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Introduction to Computer
Networks
Introduction to Protocols
This lesson offers an introduction to protocols and
their function in a networking environment.
The Function of Protocols
• Protocols are rules and procedures for
communicating.
• In a network environment:
• 1. There are many protocols.
• 2. Some protocols work only at particular OSI
layers.
• 3. Protocols can also work together in a protocol
stack, or suite.
How Protocols Work
• Protocols at the sending computer:
• 1.Break the data into smaller sections, called
packets,
• 2.Add addressing information to the packets
• 3.Prepare the data for transmission through the
NIC and out onto the network cable.
How Protocols Work (2)
• Protocols at the receiving computer :
• 1.Take the data packets off the cable.
• 2.Bring the data packets into the computer
through the NIC.
• 3.Strip the data packets of all the transmitting
information that was added by the sending
computer.
• 4.Copy the data from the packets to a buffer for
reassembly.
• 5.Pass the reassembled data to the application
Routable Protocols
• Data that is sent from one LAN to another along any
of several available paths is said to be routed.
• The protocols that support multipath LAN-to-LAN
communications are known as routable protocols.
• Because routable protocols can be used to tie
several LANs together and create new wide-area
environments, they are becoming more important
in modern internetworking environment.
Protocol Stacks
• A protocol stack is a combination of protocols.
• Each layer specifies a different protocol for
handling a function of the communication process.
The Binding Process
• The Binding Process connects protocols to each
other and the NICs.
• Protocols and NICs can be mixed and matched
on an as-needed basis.
• The binding order determines the sequence in
which the operating system runs the protocol.
• When multiple protocols are bound to a single NIC,
the binding order is the sequence in which the
protocols will be utilized to attempt a successful
connection.
Standard Stacks
• The computer industry has designated several
kinds of stacks as standard protocol models.
• The ISO/OSI protocol suite.
• The IBM Systems Network Architecture: DLC/SNA.
• Novell NetWare IPX/SPX.
• Apple's AppleTalk.
• The Internet protocol suite, TCP/IP.
Protocol Types.
• The communication tasks, that networks need to
perform, are grouped into one of three protocol type
Application Protocols
• They provide application-to-application interaction
and data exchange.
• Popular Application Protocols include:
• APPC (Advanced Program-to-Program
Communication)
• FTAM (File Transfer Access and Management)
• X.400 (e-mail standard)
• X.500 (directory standard)
Application Protocols (2)
• SMTP (Simple Mail Transfer Protocol)
• FTP (File Transfer Protocol)
• SNMP (Simple Network Management Protocol)
• Telnet
• Microsoft SMBs (Netbios)
• Novell NCP
• Http of web
Transport Protocols
• Transport protocols facilitate communication
sessions between computers and ensure that data
is able to move reliably between computers.
• Popular transport protocols include:
• TCP, UDP
• SPX
• NetBEUI (NetBIOS extended user interface)
• NWLink (The Microsoft implementation of the
IPX/SPX protocol.)
Network Protocols
• These protocols handle addressing and routing
information, and retransmission requests.
• Popular network protocols include:
• IP
• IPX
• NWLink
• NetBEUI
Manufacturer compatibility
• The OSI reference model is used to define which
protocols should be used at each layer.
Manufacturer compatibility (2)
• Products from different manufacturers that
subscribe to this model can communicate witheach
other.
Implementing and Removing Protocols
• Protocols are implemented and removed in much
the same way that drivers are added and removed.
• Essential protocols are installed automatically at
the same time the initial operating system is
installed on the computer.
• To install extra protocols, the corresponding
services should be installed too; and the binding
process should be invoked again.
• To remove protocols, the corresponding services
should be removed first. Because these services
need the protocols to work.