12. TCP/IP: A VERY BRIEF HISTORY
A brief history of TCP/IP
TCP/IP protocols were first proposed in 1973,
but it wasn't until 1983 that a standardized version was developed at the University
of California at Berkeley. This version was put into wide use as the official
transport mechanism of ARPAnet (Advanced Research Projects Agency); the forerunner
of today's Internet.
One of the most important parts of TCP/IP's growth
was the development of the testing and certification program administered by
the U.S. Government to ensure that the published standards, which were free,
were met. This "open-approach" philosophy virtually ensures a trouble-free
connection and operability between differing hardware and software platforms.
TCP/IP design goals as set forth by
the Department of Defense
When the U.S. Department of Defense began to
standardize TCP/IP network protocols their design goals included:
- Independence from all proprietary software
and hardware vendors; it must be "open-approach".
- It had to have good built-in failure recovery.
The protocol had to be able to continue to operate even if large parts of
the network suddenly disappeared from view; i.e. after an enemy attack.
- It be able to handle high error rates and
still provide completely reliable end-to-end service.
- It had to have a low-data overhead. The 20-byte
header normally used by the IP protocol is much shorter in comparison to other
network protocols. This lower overhead of data allows for fast transmission
and efficient service.
- It had to allow the addition of new networks
without any service disruption.
TCP/IP and the OSI model
Since TCP/IP was developed in partnership with
the DoD it uses the DoD's model for internet communications, rather then the
OSI model. The DoD model is four-layered. The stack from top to bottom is:
- Process/Application layer:
This layer corresponds to the Application, Presentation and Session layers
of the OSI model.
- Host-to-Host:
This layer corresponds to the OSI model's Transport layer.
- Internet:
This is the same as the Network layer in the OSI model.
- Network Access:
This layer corresponds to the Data Link and Physical layers of the OSI model.
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