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Table Of Contents  The TCP/IP Guide
 9  TCP/IP Application Layer Protocols, Services and Applications (OSI Layers 5, 6 and 7)
      9  Name Systems and TCP/IP Name Registration and Name Resolution
           9  TCP/IP Name Systems: Host Tables and Domain Name System (DNS)

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Overview and History of TCP/IP Host Names and Name Systems
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TCP/IP Domain Name System (DNS)
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TCP/IP Host Table Name System
(Page 2 of 4)

Host Table Name Resolution

Name resolution in this system is very simple. Each device reads the host table into memory when it starts up. Users of the system can make reference to the names in that host table in their invocation of various applications, by using a name instead of a numeric IP address. When the software detects a name has been used in this manner, it refers the name to the internal resolver routine in the device, which looks up the name in the host table in memory and returns its address. There is no need for any transmissions or servers to be contacted; resolution is entirely local.

Host Table Name Registration

Now, here is the part where I am supposed to say that name registration in the host table name system is simple as well, right? Well, yes and no. From a purely technical standpoint it certainly is: a name is “registered” on a particular device when the name and corresponding IP address is entered into the device's host table, and that's it.

However, name registration is much more complicated from an administrative standpoint, and this is in fact where we find the major weakness of using host tables. Each network device maintains its own host table independent of the others, usually stored as a file on its local hard disk. This is in contrast to database registration systems where the data is centrally stored and managed. This leads to two very important concerns:

  • Consistency: Since every device has its own host table, how do we ensure that information is consistent between all the tables on the different devices?

  • Modifications: How do we ensure that information about new device mappings, or changes to existing ones, is propagated to all devices?

The original mechanism for this was simply hand-editing, with administrators consulting updated published lists of device names. This was a very inefficient method that was prone to error and slow to acknowledge changes to the network. The revised system used a centrally-managed “master” file that was downloaded by all sites on a regular basis. Name registration in this method required that the name/address mapping be submitted to the authority managing the central file, the Network Information Center (NIC).


Previous Topic/Section
Overview and History of TCP/IP Host Names and Name Systems
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Pages in Current Topic/Section
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TCP/IP Domain Name System (DNS)
Next Topic/Section

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Version 3.0 - Version Date: September 20, 2005

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