Telecom OnLine: Lecture Mail

January 9, 2003 Week 1: Day 2

Welcome to the Course!

Course Notes

• Remember that we will use the Campus Pipeline Bulletin Board this semester!

Lesson 1 Notes (cont.)--

Network Services

Networks exist to provide services to users. These services encompass basic network functions like file and printer sharing, and more advanced functions such as messaging. It is often said that NOSs provide file and print services and that protocols deliver file-sharing, e-mail, and other services. Network servers exist to provide network services to clients that request them.

Network protocols define the kinds of messages and communications that computers can exchange with one another, as well as define the kinds of services that can be delivered. When networked devices communicate, they use a very structured, layered approach. The network applications use the NOS or client networking software to instruct a network protocol to access the network medium through the computer’s interface to address and exchange information. Each of the layers shown in Figure 1-4 is essential for successful communication. Starting at bottom network medium layer, each higher layer depends on the layer below for specific functions.

Quick Question:

At what layer of the communications process do network interfaces operate?

Answer it on the bulletin board for participation points.

Network Types

Peer-to-Peer Networking

In these networks, not only does each computer act as both a client and a server, but also each user administers their own machine. Resource sharing is handled by the individual users.

Implications of this model:

• As a network grows larger, it becomes more difficult to manage.
• Each resource can have a different password.
• There is no way to control who has access to a resource, just what the password is. If a person who does not need access to a particular resource learns the password to that resource, they have access.
• Data organization is exceptionally difficult. If each computer can act as a server, how many copies of a document can exist? Which copy is the most current?

What is the the best time and place to use peer-to-peer networks? Generally, peer to peer networks are best used in small companies or working groups in which every person is fairly computer savvy and security is not essential.

Peer-to-peer networks are the cheapest and easiest to install. They generally only require the operating system on the computers to cooperate. A perfect example is the Windows family of operating systems. Windows for Workgroups, Windows 95, Windows 98, Windows Millennium, Windows NT Workstation, and Windows 2000 Professional can all support peer-to-peer networks.

Server-Based Networks

In this type of network, the server’s sole purpose is to respond to client requests. Server-based networks represent the vast majority of networks installed today. The key differences between peer networks and server-based networks are centralized management and higher levels of security. In server based networks each user is assigned a username and password, which grants them access to the server and controls what resources the user can use. This implements a much higher level of security than peer-to-peer networks, where any user with the correct password can access the resource.

Windows 2000 and Windows NT use a domain model. Before the user is granted access to the network, their username and password must be validated by a domain controller. The domain controllers restrict access to any computers within the domain. By doing this, users can logon only once and access any number of services. On Windows 2000 networks, the database is called the Active Directory. Users must supply a valid user name and password to access network resources. Only administrators are able to change the information in the Active Directory. This approach provides centralized security and varying degrees of resource control. On NetWare networks, similar functions are provided through Novell Directory Services (NDS).

Server-based networks gracefully increase in size. When more users are supported, more servers are added and the network grows. This is opposed to peer-to-peer networks where management becomes a problem after around 20 users.

Case Challenge:

Here is the second case challenge for the week:

River City Printing company occupies three buildings around the city, an administrative office, a warehouse, and a print shop. Currently, there are a few standalone computers, but no network. The company plans to implement a network linking all the offices in the next few months and has asked you to help design it. There are plans for a total of 20 computers at all three sites. Security is not an issue, and the users are fairly computer savvy. What type of network should be installed and why?

Answer it on the bulletin board! We will discuss the answers in next's week lesson mail.

Have a good weekend. Quiz 1 is available now! Go to the tools section and click on quiz link. Good luck and we will see you on Tuesday.

mdm