Introduction to TCP/IP and routing : Introduction to IP : Concepts of IP
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1.1. Concepts of IP

IP is built on several principles:

packet oriented

for each packet sent, a routing decision is taken -- no circuits

end-to-end

it is the application at each end of the "circuit" that are in control (also called "edge", as opposed to "middle"), and not the equipments along the way

best-effort

"IP is robust, but not reliable" -- it makes no garantee that the packet will reach destination -- it is the responbility of higher level protocols/applications

physical abstraction

IP will run over any media -- copper, fiber, radio, smoke signals, etc... It is said of IP that it is at the center of an "hourglass" model:

+------+------+-----+-----+
| SMTP | HTTP | DNS | NTP |
\------+------+-----+----/
 \     TCP    |   UDP   /
  \-----------+--------/
   |        IP        |
  /-----+-------+------\
 /   TR | ETHER | PtP   \
/-------+-------+--------\
| UTP/STP/COAX  |Hz/MODEM|
+---------------+--------+
		

Unlike the OSI model, IP has only 4 layers (Physical/Link, Network, Transport, Application).


Introduction to TCP/IP and routing : Introduction to IP : Concepts of IP
Previous: Introduction to IP
Next: Architecture of IP