CCNA Introduction to Networks

1.0 Network of Many Sizes

Different Network Sizes

• Small Home Networks - A Small home network is referring to a few computer connect to each other to the internet.
• Small Office/Home Office Networks - Shared and centralize resources are being accessed for a small office and home office or SOHO network enables computer.
• Medium Large Networks -  In this network size, it normally used by corporation and schools and or can have more than hundred or thousand interconnected computers.
• World Wide Networks - This is the largest network size where it connected from network to different network world-wide, which it connected hundreds or million and billion of network enabled devices.

1.1.1 Clients and Servers

Clients and Servers 

All the Devices that connected/ participate to the network will be classified as host or end devices.
Servers are host where software will be installed to provide the client information examples, Email or Web Pages or to the other host on the network Depending of the usage and configuration. Example, a host that require to display or share some materials to the clients.
    -Computer with server mode, can provide services parallel/simultaneously to one or many clients at a time.

Clients are computers or end devices that have software installed to communicate with the servers to get information from the server. Example, a computer using a web browsers as a client software to display all the results get from the servers.

     -Client can run multiple type of client software simultaneously. Example, Client can access to Email services and Listening to Internet Radio at the same time.

1.1.2 Peer-to-Peer (also know as P2P)
Computer can be act as different roles at a same time where in a small business or home network, many of the computer will act as both clients and servers in the network and this is called as a peer-to-peer network.
Example of an simple P2P Network is by connecting 2 computers.

Peer-to-Peer

Multiple Computers can be connected to a larger peer-to-peer network but it requires networking devices such as hub, but the disadvantages of peer-to-peer network is the performance of the host can be slow down of acting as both of the roles of clients and servers.
In Larger network, Due to the high amounts of network traffic, it is normally to use a dedicated servers to control or support the number of service request.

1.2 Providing the resource to Network
1.2.1 Components of network
1.2.1.1 Network Component

Network Components

In a network infrastructure it contains of 3 categories of network such as Devices, Media and Services as shown in figure above.
1.2.1.2 End Devices
End devices is a device that underlying between users and the communications network where some of the examples are  Computer, Network Printers, VoIP phones, TelePresence endpoint, Security cameras, Mobile devices(Smartphones, Tablets and ext).
1.2.1.3 Intermediary Network Devices
Intermediary Devices are the device that are interconnect the end devices and the devices will provide connectivity and ensure the data flows across the network between the End Devices.
Example of Intermediary Devices, Network Access(Switches and Wireless Access Point), Inter-networking (Routers), Security(Firewalls).


Process of intermediary networking devices perform the function of:

• regenerate and re-transmit data signals.
• Maintaining the information of the pathways exist over the network and inter-network for the data.
• Notify other devices of errors and communication failure.
• Direct the data to go for a correct path way if there is a failure path.
• Classify and direct Messages according to Quality of Service(QoS) Priorities.
• Based on the security settings , It will permit or deny the data flows/

1.2.1.4 Network Media

Network Media

in communications, There will be a media that connect the devices together and transmit the data from source to destination.As shown in figure above networks media use is use to provide a pathway which data can be transmitted. Example,  Metallic Wires within cables, Glass or plastic fibers(Fiber optic), Wireless transmission.

 Different Media have different features with benefits and disadvantages. But criteria will be followed to choose a suitable network media.

• The distance of the media carry a signal
• the environment in which the media is to be installed
• the amount of data(example bandwidth) and the speed(data transfer rate) at which it must be transferred (throughput).
• The cost of the media and installation.

1.2.1.5 Network Representatives

Network Representatives (network devices icon)

Network Representatives will be used when using in the complex information or large network, to help to visualize the network with diagrams for easy understandings.

In addition, other specialized terminology network representatives will be used when each of the media devices and media will be connect with each other:

• Network Interface Card - A NIC or LAN Adapter will provide the physical connection to the PC or the other host devices to the network, where media will be plugged in directly between the devices into the NIC.
• Physical Port - A connector that is used outlet on a networking device where the media is connected to host or networking device.
• Interface - Specialize port on an inter networking devices that connect routers to individual networks. In a router it is referred as network interfaces  because it is use to interconnect networks.

1.2.1.6 Topology
Topology diagrams are mandatory for anyone working with a network. It provides a visual map of how the network is connected. Which it will be divide into 2 category as shown below:

Physical vs Logical Topology

• Physical topology diagrams - Identify the physical location of intermediary devices, configured ports, and cable installation.
•  Logical topology diagrams - Identify devices, ports, and IP addressing scheme.

1.2.2 LANs, WANs

1.2.2.1 Types of Networks

Network infrastructures can be elaborate in term of:

• Size of the area covered 
• Number of users connected 
• Number and types of services available 

Sample of Common type of Network Infrastucture

The figure above illustrates the two most common types of network infrastructures:

• Local Area Network (LAN) - A network infrastructure that provides access to users and end devices in a small geographical area. 
• Wide Area Network (WAN) - A network infrastructure that provides access to other networks over a wide geographical area. 

Other types of networks include:

• Metropolitan Area Network (MAN) - A network infrastructure that spans a physical area larger than a LAN but smaller than a WAN (e.g., a city). MANs are typically operated by a single entity such as a large organization. 
• Wireless LAN (WLAN) - Similar to a LAN but wirelessly interconnects users and end points in a small geographical area. 
• Storage Area Network (SAN) - A network infrastructure designed to support file servers and provide data storage, retrieval, and replication. It involves high-end servers, multiple disk arrays (called blocks), and Fibre Channel interconnection technology.

1.2.2.2 Local Area Networks(LAN) and Wide Area Networks(WAN)

LAN and WAN

Local Area Networks (LANs) are a network infrastructure that spans a small geographical area. In specifics:

• LANs interconnect end devices in a limited area such as a home, school, office building, or campus.
• A LAN is usually administered by a single organization or individual. The administrative control that governs the security and access control policies are enforced on the network level.
• LANs provide high speed bandwidth to internal end devices and intermediary devices.

Where as Wide Area Networks (WANs) are a network infrastructure that spans a wide geographical area.
WAN normally are govern or controlled by Service providers(SP) or Internet Service Providers (ISP). In specifics:

• WANs interconnect LANs over wide geographical areas such as between cities, states, provinces, countries, or continents.
• WANs are usually administered by multiple service providers.
• WANs typically provide slower speed links between LANs.

1.2.3 The Internet
1.2.3.1 Internet

Internetwork with Multiple LANs and WANs connnected

Individuals also need to connect to the resources from another network outside the LAN or WAN where the resources is outside of the home and compus organization. Figure above shows that the inter network (internet in short) is connected through mediums.
The Internet is a conglomerate of networks and is not owned by any individual or group. Organization were include to ensure the effectiveness of the communication across the infrastructure and recognize technologies and standards based on Network administration. Example:

• Engineering Task Force (IETF).
• Internet Corporation for Assigned Names and Numbers (ICANN).
• Internet Architecture Board (IAB).
• And many others.

Note: The term internet (with a lower case “i") is used to describe multiple networks interconnected. When referring to the global system of interconnected computer networks or the World Wide Web, the term Internet (with a capital “I”) is used.

1.2.3.2 Intranet and Extranet

Intranet and Extranet

Intranet is a term often used to refer to a private connection of LANs and WANs that belongs to an organization, and is designed to be accessible only by the organization's members, employees, or others with authorization. Intranets are basically an internet which is usually only accessible from within the organization. They could publish web pages on an intranet for internal usage, for example, notifications for the events held in the organization.

An organization may use extranet to provide an secure and safe access to individuals who work for a different organizations, but require company data, for example:

• A company providing access to outside suppliers/contractors.
• A hospital providing a booking system to doctors so they can make appointments for their patients. 
• A local office of education providing budget and personnel information to the schools in its district.

1.2.4 Connecting the Internet
1.2.4.1 Technologies to Access to Internet
Home users, teleworkers or Small Office require a connection from an ISP(Internet Service Provider) which option of the connection are vary between ISP and depending of the location, However, most of the choices including broadband cable, DSL(digital subscribet Line), Wireless WANs,and mobile services are more popular choice.
 Normally Organization require to get access to the other Organization or corporate sites and internet, a fast connection is a must to support the business servicing including Video Conference, data Center,and IP Phones.
1.2.4.2 Connection Options

Connection Options for Home user

there are a lot of ways for connection option which below explain some of the option that we could get for small Home or home business connection.

• Cable - It is normally offered by cable Television Service providers, and the internet data signal will be carried along on the same coaxial cable that deliver the data for the cable television. It provides a high bandwidth, always on, connection to the Internet. It requires a special modem that could separate the data signal of internet travels along the cable to provide an Ethernet Connection to a Host Device or LAN.

• DSL - It also provide high bandwidth, always on connection to the internet but it required a special High-Speed modem that could separate the Internet Data from the telephone signal in order to provide Ethernet connection to the LAN. In DSL connection, it runs over a telephone line, where it will be split into three channels. Which one channel is for voice telephone calls where it allows an individual to receive phone calls without disconnect from the Internet; Second channel is for a faster download channel where used to receive information or data from the Internet; where the third channel is usually slower than the download channel and it is use to send or upload information. The quality and the speed of the DSL connection is depending mainly on the quality of the phone line and the distance between the phone central office, the connection will be slower if the distance is further.

• Cellular - Cellular Internet access uses a cell phone network to connect. Wherever you can get a cellular signal, you can get cellular Internet access. Performance will be limited by the capabilities of the phone and the cell tower to which it is connected. The availability of cellular Internet access is a real benefit in those areas that would otherwise have no Internet connectivity at all, or for those constantly on the go.

• Satellite - Satellite service is a good option for homes or offices that do not have access to DSL or cable. Satellite dishes require a clear line of sight to the satellite and so might be difficult in heavily wooded areas or places with other overhead obstructions. Speeds will vary depending on the contract, though they are generally good. Equipment and installation costs can be high (although check the provider for special deals), with a moderate monthly fee thereafter. The availability of satellite Internet access is a real benefit in those areas that would otherwise have no Internet connectivity at all.

• Dial-up Telephone - An inexpensive option that uses any phone line and a modem. To connect to the ISP, a user calls the ISP access phone number. The low bandwidth provided by a dial-up modem connection is usually not sufficient for large data transfer, although it is useful for mobile access while traveling. A modem dial-up connection should only be considered when higher speed connection options are not available.

Many homes and small offices are more commonly being connected directly with fibre optic cables. This enables an Internet service provider to provide higher bandwidth speeds and support more services such as Internet, phone, and TV.

The choice of connection varies depending on geographical location and service provider availability.

Connection Option for Corporate Connection

Corporate connection options differ from home user options. Businesses may require higher bandwidth, dedicated bandwidth, and managed services. Connection options available differ depending on the number of service providers located nearby.

• Dedicated Leased Line - This is a dedicated connection from the service provider to the customer premise. Leased lines are actually reserved circuits that connect geographically separated offices for private voice and/or data networking. The circuits are typically rented at a monthly or yearly rate which tends to make it expensive. In North America, common leased line circuits include T1 (1.54 Mb/s) and T3 (44.7 Mb/s) while in other parts of the world they are available in E1 (2 Mb/s) and E3 (34 Mb/s).

• Metro Ethernet - Metro Ethernet is typically available from a provider to the customer premise over a dedicated copper or fiber connection providing bandwidth speeds of 10 Mb/s to 10 Gb/s. Ethernet over Copper (EoC) is more economical than fiber optic Ethernet service in many cases, quite widely available, and reaches speeds of up to 40 Mbps. However, Ethernet over Copper is limited by distance. Fiber optic Ethernet service delivers the fastest connections available at an economical price per megabit. Unfortunately, there are still many areas where this service is unavailable.

• DSL - Business DSL is available in various formats. A popular choice is Symmetric Digital Subscriber Lines (SDSL) which is similar to Asymmetric Digital Subscriber Line (ADSL), but provides the same upload and download speeds. ADSL is designed to deliver bandwidth at different rates downstream than upstream. For example, a customer getting Internet access may have downstream rates that range from 1.5 to 9 Mbps, whereas upstream bandwidth ranges are from 16 to 640 kbps. ADSL transmissions work at distances up to 18,000 feet (5,488 meters) over a single copper twisted pair.

• Satellite - Satellite service can provide a connection when a wired solution is not available. Satellite dishes require a clear line of sight to the satellite. Equipment and installation costs can be high, with a moderate monthly fee thereafter. Connections tend to be slower and less reliable than its terrestrial competition, which makes it less attractive than other alternatives.

The choice of connection varies depending on geographical location and service provider availability.

1.3 Network as a Platform

1.4 The Change on Network Environment

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All the above information is self understanding summarize sharing from Cisco Networking Academy Study Materials. It Information may be vary to be shared. More accurate information can be found from the below links
1) https://www.netacad.com/
2) http://www.cisco.com/web/learning/netacad/index.html

Information above cited to (Cisco Systems, Inc., 1992-2013)  and (NetAcad™, 1992-2013)

To be continued...