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TCP/IP Host Table Name System
(Page 3 of 4)
Weaknesses of the Host Table Name System
The use of a centralized master file
for name registration certainly worked better than using the equivalent
of inter-office memos to publish host name lists, but was
itself only practical in the early days of TCP/IP. As the internetwork
grew larger, the weaknesses of the host table system grew:
- Central Administration Overload: The changes
to the central file became more frequent, increasing the administrative
load on the individual managing the master file to the point
where changes were being made many times per day. As the Internet continued
to grow, it would eventually have been impossible for a human being
to enter the changes as fast as they were being submitted.
- Growth In Size Of the Master File: Every
host needed a line in the master file. When the Internet grew to be
thousands and eventually millions of devices, the file size would have
- Excessive Bandwidth Use: Since the file
was changing so often, this also meant that all the devices on the network
had to keep downloading this master file repeatedly to stay current.
At the same time, the file was also growing in size as just mentioned.
The combination of many downloads of a large file meant large amounts
of network bandwidth were being consumed on something that is, in essence,
an overhead activity.
- Flat Namespace Problems: The lack of a
hierarchical name space led to conflicts when users chose identical
names for their devices, and this further increased the workload on
the central administrator. These issues were ameliorated in part by
using naming conventions, such as using a prefix with a location before
each individual machine name, but this was not an ideal solution.
All of these are reasons why the
designers of the Internet eventually moved away from using host tables
for the entire Internet to the more capable Domain
Name System (DNS).
Key Concept: The host table name system was the original mechanism used for implementing names on the early Internet. It consists simply of a set of tables containing mappings between names and addresses maintained on each machine in the internetwork. When a name needs to be resolved the table is consulted to determine the appropriate address. This system is extremely simple, but not very capable, and not well-suited to a large global Internet, which is why it was eventually abandoned in favor of DNS.
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The TCP/IP Guide (http://www.TCPIPGuide.com)
Version 3.0 - Version Date: September 20, 2005
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