If you are using one of the pre-packaged distributions, it will most probably contain the major networking applications and utilities along with a coherent set of sample files. The only case where you might have to obtain and install new utilities is when you install a new kernel release. As they occasionally involve changes in the kernel networking layer, you will need to update the basic configuration tools. This at least involves recompiling, but sometimes you may also be required to obtain the latest set of binaries. These are usually distributed along with the kernel, packaged in an archive called net-XXX.tar.gz, where XXX is the version number. The release matching 1.0 is 0.32b, the latest kernel as of this writing (1.1.12 and later) require 0.32d.
If you want to compile and install the standard TCP/IP network applications yourself, you can obtain the sources from most FTP servers. These are more or less heavily patched versions of programs from Net-BSD or other sources. Other applications, such as Xmosaic, xarchie, or Gopher and IRC clients must be obtained separately. Most of them compile out of the box if you follow the instructions.
The official FTP site for Net-3 is sunacm.swan.ac.uk, mirrored by sunsite.unc.edu below system/Network/sunacm. The latest Net-2e patch kit and binaries are available from ftp.aris.com. Matthias Urlichs' BSD-derived networking code can be gotten from ftp.ira.uka.de in /pub/system/linux/netbsd.