An Overly Simplistic Introduction
What is it?
TCP/IP (Transmission Control Procotol/Internet Protocol) has become the standard
vehicle for communicating over the Internet. This has also led to it being largely
accepted as a standard for communicating within many companies.
IP Addresses
An IP (Internet Protocol) address is analogous to a phone number. Each individual
station on a network needs its own IP address. A well-configured station needs to
know
- its network mask: which IP addresses it can talk to "directly".
These can be considered as being "local" or "in the same neighbourhood".
- its gateway: where to send messages for IP addresses that are not
"local".
When configuring TCP/IP on most machines, it is usually possible to explicitly
assign these values. If you get them wrong, then you will probably not be
able to reach the rest of the TCP/IP network. It is more common to assign
these values to each workstation dynamically via a service called DHCP.
Packets
Data travelling between machines on a TCP/IP network is broken up into
one or more packets.
Ports
Ports allow multiple concurrent conversations at the same IP address.
A socket (one end of a conversation) can be represented as the combination
of an IP address and an port number. Certain "well known" ports are normally
assigned for specific functions. For example, telnet servers usually listen
on port 23.
The "echo" port is used by the ping utility which can be used to determine
if a given TCP/IP host can be reached over the network.
Directory Services
Name servers let you find out the IP address if you know the (host) name for
another station on the network. Again, the IP addresses for name servers are
usually provided dynamically to workstations.
Standards
TCP/IP has evolved over time and the standards have been revisited over time.
The degree of compliance to the latest standards can vary between different
implementations. Some behaviour may be considered as desirable rather than
mandatory. RFCs ("Requests for Comments") have been used as a vehicle to
document Internet Protocol standards.
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