Yerel alan ağ yönetimi ve SNMP protokol uyumlu yeni bir kullanıcı analizi
Başlık çevirisi mevcut değil.
- Tez No: 75364
- Danışmanlar: DOÇ. DR. MEHMET BÜLENT ÖRENCİK
- Tez Türü: Yüksek Lisans
- Konular: Bilgisayar Mühendisliği Bilimleri-Bilgisayar ve Kontrol, Computer Engineering and Computer Science and Control
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1998
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Kontrol ve Bilgisayar Mühendisliği Ana Bilim Dalı
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 132
Özet
ÖZET Yerel alan ağlan yönetimi konusunun ne kadar önemli olduğu, günümüzünde Internet'in büyük bir hızla gelişmesi sonucunda daha belirgin olarak ortaya çıkmıştır. Ağ yönetimi konusunda 1980'lerden sonra yapılan çalışmalar, bu konuda standartların oluşturulmasını sağlamıştır. Öncelikle ISO (International Organization for Standardization) tararından yapılan çalışmalar, IETF (Internet Engineerin Task Force) tarafından sürdürülmüş ve Internet üzerinde ağ yönetimi işlemlerini tanımlayan basit ağ yönetim protokolü (Simple Network Management Protocol SNMP) hazırlanmıştır. SNMP çok kısa bir sürede birçok ağ cihazları üreticisi firma tarafından kabul görmüş ve uygulamada önemli bir yer edinmiştir. SNMP, bu kadar kabul görmesine rağmen içinde barındırdığı güvenlik yetersizlikleri nedeniyle eleştirilmiş ve yapılan çalışmalar sonucunda 1993 yılında SNMPv2 protokolü tanımlanmıştır. SNMP protokolü esas olarak yönetici ve temsilci yaklaşımına sahiptir. Ağ yönetim yazılımını çalıştıran bilgisayar üzerinde yeralan yönetici fonksiyonları ve kullanıcı uçlarında bulunan temsilcilerin birbirleri ile etkileşimli çalışmaları sonucunda ağ yönetim işleri başarılır. SNMP, temsilci ile yönetici arasındaki haberleşmenin şeklini, yönetim bilgisinin yapısını ve yönetim nesnelerini tanımlar. SNMP, bağlantısız bir protokol olan UDP (User Datagram Protocol) üzerinde yer alır ve uygulama katmam protokolüdür. SNMP protokolüne uygun olarak hazırlanan yazılımlar, birçok noktada dağılmış olarak bulunan ağ kaynaklarının merkezi bir noktadan kontrolünü ve izlenmesini sağladığı için büyük yerel alan ağlarına sahip firmalar için vazgeçilmez olmuştur. Ağ cihazları üreten firmaların büyük çoğunluğu kendi cihazlarım yönetecek yazılımlar hazırlamış ve bunları pazara sunmuştur. Bu tez çalışmasının bir bölümü olarak hazırlanan o SNMP ağ yönetimi yazılımı ise ticari amaçlar gütmeden ve belirli bir firmaya özel olmadan yerel alan ağı üzerindeki yönetilebilen cihazların kontrolünü ve izlenmesini sağlamaktadır. Yazılım Microsoft Windows işletim sistemi kullanan bilgisayara yöneliktir. Borland Delphi 2.0 görsel programlama dili kullanılarak yazılmıştır. Vll
Özet (Çeviri)
SUMMARY LOCAL AREA NETWORK MANAGEMENT AND A NEW SNMP BASED USER INTERFACE In the next decade an impressive growth is to be expected in the use of communication networks. To initialize and optimize the operations of these networks, good network management facilities must be developed. The importance of research in this area is confirmed by a number of studies that show the state of current networks. A study in the UK, showed that LANs go down an average of twenty times a year and subsequently stays out of service for more than four hours. A study in US showed that every hour of LAN interoperability, at“Fortune 1000”companies, loose more than $30,000. The purpose of this thesis is to improve the understanding of network management and develop a new network management software. What is network management? There exist several definitions of network management. One of them as considered in this thesis is the act of initializing, monitoring and modifying the operation of the primary network functions. Primary network functions are those functions that directly support the user requirements. They users to access the network and they take care of the exchange of user data. How is management performed? While designing management functions, the designer will be confronted with a number of design questions. Two of these are important because they affect the design process to a considerable extent. These questions are;. Will management functions be performed by human beings, or will they completely be performed by hardware and software modules.. Should management functionality be distributed over the entire network or should it be concentrated as far as possible. To denote the case, in which human beings are responsible for the initiation of management operations, the term“explicit management”will be used. With this form of management, the decision to initiate management functions will explicitly be taken by human operators during the operational phase. The opposite of explicit management is called“implicit management”With this form of management, all management functions will be performed by hardware and VUlsoftware modules. Operator intervention is therefore not needed. The distinction between both types of management is primarily a matter of realization. There is also a different type of classification about management.“Centralized management”is used to denote the case in which management decisions will be taken from a limited number of central locations. The management functionality that takes these decisions is called the“manager”. The term,“distributed management”will be used as the opposite of central management. With distributed management there are no central systems from which management decisions are taken. Instead functions that take such decisions will be added to the systems that already perform the primary functions. Network Management Standards There are several organizations that have developed services, protocols and architectures for network management. Three most important organizations are:. The International Organization for Standardization(ISO).. Telecommunication Standardization Sector (T) of the International Telecommunication Union (ITU), called CCITT before.. The Internet Engineering Task Force (IETF)^ Of these three ISO was the first who started, as part of its 'Open Systems Interconnection' (OSI) program, the development of an architecture for network management. The first proposal for such an architecture appeared during early 1980. Today a large number of standards exist, such as“OSI Management Framework”and the“Common Management Information Protocol”(CMIP). Initially the aim of ISO was to define management standards for datacom networks, development of standards about telecom networks was left to ITU-T. In 1985, ITU-T started the development of such management standards; these standards have known as the“Telecommunications Management Network”(TMN) recommendations. Looking back at the last decade it may be concluded that the growth of the Internet has played a decisive role in the development of network management protocols. First, Internet Architecture Board (IAB) intended to apply the OSI Management Framework. But, need for network management protocol raised in time and then IAB requested the IETF (the organization who is responsible for the development of Internet Protocols) to define an ad hoc management protocol. This,“Simple Network Management Protocol”(SNMP) was completed within a year and soon many manufacturers started the production of SNMP compliant systems. Although SNMP has several deficiencies, it has become the de facto standard for management of datacom networks. In 1993 an attempt was made to tackle the deficiencies and an improved version of SNMP (SNMPv2) appeared. OSI Management Framework There are five functional areas of OSI management. These are fault management, configuration management, accounting management, performance management and IXsecurity management. Fault management is the set of facilities, which enables the detection, isolation and correction of abnormal operation. Configuration management is the set of facilities which; records the current configuraton, records changes in the configuration, identifies network components, initializes/closes down networks systems, changes network parameters. Accounting management is the set of facilities which enables charges to be established, and costs to be identified for the use of network resources. Performance management is needed to optimize the Quality of Service (QoS). Security management enables the manager to initialize and modify those functions that secure the network from user misbehaviour and unauthorized access. Management Information Base (MIB) Managed devices are ones that can be monitored, controlled, and are capable of reporting events. With properly designed MIBs, SNMP can be used to manage network configuration, performance, faults, accounting, and security. A MIB defines managed objects using a framework called the Structure of Management Information (SMI). The SMI defines how management functions information is grouped and named, allowed operations, permitted data types and the syntax for specifying MIBs. As well as SNMP, SMI and core MIBs are defined by working groups within the IETF. A MIB describes information that can be obtained and/or modified via a network management protocol. This information enables systems on a network to be managed. A MIB consists of a set of objects. Each object has a type and a value. The object type defines a particular kind of managed object. The definition of an object type is therefore a syntactic description. An object instance is an instantiation of an object type that has been bound to a specific value. Management objects are defined by using Abstract Syntax Notation. 1 (ASN.l). ASN.l includes a number of predefined UNIVERSAL types and a grammar for defining new types that are derived from existing types. One alternative for defining managed objects would be to define a new type called“Object”. Then every object in the MIB would be of this type. This approach is technically possible but would result in unwieldy definitions. So, because managed objects may contain a variety of entities being managed, it makes more sense to define an open-ended set of new types, one of each general category of managed objects. This could be done directly in ASN.l. An other alternative for defining objects, and the one employed with SNMP, is to use a macro to define a set of related types used to define managed objects. Figure 1 shows the macro definition for managed objects. Global Naming Tree for Managed Objects ISO and ITU-T promoted the idea of structuring information into a global naming tree and assigning an identifier to any object that needs a name. This tree is used to label just about anything of interest to a standarts organization. The administrative structure, information structure and object name structure are all integrated into the global naming tree. The assignment of unique identifiers to standards documents even has its place in this tree.Figure 1. Managed objects macro definition. There are three nodes at the top of the global naming tree. Naturally, ISO administers the subtree that sprouts from its node. ISO has defined the org node in order to delegate authority to other organizations. One of these organizations is the United States Department of Defence (dod). Dod, historically provided administration, operations, and information services to the Internet. The internet subtree under the dod node is owned by IAB and administered by the Internet Assigned Numbers Authority (IANA). There are six nodes defined under internet: directory, mgmt, experimental, private, security, and SNMPv2. The Mgmt subtree holds all of the accepted, standard network management variables. The scope of SNMP network management is enlarged through experimentation. New and unproved objects are placed under the experimental node. After a period of trial and revision, useful objects are moved from the experimental subtree to the mgmt subtree. Simple Network Management Protocol As Internet grow very fast, it is seen that management of Internet on an ad hoc basis was impossible. In 1987 three management proposals therefore appeared. One of these, High-level Entity Management System / Protocol (HEMS/HEMP) was withdrawn soon. Others were; SNMP and Common Management Over TCP/IP XI(CMOT). At the march 1988 meeting of LAB, the decision was made to use SNMP in the short term and CMOT in the long term. CMOT was an attempt to use OSI systems management standards in the Internet environment. But CMOT specifications did not appear in time and no implementations could be obtained. So, the support for CMOT slowly diminished. In 1992 all work on CMOT was stopped. SNMP is actually a further development of Simple Gateway Monitoring Protocol (SGMP). SGMP was aimed at management of intermediate systems such as gateways. Because SGMP appeared to have success, it was decided to extend its scope and include management of End Systems. To reflect the change, protocol was renamed into SNMP. SNMP Architecture The ideas behind SNMP are the manager-agent concept, use GET and SET Protocol Data Units (PDUs) for operations on management information, use ASN.l for definition of management information and use of a MIB. These ideas were same as ISO approach. With SNMP, a single manager may control many agents. SNMP is built upon User Datagram Protocol (UDP), which is a connectionless transport protocol. Since the Internet Management information as well as the formats of SNMP PDUs are defined according to ASN. 1 syntax, encoding functions, that operate according to the Basic Encoding Rules (BER), are needed. Five types of SNMP PDUs are defined; GetRequest, GetNextRequest, SetRequest, Response and trap. SNMP Operations In SNMP, communication from the manager to the agent system is performed in a confirmed way. The SNMP entity in the manager's side takes the initiative by sending one of the PDUs; GetRequest, GetNextRequest or SetRequest. First two are used to retrieve management information form the agent, SetRequest is used to store or change management information. After reception of one of these PDUs, the SNMP entity at the agent's side responds with a Response PDU (Figure 2). This PDU carries the requested information or indicates failure of the previous request. Figure 2. Manager takes initiative: GetRequest, GetNextRequest, SetRequest PDUs xnIt is also possible that the SNMP entity at the agent's side takes the initiative. This happens in case the agent detects some extraordinary event, such as a re-initialization or a status change at one of its links. As a reaction, the agent's SNMP entity sends a Trap PDU to the managing system. Reception of Trap is not confirmed. Manager side Agent side Trap Figure 3. Agent takes initiative : Trap PDU SNMP Message Formats With SNMP, information is exchanged between a management station and an agent in the form of an SNMP message. Each message includes a version number, indicating the version of SNMP, a community name to be used for this exchange, and one of the five types of PDUs. Figure 4 shows SNMP message formats. From figure, Request messages have the same format with response messages, with the error-status and error-index fields always set to 0. This convention reduces the number of different PDU formats that the SNMP entity must deal with. (a) SNMP Message (b) GetRequest, GetNextRequest and SetRequest PDU (c) GetResponse PDU (d) Trap PDU (e) variable-bindings Figure 4. SNMP message formats. SNMP Architecture SNMP was designed to be an application level protocol that is part of the TCP/IP protocol suite. It is intended to operate over the UDP. In Figure 5, there exists the protocol context of SNMP. At the management station a SNMP manager process controls the access to central MIB and provides a layer to management application. Also SNMP agent have agent process which controls agent's MIB and interpret the XlllSNMP messages. Agent process and manager process also implements UDP, IP and network dependent protocols. Also Figure 5 shows five basic SNMP messages and how they are issued. SNMP Management Station SNMP Agent Management application si ft * i I f SNMP Manager UDP IP Network-dependent prot. Application manages objects SNMP Messages Managed Resources SNMP managed objects i if s I sl «Î si t SNMP Agent UDP IP Network-dependent prot. Figure 5. Protocol context of SNMP. WinSNMP Manager API WinSNMP is also called as an open interface for prograrruning network management applications using the simple network management protocol under Microsoft Windows. The purpose of WinSNMP is to promote the development of SNMP-based network management applications running under the Microsoft Windows family of GUI/operating system products. WinSNMP provides a single interface to which application developers can program and multiple SNMP software vendors can conform. WinSNMP thus defines the procedure calls, data types, data structures, and associated semantics to which an application developer can program and which an SNMP software vendor can implement. Figure 6 shows where WinSNMP fits in one possible scenario of end-to- end SNMP connectivity from an entity acting in a manager role (far left) to an entity acting in an agent role (far right). In summary, WinSNMP offers these major benefits-all intended to accelerate the development, dissemination, and use of SNMP network management applications:. SNMP enabling technology for functional network management applications (ie.,“hides”ASN.l, BER, and SNMP protocol details).. SNMP service provider independence. A WinSNMP application will run against any compliant WinSNMP implementation.. Uniform SNMPvl and SNMPv2 support. A WinSNMP application does not xivMicrosoft Windows Environment r Appi )
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