The Illustrated Network- P66:In this chapter, you will learn about the protocol stack used on the global public Internet and how these protocols have been evolving in today’s world. We’ll review some key basic defi nitions and see the network used to illustrate all of the examples in this book, as well as the packet content, the role that hosts and routers play on the network, and how graphic user and command line interfaces (GUI and CLI, respectively) both are used to interact with devices. | CHAPTER 24 Simple Network Management Protocol 619 FIGURE SMI tree showing how the names are organized. sysUpTime 3 The time measured in 100ths of a second since the network management software not necessarily the device was reinitialized sysContact 4 The name of the local contact person responsible for the network device sysName 5 The name of the manufacturer of the network device sysLocation 6 The physical location of the network device sysServices 7 The services the network device is capable of rendering The importance of MIBs in network management should not be overlooked. From a single console a network manager can merely point a mouse at an icon and with a click determine that the device is a router located at 1194 North Mathilda Avenue in Sunnyvale California that the person responsible for the device is Walter Goralski and so on. All of this information is provided over the network on the fly from the device itself as long as it is entered and maintained on the device of course . The numbers and labels referred to previously are technically called object identifiers and object descriptors in SMI. The SMI tree is used by the network management protocol to designate objects in the MIB. Object identifiers are numeric and all SNMP manageable devices commonly found on a network begin with . shown in Figure . Identifiers are used by the network management software. Object descriptors on the other hand are labels and all SNMP manageable devices also begin with . which is the exact equivalent of the numeric string. This view of the MIB tree is shown in Figure . 620 PART V Network Management FIGURE MIB tree by number and name. The numeric strings can quickly become very long. As an example of the use of object identifiers consider the case in which a network manager may need to change the system contact for a particular network device. An SNMP command in this
