TCP IP Illustrated

TCP IP Illustrated

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Unformatted text preview: 40] Chapter 25. SNMP: Simple Network Management Protocol Figure 25.8 Simple variables in udp group. We'll use this format to describe all the MIB variables in this chapter. The column labeled "R/W" is empty if the variable is read-only, or contains a bullet (*) if the variable is read-write. We always include this column, even if all the variables in a group are read-only (since they are in the udp group) to reiterate that none of the variables can be set by the manager. Also, when the data type is an INTEGER with bounds, we specify the lower limit and upper limit, as we do for the UDP port number in the next figure. Figure 25.9 describes the two simple variables in the udpTable. UDP listener table, index = < udpLocalAddress >.< udpLocalPort > Name Datatype udpLocalAddress lpAddress udpLocalPort [0..65535] R/W Description Local IP address for this listener. 0.0.0.0 indicates the listener is willing to receive datagrams on any interface. Local port number for this listener. Figure 25.9 Variables in udpTable. Each time we describe the variables in an SNMP table, the first row of the figure indicates the value of the "index" used to reference each row of the table. We show some examples of this in the next section. Case Diagrams There is a relationship between the first three counters in Figure 25.8. Case Diagrams [Case and Partridge 1989] visually illustrate the relationships between the various MIB variables in a given group. Figure 25.10 is a Case Diagram for the UDP group. Figure 25.10 Case Diagram for UDP group. What this diagram shows is that the number of UDP datagrams delivered to applications (udpInDatagrams) is the number of UDP datagrams delivered from IP to UDP, minus udpInErrors, minus udpNoPorts. Also, the number of UDP datagrams delivered to IP (udpOutDatagrams) is the number passed to UDP from the applications. This illustrates that udpInDatagrams does not include udpInErrors or udpNoPorts. file:///D|/Documents%20and%20Set...
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This test prep was uploaded on 04/04/2014 for the course ECE EL5373 taught by Professor Guoyang during the Spring '12 term at NYU Poly.

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