SNMP learning notes
Version: 1.0
Author: Soundboy
Date: 2004-8-26
Remarks: This article is to learn about the SNMP protocol related knowledge is taken from different books, and therefore absorbed on the document, so it is more disabled.
Glossary
SNMP
At the end of the 1970s, in the early 1980s, computer networks were gradually developed into large-scale networks from several computers within a small range. With the development of network jump, management operations such as monitoring and maintenance of the network have become more difficult, thus put forward urgent requirements for the development of the proposal to meet the needs of network management. The first network management protocol starting is SNMP. At that time, people just treated SNMP as an emergency measures, waiting until the future, there is a more successful new agreement, will be nature. However, although there is a continuous launch of new agreements, SNMP has been widely used in the simple use of its simple structure. The working mechanism of the SNMP protocol is very simple, mainly through a variety of different types of messages, ie PDU (protocol data units) to implement network information exchange. The PDU is actually a variable object, each of which is composed of two parts of the title and variable value. SNMP mainly uses five types of PDUs to monitor network implementation, two types of terminal information, two terminal data, and the last one is used to monitor various terminal events, such as startup and closure of the terminal, etc.. Thus, if the user wants to know if a terminal has been accessed to the network, the SNMP can be transmitted to the terminal to send a PDU with an information reading function. If the terminal has been connected to the network, the user will get the returned confirmation information. When there is a terminal being turned off, a packet can be issued by an event variable (TRAP) to notify the user of the terminal system has been turned off. The biggest advantage of the SNMP protocol The biggest advantage of the SNMP protocol is the design simple, neither a complex implementation process, nor does it take much network resources, which is very easy to use. In general, the various variables used in the SNMP protocol mainly include the following information: 1. Variable headings; 2. Variable data type, such as integer, string, etc. 3. Whether the variable has information reading or reading and writing. Another advantage of the variable value SNMP protocol is to use very widely, almost all network managers prefer to use simple SNMP to complete work operations. This promotes the support of the SNMP protocol when designing and manufacturing network devices such as bridges, routers, and routers. Good scalability is another advantageous of the SNMP protocol. Because the agreement itself is very simple, any upgrade or extension of the agreement is also very convenient to meet the development needs of the future network. In the shortcomings of the SNMP protocol, although SNMP has become the most popular network management protocol with its simple and easy-to-use features, no matter how SNMP cannot be a design perfect agreement. First, there are some security vulnerabilities in the SNMP protocol, and the network intruder is easy to obtain various information passed through the network, and the settings can close certain terminals. In this regard, SNMP puts forward its own solution, adding some security mechanisms in the new version of SNMPv2, can effectively solve the following security issues: data confidentiality, prevent network intruders from obtaining network information; verification, Preventing network intruders from sending false data over the network; access control limits the types of variables that different users can use, thereby avoiding crashs caused by the network caused by the error operation of a single user. The biggest problem of the SNMP protocol is also due to too simple and unable to process various details information, and cannot meet the development needs of today's increasingly inflated networks. Similarly, SNMPv2 has also improved this issue. The new version of the protocol allows you to use more, more detailed variable specifications, and add two new PDUs to manage and control the table data structural objects read for data read. In fact, there are so many new features in SNMPv2, so that protocol regulations increase from the first 36 pages to 416 pages.
Some people think that SNMPv2 has lost its original simplicity, but from another aspect, the transformation of SNMP is also necessary. After decades of rapid development, SNMP must be able to adapt to network requirements of the new era. SNMPv2 When we introduced here, everyone may all be able to become a new generation of network management standard protocols in terms of NMPv2. However, the facts are just the opposite, SNMPv2 is still only staying in theoretical stage. The failure of SNMPv2 should mainly be attributed to developers' unanimous issues. In addition, it is difficult to find products that fully support the various extensions of the SNMPv2 protocol. In fact, SNMP has also affected the further development of SNMPv2 in a sense, whether SNMPv2 or higher SNMPv3 does not seem to be a qualified successor of SNMP. What is MIB?
The MIB = Management Information Information Base Network Management Information Library (MIB) is the standard of network management data. The data items, data types, data types, data types, and allowed operations in each data item are specified in this standard. By accessing access to these data items, all statistical contents of the gateway can be obtained. Basic network management can be achieved by comprehensive analysis of multiple gateway statistics.
Management Information Base (MIB) describes a collection of objects. If the SNMP service program supports MIB, a manager can manipulate this object on a specific computer.
Each device in the network is an object element, and their collection is MIB. As the access set, the function of MIB is to specify a proxy for the management workstation. The settings configured in the agent can be changed by modifying the variables.
For SNMP, MIB is essentially a tree structure database. And the objects used to indicate a particular resource must be the same in each system. By defining a SMI (Structur Of Management Information, the Management Information Structure). It determines how the data type can be used in the MIB and indicates how objects represent and name it in the MIB.
How can I create my own MIB?
First of all: To define your own MIB, you must first familiarize yourself with the syntax of Asn.1, where an old one MIB book is very good, MIB's RFC document is the seemingly as if it defines. Second: See more other MIBs, in fact, it is relatively simple, it is Type, scalar, and three main things.
Miscellaneous
SNMP (Simple Network Management Protocol) is an application layer protocol for exchange management information between network devices, which is part of the TCP / IP protocol suite. It is the network management personnel to manage networks, discover and solve network problems, and plan the development of the network. SNMP management data includes three main components managed, Agent, and Network Management System (NMS). Managed equipment is a network node, including a resident SNMP agent (Agent). Agent is a network sensation software module resides in a managed device; NMS monitors and controls managed devices. SNMP's basic command: Read, Write, Trap and Traversal. NMS monitors the managed device with the read command; NMS controls the managed device with the WRITE command; the management device uses trap command to report events to NMS; NMS uses Traversal operation to determine which variable value supported by the management device, and constantly for parameter table Collect information, such as routing information. The SNMP Management Information Library (MIB) is a collection of information, which is layered to form a tree structure. Use the network management protocol to access the MIB. The MIB consists of managed objects and has an object label identity. The object identifies uniquely identifies a managed object in the MIB tree species. There are two sides of the SNMP network management approach: Manager side and the Agent side. The Agent side refers to a network management, such as a device, such as a switch such as a switch, etc .; Manager side refers to the network management workstation, which can be programmed to implement the SNMP solution to manage the managed device, and can choose the SNMP package, free and provided by HP. Source code, and is for vc . What you said is mainly to be the programming of the Manager side, SNMP is enough. In addition, you must also know the MIB library structure and content of the tube equipment! ! !
RMON
Remote Monitoring, remote monitoring. RMON can monitor the subnet as an overall, without monitoring each device.
RFC
Request for Command, request annotation. A manufacturer has developed a new product that releases an RFC to ask for comments. Therefore, RFC is a network specification and has its own version number.
Management workstation
It is a typical independent device. Includes applications, administrators, translation administrator information modules, information library MIBs in various devices in the network.
Management agent
Key Platform (host, bridge, router, hub) may have SNMP proxy to manage from management workstations. Respond to the request of the workstation and provide important information in asynchronous mode (even if not requested).
SNMP protocol structure
SNMP operates on UDP, User DataGram Protocol.
OID
OID is "Object Identifier". It is identified a digital sequence with a specific object in this tree.
ASN.1
It is a formal language developed and standardized by ccitt (x.208). Is a language that can be used to define data structures
SNMP overview
Net management software generally supports SNMP (Simple Network Management Agreement), which is capable of combined with HP's Open View Professional Suite professional assembly and Open View Network Node Manager Node Manager, and provides MIB (management information base), RMON (remote) Monitoring) and so on. SNMP (Simple Network Management Protocol) is a widely implemented network protocol that uses proxy software embedded in the network facility to collect network communication information and statistics on network devices. The agent software constantly collects statistics and records these data into a management information library (MIB). The network administrator can get this information by emitting query signals to the agent's MIB, which is called polling. Although the MIB counter will record the total record of statistics, it cannot analyze the daily traffic. In order to fully view the traffic and change rate of the day, the management must constantly poll the SNMP agent, poll once every minute. In this way, the network administrator can use SNMP to evaluate the operation of the network and reveal the trend of communication, such as which network segment is close to the maximum capacity of communication load or is making communication errors. Advanced SN? The MP network management station can even handle the history of network data by programming to turn off the port or take other corrective measures. However, SNMP polls a significant weak point: it has no scalability. In a large network, polling produces huge network management traffic, thus causing the occurrence of communication crowding. It will collect the burden of data to the network management console. The management station may easily collect information about 8 network segments. When they monitor 48 network segments, they may not be able to pay. 1 Overview Telecommunications Management Network is the same as the signaling network, the synchronization network is the support network that guarantees the normal operation of the telecommunications network. With the continuous development of the telecommunications network technology, the telecommunications network is more and more dependence, just like the construction of the telecommunications network, the equipment network needs to be tested, the construction of the telecom management network must also follow the same methodology. Currently, for the study of telecommunications management network, mainly focused on network management frameworks, network management research methods and network management interfaces. Among them, the core content is a network management interface. What kind of management function is provided for the manufacturer, what kind of management functions are provided, what kind of technique is used, how much cost is needed, which directly affects business operators and equipment The sovereignty and benefit allocation between providers can be said that the contents of the network management standards are the strategic places of this entry between business operators and equipment suppliers. 2 The current situation of my country's network management standards has achieved great results in terms of network management standards in my country, and there are some profound lessons. Summarize past experiences and lessons, learn from ITU-T and other international, regional, professional standardized standardization, and my country has basically completed the construction of the network management standardization system. In the theory of telecommunications management network, the content and methodology of standardization research on telecom management network is determined; on this basis, a series of industry standards and corporate standards have been developed, and ITU-T is recommended to formulate tasks; in standard implementation Aspects, a set of guarantees, all of which have produced better social and economic benefits. 2.1 Net Management Theory With the continuous development of computer technology used by Telecom Network Technology and Telecom Management Network, the research on network management theory is also constantly in-depth, currently, this research content mainly includes the following aspects: 2.1.1 Network management Framework Research Currently, the most typical network management architecture mainly has three types of Internet / SNMP management architecture, TMN management architecture and TINA architecture. As theoretical research and practical application continue to improve, TMN is constantly improving by absorbing certain thoughts of other two structures, and gradually occupying the dominant position in the field of telecom network management.
TMN's core idea is a network management network concept, which separates the management business provided by the management network and the telecommunications service provided by the telecommunications network, which belongs to an out-of-band management relative to the managed telecommunications network. TMN separates the business network and management network, while maintaining the interface relatively stable, as far as possible, the development of telecommunications network technology and network management technology on each other's impact. At the same time, TMN shortens the development cycle of the network management system by introducing the concept of software reuse, the reuse of the information model management function and the reuse of the software architecture, and the reuse of the development method, and shorten the development cycle of the network management system and improves the quality of the network management software. Compared to the TMN management architecture, the TINA architecture will manage business and telecommunications business unified considerations. It is more like a band management method. From theory, it is easier to meet the requirements of network management real-time, especially suitable for processing high-level network management issues. . However, it requires a high calculation technology, and it is impossible to achieve practicalization in a short time. If there is no market identity, its influence will be lost. The Internet / SNMP management architecture has achieved great success in the network management of the computer network. According to the characteristics of less management information in computer network, the way to manage in this band is generally not impact on the performance of the network, but the shortcomings inherent in the polling mechanism limit the number of the managed nodes and The operation response time determines the real-time management of the architecture that cannot be used for large networks. Today, in the traditional telecommunications network and IP network fusion trend, based on the TMN management system structure, how to solve the comprehensive management of information networks is the main content of the standardization research of network management architecture. 2.1.2 Methodology of Network Management Interface Research In the TMN Management framework, the core problem of network management standardization research is a network management interface issue. ITU-T gives the methodology of the telecommunications management network interface specification standardization research in M.3020, thereby defining network management interfaces from three aspects, respectively, is the Management Service Definition Guide (GDMS), management function Define Guide (GDMF) and Administrative Object Definition Guide (GDMO). Its basic idea is to divide the network management interface definition process into a series of tasks (TASK), each stage task has associated task information libraries (TIB), TIB describes the knowledge and methods necessary to complete the task and The result produced after this task was completed. After completing the specified task sequence in accordance with a certain timing, a network management interface specification that meets the user needs can be obtained depending on the generated TIB. The 1995 version of M.3020 proposed in Figure 10 details two copies of the two categories defined in the network management interface method are detailed, and TIBs associated with each task and the flow definition of the entire network management interface are completed. This method play a good role in the process of NMD-based network management interface based on Q3 interface, according to this methodology, ITU-T has completed a series of universal network management interface recommendations. On this basis, my country has also developed a range of network management interface specifications for specific business networks. However, there are some shortcomings in traditional management information modeling methods. First, the description of GDMO itself is insufficient, such as the description of the behavior in the model, which cannot be clearly defined to define the specific behavior of the object, which may cause erlish and disambigand; second, in the information modeling process, the demand, analysis and The clip of the design phase cannot reflect the whole process of information modeling; again, it is often the finally static information model, which cannot describe the dynamic characteristics of the managed object; Finally, the information model is only applicable to this management Framework cannot be reused in other management frameworks. With the emergence of CORBA (Public Object Request Agent Architecture) platform management applications, the information model is increasingly required to implement intercommunication in different management frameworks, such as traditional Q3-based information models can be applied in CORBA-based platforms.
The statically and dynamic GDMO / IDL mapping proposed by the JIDM Working Group can solve the interoperability of the information model to a certain extent, but there is an inevitable semantic loss in the model translation. Therefore, only from the management information modeling method itself, finds a modeling method that can get information models that are not related to the management framework to solve this problem. To this end, ITU-T decided to simplify the methodology of the NMS interface specification in March 1999, proposed RAD (Requirements, Analysis, And Design) method. Unlike traditional management information, the RAD method divides the entire modeling process into three phases of demand, analysis and design. However, these three phases are not strict from top to bottom, but a process of repeated gradual refinement. The demand phase mainly involves the definition of problem domain space, system policy, and external system and the role played by the system, which can be divided into transactional requirements definitions and details (Specification) requirements definitions. Transaction needs From a macroscopic perspective to define the needs of the resolved management problem; detail the requirements of the demand given the detailed demand details that can be used directly, detail the source of the final analysis and design results. The analysis stage is mainly based on the results of the demand phase, defines the relationship between entities and entities and the interface supported by the entity, and the work of the analysis phase is independent of the specific design requirements. The information in the analysis phase mainly includes the description of the object class, the definition of the data in the class, the relationship between the object class, the action in the class, and the script between the class intercommunications. The design phase is mainly based on the work of demand and analysis, based on a specific management framework, such as Q3 or CORBA, the demand and analysis results are mapped to the management information model associated with the specific management framework. For example: Q3 uses GDMO description, CORBA uses IDL description. By dividing the modeling process into the RAD three-stage, the model can be done with the specific management framework in the demand and analysis phase, while in the design phase associated with a specific management framework, this makes the information model and management framework Not related to the interworking between the information model. ODP's corporate viewpoint, information viewpoint, and calculating viewpoints are combined in the third phase of the RAD. The main description language used in the whole process of modeling is UML. In the design phase, modeling languages related to specific management frameworks are GDMO or IDL. At present, the ITU-T internal network management standardization work group is assessing the impact of the RAD methodology to the work that has been completed in the past. For the standards that have been developed in my country, they should also re-examine the impact of the introduction of new methodology; at the same time, new standards should be carried out directly under the guidance of new methodology. 2.1.3 The content of the network management interface research As the core of the network management standardization, the standardization of network management interface mainly includes three aspects: interface communication protocol, interface information model, and interface test. For interface communication protocols, currently, the CMIP based on Q3 interfaces, CORBA-based IIOP, and SNMP based on the Internet / SNMP frame structure. For the interface information model, it corresponds to the above three interfaces, and the information model is performed by GDMO / ASN.1, IDL / UML, and MIBII modes, respectively. In this regard, the parties have reached a consensus, and future work is mainly focused on how to complete the design model of specific business networks. However, the implementation of the above two parts must have enough technical guarantee. As the equipment network of the telecommunications network needs to test, the construction of the telecom management network must also follow the same methodology. The development of the NMS standard should focus on the standardization of the network management interface, accordingly, the test of the network management system should also focus on the test of the network management interface. From a pure technical point of view, like other tests in the telecommunications network, the products and specifications provided by the manufacturers are not always consistent. Relatively, the contents of the network management interface are more complex, including communication protocol testing, information model testing, and interface functions. To solve the standardization of network management interfaces, interface testing is essential.
From the market perspective of the network management product, the manufacturer is in order to achieve advertising effects, and the implementation of the network management interface is often inconsistent. From the results of the test, this inconsistency is inevitable. Business operators can only be tested by the network management interface of the product supplier. From the status quo of my country's telecom management network, we have tasted a painful history lesson. For some important telecom infrastructure that has been built, because it is not possible to standardize and test in the network management interface, it has led to the passive of subsequent network management construction. . The objective reason is that our methodological understanding of the network management should not be understood, and the content of the network management standard should be understood, and there is no test of the so-called standard interface of the manufacturer. At present, under the joint efforts of the Ministry of Information Industry and China Telecom, a methodology of a guide network management interface test has been formed; under this guidance, multiple enterprise-level test specifications have been completed, and the relevant test system has already have. The Beijing Posts and Telecommunications Network Management System Testing Center that undertakes the test task has been able to provide Q3 interface, CORBA interface, and traditional TCP / IP code-based test business, and have had a big impact at home and abroad, causing major products from the world. High attention. 2.2 Industry Standards Up to the first half of 1999, my country has been released in the telecommunications management network as shown in Table 1. Among them, most of them are the standards of the basic framework structure of TMN. Through the formulation of these standards, the basic system of a telecommunications management network standard has been formed, and the basis for the standardization of specific business network management standardization work. Within the TMN framework specified by the Ministry of Information Industry, the company represented by China Telecom and China Mobile Group (raised) "has completed or is developing network management standards about specific business networks, including telephone exchange. Internet, mobile communication network, data communication network, seven signaling network, paging network, access network, transfer network and telecommunications management network itself, etc. It is representative: 2.2.1 China Telecom's standard series of access network management This standard series includes access network management standards, access network management test specifications, access network management test systems, and NMS test laboratories. The development of these industry standards regulates the construction of the access network, providing a full technical guarantee for the construction of access network management. During the standard development process, China Telecom as a business operator is based on the definition of the network management interface information model, and only Q3 is selected when the interface implementation technology is selected, and the CORBA or other communication protocol that is not less mature is not selected. Under the premise of the interests of business operators as much as possible, select one and select one interface technology as industry standards is very reasonable, and the fact that Q3 technology is currently the most mature interface technology. The CORBA product also stayed only in the experimental stage. As a network management interface technology, the relevant subsequent preparation measures are not sufficient, and there is still a big gap between practicalization. Moreover, only the technical perspective is considered to be converted to the IDL information model in the semantic equivalent of the interface information model defined by GDMO / ASN.1, which is also very easy to use CORBA interface technology. 2.2.2 GSM NMS Interface Technical Specifications China Mobile provides the benefits of equipment suppliers in the development of the manufacturer OMC to the upper network management system, fully considering the benefits of equipment suppliers, in order to find a balance point between the interests, using Q3 and CORBA Two interface technologies. However, for business operators, the development effort of its upper network management system is added. During the standard development, first, based on Q3 interface technology, the network management interface information model is standardized, thereby preparing for device vendors that support Q3 interfaces can follow the standard for the development of the network management interface; at the same time, ITU-T latest The methodology, semantic equivalence of the proposed interface standard, semantic, and the like will convert the Q3 interface information model to the information model of CORBA.
2.3 International Standard Since the first time, Beijing University of Posts and Telecommunications submitted the "Management Target Definitions used by the TMN Interface ATM Network Management" in China, after the implementation of TMN Interface ATM Network Management, I have completed M. 3208.3 The draft recommendation was discussed at the ITU-T plenary in March 1999. At the same time, M.3108.3 will also be approved in January 2000 in January 2000. This is the first time in China's Telecom Network Management Standardization. -T acceptance will have advantages in China's research, implementation, and standardization in China. 3 Network Management Standard Development Trends On the basis of the basic system of telecommunications management network standards, the next step in my country's network management standard research should be actively involved in the development of ITU-T, tracking the development of other relevant standardized organizations; at the same time Practical, national or industry standards in line with China's actual situation. In the future, problems needed to be resolved in the following aspects: 3.1 The improvement of the research methodology of NMS standards in 1999, ITU-T requires the current status of the current network management technology, for M.3010 and M.3020 Make a modification. Among them, the TMN architecture defined by the M.3010 is more emphasized with technical irrelevant and the agreement. This will affect the connotation of the future Q3 interface; M.3020 determines UML as the future about information modeling and function description in TMN recommendations method. In this regard, my country should make amendment to the existing relevant industry standards as soon as possible, and formulate relevant standards for standardization tools, so that my country's standardization work is synchronized with international maintenance. For network management standards for existing specific business networks, all relevant units should conscientiously think about the impact of the RAD methodology for the work that has been completed in the past, and should directly complete the new standard formulation under the guidance of new methodology. 3.2 Positioning of Net Management Standardization Working from the role of the standards of standards and standards, the standards of Telecom Management Network can be divided into three levels, namely, international recommendations, national standards, and industry standards. According to TMN methodology, the standard specification should include four phases of testing, analysis, design, and product verification and standard testing of the object of the study. For different standards, the main body is made, and its standardized content of the object being studied can be different, as shown in Table 2. For international recommendations and national standards, the standard development can only involve the requirements and analysis phase, not the specific technologies adopted by the design phase; in order to strengthen the control of products and markets, it is also possible to design the design stage for national standards. Some techniques are defined. For industry standards, it is necessary to pay attention to all the contents of the three phases, but also to standardize the specific content of product implementation according to standards; at the same time, we must solve the consistency of products and standards through testing. Sustainable construction of the network management system in the heterogeneous environment. In the future standardization work, different standards have developed a balance point in accordance with the actual situation of different objects, and found a balance point between the national interests, business operators' interests and product suppliers, and the content of the relevant standardization work. Locate. 3.3 NMS Specific implementation technology According to the methodology of TMN, standardization work must be combined with specific techniques in realization. At present, it is the application of two technologies for CORBA and Q3. It will be compared to the two techniques: First, CORBA represents the future of distributed computing technology. When we transfer your eyes to the reality of the network management system products. When it is found to provide a valid environment (including reliable network, high-speed operation hardware, etc.), which is quite expensive.
In my country, although the construction of information networks is developing in ultra-high-speed, many telecom network operators cannot provide such an expensive DCN (Data Communication Network) for Telecom Management Network due to many specific history, economic and natural conditions. Some places, even traditional MODEM communication methods have a longer period. Therefore, for the network management system running on the existing online, regardless of CORBA technology, the Q3 technology is used as a data communication interface technology. Through the communication interface, all of the network management data is collected to the local NMS, and then the data is concentrated, processed without sufficiently utilizing the characteristics of distributed calculations. From the perspective of methodology, in the analysis and design phase of the network management system, the GDMO / ASN.1 description language used by Q3 interface technology can be more convenient to model the information modeling, if the UML is combined with IDL, It is possible to meet the modeling requirements of Telecom Management Network. The current status is that if a GDMO / ASN.1 describes the information model described, it can accurately understand it; if given the same information model described with IDL, the interface will It takes a lot of time to discuss its details. From the software repeated use angle, CORBA's standard object service is not easy to easily use the development of the network management system. In the TMN framework based on the Q3 interface, a series of universal system management functions such as similar event management, log management, performance management has been widely accepted as standards. However, Most of the CORBA service defined by OMG is some services that support distributed processing, and there is a lot of access to services in network management or with ITU-T's recommendations, or have not been involved, in short, Distance to TMN far away. In the CORBA specification 3.0 version, it may be clearly specified to a certain extent. From the system development angle analysis, the omg IDL converted to the programming language is better than GDMO / ASN.1 to convert to the standardization of programming languages. On the standardization issue that is resolved into the programming language, ITU-T is not involved. In this regard, TMF has made great efforts, but due to certain historical and business reasons, it uses the conversion method used in the product that a manufacturer that has implemented, so that the so-called standard has become a paper empty text, and most of the main major Support for network management platform developers. However, during the development of the CORBA specification, the OMG IDL is completed directly into the standardized task of the programming language, and standardizes the conversion method of various popular programming languages, which has been supported by all CORBA product suppliers. Factual standard. At the same time, the developer is encouraged to get X / Open support. From the current status of the current product, after more than ten years of development, network management development based on Q3 technology, the operation platform is more stable than the product of CORBA technology, and has been verified in a large number of practical works. The interconnection between the products, the interoperability has been well guaranteed. For the current CORBA products, on the one hand, the CORBA specification is so perfect; on the other hand, there is no special organization and measures to test the consistency of CORBA products and CORBA specifications, leading to the interconnection between CORBA products from different manufacturers. There is a problem without reaching the goals you want in Corba itself. More unfortunately, even if the same product supplier's CORBA products based on hardware platforms cannot perform a good interconnection, it should believe that CORBA products have been tempered for a period of time, and the corresponding problems will be solved, we have reason Future confidence in its future.
3.4 Integrated Network Management Problems Due to the rapid development of IP businesses and networks, how to solve the IP network and circuit concept-based traditional telecommunications networks is the focus of current network management standardization. In September 1998, ITU-T held IP technology seminars in Orlando, USA, and convened TSAG conferences, unanimously strengthened the recommendations of IP network management by the demand for increasing IP business and technical standardization. At present, all research groups of ITU-T have been carried out in IP, and the fourth study group has specially added related topics, and the unified management framework of circuit exchange and package exchange integrated network, the control function of unified IP and circuit switched networks. Standardization Research on the Management of Server-based Applications. The development of the NMS standards only creates technical conditions for the construction of the network management system, but how to ensure the implementation of the network management standards, and the corresponding administrative measures are required to cooperate. In this regard, China Telecom has accumulated a set of effective experience in the construction of interface testing and distribution of entry testing and issuing netbooks in the access network and DWDM transmission network management. Reply: Playpcgame (2000-10-10 15:22:00) 0 points network management software generally support SNMP (simple network management protocol), able to compete with HP's Open View Professional Suite Professional Agerators and Open View Network Node Manager The node manager combines the top of the sky and provides functions such as MIB (management information base), RMON (remote monitoring). SNMP (Simple Network Management Protocol) is a widely implemented network protocol that uses proxy software embedded in the network facility to collect network communication information and statistics on network devices. The agent software constantly collects statistics and records these data into a management information library (MIB). The network administrator can get this information by emitting query signals to the agent's MIB, which is called polling. Although the MIB counter will record the total record of statistics, it cannot analyze the daily traffic. In order to fully view the traffic and change rate of the day, the management must constantly poll the SNMP agent, poll once every minute. In this way, the network administrator can use SNMP to evaluate the operation of the network and reveal the trend of communication, such as which network segment is close to the maximum capacity of communication load or is making communication errors. Advanced SN? The MP network management station can even handle the history of network data by programming to turn off the port or take other corrective measures. However, SNMP polls a significant weak point: it has no scalability. In a large network, polling produces huge network management traffic, thus causing the occurrence of communication crowding. It will collect the burden of data to the network management console. The management station may easily collect information about 8 network segments. When they monitor 48 network segments, they may not be able to pay. SNMP Usage Overview
1. SNMP Management Model 1.1 What is SNMP SNMP (Simple Network Management Protocol) is an industrial standard that is widely accepted and put into use. Its goal is to ensure that management information is transmitted in any two points, which is convenient for any network administrator on the network. The node retrieves information, modifies, finds faults; completes troubleshooting, capacity planning, and report generation. It uses a polling mechanism to provide the most basic function set. It is best for small, fast, low prices. It only requires unconfirmed transport layer protocol UDP, which is widely supported by many products. The status of SNMP in the TCP / IP protocol family is shown below: 1.2 SNMP Basic Operation: SNMP replaces complex command set in Get-SET, and uses basic operations to perform all operations. Users can use the management information library standard or to define their own management information library (MIB) in a standard way. The advantage of this is to reduce the cost of the entire network management system by reducing the cost of most of the agency components in the network management system. 1.3 NMS and Proxy Network Management Station (NMS) Send various query packets for network devices, and receives the response and traps (trap) packets from the managed device, showing the results. Agent is a process residing on the managed device, responsible for accepting request packets from the network management station, then obtain the value of the management variable from other protocol modules on the device, forming a response message, reverse delivery NMS. In some emergency, if the interface is changed, the call is successful, etc., the NMS (send trap TRAP packet) is actively notified. Their relationship is as follows: SNMP is used to specify how the NMS and Agent is delivered to the application layer protocol for management information. 1.4 ASN.1 and SMI SNMP are application layer protocols that require protocol entities at both ends to exchange various messages, while low-level requirements user data are BYTE sequences, which produces a problem: SNMP protocol entity how to accept one The BYTE sequence identifies how messages in turn convert a message represented by an internal data structure into a BYTE sequence that is available, which is the codec problem. To solve this problem, it is necessary to define a representation method of data types from the actual software data structure, called an abstract syntax. ASN.1 is used to describe the language of abstract notes, in fact applicable to any protocol layer, on its basis, by specifying coding rules, you can determine the value of the eight-bit group in the transfer. SMI (STRUCT OF Management Imformation), defines a macro Object-Type, which specifies the representation of the management object, in this sense, it is a subset of ASN.1. In addition, it also defines several basic types and values commonly used by SNMP. MIB (Management Imformation Base), is a collection of standard variables defined by the monitored network device. SNMP uses hierarchical naming scheme to identify management objects, just like a tree, the node of the tree represents the management object, which can be identified by a path starting from the root. See below: Managing object B can use a string number unique to determine {1.2.1.1} This string number is the Object Identifier of the management object. A path from the root to B can be determined by Object Identifier. Object Identifier of Management Object A is {1.2.1.1.5}, or {B 5}, the latter representation indicates that A is the 5th child of B. This tree in Agent is implemented with a more complex data structure. Fortunately, this work can be done by the MIB compiler.
In the leaf node of the tree, the pointer to the access function is stored, and the Agent is the value of the management variable from the relevant module by calling these functions. 1.5 SNMP message SNMP packet structure is as follows: (Before encoding) SNMP has a total of 5 packets, so its PDU is also 5, which is only used as a getRequest-PDU as an example 2. Management variable representation management variables indicate management object types in some The value (or instance of this type), SNMP is managed as an operation object. The representation of the management variable is specified: shaped as x.y, where x is the object identifer of the management object. Y is a set of numbers that can uniquely determine the type value of the object, 0 in the non-table variable, the index of this table in the phenotypic variable, such as the interface number in the interface table, or the destination network address in the routing table, etc. Wait. Such as: In the MIB file, it is 1.3.6.1.1.5.6.1.3. It is one of the routing tables. It is an instance of its routing table. Code, if the index of this line, the destination network address is 129.102.1.0. Then this variable name is: 1.3.6.1.1.5.6.1.3.129.102.1.0. In the later description, for convenience, a set of numbers of the uniquely determined management variables are also called examples in x.y. 3. The running process of SNMP resides in the tube device accepts serialization packets from the NMS from the UDP port 161, decoded, group authentication, and analyzes the corresponding nodes corresponding to the MIB tree, from the UDP port 161. The value of the management variable is obtained in the corresponding module, and then the response packet is formed, and the encoding is sent back to the network management station. After the network management station gets the response message, the same processing is finally displayed. Next, according to the RFC1157, the action taken after the Agent is received: first decoding the generated packet represented by the internal data structure, decoding the basic coding rule based on ASN.1, if there is an error in the process, the decoding failure is discarded Packets, do not do further processing. Step 2: Remove the version number in the message, if the SNMP version supported by this Agent is inconsistent, discard the message and not further processing. The current data communication product that is currently supported only SNMP version 1. Step 3: Remove the group name in the packet, this group name is filled out by the requesting network management station. If the group name approved with this device does not match the name, the message is discarded, and it is not further processed while generating a trap message. SNMPv1 only provides weak security measures, which will greatly strengthen this feature in version 3. Step 4: From the verified ASN.1 object, the protocol data unit PDU is proposed, if it fails, discard the packet, and does not do it. Otherwise, the PDU will be processed, and a message will be generated, and the send destination address of the message should be consistent with the source address received from the packet. According to different PDUs, the SNMP protocol entity will do different processing: 1), getRequest PDU: The first case: If the variable name in the PDU does not exist in the MIB tree in the local maintenance, the protocol entity that accepts this PDU will Send a getResponse packet to the sender, where the PDU is only a point: set ERROR-STATUS to Nosuchname and pointed out in Error-Index to generate this variable in the location of the variable LIST.
Second: If the local protocol entity will generate the length of the response packet, a getResponse message will be sent to the PDU's emitter, which is set to TOOBIG, Error-Index in addition to Error-Status. Outside 0, the same source PDU. The third case: If the local protocol entity cannot generate the correct response packet because other reasons, the PDU will send a getResponse message, which is set to generr, Error-index in addition to error-status. The position in the variable List is the same as the source PDU. The fourth situation: If there is no situation above, the local protocol entity sends a getResponse message to the emitter of the PDU, which generally contains the variable name and the corresponding value of the corresponding value, Error-Status is noerror, Error- INDEX is 0, the value of the Request-ID domain should be the same as the Request-ID received by the PDU. 2) The most important feature of the GetNextRequest PDU GetNextRequeest PDU is the traversal of the table, which is supported by the representation of the management variables mentioned earlier, so that you can access a set of related variables, just like they are in a table. Inside. The following example explains the process of interpretation of the table traversal: The managed equipment is maintained under the routing table: Destination nextop metric 10.0.0.99 89.1.1.0.3 3 10.0.0.51 89.1.1.42 5 Suppose the network management station wants this route The information of the table, the index of the table is the destination network address. NM station sends a GetNextRequest PDU to the managed device, wherein the managed objects identified as follows GetNextRequest (ipRouteDest, ipRouteNextHop, ipRouteMetric1) SNMP agent response as GetResponse PDU: GetResponse ((ipRouteDest.9.1.2.3 = "9.1.2.3"), (iProutenexthop.9.1.2.3 = "99.0.0.3"), (iProuteMetric1.9.1.2.3 = 3)) Network management station continues: getNextRequest (iProutedSt.9.1.2.2.3, iProuteMetric1.9.1.2.3) Agent response : GetResponse ((iProutedSt.10.0.0.0.0.0.0.0.0.0.51 = "89.1.1.0.0.0.51 =" 89.1.1.0.0.51 = 5))) It is worth noting that the Agent must be able to determine A management variable name to ensure that all variables can be taken and only taken once.
