February 18, 2003 Week 7: Day 1
Welcome to Lesson 7 - Network Communications and Protocols Part II
Note that data is divided into packets for manageability and reliability. Smaller
chunks of data are easier to manage and if the packet is damaged during transmission,
just a small piece of the original data will need to be resent.
Note that the exact
structure of a packet is determined by the protocol and media being used. As
you’ll see in Chapter 7, different protocols use different packet structures
or frames. However, all packets have three basic parts: the header, data, and
trailer.
Figure 6-3 shows the
process of creating a packet. As the data is passed through the layers of the
OSI model, each layer on the sending computer adds its own header or trailer
information, whereas this information is removed on the receiving end.
State that, by definition, protocols
are rules for communication. This term, of course, was used when discussing
rules for meeting and communicating with people. This also applies to communication
between computers.
There is no single protocol which
encompasses all aspects of network communication. When a group of protocols
is designed to work together to communicate effectively over a network, it is
called a protocol suite or protocol stack.
Connectionless protocols assume that the data will get to its destination by
relying on the other protocols in the suite. Connectionless protocols are generally
very fast because of this assumption. Connection-oriented protocols, on the
other hand, establish a connection to ensure reliable delivery of the data.
This comes at a price, however, because connection-oriented protocols are slower.
Protocol suites that function at
the Network Layer are called routable. That is, the hardware device known as
the router moves the packets across teh network at the Network layer of the
OSI model. Protocol suites that do not have encompass the Network layer are
called nonroutable. It is very important to understand that some protocols,
most particularly NetBEUI, do not contain Network layer information and, consequently,
are not routable. This is addressed in questions on the Microsoft certification
test.
There are three main protocol types: Application Protocols, Transport Protocols, and Network Protocols.
It is important that you get a clear understanding of which protocols belong to each category.
1. Why are network messages divided
into small chunks for transmission?
Think about it, then click HERE
to see the answer.
2. As the data packet is passed up from the Transport layer to the Session layer
on the receiving computer, how many header sections are part of the packet?
Think about it, then click HERE
to see the answer.
3. Which data delivery method uses datagrams to provide faster communication?
Think about it, then click HERE
to see the answer.
4. Which OSI layer is used by routable protocols?
Think about it, then click HERE
to see the answer.
You have been asked to design a network for a small advertising firm. They are currently running a mix of Windows 95 and Macintosh computers, and are interested in installing a Windows NT Server. Except for the price of the server, they would like to keep costs low. Describe the channel access method and protocols which could be used in this environment.
Next time we will discuss IP Addressing.
This section is the most important in this chapter and, perhaps, in the entire course. Current network topologies and the Internet rely heavily on TCP/IP and fully understanding IP addressing is imperative.
Remember to keep up with your on-line lessons and quizzes!
mdm