Chapter_01_1

First Wireless Communication Network in Ancient Greece

Networks change the way we

• work
• learn
• play

External factors affecting the success of communication include:

• The quality of the pathway between the sender and the recipient
• The number of times the message has to change form
• The number of times the message has to be redirected or readressed
• The number of other messages being transmitted simultaneously on the communication network
• The amount of time allotted for successful communication

Internal factors affecting the successful communication across the network include:

• The size of the message
• The complexity of the message
• The importance of the message

all networks have four basic elements in common:

• Rules or agreements to govern how the messages are sent, directed, received and interpreted.
• The messages or units of information that travel from one device to another
• A means of interconnecting these devices - a medium that can transport the messages from one device to another
• Devices on the network that exchange messages with each other

Elements of a Network:

• Rules
• Medium
• Messages
• Devices

Converged networks & Unified Communications

Technology advances are enabling us to consolidate these disparate networks onto one platform - a platform defined as a converged network. The flow of voice, video, and data traveling over the same network eliminates the need to create and maintain separate networks. On a converged network there are still many points of contact and many specialized devices - for example, personal computers, phones, TVs, personal assistants, and retail point-of-sale registers - but only one common network infrastructure.

The underlying architectures of a Network needs to address:

• Fault tolerance
• Scalability
• Quality of service
• Security

Packet Switched and Circuit Switched Networks

Network bandwidth is the measure of the data carrying capacity of the network.

Classification of Data traffic to achieve QoS

QoS mechanisms enable the establishment of queue management strategies that enforce priorities for different classifications of application data. Without properly designed and implemented QoS mechanisms, data packets will be dropped without consideration of the application characteristics or priority. Examples of priority decisions for an organization might include:

• Time-sensitive communication - increase priority for services like telephony or video distribution.
• Non time-sensitive communication - decrease priority for web page retrieval or e-mail
• High importance to organization - increase priority for production control or business transaction data.
• Undesirable communication - decrease priority or block unwanted activity, like peer-to-peer file sharing or live entertainment.

Security measures taken in a network should:

• Prevent unauthorized disclosure or theft of information
• Prevent unauthorized modification of information
• Prevent Denial of Service

Means to achieve these goals include:

• Ensuring confidentiality
• Maintaining communication integrity
• Ensuring availability

1.Ensuring Confidentiality

Data privacy is maintained by allowing only the intended and authorized recipients - individuals, processes, or devices - to read the data.

Having a strong system for user authentication, enforcing passwords that are difficult to guess, and requiring users to change them frequently helps restrict access to communications and to data stored on network attached devices. Where appropriate, encrypting content ensures confidentiality and minimizes unauthorized disclosure or theft of information.

2.Maintaining Communication Integrity

Data integrity means having the assurance that the information has not been altered in transmission, from origin to destination. Data integrity can be compromised when information has been corrupted - willfully or accidentally - before the intended recipient receives it.

Source integrity is the assurance that the identity of the sender has been validated. Source integrity is compromised when a user or device fakes its identity and supplies incorrect information to a recipient.

The use of digital signatures, hashing algorithms and check sum mechanisms are ways to provide source and data integrity across a network to prevent unauthorized modification of information.

3.Ensuring Availability

Ensuring confidentiality and integrity are irrelevant if network resources become over burdened, or not available at all. Availability means having the assurance of timely and reliable access to data services for authorized users. Resources can be unavailable during a Denial of Service (DoS) attack or due to the spread of a computer virus. Network firewall devices, along with desktop and server anti-virus software can ensure system reliability and the robustness to detect, repel, and cope with such attacks. Building fully redundant network infrastructures, with few single points of failure, can reduce the impact of these threats.