Specifications

Niagara Release 2.3
Revised: May 22, 2002 Niagara Networking & Connectivity Guide
Chapter 1 Understanding Networking and IP Addressing
Introduction to Networking
1–12
Protocols are typically created by vendors and networking standards organizations.
Once established, hardware and software vendors implement them into their
products. There is a variety of standard protocols each one has particular advantages
and disadvantages. For instance, some are simpler than others, some are more
reliable, and some are faster.
From the point of view of the user, the only interesting aspect about protocols is that
your computer or device must support the right ones if you want to communicate with
other computers. Protocols can be implemented either in hardware or in software.
How Protocols
Work
At the transmitting computer, the protocol breaks the data down into small segments
called packets. Packets are necessary so that when a computer attempts to transmit a
large amount of data, other computers do not transmit until the entire transmission is
completed. By breaking data down into smaller segments, individual data
transmissions are quicker, allowing more computers the opportunity to transmit.
Protocols are also responsible for adding the address of the destination computer and
preparing the data for transmission through the NIC onto the data transmission
media.
At the destination computer, the protocol is responsible for collecting the packets,
stripping off transmitting information, and copying just the data portion of the
message to a memory buffer. Then it is responsible for reassembling the data portions
of the packets in the correct order and checking the data for errors.
Protocols and
the OSI Model
In the OSI architecture, several protocols must work together to ensure that the data
is prepared, transferred, received, and acted upon. The work of the various protocols
must be coordinated so that there are no conflicts or incomplete operations. This
coordination of efforts is referred to as layering.
Protocol Stacks
A protocol stack is a combination of protocols. Each layer specifies a different
protocol for handling a function or subsystem of the communication process. Each
layer has its own set of rules.
• The application layer initiates or accepts a request.
• The presentation layer adds formatting, display, and encryption information to
the packet.
• The session layer adds traffic flow information, which allows stations to
determine when a packet is sent.
• The transport layer adds error-handling information.
• The network layer adds sequencing and address information to the packet.
• The data link layer adds error-checking information and prepares data to be
placed onto the data transmission media.
• The physical layer sends the packet as a bit stream.