CISCO CHAPTER 1

Networks Support the Way We Learn
  Networks have changed the way we learn. Access to high quality instruction is no longer restricted to students living in proximity to where that instruction is being delivered. Click Play in the figure to view a video about the ways that the classroom has expanded.

Some forms of communication include:

• Texting – Texting enables instant real-time communication between two or more people.

• Social Media – Social media consists of interactive websites where people and communities create and share user-generated content with friends, family, peers, and the world.

• Collaboration Tools - Without the constraints of location or time zone, collaboration tools allow individuals to communicate with each other, often across real-time interactive video. The broad distribution of data networks means that people in remote locations can contribute on an equal basis with people in the heart of large population centers.

• Blogs - Blogs, which is an abbreviation of the word “weblogs”, are web pages that are easy to update and edit. Unlike commercial websites, blogs give anyone a means to communicate their thoughts to a global audience without technical knowledge of web design.

• Wikis - Wikis are web pages that groups of people can edit and view together. Whereas a blog is more of an individual, personal journal, a wiki is a group creation. As such, it may be subject to more extensive review and editing. Many businesses use wikis as their internal collaboration tool.

• Podcasting - Podcasting allows people to deliver their audio recordings to a wide audience. The audio file is placed on a website (or blog or wiki) where others can download it and play the recording on their computers, laptops, and other mobile devices.

• Peer-to-Peer (P2P) File Sharing – Peer-to-Peer file sharing allows people to share files with each other without having to store and download them from a central server. The user joins the P2P network by simply installing the P2P software. P2P file sharing has not been embraced by everyone. Many people are concerned about violating the laws of copyrighted materials. 

-Small Home Network connect a few computer to each other and the internet.
-Small Office/Home Office or SDHO Network enables computer within a home office or a remote    office to connect to a corporate network or access centarlized, shared resources.
-Medium to Large Network such as those used by corporation and schools, can have many locations with hundreds or thousand of interconnected computers.
 -World Wide Network, The internet is a network of network that connect hundreads of milions computers world-wide.


Web Client and Server : The Web Server runs web server software and client use their browser software, such as windows internet explorer, to access web pages on the server.
Email Client and Server : The Email Server runs email server software and client use their mail client software, such as Microsoft Outlook, to access email on the server.

• Wide Area Network (WAN) - A network infrastructure that provides access to other networks over a wide geographical area, which is typically owned and managed by a telecommunications service provider.

         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.

  Local Area Networks
  LANs are a network infrastructure that spans a small geographical area. Specific features of LANs include:

• 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.

  Wide Area Networks
  WANs are a network infrastructure that spans a wide geographical area. WANs are typically managed by service providers (SP) or Internet Service Providers (ISP).
Specific features of WANs include:

• 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.

  The Internet
  The Internet is a worldwide collection of interconnected networks (internetworks or internet for short). The figure shows one way to view the Internet as a collection of interconnected LANs and WANs. Some of the LAN examples are connected to each other through a WAN connection. WANs are then connected to each other. The red WAN connection lines represent all the varieties of ways we connect networks. WANs can connect through copper wires, fiber optic cables, and wireless transmissions (not shown).

  Intranets and Extranets
  There are two other terms which are similar to the term Internet:

• Intranet

• 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.
An organization may use an extranet to provide secure and safe access to individuals who work for a different organization, but require access to the organization’s data. Examples of extranets include:

• A company that is providing access to outside suppliers and contractors.

• A hospital that is providing a booking system to doctors so they can make appointments for their patients.

• A local office of education that is providing budget and personnel information to the schools in its district.

  Internet Access Technologies
  There are many different ways to connect users and organizations to the Internet.
Home users, teleworkers (remote workers), and small offices typically require a connection to an Internet Service Provider (ISP) to access the Internet. Connection options vary greatly between ISP and geographical location. However, popular choices include broadband cable, broadband digital subscriber line (DSL), wireless WANs, and mobile services.

• 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.

• Satellite - The availability of satellite Internet access is a real benefit in those areas that would otherwise have no Internet connectivity at all. Satellite dishes require a clear line of sight to the satellite.

• Dial-up Telephone - An inexpensive option that uses any phone line and a modem. 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. 

  Businesses Internet Connections

• Dedicated Leased Line - Leased lines are actually reserved circuits within the service provider’s network that connect geographically separated offices for private voice and/or data networking. The circuits are typically rented at a monthly or yearly rate. They can be expensive.

• Ethernet WAN - Ethernet WANs extend LAN access technology into the WAN. Ethernet is a LAN technology you will learn about in a later chapter. The benefits of Ethernet are now being extended into the WAN.

• DSL - Business DSL is available in various formats. A popular choice is Symmetric Digital Subscriber Lines (SDSL) which is similar to the consumer version of DSL, but provides uploads and downloads at the same speeds.

• Satellite - Similar to small office and home office users, satellite service can provide a connection when a wired solution is not available.

  Quality of Service
   Quality of Service (QoS) is also an ever increasing requirement of networks today. New applications available to users over internetworks, such as voice and live video transmissions, create higher expectations for the quality of the delivered services. Have you ever tried to watch a video with constant breaks and pauses? As data, voice, and video content continue to converge onto the same network, QoS becomes a primary mechanism for managing congestion and ensuring reliable delivery of content to all users.
  Congestion occurs when the demand for bandwidth exceeds the amount available. Network bandwidth is measured in the number of bits that can be transmitted in a single second, or bits per second (bps). When simultaneous communications are attempted across the network, the demand for network bandwidth can exceed its availability, creating network congestion.
   When the volume of traffic is greater than what can be transported across the network, devices queue, or hold, the packets in memory until resources become available to transmit them. In the figure, one user is requesting a web page and another is on a phone call. With a QoS policy in place, the router can manage the flow of data and voice traffic, giving priority to voice communications if the network experiences congestion.


  Security
  The network infrastructure, services, and the data contained on network-attached devices are crucial personal and business assets. There are two types of network security concerns that must be addressed: network infrastructure security and information security.
Securing a network infrastructure includes the physical securing of devices that provide network connectivity, and preventing unauthorized access to the management software that resides on them, as shown in Figure 1.
Information security refers to protecting the information contained within the packets being transmitted over the network and the information stored on network attached devices. In order to achieve the goals of network security, there are three primary requirements, as shown in Figure 2:

• Confidentiality - Data confidentiality means that only the intended and authorized recipients can access and read data.

• Integrity - Data integrity means having the assurance that the information has not been altered in transmission, from origin to destination.

• Availability - Data availability means having the assurance of timely and reliable access to data services for authorized users.

  New Trends
  As new technologies and end user devices come to market, businesses and consumers must continue to adjust to this ever-changing environment. The role of the network is transforming to enable the connections between people, devices, and information. There are several new networking trends that will effect organizations and consumers. Some of the top trends include:

• Bring Your Own Device (BYOD)

• Online collaboration

• Video communications

  Cloud computing
  Bring Your Own Device
The concept of any device, to any content, in any manner, is a major global trend that requires significant changes to the way devices are used. This trend is known as Bring Your Own Device (BYOD).
  BYOD is about end users having the freedom to use personal tools to access information and communicate across a business or campus network. With the growth of consumer devices, and the related drop in cost, employees and students can be expected to have some of the most advanced computing and networking tools for personal use. These personal tools include laptops, netbooks, tablets, smartphones, and e-readers. These can be devices purchased by the company or school, purchased by the individual, or both.
BYOD means any device, with any ownership, used anywhere. For example, in the past, a student who needed to access the campus network or the Internet had to use one of the school’s computers. These devices were typically limited and seen as tools only for work done in the classroom or in the library. Extended connectivity through mobile and remote access to the campus network gives students tremendous flexibility and more learning opportunities for the student.

  Online Collaboration
  Individuals want to connect to the network, not only for access to data applications, but also to collaborate with one another. Collaboration is defined as “the act of working with another or others on a joint project.” Collaboration tools, like Cisco WebEx shown in the figure, give employees, students, teachers, customers, and partners a way to instantly connect, interact, and achieve their objectives.

  Video Communication
  Another trend in networking that is critical to the communication and collaboration effort is video. Video is being used for communications, collaboration, and entertainment. Video calls can be made to and from anywhere with an Internet connection.

  Cloud Computing
  Cloud computing is another global trend changing the way we access and store data. Cloud computing allows us to store personal files, even backup our entire hard disk drive on servers over the Internet. Applications such as word processing and photo editing can be accessed using the Cloud.

  Wireless Broadband
Wireless Internet Service Provider (WISP)
Wireless Internet Service Provider (WISP) is an ISP that connects subscribers to a designated access point or hot spot using similar wireless technologies found in home wireless local area networks (WLANs). WISPs are more commonly found in rural environments where DSL or cable services are not available.

Wireless Broadband Service
Another wireless solution for the home and small businesses is wireless broadband, as shown in the figure. This uses the same cellular technology used to access the Internet with a smart phone or tablet. An antenna is installed outside the house providing either wireless or wired connectivity for devices in the home. In many areas, home wireless broadband is competing directly with DSL and cable services.

  Security Threats
  Network security is an integral part of computer networking, regardless of whether the network is limited to a home environment with a single connection to the Internet or as large as a corporation with thousands of users. The network security that is implemented must take into account the environment, as well as the tools and requirements of the network. It must be able to secure data while still allowing for the quality of service that is expected of the network.
Securing a network involves protocols, technologies, devices, tools, and techniques to secure data and mitigate threats. Threat vectors may be external or internal. Many external network security threats today are spread over the Internet.
The most common external threats to networks include:

• Viruses, worms, and Trojan horses - malicious software and arbitrary code running on a user device

• Spyware and adware - software installed on a user device that secretly collects information about the user

• Zero-day attacks, also called zero-hour attacks - an attack that occurs on the first day that a vulnerability becomes known

• Hacker attacks - an attack by a knowledgeable person to user devices or network resources

• Denial of service attacks - attacks designed to slow or crash applications and processes on a network device

• Data interception and theft - an attack to capture private information from an organization’s network

• Identity theft - an attack to steal the login credentials of a user in order to access private data