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Unformatted text preview: al or nonlocal (Section 18.4), and whether directed broadcasts
are forwarded or not (Section 12.3). Indeed, many operating characteristics of a given
TCP/IP implementation can be modified by the system administrator.
This appendix lists some of the configurable options for the various TCP/IP
implementations that have been used throughout the text. As you might expect, every
vendor does things differently from all others. Nevertheless, this appendix gives an idea
of the types of parameters different implementations allow one to modify. A few options
that are highly implementation specific, such as the low-water mark for the memory
buffer pool, are not described.
These variables are described for informational purposes only. Their names, default
values, or interpretation can change from one release to the next. Always check your
vendor's documentation (or bug them for adequate documentation) for the final word on
This appendix does not cover the initialization that takes place every time the system is
bootstrapped: the initialization of each network interface using ifconfig (setting the
IP address, the subnet mask, etc.), entering static routes into the routing table, and the
like. Instead, this appendix focuses on the configuration options that affect how TCP/IP
operates. E.1 BSD/386 Version 1.0
This system is an example of the "classical" BSD configuration that has been used since
4.2BSD. Since the source code is distributed with the system, configuration options are
specified by the administrator, and the kernel is recompiled. There are two types of
options: constants that are defined in the kernel configuration file (see the config(8)
manual page), and variable initializations in various C source files. Brave and
knowledgeable administrators can also change the values of these C variables in either
the running kernel or the kernel's disk image, using a debugger, to avoid rebuilding the
kernel. Here are the constants that can be changed in the kernel's configuration file.
The value of this constant initializes the kernel variable ipforwarding. If 0 (default),
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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.
- Spring '12