of a telecommunication network management

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1 On Telecommunication Management Dilmar M. Meira Jose M. S. Nogueira University of Minas Gerais, Belo Horizonte, Brazil Son T. Vuong University of British Columbia, Vancouver, Canada Abstract - This paper reviews some basic concepts about network management and introduces a new approach for the management of telecommunication networks, using SIS (System for the Integration of Supervision). The approach is based on the gradual integration of the existing proprietary management systems, while simultaneously moving towards the new ITU-T network management standards, namely TMN. 1 Introduction A telecommunication network can be roughly seen as a set of switches (exchanges), interconnected by a set of transmission systems. There is also an access network, which connects the user equipment (computer, telephone set, switch, etc.) to one of the system's switches. Through the access network, users gain access to the rest of the telecommunication network. A large number of other equipment, such as rectiers, batteries, cables, antennas and air conditioning, must also be adequately operated and maintained in order to keep the high standards of quality and reliability of the services. Usually, the equipment and systems used on a telecommunication plant dier from each other in respect to functionality, architecture, and implementation technology. The high degree of distribution makes it impossible to have all the network resources attended by human operators. Furthermore, a signicant portion of the equipment is installed on remote locations, such as radio stations on top of mountains and needs to be remotely monitored and controlled. As a consequence of heterogeneity, there is a trend towards the installation of a new monitoring and control system for each new equipment deployed in the telecommunication plant. Generally, those monitoring and control systems are specially designed for a specic application and do not cooperate very much among them. Managing those gigantic, heterogeneous and highly distributed networks became necessarily a very complex task. The main diculty is not due to the lack On leave at UBC when paper was written of monitoring and control systems. In fact, some of those systems are available since the 60's [Tell68]. The real problem is the low degree of integration between these systems, which prevents an user from having a systemic view of the network. TMN (Telecommunications Management ) which is presented in Section 2, was conceived to remedy this situation. It is a general model for a network to support the management requirements of a telecommunications company to plan, provision, install, maintain, operate and administer telecommunications networks and services. Section 3 presents the main concepts involved in modeling information in a telecommunication network management environment, while Section 4 briey presents the two most known sets of protocols and services for the network management information exchange. Section 5 is dedicated to SIS, or System for the Integration of Supervision, which is a practical implementation of a telecommunication network management system. Finally, Section 6 has some concluding remarks. 2 An Overview of the TMN Architecture The concept of TMN has been developed by the CCITT (now ITU-T) since the fall of 1985 [Mine87]. The Recommendation M.3010 [ITU93-1] describes the functional, physical and information architectures, whereas several other ITU-T documents give further detail of TMN. This section summarizes some important aspects of TMN, as recommended by the ITU-T. Figure 1, which conforms to Figure 1 of the Recommendation M.3010, shows a telecommunication network, made up of several network elements. Conceptually, TNM is separate from the telecommunication network, except for a shared portion of each Element (). A network element may vary from a very small component of a telecommunication network, such as a modem or an air conditioning equipment, up to an entire telephone switch or a transmission route.

2 Telecommunication TMN Data Communication WS WS Figure 1: How TMN is Related to a Telecommunication Besides the network elements, Figure 1 also presents three other components of TMN: A Data Communication (DCN), to give support to data interchange inside the TMN. Although conceptually independent, this part of TMN may use the facilities provided by the telecommunication network. Several Work Stations (WS), to provide the access of human users to TMN. The work stations do not necessarily include workstations in the sense commonly understood in the computer terminology. It can be seen from the gure that, similarly to the network elements, part of the work stations is located outside TMN. Several Operations Systems (), which include software modules used as tools to help the operation and management of a specic aspect of the telecommunication network. The concept of was not invented by the TMN designers. In fact, the proliferation of separate s, and the need for standard interfaces and protocols for the interconnection of s, were motivations for the denition of TMN. A TMN may have other kinds of components not shown in Figure 1: Mediation devices, which modies the information exchanged between operations systems and network elements to make it conform to the expectations of both components. Mediation functions may include information storing, adaptation, ltering, thresholding and condensation. Special adaptors (named \Q-adaptors"), used to support the connection of non-tmn entities to the TMN. 3 Information Modeling To facilitate the denition of managed resources, TMN adopts the I systems management principles and is based on the object-oriented paradigm. According to this approach, the information exchanged inside a management system is modeled in terms of managed objects, which are abstract views of the resources being managed. The managed object abstraction expresses the object's properties as seen by management. According to [ITU93-1], a managed object is identied by the attributes visible at its boundary, its response to management operation stimulations, the management operations dened upon it, and the notications it can issue. There may exist managed objects which represent logical resources of the TMN itself, rather than resources of the managed network. In the I systems management model, its is implied that each managed object or, more precisely, the system that implements it, has a considerable degree of intelligence [Lang93]. In order to exchange information, two TMN applications must rst establish a relationship known as application association. For each association one management process must take one and only one of two possible roles: Manager role: This is the part of the distributed application that issues management operation directives and receives notications; Agent role: This part of the application responds to the directives issued by the manager; the agent also emits notications to the manager, re- ecting the behavior of the associated managed objects. The information concerning both the managed objects and the managing system is stored in management information bases (MIB). 4 Management Information Exchange Two independent eorts have been made towards the standardization of the network management information exchange. The rst one is a joint work of the ISO and the ITU, and resulted in a set of standard protocols and services that include CMIP, or Common Management Information Protocol [ITU91-2], and CMIS, or Common Management Information Service [ITU91-1]. These services and

3 protocols were adopted for the interchange of management information among managers and agents of a TMN. The second approach is due to the so called Internet Community, and gave origin to the SNMP, or Simple Management Protocol, and its new version, SNMPv2 [Rose94]. Despite the fact that both approaches make use of the concepts of manager and agent, and that in both cases the information architecture refers to the object-oriented paradigm, there are several important dierences between the two models [Geri93]. As the name suggests, when compared with CMIS/CMIP, SNMP has a lighter information structure, as well as fewer primitive management functions and a simpler communication protocol. This contributed to make SNMP a much more \popular" network management option, on one hand, but narrowed down its eld of application on the other hand. CMIS/CMIP and SNMP oer common services, on top of which must be implemented the services and protocols needed by specic functional management areas, such as fault, performance, conguration, accounting, and trac. 5 SIS The System for the Integration of Supervision (SIS) [Nogu93] is a network management system developed in Brazil by the Federal University of Minas Gerais (UFMG) jointly and funded by the Minas Gerais State Telecommunications Company (TELEMIG). One remarkable point about the SIS project is the realistic strategy adopted concerning its development and evolution. It started as a solution to a specic problem and incrementally is being made compliant to the ITU-T telecommunication management standards, that is, TMN. By their nature, telecommunication networks are complex, and so is the set of TMN standards. Instead of trying to implement and put into operation the whole set of primitive operations and data model for a particular functional area, the strategy has been to choose some aspects that are more relevant by the time being. From this point on, the improvements are much easier. 5.1 The telecommunication network management scenario A typical telecommunications network is made of several equipment and systems, which dier from each other in terms of age, technology, network domain, manufacturer, etc. Each kind of equipment usually communicates to a particular supervisory system, which is responsible for transferring the equipment's operation and maintenance information to one or more operations centers. The supervisory systems are also responsible for sending commands from the operations' sta to the supervised equipment. Since the beginning of the 80's, as a result of the growth of network's size and complexity, the amount of management information arriving to the network operations centers increased in such an extension that it became very dicult to handle it. To complicate things a little further, the incoming management information syntax and semantics diered among managed systems, preventing the users from having a systemic overview of the managed network. This situation led to the need for an integrated network management tool. In 1985, by the time CCITT started specifying TMN, the network management situation was so critical for some telecommunications companies, that they could not wait for the results of CCITT's ongoing work. Also, a signicant part of the existing telecommunications equipment and systems did not have the required intelligence to implement the network element function of TMN. As a result, it was conceived SIS, which was primarily a tool to integrate the Company's network management systems. One of the main requirements of the system was that it might be able to be easily modied or extended to meet the changing operation and maintenance needs. 5.2 A Supervisory System At a rst approach, a supervisory system may be thought as been formed from two kinds of equipment: remote terminal units (UTR) and central units (UC) (Figure 2). UTRs are installed near the managed equipment. Its function is to gather, code and transmit information related to the managed equipment or systems, as well as to receive, decode and distribute command signals to those equipment or systems. Each central unit must be able to receive, decode, process, store, and display management information coming from the remote terminal units. In general, a central unit is also capable of issuing command signals to its remote terminal units. A group of supervisory systems constitutes a supervisory system plant, where each supervisory system collects information from a specic segment of the managed network and sends this information to one or more operations centers. Conversely, one or more operations centers may be able to send commands to the segment of the plant connected to a given supervisory system. One of the most important drawbacks of this scheme is that it is very dicult to correlate the information carried by the various systems; this limitation implies in several operational diculties.

4 Supervisory System Managed Telecommunication Equipment and Systems SIS UCP UCR UCR UCR UCP - Main Central Unit Sees the whole plant UCR - Regional Central Unit Sees one region - Sub-regional Central Unit Sees one sub-region - Element Supervisory Systems To be Adaptor IAC ETS ETS IAC - Communications Adapter ETS - Supervisory Terminal Remote Terminal Unit (UTR) Integrated Element Central Unit (UC) Element Figure 2: A Supervisory System SIS -- FUNCTIONAL ARCHITECTURE Figure 3: SIS Functional Architecture One of the main objectives of SIS is to overcome this diculty. 5.3 Functional Architecture of SIS Functionally, SIS is a three-level hierarchy of central units (Figure 3). This organization reects the structure adopted by many telecommunication companies for their operations and maintenance centers. The UCP, or main central unit, is located on the highest level of the hierarchy, and is responsible for the management of the whole plant. Each operations region has one UCR, or regional central unity, that allows the autonomous operation of the region's plant. Each sub-regional central unit () allows the autonomous operation of the corresponding subregion's plant. This is the lowest level of the SIS hierarchy, and is also the the point where the information coming from the several existing supervisory sub-systems is fed into SIS. For the integration of some of the supervisory sub-systems or network elements, it is necessary to develop a special communication adapter interface (IAC), which is responsible for interfacing SIS with the existing sub-systems. 5.4 Physical Architecture Despite behaving as an hierarchy of central units, the underlying physical architecture of SIS is very exible and modular. The main and regional central units are implemented by RISC workstations, running the UNIX operating system. The secondary central units are also implemented in RISC workstations, with the exception of some communications adaptor interfaces (IAC) where special hardware was demanded for the interconnection with the existing supervisory systems. The SIS network is a collection of LANs, making an internet. 5.5 Software Architecture Each central unit of SIS is a logical module running in UNIX-based workstations, and is implemented through several processes, which communicate using the technique of message passing. The main processes comprising a central unit are shown in Figure 4. It must be noticed that there usually be several instances of managers, SSS Monitors, BD Interfaces and SISterms in each central unit. Figure 4 refers to a secondary central unit, but the other central units are very similar to respecting to software architecture. Each SSS Monitor has the role of a manager and is specic to a segment of the existing managed plant. Each SSS is equivalent to a network element of a TMN. The data concerning the managed systems and the managing system itself, as well as the data collected from the plant, are distributed over a wide geographical area. Some data are fully replicated, whereas other are vertically replicated. The data bases follow the relational model.

5 SSS N.E. being considered as a possible point to be explored throughout the evolution of SIS. SSS Terminal Terminal SSS Monitor SISTerm SSS - Supervisory SubSystem Management Module Manager DB Interface N.E. Element N.E. DBMS DBMS Figure 4: SIS Software Architecture () 5.6 Some Management Functions The SIS basic platform, now being deployed, is able to perform what was dened as \common network supervision", that corresponds to the following functions, among others: network status; network summary tables; alarm report; outstanding events report; remote command; remote regulation; trouble ticketing. 5.7 Evolution The evolution of SIS consists of the development of new capabilities, as well as the improvement of the existing ones. Currently, the main research subjects are: Incorporation of ISO and ITU-T interfaces and protocols, in order to make possible the integration of TMN-compliant network elements; Real-time conguration management; Real-time performance and quality of service management; Development of some specic interfaces for the integration of a number of sub-systems having no standard interfaces The adequacy of the existing network management systems to the management of high-speed networks is a subject of much discussion nowadays. Besides being an important research topic, this issue is also 6 Conclusions The contemporary telecommunication networks are some of the world's most reliable systems. The use of \old" and thoroughly proven technologies is often one of the factors contributing to this remarkable situation. While needing to be continuously managed in order to keep up this high reliability, the elements of such networks are not prepared to be directly integrated to a TMN-compliant management system. The System for the Integration of Supervision (SIS) integrates into one single system several existing network management systems. Its rst version has already been deployed. Now, a great deal of research and development eort is being made to make SIS interfaces and protocols compliant to the ITU Recommendations. The next version of SIS will certainly be much more TMN-oriented than its existing rst version. References [Geri93] Michael Gering. CMIP versus SNMP. IFIP Symposium on Integrated Management, 1993, pp [ITU91-1] ITU. Common Management Information Service Denition for CCITT Applications { Rec. X.710, Geneva, [ITU91-2] ITU. Common Management Information Protocol Specication for CCITT Applications { Rec. X.711, Geneva, [ITU93-1] ITU. Principles for a Telecommunications Management { Recommendation M ITU, Geneva, [Lang93] Alwyn Langsford and Jonathan D. Moffet. Distributed Systems Management. Addison-Wesley, England, [Mine87] James A. Mines. Overview of the Telecommunications Management. IEEE Globecom'87, pp [Nogu93] Jose M.S. Nogueira (ed.). Projeto SIS: Colet^anea de Relatorios Tecnicos (SIS Project: Collection of Technical Reports 1991 to 1993). TELEMIG/UFMG, Belo Horizonte, Brazil, [Rose94] Marshall T. Rose. The Simple Book. Second Edition. Prentice Hall, Englewood Clis, [Tell68] Telettra S.p.A. Time Division Multiplex for Transmission of up to 6000 Remote Controls and up to 6000 Remote Indications or 600 Measurements. Telettra, Milano, 1968.

Carlos Samitier Joaquin Luque Fernando Gonzalo DIMAT S.A. Manuel Mejías Grupo Endesa Spain Universidad de Sevilla (Spain) Spain

Carlos Samitier Joaquin Luque Fernando Gonzalo DIMAT S.A. Manuel Mejías Grupo Endesa Spain Universidad de Sevilla (Spain) Spain NETWORK MANAGEMENT ARCHITECTURE FOR POWER UTILITY NETWORKS ABSTRACT Telecommunication