Managing Networks with the Global Naming Tree Gilbert Held

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1 Managing Networks with the Global Naming Tree Gilbert Held Payoff An often-overlooked and hidden-from-view characteristic of network management systems is their use of the global naming tree. An understanding of the global naming tree's structure and the addressing method used to locate objects (i.e., network devices) can make it easier for network administrators to effectively support different network management systems. Introduction Tree structures are a common method for accessing information. The reason for the use of a tree structure is that the path from the root via one or more branches to a leaf provides a unique method for addressing information stored at the end of the path. The most common use of a tree structure inverts the tree, placing the root at the top. From the root, one or more branches flow downward and separate into sub-branches. This subdivision can theoretically continue indefinitely, with the major restriction being the number of characters, digits, or identifiers that can be used to define a path through the tree. The most commonly used tree structure employed in computer-based systems provides data management in the form of a directory structure. When used to manage data within a directory structure, the root of the tree represents the top of the directory, while subdirectories represent branches under the root. Another common tree structure is employed by data base management systems. The International Standards Organization (ISO) and the International Telecommunications Union-Telecommunications Standardization Sector (ITU-TSS) have jointly developed a tree-based structure for assigning unique identifiers to different types of objects. That tree is known as a global naming tree. Structure of the Global Naming Tree Objects in the global naming tree can represent any type of information. In addition, the tree structure makes it possible for network managers to delegate responsibility for information structuring to other organizations under different nodes within the global naming tree. Use in Network Management Applications Exhibit 1 illustrates the basic structure of the global naming tree that is oriented toward its use in network management applications. Under the root are three top-level nodes. The Network Management Portion of the Global Naming Tree As Exhibit 1 shows, each node in the tree has both a label and a numeric identifier. The top-level nodes indicate the organization that administers the subtree under the node. The three top-level nodes allow the International Telecommunications Union, International

2 Standards Organization, and the ISO and ITU jointly to administer distinct portions of the global naming tree. The third node (Org) under the ISO node was defined as a mechanism to delegate authority to other organizations. One of those organizations is the US Department of Defense (DOD), which is the sixth node under the Org node. Because the US Department of Defense initially funded the Advanced Research Projects Agency network (ARPAnet), which is considered as the predecessor to the Internet, and still provides a degree of administrative and operational support for certain Internet activities, the first node under the DoD node is the Internet node. The Internet node and the subtree residing under it is owned by the Internet Activities Board (IAB) and administered by the Internet Assigned Numbers Authority (IANA). The IANA is responsible for maintaining a document of assigned numbers, which tracks the complete set of parameters used in the Transmission Control Protocol/Internet protocol (TCP/IP) suite to include addresses in the Internet subtree that identify simple network management protocol (SNMP) and Remote MONitoring objects. Organizations that wish to develop extensions to SNMP and remote monitoring (RMON) standard objects are assigned distinct identifiers within the Internet subtree. The Internet Subtree Currently, six nodes are defined under the Internet node directory, management, experimental, private, security, and SNMPV2. Two of those nodes, security and SNMPV2, are being standardized and may not be completely defined for a few years. The experimental node provides a location for the placement of newly developed and unproved objects. After a trial period, objects deemed to be useful are then moved to a standardized location under the management subtree. That tree (Mgmt) is used to hold all standardized network management variables and represents the portion of the global naming tree most network management systems are designed to work with. The private subtree represents a location where equipment vendors, software developers, universities, and government agencies can develop extensions to SNMP. To do so, an organization is assigned a node under private/enterprises that represents an assigned subtree within the global naming tree. Within that subtree, an organization is free to define its own structure for product identifiers and Management Information Base object definitions that are required to manage a specific product or group of products. Because it is almost impossible for any one network management product to be aware of every vendor-specific set of managed objects located under the private/enterprise node, the use of these path identifiers gives network managers and administrators a way to walk through the global naming tree structure, so they can set or retrieve information from any vendor subtree. This is a capability network managers might not otherwise obtain by relying on the standard features of a network management system. The MIB Subtree The SNMP standard defines a data base of network management information as a management information base (MIB). The management information base (MIB) consists of a combination of hardware and software settings that represent objects needed to manage different types of products. To simplify network management, objects were organized into units known as groups. Groups have a common management function. Depending on the operating characteristics of a device, it may or may not support one or more of the groups shown

3 under the management information base (MIB)-2 node in Exhibit 1. (The original management information base (MIB) for managing a TCP/IP network is known as management information base (MIB)-1; its new version is labeled Management Information Base-2. management information base (MIB)-2 is recognized by the IANA under the management node in the global naming tree.) Object Groups. The system group permits configuration information to be defined to include what the device is, where it is located, and the person or persons to call when something goes wrong. Because of the importance of the system group, it is required to be supported by every device. In comparison, other groups are optional and are only required to be implemented if applicable to a specific device. Examples of optional groups include: IP group, which includes objects needed for the configuration and management of Internet protocol hosts and routers. The TCP group, which is applicable to TCP devices. The UDP group, which is applicable for devices that support User Datagram Protocol. One group that requires some explanation is the transmission group. This group more correctly represents a node position in the global naming tree under which groups applicable to different transmission technologies are placed. Three examples of transmission technologies are shown in Exhibit 1 under the transmission node--dot3, DOT5, and FDDI. The DOT3 and DOT5 nodes reference local area networks standardized by the IEEE as 802.3and Those standards are better known as Ethernet and Token Ring. Assigning Identifiers and Managing Objects Each object in a device to be managed is represented by a unique address within the global naming tree. That address, which is referred to as an object identifier in standards documents, can be expressed in several ways. The most commonly used method to express an object identifier is through the use of a string of integers separated by dots to form a path to the object. For example, the path to the system group shown in Exhibit 1 would be The first object in that group would be located at in the global naming tree. Some object identifiers can have more than one value. For example, a bridge or router would have at least two interfaces, which would make it necessary to append a digit to the identifier path to denote the specific interface the administrator wishes to retrieve information from. However, many objects represent a one-of-a-kind value, such as the location of a device. To provide consistency, an index is always added at the end of an identifier. Thus, if the object is a one-of-a-kind object, the administrator would add a zero (0) to its path. Because the first object in the system group is a one-of-a-kind object, its path identifier becomes The omission of the trailing zero is a common error when users of a network management system use path addresses to retrieve object values.

4 Other methods used for object identifiers can include linking text labels with underscores or combinations of text labels and numerics. Because programming operations are easier and faster when working with numerics rather than text identifiers, most network management systems that allow users to enter tree identifiers do so by supporting integer strings with dots used as separators. Standardization and Its Benefits In actuality, there are two types of addresses network administrators need to assign to manage a device. The first address is the IP address of a device installed in a network, which defines its location. The second address is the set of addresses within the global naming tree that defines the location of counters, registers, and memory locations that the administrator may be able to read from, write into, or read and write, depending on the access method defined for the object. By having a standard method for defining objects in the global naming tree, different vendors can independently develop managed objects, avoiding the potential for the occurrence of addressing conflicts. In addition, vendors can design their products to support applicable SNMP and Remote MONitoring groups in a standardized manner, and other vendors can develop network management systems without having to know full details of different vendor products. In short, if a network management system supports the global naming tree structure, any user who understand tree addressing concepts is able to read, write, or read and write to and from different managed devices manufactured by different vendors. Sample Application Using Sample Tool For purposes of further illustrating the use of the global naming tree in network management operations, this section uses the example of an application developed using SimpleView from Triticom (Eden Prairie MN). To use this program to manage an object, the user must first select the object. The screen shot in Exhibit 2 shows that the Ethernet probe at IP address was selected. Exhibit 3 represents the values of object identifiers in the system group of the Ethernet probe. This system group contains seven object identifiers.

5 Notes: Although the system group must be included in every managed device, the setting of some objects in the system group will depend on the user of the device. The syscontact identifier could be set by the organization using the device. Some organizations will set this identifier while others may elect to leave it at its default Not Set string value. The location is the object identification number. If the object (e.g., sysuptime) is a one-ofa-kind object, tools such as SimpleView automatically append a zero (0) to the path address. Object Identifier Location Description sysdescr A text description about the device. sysobjectid An identifier assigned to the device by its vendor. sysuptime The time in hundredths of a second since the system was last reinitialized. syscontact The person responsible for the device. sysname An administratively assigned name. syslocation The physical location of the device. sysservices A coded number which indicates the layer in the ISO model at which device performs services. Notes: Although the system group must be included in every managed device, the setting of some objects in the system group will depend on the user of the device. The syscontact identifier could be set by the organization using the device. Some organizations will set this identifier while others may elect to leave it at its default Not Set string value. The location is the object identification number. If the object (e.g., sysuptime) is a one-of-a-kind object, tools such as SimpleView automatically append a zero (0) to the path address. Tools such as SimpleView allow a network administrator to retrieve basic SNMP or Remote MONitoring information. Because there are more than 1,000 vendors that are assigned subtrees under the private enterprises node in the global naming tree (which would make their support difficult, if not impossible, to accomplish via a menu that identifies the name of each object identifier), the sample tool uses a series of SNMP commands to access information in managed objects developed by different vendors. The Get, Get Next, and Set entries shown in the Manage menu in Exhibit 2 represent three SNMP commands. The Get command is used to request the values of one or more Management Information Base variables. The Get Next command is used to read values sequentially. By selecting the Get Next command, the user can either go directly to a specific tree address (by typing in the address) or, if they do not know the address, browse predefined portions of the global naming tree that locate commonly used objects. The third SNMP command supported, the Set command, allows the network administrator to update one or more management information base (MIB) values.

6 Once a command is executed, SimpleView displays the results in the program's Trap Log. Exhibit 4 shows an entry that occurred as a result of the execution of the Get Next command using a tree address to retrieve the value of the object. Although the time is displayed in hundredths of a second, such tools can also convert that time into days, hours, minutes, and seconds. By issuing several Get Next Commands, the values for sysname and subsequent objects in the group would also be displayed in the Trap Log. Thus, once the user knows an address they can walk through a path using a series of Get Next commands to retrieve subsequent object values. SimpleView Trap Log Window Conclusion The global naming tree provides a mechanism for labeling and identifying objects while eliminating the possibility of addressing conflicts. By understanding how to use path addresses in conjunction with object identifier information, network administrators can manage any device that complies with the global naming tree method for identifying objects. The easiest way to retrieve information from proprietary products developed to comply with the global naming tree is for the user to refer to the device user manual to determine the path to different managed objects in the device. Author Biographies Gilbert Held Gilbert Held is director of 4-Degree Consulting, a Macon GA-based high-tech consulting group. He is an internationally recognized author and lecturer. He has written more than 40 books and 300technical articles and received numerous awards for excellence in technical writing.

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