TCP IP Illustrated

TCP IP Illustrated

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Unformatted text preview: P system. This allows reconfiguration without having to modify source files and rebuild a kernel. The configuration program is ndd(l). We can run the program to see what parameters we can examine or modify in the UDP module: file:///D|/Documents%20and%20Settings/bigini/Docu...homenet2run/tcpip/tcp-ip-illustrated/append_e.htm (5 of 16) [12/09/2001 14.48.06] Appendix E: Configurable Options solaris % ndd /dev/udp \? udp_wroff_extra udp_def_ttl udp_first_anon_port udp_trust_optlen udp_do_checksum udp_status (read (read (read (read (read (read and write) and write) and write) and write) and write) only) There are five modules we can specify: /dev/ip, /dev/icmp, /dev/arp, /dev/udp, and /dev/tcp. The question mark argument (which we have to prevent the shell from interpreting by preceding it with a backslash) tells the program to list all the parameters for that module. An example that queries the value of a variable is: solaris % ndd /dev/tcp tcp_mss_def 536 To change the value of a variable we need superuser privilege and type: solaris # ndd -set /dev/ip ip_forwarding 0 These variables can be divided into three categories: 1. Configuration variables that a system administrator can change (e.g., ip_forwarding). 2. Status variables that can only be displayed (e.g., the ARP cache). Normally this information is provided in an easier to understand format by the commands ifconfig, netstat, and arp. 3. Debugging variables intended for those with kernel source code. Enabling some of these generates kernel debug output at runtime, which can degrade performance. We now describe the parameters in each module. All parameters are read-write, unless marked "(Read only)." The read-only parameters are the status variables from case 2 above. We also mark the "(Debug)" variables from case 3. Unless otherwise noted, all the timing variables are specified in milliseconds, which differs from the other systems that normally specify times as some number of 500-ms clock ticks....
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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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