1.2 Network components
Host
All computers that are connected to a network and participate directly in network communication are classified as hosts. some are called end devices, and also clients.
Internet Protocol (IP) address is the number that identifies a host on a network.
- Servers, computers that provide services to end devices e.g. web servers, mail servers, file servers, etc. Each service requires separate server software.
- Clients, computers that use (or send request to the servers) services provided by servers e.g. web browsers, mail clients, etc.
Peer to peer
Peer to peer (P2P) is when a computer functions as both a client and a server.
| Advantages | Disadvantages |
|---|---|
| Easy to set up | No centralized administration |
| Less complex | Not as secure |
| Lower cost | Not scalable |
| Used for simple tasks: transferring files and sharing printers | Slower performance |
End devices
An end device is either the source or destination of a message transmitted over the network. each end device on a network has an address that is used to identify it.
Intermediary Network Devices
Intermediary network devices are used to connect individual end devices to the network. They are also used to connect networks together to form an internetwork.
Their job is to provide connectivity and ensure data flow across the network.
They use the end device destination address in conjunction with info about the network interconnections to determine the path the message should take.
Other roles include:
- Regenerate and retransmit data signals.
- Maintain information about what pathways exist in the network.
- Notify other devices of errors and communication failures.
Network Media
Network media is the physical medium that carries the data signals from one device to another. e.g copper wire, fiber optic cable, radio waves, etc.
| Media Types | Description |
|---|---|
| Metal wires within cables | Uses electrical impulses |
| Glass or plastic fibers within cables (fiber-optic cable) | Uses pulses of light. |
| Wireless transmission | Uses modulation of specific frequencies of electromagnetic waves.(bluetooth, WiFi, infrared…. ) |
1.3 Network Representations and Topologies
Network Representation
Network diagrams, often called topology diagrams, use symbols to represent devices within the network.
Specialized terminology used to describe how each of these devices and media connect to each other:
- Network interface card (NIC) - physically connects an end device to the network.
- Physical port - a connector on a network device that connects to a media.
- Interface - specialized ports on a networking device that connect to individual networks. Because routers connect networks, the ports on a router are referred to as network interfaces.
Topology Diagrams
They provide a visual map of how the network is connected. There are two types of topology diagrams: physical and logical.
- Physical topology diagrams illustrate the physical location of devices and media, lets you see the actual location of intermediary devices and cable installations.
- Logical topology diagrams illustrate devices, ports, and the addressing scheme of the network, lets you see which end devices are connected to which intermediary devices and what media is being used.
1.4 Common Types of Networks
Networks of Many Sizes
| Size | Description |
|---|---|
| Small Home Networks | connect a few computers to each other and the Internet |
| Small Office/Home Office | enables computer within a home or remote office to connect to a corporate network |
| Medium to Large Networks | many locations with hundreds or thousands of interconnected computers |
| World Wide Networks | connects hundreds of millions of computers worldwide – such as the internet |
LANs and WANs
Network infrastructures vary greatly in terms of:
- Size of the area covered
- Number of users connected
- Number and types of services available
- Area of responsibility
The Internet
The internet is a worldwide collection of interconnected LANs and WANs (basicly just collection of interconnected networks).
- LANs are connected to each other using WANs.
- WANs may use copper wires, fiber opticcables, and wireless transmissions
Internet is not owned by any single entity. There are organizations that were developed to help maintain the structure and standardization of internet protocols and processes. e.g. Internet Engineering Task Force (IETF), Internet Corporation for Assigned Names and Numbers (ICANN), Internet Architecture Board (IAB), etc.
Intranet and Extranet
Intranet, Intranet is a term often used to refer to a private connection of LANs and WANs that belongs to an organization.
Extranet, Extranet is a term often used to refer to a private connection of LANs and WANs that belongs to an organization but is shared with other organizations. so basically it’s a private network that is connects more than one organization together.
1.5 Internet Connections
Internet Access Technologies
- Home users/Small offices
- typically require a connection to an internet service provider (ISP) to access the internet.
- connection options vary depending on the type of ISP and geographic location, including:
- DSL (Digital Subscriber Line)
- Cable
- Satellite
- Wireless WANs
- Large organizations
- Fast connections are required to support business services including IP phones, video conferencing, and data center storage.
- Service providers (SPs) offer business class interconnections to fulfill these needs. these services include:
- business DSL
- Metro Ethernet
- eased lines
Home and Small Office Internet Connections
| Connection | Description |
|---|---|
| Cable | high bandwidth, always on, internet offered by cable television service providers. |
| DSL | high bandwidth, always on, internet connection that runs over a telephone line. |
| Cellular | uses a cell phone network to connect to the internet. |
| Satellite | major benefit to rural areas without Internet Service Providers. |
| Dial-up telephone | an inexpensive, low bandwidth option using a modem. |
Businesses Internet Connections
Businesses may require higher bandwidth, dedicated bandwidth, and managed services.
| Connection | Description |
|---|---|
| Dedicated Leased Line | These are reserved circuits within the service provider’s network that connect distant offices with private voice and/or data networking. |
| Ethernet WAN | This extends LAN access technology into the WAN. |
| DSL | Business DSL is available in various formats including Symmetric Digital Subscriber Lines (SDSL). |
| Satellite | This can provide a connection when a wired solution is not available. |
The Converging Network
| Traditional Separate Networks | Converging Networks |
|---|---|
| Each network uses different technologies to carry the communication signal | Capable of delivering data, voice, and video between many different types of devices over the same network infrastructure |
| Each network had its own set of rules and standards | Uses the same set of rules, agreements, and implementation standards |
| Multiple services ran on multiple networks. | Multiple services run on a single network. |
1.6 Reliable Networks
Network Architecture
In this context, network architecture refers to the technologies used to build the network. It is the foundation of the network and is the most important factor in determining the reliability of the network. to meet user expectations, the network must address the following: Fault Tolerance, Scalability, Quality of Service (QoS), Security
Fault Tolerance
Fault tolerance network limits the number of devices affected during a failure.
it does that by having multiple paths between the source and destination devices. this is called Redundancy.
Packet switching networks are inherently fault tolerant because they use multiple paths to send data. it breaks down a single message into smaller packets and sends them along different paths. that way the UX is not affected if one of the paths fails.
Scalability
When a network is scalable, it means it can quickly expand to support new users and applications without affecting(degrading) the performance of the network.
These networks are scalable because the designers follow accepted standards and protocols.
Quality of Service (QoS)
Network congestion, occurs when the demand for network bandwidth exceeds its availability.
Network bandwidth is measured in the number of bits that can be transmitted in a single second, or bits per second (bps).
Devices will hold the packets in memory until resources become available to transmit them.
This is handled by having a QoS policy that prioritizes certain types of traffic over others. The type of traffic is important not the content of the traffic.
Security
Tow types of security:
- Network infrastructure security: Physical security of network devices by preventing unauthorized access to the network.
- Information security: Protecting the data that is transmitted over the network.
Three goals of network security:
- Confidentiality – only intended recipients can read the data
- Integrity – assurance that the data has not be altered with during transmission
- Availability – assurance of timely and reliable access to data for authorized users
1.7 Network Trends
Bring Your Own Device (BYOD)
Allows users to use their own devices giving them more opportunities and greater flexibility. BYOD means any device, with any ownership, used anywhere.
Online Collaboration
Online collaboration is the ability to work together on a project in real time, regardless of geographic location.
Collaboration is a very high priority for businesses and in education.
Video Communication
- Video calls are made to anyone, regardless of where they are located.
- Powerful tool for communicating with others.
- Critical requirement for effective collaboration.
- Cisco TelePresence powers is one way of working where everyone, everywhere.
Cloud Computing
- Allows us to store personal files or backup our data on servers over the internet.
- Applications can also be accessed using the Cloud.
- Allows businesses to deliver to any device anywhere in the world.
It is mad possible by data centers that are located in different parts of the world: smaller companies that can’t afford to build their own data centers can lease server and storage services from large data center organizations.
Four types of Clouds:
- Public Clouds: Available to the general public through a pay-per-use model or for free.
- Private Clouds: Intended for a specific organization or entity such as the government.
- Hybrid Clouds: Made up of two or more Cloud types – for example, part custom and part public. Each part remains a distinctive object but both are connected using the same architecture.
- Custom Clouds: Built to meet the needs of a specific industry, such as healthcare or media. Can be private or public.
Technology Trends in the Home
Smart home technology is a growing trend that allows technology to be integrated into every-day appliances which allows them to interconnect with other devices. e.g. Nest thermostat, Amazon Echo, etc.
Powerline Networking
Using the same electrical wiring in your home to connect devices to the network.
Powerline networking can allow devices to connect to a LAN where data network cables or wireless communications are not a viable option by Using a standard powerline adapter
Wireless Broadband
- More commonly found in rural environments
- a Wireless Internet Service Provider (WISP) is an ISP that connects subscribers to designated access points or hotspots.
- Wireless broadband is another solution for the home and small businesses.
- Uses the same cellular technology used by a smart phone.
- An antenna is installed outside the house providing wireless or wired connectivity for devices in the home.
1.8 Network Security
Security Threats
External Threats:
- Viruses, worms, and Trojan horses
- Spyware and adware
- Zero-day attacks
- Threat Actor attacks
- Denial of service attacks
- Data interception and theft
- Identity theft
Internal Threats:
- lost or stolen devices
- accidental misuse by employees
- malicious employees
Security Solutions
Network security components for home or small office network:
- Antivirus and antispyware software should be installed on end devices.
- Firewall filtering used to block unauthorized access to the network.
Larger networks have additional security requirements:
- Dedicated firewall system
- Access control lists (ACL)
- Intrusion prevention systems (IPS)
- Virtual private networks (VPN)