Message Timing

These are the rules of engagement for message timing.

Access Method

Access method determines when someone is able to send a message. If two people talk at the same time, a collision of information occurs and it is necessary for the two to back off and start again, as shown in Figure 1. Likewise, it is necessary for computers to define an access method. Hosts on a network need an access method to know when to begin sending messages and how to respond when collisions occur.

Flow Control

Timing also affects how much information can be sent and the speed that it can be delivered. If one person speaks too quickly, it is difficult for the other person to hear and understand the message, as shown in Figure 2. In network communication, source and destination hosts use flow control methods to negotiate correct timing for successful communication.

Response Timeout

If a person asks a question and does not hear a response within an acceptable amount of time, the person assumes that no answer is coming and reacts accordingly, as shown in Figure 3. The person may repeat the question, or may go on with the conversation. Hosts on the network also have rules that specify how long to wait for responses and what action to take if a response timeout occurs.

Read more »

Message Size

Another rule of communication is size. When people communicate with each other, the messages that they send are usually broken into smaller parts or sentences. These sentences are limited in size to what the receiving person can process at one time, as shown in Figure 1. An individual conversation may be made up of many smaller sentences to ensure that each part of the message is received and understood. Imagine what it would be like to read this course if it all appeared as one long sentence; it would not be easy to read and comprehend.

Likewise, when a long message is sent from one host to another over a network, it is necessary to break the message into smaller pieces, as shown in Figure 2. The rules that govern the size of the pieces, or frames, communicated across the network are very strict. They can also be different, depending on the channel used. Frames that are too long or too short are not delivered.

The size restrictions of frames require the source host to break a long message into individual pieces that meet both the minimum and maximum size requirements. The long message will be sent in separate frames, with each frame containing a piece of the original message. Each frame will also have its own addressing information. At the receiving host, the individual pieces of the message are reconstructed into the original message.

Read more »

Rule Establishment

Before communicating with one another, individuals must use established rules or agreements to govern the conversation. For example, consider Figure 1, protocols are necessary for effective communication. These rules, or protocols, must be followed in order for the message to be successfully delivered and understood. Protocols must account for the following requirements:

• An identified sender and receiver

• Common language and grammar

• Speed and timing of delivery

• Confirmation or acknowledgment requirements

The protocols that are used in network communications share many of these fundamental traits. In addition to identifying the source and destination, computer and network protocols define the details of how a message is transmitted across a network. Common computer protocols include the requirements shown in Figure 2. Each of these will be discussed in more detail.

Read more »

Communication Fundamentals

A network can be as complex as devices connected across the Internet, or as simple as two computers directly connected to one another with a single cable, and anything in-between. Networks can vary in size, shape, and function. However, simply having a wired or wireless physical connection between end devices is not enough to enable communication. For communication to occur, devices must know “how” to communicate.

People exchange ideas using many different communication methods. However, regardless of the method chosen, all communication methods have three elements in common. The first of these elements is the message source, or sender. Message sources are people, or electronic devices, that need to send a message to other individuals or devices. The second element of communication is the destination, or receiver, of the message. The destination receives the message and interprets it. A third element, called a channel, consists of the media that provides the pathway over which the message travels from source to destination.

Communication begins with a message, or information, that must be sent from a source to a destination. The sending of this message, whether by face-to-face communication or over a network, is governed by rules called protocols. These protocols are specific to the type of communication method occurring. In our day-to-day personal communication, the rules we use to communicate over one medium, like a telephone call, are not necessarily the same as the protocols for using another medium, such as sending a letter.

For example, consider two people communicating face-to-face, as shown in Figure 1. Prior to communicating, they must agree on how to communicate. If the communication is using voice, they must first agree on the language. Next, when they have a message to share, they must be able to format that message in a way that is understandable. For example, if someone uses the English language, but poor sentence structure, the message can easily be misunderstood. Each of these tasks describe protocols put in place to accomplish communication. This is also true of computer communication, as shown in Figure 2.

Many different rules or protocols govern all methods of communication that exist in the world today.

Read more »

Chapter 2: Configure a Network Operating System

Cisco IOS is a term that encompasses a number of different operating systems, which runs on various networking devices. The technician can enter commands to configure, or program, the device to perform various networking functions. Cisco IOS routers and switches perform functions that network professionals depend upon to make their networks operate as expected.

The services provided by the Cisco IOS are accessed using a command-line interface (CLI), which is accessed by either the console port, the AUX port, or through SSH or Telnet. After connected to the CLI, network technicians can make configuration changes to Cisco IOS devices. The Cisco IOS is designed as a modal operating system, which means a network technician must navigate through various hierarchical modes of the IOS. Each mode supports different IOS commands.

Cisco IOS routers and switches support a similar modal operating system, support similar command structures, and support many of the same commands. In addition, both devices have identical initial configuration steps when implementing them in a network.

This chapter introduced the Cisco IOS. It detailed the various modes of the Cisco IOS and examined the basic command structure that is used to configure it. It also walked through the initial settings of a Cisco IOS switch device, including setting a name, limiting access to the device configuration, configuring banner messages, and saving the configuration.

The next chapter explores how packets are moved across the network infrastructure and introduce you to the rules of packet communication.

Read more »

Lab - Configuring a Switch Management Address

In this lab, you will complete the following objectives:

• Part 1: Configure a Basic Network Device

• Part 2: Verify and Test Network Connectivity

Lab - Configuring a Switch Management Address

Read more »

Lab - Building a Simple Network

In this lab, you will complete the following objectives:

• Part 1: Set Up the Network Topology (Ethernet only)

• Part 2: Configure PC Hosts

• Part 3: Configure and Verify Basic Switch Settings

Lab - Building a Simple Network

Read more »