Lesson 15

You are now equipped with basic knowledge about the foundation of the Internet. This module discussed network architecture essentials such as the different network diagnostic tools and their functions and connectivity hardware such as bridges, firewalls, gateways, hubs, repeaters, routers, and switches. Key terms and concepts included OSI and Internet bandwidth technologies.
You should now be able to:

1. Explain the OSI model
2. Describe the core components of the Internet infrastructure and how they relate to each other
3. Describe the uses of hardware and software network connection devices
4. Describe the various Internet bandwidth technologies
5. Describe the purposes, functions, and features of various types of servers
6. Troubleshoot problems with Internet connectivity using various diagnostic tools

Calculate the total number of kilobytes and multiply them by 8 to determine kilobits.
Recall that server load (as a product of data transfer) is calculated in bits, not bytes. Use the formula to estimate the server's transfer load:

Data traveling on a network is split into packets. In addition to the data that it carries, each packet includes about 20 bytes of header information and other network protocol information which is known as overhead. The amount of data in a packet is not fixed, and thus the ratio of overhead to data can vary. Most incoming HTTP requests are small. A typical request (for example, GET http://www.seotrance.com/index.php), including the TCP/IP overhead, consists of no more than a few hundred bytes as it travels across the network. Overhead can become an important consideration when you are estimating your sites bandwidth requirements and deciding how fast a connection you need. If current usage is close to the limits of your connections capacity, an extra 20 percent for overhead might mean that you need the next faster type of connection. Think of a server that displays static Hypertext Markup Language (HTML) text-only pages that average 6 kilobytes (KB), which is nearly equivalent to a full page of printed text. The server is connected to the Internet through a DS1/T1 line, which can transmit data at 1.537 megabits per second. Inherent overhead makes it impossible to use the full-rated T1 bandwidth of 1.543 megabits per second. For this 6-KB file, protocol overhead is significant, amounting to about 31 percent of the files size. For larger files, the overhead accounts for a smaller percentage of network traffic.

When dealing with networking, you may hear the terms network model or layer. Network models define a set of network layers and how they interact. There are several different network models depending on what organization or company started them. The most important two are:

1. TCP/IP Model:This model is sometimes called the DOD model since it was designed for the department of defense and is also called the internet model because TCP/IP is the protocol used on the NET.
2. OSI Network Model: The (ISO) International Standards Organization has defined a standard called the (OSI) Open Systems Interconnection reference model.

In this module, you were introduced to the following terms:

1. backbone High-speed WAN connections, servers, and ISPs that carry Internet traffic over very high-bandwidth lines.
2. OSIL: A seven-layer network model for implementing protocols and developed by the International Standards Organization (ISO).
3. Network operating system (NOS):Software that facilitates hardware and software working together as a network. Examples include Linux and Windows NT.
4. Bridge: A network connection device that isolates traffic into segments but lets the segments appear to be a single network.
5. Firewall: Network security device that blocks a specific type of data or prevents data from specified sources from entering the network.
6. Hub: Interconnects multiple devices (in a minimum of three) in a network. Enables distribution of information among connected devices.
7. Repeater: Physical layer device that extends the length of a network segment. A repeater receives and transmits signals and duplicates them onto another network segment.
8. Router: A device that forwards packets and filters traffic, based on protocol-specific software address, source and destination port numbers.
9. Switch: A device used to connect network segments with high usage percentages. A switch offers higher performance than bridges or routers and is used to create virtual LANS.
10. Pipe: A transmission wire that passes data through a network. The size of a pipe is measured in how many bits, or binary digits, it can transmit per second.
11. ATM: Asynchronous Transfer Mode (ATM) is a pipe protocol that uses fixed-size, very high-speed, high-capacity packet relay technology.
12. Frame Relay: A high-speed networking protocol for connecting multiple LANs across remote distances. Frame Relay is a packet switching protocol.
13. ISDN: Integrated Services Digital Network is a pipe protocol that operates basic communication service over regular phone lines and provides 128 kbps. ISDN uses special switching techniques to obtain higher bandwidth from telephone lines.
14. Point-to-Point Protocol (PPP): Point-to-Point protocol provides dial-up access over serial lines.
15. X.25: A pipe protocol that provides connection-oriented technology for transmission over error-prone facilities.
16. PING: A network diagnostic tool used to test whether a remote host can be reached from a specific computer.
17. Winipcfg: A Windows specific utility used to provide information about IP address, network connections, and Internet resources.
18. TRACERT: A trace route utility that shows routing and delay times. Tracert tools are available as either command line tools or as graphical tools.
19. NETSTAT: A utility that displays a list of server-side TCP/IP connections. Netstat is also used to obtain network statistics; display the contents of the local routing table; and obtain statistics on a particular protocol such as UDP.

In the next module, you will learn about Internet protocols.

Click the Quiz link below to check your knowledge of network hardware and software and troubleshooting solutions.
Network Devices - Quiz