Module 6 Networking

Why Network? Despite the costs of implementation and maintenance, networks actually save organizations money by allowing them to: Consolidate (centralize) data storage Share peripheral devices like printers Increase internal and external communications Increase productivity and collaboration

Networking A network is a group of computers that can share information through their interconnections. 1.Computers (nodes or hosts). 2.Transmission media provides a path for electrical signals between devices. 3.Network interfaces are devices that send and receive electrical signals. 4.Protocols are rules or standards that describe how hosts communicate and exchange data.

Networking Network Type Description Peer-to-peer In peer-to-peer networking (also called workgroups), each computer controls access to its own resources. Security controls on each computer identify who can have access to the computer's resources. Client/server In client/server networking, shared resources reside on special computers called servers. Other computers, called clients connect to the server to access resources. Security controls on the server identify which clients can have resource access. Windows computers use the concept of a domain for client/server networking. The domain identifies a group of computers with the same security and administrative boundaries. Active Directory is a service that provides a centralized database of resources within a domain.

Protocols A protocol is a rule that identifies some aspect of how computers communicate on a network. For two computers to communicate, they must be using the same protocols. Protocols are grouped into protocol suites, or sets of related protocols. Virtually all operating systems today provide native (built-in) support for TCP/IP. Most older versions of some operating systems used a different protocol as the default protocol suite. For example, older NetWare servers used IPX/SPX, while Mac OS systems used AppleTalk. – Older operating systems without native TCP/IP support enabled TCP/IP communications by either installing the protocol stack or through a process known as encapsulation or tunneling. With this process, non- TCP/IP packets are re-packaged as TCP/IP packets at the sending device. The receiving device strips off the TCP/IP headers to reveal the original packets.

Protocols ProtocolDescription HTTP HyperText Transfer Protocol is used by Web browsers and Web servers to exchange files (Web pages) through the World Wide Web and intranets. HTTP can be described as an information requesting and responding protocol. HTML HyperText Markup Language is a data format that is used to create hypertext documents that can be viewed from multiple platforms. HTML has become a common language used for programming information in a format that is readable by web browsers. DNS Domain Name System is a system that is distributed throughout the Internet to provide Host name/IP address resolution. For example, the name would be identified with a specific IP address.

Protocols ProtocolDescription Telnet Remote Terminal Emulation allows an attached computer to act as a dumb terminal, with data processing taking place on the TCP/IP host computer. SSH Secure Shell allows for secure interactive control of remote systems. SSH is a secure and acceptable alternative to Telnet. SSL Secure Sockets Layer secures messages being transmitted on the Internet. It uses RSA for authentication and encryption. Web browsers use SSL (Secure Sockets Layer) to ensure safe Web transactions. URLs that begin with trigger your Web browser to use SSL. HTTPS HyperText Transfer Protocol over Secure Socket Layer or HTTP over SSL. HTTPS is a secure form of HTTP that uses SSL as a sublayer for security.

Addressing Network devices use addresses to identify other devices. These addresses are used to send and receive packets of electronic data over the network. The addresses used depend on the physical make-up of the network as well as the protocol suite being used. Each network device is identified using a: physical address or MAC (like a serial number) logical network address (subnet) identifies a network segment. – All devices on the same network segment share the same logical network address. logical host address (name) identifies a specific host on the network. – Each device must have a unique logical host address.

Physical Addressing (MAC) Each network device is identified using a physical address. Ethernet networks use a MAC Address (physical device address) The MAC address is a unique hexadecimal identifier burned into the ROM (physically assigned address) of every network interface. When you change the network card, the host will have a new physical device address. When you move a device to another network, the physical address remains the same (as long as the network card has not been changed). The MAC address is guaranteed unique through design. – The first half (first 6 digits) of the MAC address is assigned to each manufacturer. – The manufacturer determines the rest of the address, assigning a unique value which identifies the host address.

Logical Network Address With TCP/IP, the logical network and logical host addresses are combined into a single address called the IP address. An IP address is a 32-bit binary number represented as four octets (four 8-bit numbers). Each octet is separated by a period. A subnet mask is used to differentiate the network and host addresses. Each IP address has a default class that includes a default subnet mask value. The class defines the default network address portion of the IP address. For example, an IP address of with a default mask of The network address is and the host address is 11. Instead of using the default subnet mask, you can use custom subnet masks to define different network addresses. This process is called subnetting. Note: The address range from to is reserved for broadcast messages to the current network. The address range from to is reserved for loopback addresses to the local host.

Logical Host Address Humans remember names (or hostnames) much easier than numbers (especially binary numbers). A hostname is a label (name) assigned to a device connected to a computer network. Hostnames are used to identify the device in a Domain Name System (DNS) such as the World Wide Web. Hostnames that include DNS domains are often stored in the Domain Name System together with the IP addresses of the host they represent for the purpose of mapping the hostname to an address, or the reverse process.

Networking Devices ComponentDescription Media The networking medium is the pathway for signals to pass between two devices.  Copper cables use electrical signals.  Fiber optic cables use light pulses.  Wireless networks use radio waves with the air being the transmission medium. Network adapter A network adapter creates the signals that are sent along the networking medium.  The term network interface card (NIC) typically describes an adapter that uses a cable medium (such as copper or fiber optic cables).  A modem (modulator/de-modulator) converts binary data to an analog signal.  A wireless network adapter sends radio waves.

Networking Devices ComponentDescription Hub A hub provides a central connection for multiple media segments on the same subnet. The hub repeats a signal received on one port out all other ports. Hubs operate in half-duplex mode because the path between devices is shared and can only send when no other devices are sending data. Bridge A bridge connects two segments within the same subnet that use different media types. For example, use a bridge to connect wireless clients to wired clients on the same network.

Networking Devices ComponentDescription Switch A switch provides a central connection for multiple media segments on the same subnet. The switch receives a signal on one port, and forwards that signal only to the port where the destination device is connected. Switches use the MAC address to send frames to the destination device. Switches can operate in full duplex mode where a device uses a different channel for sending and receiving, and where the transmission paths are dedicated to only the communicating devices. When possible, use switches instead of hubs.

Networking Devices ComponentDescription Router A router connects two network segments that have a different subnet addresses. A router has multiple network connections, with each connection being on a different subnet. Routers use the IP address within a packet to move packets between networks. Routers maintain a list of known networks and the next router in the path to reach the destination network.

Networking Standards MethodDescription Ethernet Ethernet is the most common local area networking standard for wired networks. Ethernet can use copper and fiber optic cables. Ethernet uses network interface cards, hubs, switches, and routers to connect devices. Wireless Wireless networking uses radio waves for sending network data within a local area network. An access point with an integrated router allows wireless clients to communicate with hosts on different networks (such as the Internet). Dialup A dialup connection uses a modem connected to the phone line to communicate with another host through a wide area connection. Dialup connections are available anywhere a dialup telephone line exists. Data transfer rate 56 Kbps. Dialup connections cannot be used for both voice (phone calls) and data at the same time.

Networking Standards MethodDescription (DSL) Digital Subscriber Line provides broadband digital data transmission over existing telephone lines. A DSL router (sometimes called a DSL modem) connects the computer to the telephone line. DSL is not available to every location; the end location must be within a fixed distance of telephone switching equipment. Cable Cable networking uses a cable TV connection to create a wide area connection to the Internet. A cable modem (router) connects the computer to the cable network for sending networking signals. Cellular Cellular networking uses a digital mobile phone for Internet access. Mobile phones with digital data plans use cellular calls to connect to the Internet. You can install a cellular adapter in a notebook computer to provide cellular access. Satellite Satellite networking uses radio signals sent and received from a satellite. Requires direct line of sight (dish placement is crucial). Is subject to mild atmospheric and weather conditions (fog or slight wind can disrupt service). Provides nearly 100% global coverage.

Coaxial Cable Coaxial cable is an older technology that is usually implemented with a bus topology. Advantages Highly resistant to Electromagnetic Interference (EMI) Highly resistant to physical damage Disadvantages Expensive Inflexible construction (difficult to install) Unsupported by newer networking standards

Twisted Pair cable Twisted pair cables support a wide variety of fast, modern network standards Advantages Inexpensive compared to other media types Easy to install and manage Very common (media and tools are easy to obtain) Disadvantages Most susceptible to EMI of all the media types Cables are more easily damaged than other types

Fiber Optic Cable With fiber optic cabling the plastic or glass core carries the signal. Advantages Totally immune to Electromagnetic Interference (EMI) Highly resistant to eavesdropping Supports extremely high data transmission rates Allows greater cable distances without a repeater Disadvantages Very expensive Difficult to work with and requires special training