Chapter Seven Wireless Technologies

                             Types of Wireless Networks and Their Boundaries
                               Their are three major categories of wireless network.


WPAN--Is the smallest wireless network used to connect various peripheral devices. Mice, keyboards, and PDAs use WPAN. All these devices are dedicated to a single host and usually use IR or Bluetooth technology. IR is electromagnetic waves with a frequency range above that of microwaves, but below that of the visible spectrum. Bluetooth is wireless industy standard that uses an unlicensed radio frequency for short-range communication enabling portable devices to
                                                      communicate over short distances.

WLAN-- Is typically used to extend the boundaries of the local wired network. Use RF technology and conform to the various IEEE 802.11 standards. Allow many users to connect to a wired network through a device known as an access point. Access point acts as a connection between the wireless network and the Ethernet wired network.RF is radio frequency which means electromagnetic waves generated by AC and sent to an antenna within the electromagnetic spectrum.  Their are four types of IEEE 802.11 standards: 802.11a, 802.11b, 802.11g and 802.11 n.



WWAN-- Is coverage over extremely large areas. An example of WWAN is the cell phone network. WWAN is often regulated by government agencies that use technologies like, code division multiple access and global system for mobile communication. CDMA is a communication channel access method that uses spread-spectrum technology and a special coding scheme. GMS is an international standard for cell phones.

Despite these distinct categories, placing boundary limitations on a wireless network is difficult. Because unlike a wired network,  a wireless network does not have precisely defined boundaries. The range of wireless transmissions can vary due to many factors. The range of wireless networks can be affected by natural and man-made interference, fluctuation in environmental conditions, as well as the composition and placement of obstacles within the wireless coverage area.

Chapter Six Networking Services

                                           Roles Of Protocols In Client/Server Communication


Uses specific protocols and standards in the process of exchanging information to ensure that the message are received and understood. Four protocols are application, transport, internetwork, and network access layer.

Application Protocol--Is hypertext transfer protocol. HTTP governs the way that a web server and a web client interacts. HTTP defines the format of the requests and responses exchanged between the client and server.





Transport Protocol--Is transmission control protocol. TCP manages the individual conversations between web servers and web clients. TCP formats the HTTP messages into segments and provides flow control and acknowledgement of packets exchanged between hosts.





Internetwork Protocol--Is internet protocol. IP is responsible for taking the formatted segments form TCP, assigning the logical addressing, and encapsulating them into packets for routing to the destination host.





   HTTP, TCP, and IP are the KEY protocols required to download a web page for an internet server.

Network Access Protocols-- Is data link management and physical network transmissions. Data link management protocols take the packet from IP and encapsulate them into the appropriate frame format for the local network. These protocols assign the physical addresses to the frames and prepare them to be transmitted over the network.

Chapter Five Networking Addressing

                                          Unicast, Broadcast, Multicast Addresses

Unicast Address is one-to-one. Is the most common type on the IP network. For a unicast packet to be sent and received, a destination IP address must be in the IP packet header. A corresponding destination MAC address must also be present in teh Ethernet fram header. The IP address and MAC address combine to deliver data to one specific destination host. If the destination IP address is on another network, the initial destination MAC address used in the fame is that of the router interface on the same network as the source IP.

Multicast Address is one-to-many. Allows a source device to sen a packet to a group of devices. Devices that belong to a multicast group are assigned a multicast group IP address. The range of multicast addresses are 224.0.0.0 to 239.255.255.255. Multicast Addresses can only be used as  the destination of a packet because they represent a group of addresses (also called a host group). Needs a special corresponding multicast MAC address that begains with 01-00-5E in hexadecimal.

Broadcast Address is one-to-all. The packet contains a destination IP address of all 1s in the host portion. That means that all hosts on that local network will receive and look at the packet. Many network protocols, such as ARP and DHCP, use broadcasts. A broadcast IP address for a network needs a corresponding broadcast MAC address in the Ethernet frame. On Ethernet networks, the broadcast MAC address is 48 ones displayed as hexadecimal FF-FF-FF-FF-FF-FF.

  

Chapter Four

                                     Connecting to the Internet Through an ISP

Different types of cables exist to interconnect the various devices in a network operating system (NOC) or local network.
There are two general categories of physical cable - Metal and Fiber-optic.
Metal cables - made of copper and have electrical impulses applied to them to convey information. Twisted-pair and coaxial cable is apart of metal cables.
Fiber-optic - made of glass or plastic and uses flashes of ligt to convey information.

Twisted Pair - is most commonly used cable in networking. The wires are grouped in pairs and twisted together. A common type of Unshielded Twisted-Pair cable used with Ethernet network is Category 5 (CAT5). It is a cable containing four twisted pairs of wires, for a total of eight wires.

Coaxial Cable - is usually constructed of either copper or aluminum and is used by cable television companies to provide service. Most coaxial cable has a single copper core surrounded by layers of shielding and insulation. It is used as a high-frequency transmission line to carry a high-frequency or broadband signals.

Fiber-Optic - are made of glass or plastic, as small as the human hair. Fiber is used in backbone networks, large enterprise environments, and large data centers. It has many other uses other than communication, such as medical imaging, medical treatment, and mechanical engineering inspection.