL frames, used by PSTN protocol and control protocol and ISDN LAPD frames, used by ISDN subscriber ports. EF address is a 13-bit number. In real life, EF address is used to identify an ISDN subscriber port (or also called an ISDN user port) Layer 3 Address ETSI defines an Layer 3 (L3) address as "An address within layer 3 messages of EF address types PSTN signaling or control only" [23]. In simple terms, an L3 address references a user port or a common control function and is unique in a network. It is 15-bit number in case of a PSTN user port and 13 bit long in case of an ISDN user port and common control function. In real life, an L3 address is used to identify a PSTN user port. 2.3 Summary The transmission part of a telecommunications network consists of access networks and trunk networks. Access network used to consist of local exchanges connected to the subscribers directly but nowadays access nodes are used to multiplex the subscriber lines and transmit those lines to the local exchange via a high-speed link. The high-speed link is a 2Mbps link capable of carrying 30 PSTN calls or 15 ISDN calls simultaneously. V5 is the ETSI standard for signaling message between access nodes and local exchanges and has two forms: V5.1 and V5.2. V5.1 has only control and PSTN protocols whereas V5.2 has all the five protocols: control, PSTN, link control, BCC and protection protocol. V5 stack consists of the lowest three layers of the OSI stack: physical layer (layer 1), data link layer (layer 2) and network layer (layer 3).

24 Network Management Page 24 of 77 3 NETWORK MANAGEMENT Network equipment, also referred to as network elements, have become more intelligent and robust than ever before. At the same time customers are demanding a lot of flexibility in the services that they obtain from the service providers or the network operators. For these operators it is very important that their equipment are less prone to failures and easily manageable so that they are capable of handling any possible problems in the network and at the same time be flexible in providing services. This chapter focuses on network management. First, the term network management is defined and its importance is highlighted. Then several functional areas and management layers are described. The network management architecture shows how a network element is managed. Two network management protocols: SNMP and CMIP are briefly mentioned and finally the chapter describes the principles behind TMN. 3.1 What is Network Management? Network management is about managing a network so that the network is available and functional all the time. The management concept can be divided into two main categories: monitoring and controlling. [13] Monitoring means observing and analyzing the status and behavior of the network, which involves end systems, intermediate systems and the core network. End systems generally interface with customers or the customers equipment. An access node can be considered as an example of an end system. The core network, also known as the backbone network, is the central part of the whole network. Smaller networks are connected to the core network. For instance more than one access network can be connected to the core network. The trunk network of Figure 2 is an example of a core network. Intermediate systems lie somewhere between the end systems and the core network. A local exchange is an example of an intermediate system. By monitoring a network, the management system can get the static, dynamic and statistical information of the network. Things that can be monitored in a network are fault, performance, accounting information etc. [10] Management of fault, performance and accounting information are explained in 3.3. Controlling involves modifying parameters and invoking some actions on the network, which involves end systems, intermediate systems and the core network. Things that fall into this category of network management are mainly the configuration and security aspects of the network. Configuring a network involves initialization, maintenance and shut down of individual equipment whereas security is mainly concerned with the security of the total network. [10] Details of configuration and security management are explained in 3.3.

25 Network Management Page 25 of Why is Network Management Important? The tremendously growing size and the complexity of telecommunication networks presents a challenge to manage them efficiently and properly. Today, networks have become critical to many more enterprises than ever. Seamless flow of information across networks, more efficient use of bandwidth and more intelligent use of network information are vital for service providers to offer services to their customers. In today's competitive business environment no-one can afford to let their network go down. The cost of network downtime is so high that it can easily become the weapon for the competitors to drive a provider out of business. Network downtime shows how long the network has been down or out of service. In order to avoid or at least minimize the possibility of this catastrophe the network has to be managed in such a way that any possible problem can be detected or predicted and necessary steps can be taken. [1, 2] With a proper management system the network elements can be monitored and controlled efficiently all the time. The main functional areas a management system concentrates on are fault management, configuration management, accounting management, performance, and security management. These functional areas are further illustrated in Network Management Functional Areas ITU-T provides some guidelines to support a wide variety of management features which cover the planning, installation, operations, administration, maintenance and provisioning of telecommunications network and services [15]. The specification and development of the required features totally depends on the vendors, however, this guidance is aimed at creating an open interface so that it works in multi-vendor environment. This guidance is categorized into five broad functional areas. These areas are sometimes referred to as FCAPS (Fault, Configuration, Accounting, Performance & Security) for convenience Fault Management The goal of fault management is to detect, log, notify and if possible automatically fix network problems to keep the network running efficiently. Fault management includes functions such as localizing a fault, correcting a fault, testing, administrating troubles and alarm surveillance Configuration Management The main purpose of configuration management is to monitor and control the configuration information of the network. This is probably the most important part of network management in the sense that the network cannot be accurately managed unless the configuration of the network is managed. Configuration

26 Network Management Page 26 of 77 management includes functions such as installing the network equipment, network planning and engineering, service planning and negotiating Accounting Management Accounting management is responsible for the measurement of the use of network services, determination of costs to the service provider and charging the customer for such use [14]. This includes services such as measuring the usage of the resources in the network, collecting and handling the pricing and financial information and enterprise control. Enterprise control involves controlling the flow of funds within the enterprise and between the enterprise and its owners and creditors Performance Management Performance management provides functions to evaluate and report upon the behavior of telecommunication equipment and the effectiveness of the network or network elements [14]. It does so by collecting and analyzing statistical data and then using that data to monitor and correct the behavior of the network or network elements. This data can also be used to maintain and measure the quality of the network or the network elements. Performance management includes functions such as establishing the quality, monitoring the performance, controlling the performance and processing and analyzing the performance data in order to evaluate the performance level of network elements Security Management Security management is responsible for securing the network and network elements. In addition, security has to be implemented for all other management functional areas described above. Security management includes functions such as prevention of intrusion, detection of intruder in case intrusion occurs, administering security policy, managing security related information and containment and recovery. Containment and recovery function are needed to deny access to an intruder, to repair damage done by and intruder and to recover losses. All of these functional areas are related to both network monitoring and network control parts of the management. Fault management, accounting management and performance management are more important for network monitoring whereas configuration and security management are more important for network control part of the management. [10, 13] 3.4 Network Management Architecture In order to implement an automated network management system, a network has to be integrated with some extra equipment that can help in managing the

27 Network Management Page 27 of 77 network. This network element, which manages other network elements, is called Network Management System (NMS). An NMS is sometimes called simply a manager. The primary role of a manager is to issue management commands and receive notifications. The devices or the network elements, which are to be managed, are called managed devices or managed elements. These two terms are often used interchangeably. An NMS uses a network management protocol to manage the managed devices. Figure 8 shows the basic network management architecture. Figure 8: Network management architecture [10] The piece of software in managed devices, with which the NMS communicates, is called an agent. Sometimes an agent uses a proxy to manage a device. A proxy is an entity, which works on behalf of another entity Information model ITU-T defines information model as 'The management information model presents an abstraction of the management aspects of network resources and the related support management activities. The model determines the scope of the information that can be exchanged in a standardized manner. This activity to support the information model takes place at the application level and involves a variety of management application functions such as storing, retrieving and

28 Network Management Page 28 of 77 processing information' [15]. In simple terms an information model describes how functions in a managed device are represented to the NMS [17]. In theory, the management system should be able to manage all the devices of the same type even though they are from different vendors. The management system sees the device as a collection of logical entities called the managed objects. A managed object represents a real physical or a logical resource that needs to be managed through the use of a management protocol. The information model also contains the relationships between managed objects, which are often arranged in a tree structure called the Management Information Tree (MIT). The management system accesses the managed objects through a virtual information store called the Management Information Base (MIB). The MIB contains descriptions of the relationships between the objects and of the operations or events they are involved in [17]. 3.5 Network Management Protocols Network management protocols are used by the NMS to access the managed devices. Two network management protocols that are commonly used are Simple Network Management Protocol (SNMP) and Common Management Information Protocol (CMIP). CMIP is an International Standardization Organization (ISO) standard SNMP SNMP is mainly used in computer networks, which run the Transmission Control Protocol/Internet Protocol (TCP/IP) protocol. The first and simplest version of this protocol is known as SNMPv1, which developed to SNMPv2 and now the latest standard is SNMPv.3. SNMP needs to run both on the NMS (called SNMP manager) and the managed device (called SNMP agent). The manager communicates with the agent, which in turn talks to the agent software running on the given managed device in order to manage the device. Figure 9 shows the architecture of SNMPv3 management entity.

29 Network Management Page 29 of 77 Figure 9: SNMPv3 architecture [8] The SNMP entity consists of SNMP engine and application as shown in Figure 9. The SNMP engine is in both the manager and the agent. The applications labeled as (M) are only in the manager and the ones labeled as (A) are only in the agent. Among the six applications, only notification originator is both in the manager and the agent CMIP The fundamental function within OSI systems management is the exchange of management information between two entities (manager and agent) by means of a protocol. This functionality within OSI systems management is referred to as the Common Management Information Service Element (CMISE). CMISE is specified in two parts: Common Management Information Service (CMIS) and Common Management Information Protocol (CMIP). [13] CMIS provides seven services for performing management operations. A management system can remotely invoke these services. The services are association services, management notification services or management operation services. The services are specified in terms of primitives that can be viewed as commands or procedure calls with parameters. The seven services are listed below: M-EVENT-REPORT: Reports an event about a managed object to peer CMISE service user.

30 Network Management Page 30 of 77 M-GET: Requests the retrieval of management information from a peer CMISE service user. M-SET: Requests the modification of management information by a peer CMISE service user. M-ACTION: Requests that a peer CMISE service user perform an action. M-CREATE: Requests that a peer CMISE service user create an instance of a managed object. M-DELETE: Requests that a peer CMISE service user delete an instance of a managed object. M-CANCEL-GET: Requests that a peer CMISE service user cancel a previously requested and currently outstanding invocation of the M-GET service. CMIP defines procedures for the transmission of management information and defines the syntax for the management services [13]. All the management services use this protocol to transfer data from the manager to the agent. 3.6 Telecommunications Management Network (TMN) Telecommunications Management Network (TMN) is an ITU-T standard designed to structure the management of telecommunications networks. It provides management functions for telecommunication networks and services and offers communications between itself and the telecommunication networks, service and other TMNs. In this context a telecommunication network is assumed to consist of both analogue and digital telecommunications equipment and associated support equipment. A telecommunication service in this context consists of a range of capabilities provided to customers. [15] The fundamental concept behind a TMN is to provide an organized architecture to achieve the interconnection between various types of Operations Systems (OSs) and/or telecommunications equipment for the exchange of management information using an agreed architecture with standardized interfaces including protocols and messages. Accurate definition of an OS is presented in , but for the time being it can be considered as an equipment, which performs management operations. Several M-Series recommendations describe different aspects of the TMN. [15] Conceptually, a TMN is a separate network that interfaces to a telecommunications network at several different points to send and receive information to and from it and to control its operations. This is illustrated in Figure 10. A TMN may use parts of the telecommunications network to provide its communications.