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TCP/IP Host Table Name System
(Page 4 of 4)
Use of the Host Table Name System In Modern Networking
That said, the host table name system
has not gone away entirely. There are two circumstances in which this
technique is still of value:
- Small Island Networks: If
you are setting up a small local area network using TCP/IP, and you
don't need the names of your devices to be accessible by those outside
your network, then guess what? You have the equivalent, of sorts, of
the early Internet, and the host table system is as applicable to you
as it was to the Internet in the 1970s. You can simply set up host tables
on each device and manage them manually. As long as the LAN is small
enough that editing these files periodically is not a hassle, this is
actually a fast and effective name system, because no exchange of messages
is needed for resolution. You can even maintain a master file on one
machine and copy it to the others when changes are required using a
script, to save time.
- Providing Local Name Mappings To Supplement
DNS: Even though modern systems use DNS for most name resolution,
they also usually still support the use of host table files. You can
manually enter common name mappings into this file, even for devices
that are on the global Internet. Your system can then be set up to consult
this list before making use of its assigned DNS server.
The use of the HOSTS file in conjunction
with DNS allows you to manually specify mappings for commonly-accessed
sites, which may provide a slight performance improvement since there
is no need to access a server. Since the HOSTS file doesn't enforce
any particular structure to names, it is naturally quite possible to
put DNS-style hierarchical names into the file, as I showed in Table 161.
The file is loaded into memory and used to override the normal
DNS process for names listed in it.
Of course, you then subject yourself
to all the potential maintenance headaches of manually-edited files:
you must update these files as host names or addresses are changed in
the DNS system. For this reason, this second use of the HOSTS file for
Internet sites served by DNS is less popular than the use of the file
for local machines.
Key Concept: Even though the host table name system is not the primary mechanism used for TCP/IP naming, it still used in two circumstances. The first is to implement a basic name system in a small local TCP/IP internetwork.The second is as an adjunct to DNS, where it allows manual mappings to be created that override the DNS process when needed.
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The TCP/IP Guide (http://www.TCPIPGuide.com)
Version 3.0 - Version Date: September 20, 2005
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