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Group 20


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Rice 3.17. Multiple entrance of routers in the reserving groups

B this case the Ml router at the same time is the main for nodes and and reserve for and


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The M2 router performs mirrorly opposite functions. It is apparent that such diagram of switching on, in addition to support of dynamic reservation, allows to use much more efficiently resources of network devices as reserve routers do not stand idle, and process a traffic on an equal basis with the main routers.

SNMP protocol

The SNMP protocol (Simple Network Management Protocol, the Simple network management protocol) is intended for support of steering and monitoring of network points. It allows managing stations to assemble information on “situation” on an under control network.

Today SNMP is the most popular protocol of steering of the different commercial, university and research integrated networks. SNMP represents the application layer protocol intended for support of exchange of control data between network devices. Using the information provided by the SNMP protocol, network administrators can more quickly and just steer network performance, find and solve many problems arising in use networks.

B creation of the SNMP protocol made the contribution of development in three directions.

1. HEMS (High-level Entity Management System). HEMS is an entity management system of the highest level. It intended for determination of the principles and control linkages networks with the nestavdartny technical features managing information databases of venues, access mechanisms and the system of creation of reporting information including languages of creation of requests with use of RPC gears. K to a regret, the HEMS system was used only in places of its development, as led to extinction of its development.

2. SGMP (Simple Gateway Monitoring Protocol) is the Simple gateway management protocol. Originally this protocol intended only for steering of network components. Development was executed by an initiative group of network engineers for support of the problem resolution of steering of quickly growing Internet. The protocol intended for steering of routers on the Internet became result of their efforts. B the present the SGMP protocol is realized in many regional branches of the Internet.

3. CMOT(CMIP over TCP). This protocol provides steering of network components with use of the standard OSI protocols, in particular, of the CMIP protocol (Common Management Information

Protocols of steering and monitoring of network components


Protocol is the protocol of general management). The CMIP protocol is intended for facilitation of steering of the integrated TCP networks.

B in case of the problem resolution of standardization of control linkages all these three directions were actively discussed 1987. For forming of the uniform specification of the protocol of network steering at the beginning of 1988 under the direction of IAB (Internet Activities Board is the group responsible for engineering development of internet protocols) two working groups were formed.

One group began to be engaged in the specification and development of elements of information basis of steering — MIB (Management Information Base). B further operation in this direction developed into creation of a management structure venues — SMI (Structure for Management Information).

Other group which was engaged in development of the protocol of steering came to a conclusion that the improved version of the SGMP protocol (Simple Network Management Protocol) which was called SNMP (Simple Network Management Protocol) later can become temporary solution of a problem of steering. For long-term use, after deep and detailed finishings, one of the technologies which are based on OSI (either CMOT, or CMIP) shall be used.

Besides, it was solved in all management systems by networks to use ASN.1 specification (Abstract Syntax Notation One, the Specification of syntax number one) which represents a universal language of the description of formats of management structures. This specification is used for the description of structures and the MIB elements now.

Finishing of the specification of the SNMP protocol continues as the modern application programs of steering based on use of this protocol are developed.

In spite of the fact that SNMP is rather simple protocol, the set of its characteristics is rather powerful for the solution of the majority of the problems arising when steering heterogeneous networks.

Principles of creation of a network management system

The network management system on the basis of the SNMP protocol represents a complex of managing stations of a network and managed objects. Ha managing stations applications which control are run and manage actions of “agents” of SNMP located on network elements of a steered network. Network elements are such venues as terminal nodes, gateways, terminal servers and other venues on which modules of network agents can be executed.

Agents in SNMP are called the special software modules placed on managed objects — network elements. Agents assemble information on managed objects and place it in the local


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variables which are constituent elements of a uniform information basis of a dannykhupravleniye a network — MIB (Management Information Base).

The SNMP protocol is used for exchange of control and control data between managing stations and elements of a network. Thus, by means of the SNMP protocol local information becomes available to management systems the NMS networks (Network Management Systems) and management systems the MIB database.

The managed object can be the node of any type which is in any network: it can be a node, the auxiliary communicating device, the printer, po-wiped, the bridge or the hub. Some of these systems can have limited capabilities of software management, for example, they can have processors with rather small high-speed performance or limited scope of memory. Therefore management programs shall be constructed so that to minimize influence on a managed object the main loading in case of performing procedures of steering laid down on managing stations.

B quality of the managing stations NMS are usually used rather powerful computers which have rapid central processors, the considerable volume of drives and high-performance peripheral devices. B of a steered network can be available one or more NMS stations. Ha NMS stations are executed the application programs of network steering intended for data collection and processing about control objects.

Ha of fig. 3.18 is shown the general diagram of system operation of network management of NMS.

Steered device Steered device Steered device of Fig. 3.18. NMS network management

Protocols of steering and monitoring of network components


Global tree of names

All managed objects of a wide area network are located in uniform virtual “tree” of venues — the Information basis of steering (MIB — Management Information Base) which “leaves” are separate information items. The syntax of the description of “tree” is defined by ASN.1 specification.

Each venue of “tree” has a name which reflects functions of a venue and the identifier. The identifier represents the sequence of the integral numbers marking a way to a venue from “a tree root” (fig. 3.19).

The root of “tree” has no identifier. The first level from a root is made by venues: itu — it administers subtree 0; iso — administers the “tree” which is going down from node 1; joint-iso-itu — node 2. Bo the second level of main “tree” is located an organizational node — org (3) which falls into to the subtree ISO. This node was defined by ISO for delegating of responsibility for continuation of “tree” on other organizations. One of such organizations of the third level is dod (6) (U. S. Department of Defense) to which, according to hierarchy of steering, and the packet network the Internet (1) located at the fourth level of global “tree” of control objects belongs.

Thus, according to this hierarchy, object IDs of the Internet begin with code Directly under a node of the Internet 6 nodes are located: directory (reference manual), mgmt (steering), experimental (experimental), private (private), security (security) and snmp-2.

For example, the private node has only one subtree now — enteiprises (enterprise). “Branch” of enteiprises consists of more than 1000 nodes which are occupied by different equipment providers, software developers, state institutions, the universities, etc. Each of these nodes allows the organization to define the identifiers of products and structure necessary for steering of these products. For example, a node 348 ( occupies Procter&Gamble, and a node 743 ( – CIA.

“Tree” mgmt contains variables of network steering. For example, the system ip (4) group, “branches” of mib-2 (1) of “tree” of MGMT (2) which identifier, gives information necessary for steering of computers and routers.

“Tree” of MIB permanently extends, thanks to experimental and private “branches”. For example, software providers can define own “branches” for the products. B the present all standardization effort is carried on experimental “branch”.


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Fig. 3.19. Part of global “tree” of names

From the point of view of network management, the task of global “tree” of names is support of a standard method of determination (reading) and forming (recording) of parameter values of managed objects. At the same time some venues can provide information on several points, for example, the bridge or the router with several interfaces shall provide information on each of the interfaces.

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