TCP IP Illustrated

512000067 udplocalport000067 0000 67 2

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Unformatted text preview: Sample UDP listener table. This implies that the system is willing to receive UDP datagrams on any interface for ports 67 (BOOTP server), 161 (SNMP), and 520 (RIP). The three rows in the table are referenced as shown file:///D|/Documents%20and%20Settings/bigini/Docu...homenet2run/tcpip/tcp-ip-illustrated/snmp_sim.htm (9 of 33) [12/09/2001 14.47.40] Chapter 25. SNMP: Simple Network Management Protocol in Figure 25.12. Lexicographic Ordering There is an implied ordering in the MIB based on the order of the object identifiers. All the entries in MIB tables are lexicographically ordered by their object identifiers. This means the six variables in Figure 25.12 are ordered in the MIB as shown in Figure 25.13. Two key points result from this lexicographic ordering. Row Object identifier Abbreviated name Value 1 1.3.6.1.2.1.7.5.1.1.0.0.0.0.67 udpLocalAddress.0.0.0.0.67 1.3.6.1.2.1.7.5.1.2.0.0.0.0.67 udpLocalPort.0.0.0.0.67 0.0.0.0 67 2 1.3.6.1.2.1.7.5.1.1.0.0.0.0.161 udpLocalAddress.0.0.0.0.161 1.3.6.1.2.1.7.5.1.2.0.0.0.0.161 udpLocalPort.0.0.0.0.161 0.0.0.0 161 3 1.3.6.1.2.1.7.5.1.1.0.0.0.0.520 udpLocalAddress.0.0.0.0.520 1.3.6.1.2.1.7.5.1.2.0.0.0.0.520 udpLocalPort.0.0.0.0.520 0.0.0.0 520 Figure 25.12 Instance identification for rows in UDP listener table. Column Object identifier (lexicographically ordered) Abbreviated name 1 1.3.6.1.2.1.7.5.1.1.0.0.0.0.67 udpLocalAddress.0.0.0.0.67 1.3.6.1.2.1.7.5.1.1.0.0.0.0.161 udpLocalAddress.0.0.0.0.161 1.3.6.1.2.1.7.5.1.1.0.0.0.0.520 udpLocalAddress.0.0.0.0.520 2 1.3.6.1.2.1.7.5.1.2.0.0.0.0.67 udpLocalPort.0.0.0.0.67 1.3.6.1.2.1.7.5.1.2.0.0.0.0.161 udpLocalPort.0.0.0.0.161 1.3.6.1.2.1.7.5.1.2.0.0.0.0.520 udpLocalPort.0.0.0.0.520 Value 0.0.0.0 0.0.0.0 0.0.0.0 67 161 520 Figure 25.13 Lexicographic ordering of UDP listener table. 1. Since all instances for a given variable (udpLocalAddress) appear before all instances for the next variable in the table (udpLocalPort), this implies that tables are accessed in a column-row order. This results from the lexicographic order...
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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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