TCP/IP Protocol Suite
By Stephen Bucaro
Transmission Control Protocol/Internet Protocol (TCP/IP) is based on ARPANET a
network designed by the U. S. Department of Defense Advanced Research Projects Agency
in 1969. Its purpose was to develop a mechanism to communicate between dissimilar
operating systems and networks. Because TCP/IP is an open standard protocol it has
become the industry standard and is used by the Internet.
The TCP/IP suite of protocols is managed by volunteer organizations. These organizations
ensure that TCP/IP is developed in a consistent way. A process has been defined that
allows for proposals to add new features or make changes to the protocol suite. A
proposed change is published as a Request For Comment (RFC) which is considered by one
of the managing organizations.
Internet Managing Organizations
• Internet Activities Board (IAB)
• Internet Engineering Task Force (IETF)
• Internet Research Task Force (IRTF)
• Internet Assigned Numbers Authority (IANA)
Knowledge Required to be a Network Technician
A good portion of the knowledge required to be a Network Technician relates to the
TCP/IP protocol suite. You might divide your study of TCP/IP into four sections as outlined below.
• TCP/IP and the OSI model
• TCP/IP Addressing
• TCP/IP Protocols
• TCP/IP Utilities
• TCP/IP Configuration
TCP/IP Protocols
This is a list of the most important protocols in the TCP/IP protocol suite. The
suite contains many other less frequently used protocols.
Transmission Control Protocol (TCP)
TCP operates at the Transport layer to provide a connection-based protocol that
provides reliable data delivery. TCP opens up a communications tunnel for a specific
port and service between two computers. At the transmitting end it breaks the stream
of data into segments. It performs a mathematical operation on the data bits in the
segment and attaches the result (called the checksum) to the segment. It then assigns
a sequence number to each segment as it is sent. TCP uses IP as the transport mechanism
between the two computers.
At the receiving end TCP reads the checksum to determine if the data segment has
been corrupted. It returns an acknowledgement each time a segment is received without
errors. If the data segment has been corrupted, the receiving end discards it without
sending an acknowledgement, causing the sending computer to re-send the data segment.
If the data segment is in good condition, It reads the sequence number and reassembles
the data segments in order. If a segment is received out of sequence, the receiving
computer knows more data is on the way.
Internet Protocol (IP)
IP is a connection-less protocol that operates at the Network layer. At the
transmitting end it divides the data segments into packets and attaches source and
destination addresses to the packets. It provides the rules for routing the packets
across the network.
At the receiving it reassembles the packets into data segments. Because IP is a
connection-less protocol, it does not return an acknowledgement each time a packet is
received. It relies on TCP to perform error checking at the Transport level.
User Datagram Protocol (UDP)
UDP provides a connection-less protocol at the Transport layer. Because a connection-less
protocol has lower overhead, it can be used to communicate time critical messages.
Unlike TCP, it does not return an acknowledgement each time a packet is received. It
can be used to send messages that do not require a guarantee of delivery, such as
messages used for management of a network or gathering operating statistics about the
network. UDPs lower overhead might be used to communicate audio or video over the
network at a higher speed.
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