I ntroduction

1. Introduction Advance Mobile Computing

2. Wired Networks Wired networks, also called Ethernet networks, are the most common type of local area network (LAN) technology. A wired network is simply a collection of two or more computers, printers, and other devices linked by Ethernet cables. Ethernet is the fastest wired network protocol, with connection speeds of 10 megabits per second (Mbps) to 100 Mbps or higher.

3. Ethernet Cable • Ethernet cable is a popular type of network cable used for high-speed networking between two devices. Ethernet cables have been evolving since the beginning of the Ethernet standard in 1985. Many different categories of Ethernet cable have been developed, and each category has different specifications as far as shielding from electromagnetic interference, data transmission speed, and the possible bandwidth frequency range required to achieve that speed. It is understandable that some confusion can arise when looking at all the available options for Ethernet cabling.

4. Types of Ethernet Cable There are also certain types of cables recognized as common industry standards. Category 3 It is also known as Cat 3 or station wire, is one of the oldest forms of Ethernet cable still in use today. It is an unshielded twisted pair (UTP) cable that is capable of carrying 10 megabits per second (Mbps) of data or voice transmissions. Its maximum possible bandwidth is 16 MHz. Cat 3 cable reached the peak of its popularity in the early 1990s.

5. Category 5 • Category 5 ( Cat 5) Ethernet cable is the successor to the earlier Category 3. Like Cat 3, it is a UTP cable, but it is able to carry data at a higher transfer rate. Cat 5 cables introduced the 10/100Mbps speed to the Ethernet, which means that the cables can support either 10 Mbps or 100 Mbps speeds. A 100 Mbps speed is also known as Fast Ethernet, and Cat 5 cables were the first Fast Ethernet-capable cables to be introduced. They also can be used for telephone signals and video, in addition to Ethernet data.

6. Category 5e • The Category 5 e standard is an enhanced version of Cat 5 cable, which is optimized to reduce crosstalk, or the unwanted transmission of signals between data channels. This category works for 10/100 Mbps and 1000 Mbps (Gigabit) Ethernet, and it has become the most widely used category of Ethernet cable available on the market. While Cat 5 is common in existing installations, Cat 5e has completely replaced it in new installations. While both Cat 5 and Cat 5e cables contain four twisted pairs of wires, Cat 5 only utilizes two of these pairs for Fast Ethernet, while Cat 5e uses all four, enabling Gigabit Ethernet speeds. Bandwidth is also increased with Cat 5e cables, which can support a maximum bandwidth of 100 MHz. Cat 5e cables are backward compatible with Cat 5 cables, and can be used in any modern network installation.

7. Category 6 • One of the major differences between Category 5e and the newer Category 6 is in transmission performance. While Cat 5e cables can handle Gigabit Ethernet speeds, Cat 6 cables are certified to handle Gigabit Ethernet with a bandwidth of up to 250 MHz. Cat 6 cables have several improvements, including better insulation and thinner wires, that provide a higher signal-to-noise ratio, and are better suited for environments in which there may be higher electromagnetic interference. Some Cat 6 cables are available in shielded twisted pair (STP) forms or UTP forms.

8. Category 6a • Category 6 a cable or augmented Category 6 cable, improves upon the basic Cat 6 cable by allowing 10,000 Mbps data transmission rates and effectively doubling the maximum bandwidth to 500 MHz. Category 6a cables are usually available in STP form, and, as a result, must have specialized connectors that ground the cable.

9. Category 7 • Category 7 cable, also known as Class F, is a fully shielded cable that supports speeds of up to 10 Gbps (10,000 Mbps) and bandwidths of up to 600 Mhz. Cat 7 cables consist of a screened, shielded twisted pair (SSTP) of wires, and the layers of insulation and shielding contained within them are even more extensive than that of Cat 6 cables.

10. Comparisons of Cables

11. Topologies • There are three basic network topologies that are most commonly used today. • The star network, a general more simplistic type of topology, has one central hub that connects to three or more computers and the ability to network printers. This type can be used for small businesses and even home networks. The star network is very useful for applications where some processing must be centralized and some must be performed locally. The major disadvantage is the star network is its vulnerability. All data must pass through one central host computer and if that host fails the entire network will fail.

12. Bus Topologies • Bus network has no central computer and all computers are linked on a single circuit. This type broadcasts signals in all directions and it uses special software to identify which computer gets what signal. One disadvantage with this type of network is that only one signal can be sent at one time, if two signals are sent at the same time they will collide and the signal will fail to reach its destination. One advantage is that there is no central computer so if one computer goes down others will not be affected and will be able to send messages to one another.

13. Ring Topologies • The ring network Similar to the bus network, the ring network does not rely on a central host computer either. Each computer in the network can communicate directly with any other computer, and each processes its own applications independently. A ring network forms a closed loop and data is sent in one direction only and if a computer in the network fails the data is still able to be transmitted.

14. Wireless Networks • A wireless network, which uses high-frequency radio waves rather than wires to communicate between nodes, is another option for home or business networking. Individuals and organizations can use this option to expand their existing wired network or to go completely wireless. Wireless allows for devices to be shared without networking cable which increases mobility but decreases range. • There are two main types of wireless networking; peer to peer or ad-hoc and infrastructure.

15. Peer-to-Peer wireless network • An ad-hoc, or peer-to-peer wireless network consists of a number of computers each equipped with a wireless networking interface card. Each computer can communicate directly with all of the other wireless enabled computers. They can share files and printers this way, but may not be able to access wired LAN resources, unless one of the computers acts as a bridge to the wired LAN using special software.

16. Infrastructure Based • An infrastructure wireless network consists of an access point or a base station. In this type of network the access point acts like a hub, providing connectivity for the wireless computers. It can connect or bridge the wireless LAN to a wired LAN, allowing wireless computer access to LAN resources, such as file servers or existing Internet Connectivity. • There are two types of access points:

17. Dedicated hardware access points (HAP) Dedicated hardware access points (HAP) such as Lucent's WaveLAN, Apple's Airport Base Station or WebGear'sAviatorPRO. Hardware access points offer comprehensive support of most wireless features.

18. Software Access Points Based • Software Access Points which run on a computer equipped with a wireless network interface card as used in an ad-hoc or peer-to-peer wireless network. The Vicomsoft InterGate suites are software routers that can be used as a basic Software Access Point, and include features not commonly found in hardware solutions, such as Direct PPPoE support and extensive configuration flexibility, but may not offer the full range of wireless features defined in the 802.11 standard.

19. Transmissions standards for wireless • There are four basic types of transmissions standards for wireless networking. These types are produced by the Institute of Electrical and Electronic Engineers (IEEE). These standards define all aspects of radio frequency wireless networking. They have established four transmission standards; 802.11, 802.11a, 802.11b, 802.11g. • The basic differences between these four types are connection speed and radio frequency. 802.11 and 802.11b are the slowest at 1 or 2 Mbps and 5.5 and 11Mbps respectively. They both operate off of the 2.4 GHz radio frequency. 802.11a operates off of a 5 GHz frequency and can transmit up to 54 Mbps and the 802.11g operates off of the 2.4 GHz frequency and can transmit up to 54 Mbps. Actual transmission speeds vary depending on such factors as the number and size of the physical barriers within the network and any interference in the radio transmissions.

20. Wired vs. Wireless Networking The biggest difference between these two types of networks is one uses network cables and one uses radio frequencies. A wired network allows for a faster and more secure connection and can only be used for distances shorter than 2,000 feet. A wireless network is a lot less secure and transmission speeds can suffer from outside interference. Although wireless networking is a lot more mobile than wired networking the range of the network is usually 150-300 indoors and up to 1000 feet outdoors.

21. Questions. • What is wireless networking? • What is a wireless network made up of? • What is the range of a wireless network? • How many wireless networked computers can use a single access point? • Can I have more than one access point?

22. Networks

23. 60 Why are networks so useful? • They facilitate communications • They allow for sharing of resources • Both of the above

24. Network • Uses of communications technologies • Internet • Global Positioning System (GPS) • Short Message Service (SMS) • Network • Interconnected group of computers and devices connected via communications devices and media • Facilitates sharing of resources and supports communications • Requires • Sending & receiving devices • Communications devices • Communications channel or path • Network OS (NOS)

25. Networks – Communications Devices • Communications Device • Hardware capable of sending/receiving data • Convert signals so that they are suitable for the communications channel • May convert between analog and digital • Common types • Dial-up modems • ISDN and DSL modems • Cable modems • Network interface cards • Wireless access points • Routers

26. Networks – Communications Devices • Dial-up Modem • Modulate/demodulate • External modem • Connects to serial or RS-232 port • Internal modem • Card inserted to expansion slot/PC Slot • ISDN and DSL Modems • Do not modulate/demodulate • External • Sends and receives data over a digital telephone line • ISDN line • DSL line

27. Networks – Communications Devices • Cable modem • Cable television network • Faster than dial-up access or ISDN line • Splitter runs separate cables to TV’s and cable modem • External • USB port or Ethernet NIC via a cable • Network Interface Card (NIC) • Coordinates transmission/receipt of data to/from the device • Card installed in an expansion slot of a PC, printer, PC slot • Wireless transmission includes antenna • Works with a particular network technology • Ethernet or token ring

28. Networks – Communications Devices • Hub • Provides a central point of connectivity for cables in a network • May include a router • Router • Connects multiple computers and routers together • Transmits packets to correct destination • May include built-in firewall • Wireless access point • Allows computers and devices to communicate wirelessly • Allows data transfer to a wired network

29. 45 Communications devices include ______. • routers • hubs • modems • NICs • All of the above

30. Networks – Communications Channels • Channel • Communications path between two devices • Transmission rate • Speed at which data flows through the channel • Bandwidth of the channel • Bits per second (bps), Hertz (cycles per second) • Transmission media • Materials or techniques capable of carrying one or more signals • Baseband media – carry one signal at a time • Broadband media – carry multiple signals concurrently • Physical transmission media • Twisted pair, Coaxial, Fiber Optic • Wireless transmission media • Infrared, Radio Frequency, Infrared, Microwave

31. Networks – Physical Transmission Media • Twisted-pair cable • Used for network cabling and telephone systems • One or more twisted-pair wires bundled together • Each pair has two insulated copper wires twisted together • Coaxial cable (coax) • Used for network cabling and cable TV • Single copper wire surrounded by 3 layers • Insulating material • Woven/braided metal • Plastic outer coating

32. optical fiber core glass cladding Networks – Physical Transmission Media • Fiber optic cable • Light used to send signals • Thin glass or plastic strands • Surrounded by insulating glass cladding and a protective coating • Carries many signals • High speed • Less noise • Smaller size • Expensive, difficult to install and modify Protective coating

33. Networks – Physical Transmission Media

34. 45 All of the following except ______ are examples of physical media. • coaxial cable • twisted pair • microwave cable • fiber optic cable

35. Networks – Wireless Transmission Media • Microwaves • High-speed signal transmission • Signals sent between microwave stations • Fixed-point wireless • Requires line-of-sight • Communications Satellites • Satellite receives microwave signal and amplifies • Retransmits over wide-area, to a number of land-based stations • Radio Frequency • Antenna, transmitter, receiver • Bluetooth (2.45 GHz) • 802.11b & g (2.4 GHz) • Cellular Radio Waves • Cell phones, mobile devices • High frequency radio waves • 824 to 849 MHz • Infrared Signals • IR light waves with line-of-sight transmission

36. Networks – Wireless Transmission Media

37. 45 All of the following except ______ are examples of wireless media. • microwaves • satellites • radio frequency waves • fiber optic waves

38. Networks • Classified according to • Geography – Geographic Distribution • LAN • MAN • WAN • Architecture • Topology • Protocol/Communications Technology

39. Networks –Geographic Distribution • Local Area Network (LAN) • Connects computers in a limited geographical area • Each computer and device is a node • Metropolitan Area Network (MAN) • High-speed network that connects LANs in a metropolitan area • Managed by a consortium of users or a single network provider

40. Networks –Geographic Distribution • Wide Area Network (WAN) • Connects computers and devices in a large geographical area • Connected via many types of media • One large network or two or more interconnected LANs, MANs • Others • CAN • HAN • TAN

41. 45 A ______ is a network that encompasses a limited geographic area. • MAN • WAN • LAN • PAN

42. Networks • Classified according to • Geography • Architecture – Broad outline of the network • Peer-to-Peer • Client/Server • Topology • Protocol/Communications Technology

43. client client client printer server Network Architectures –Client/Server and Peer-to-Peer • Client/Server • Server controls resources • More storage space, power • Serves as a repository • Dedicated servers • Client relies on the server for access to resources • Peer-to-Peer • Share peripheral devices • Up to 10 “peer” computers • NOS & applications software, storage • Internet Peer-to-Peer (P2P) • Users connect directly to each other’s hard disk • Popular, inexpensive

44. Networks • Can be classified according to • Geography • Architecture • Topology – Physical arrangement of devices connected to the network • Bus • Ring • Star • Networks often use a combination of topologies • Protocol/Communications Technology

45. Network Topologies – Bus and Ring Networks • Bus Network • Single central cable connects computers and devices • Transmits in both directions • If a device fails, network continues to function • Reliable • Popular, inexpensive • Ring Network • Cable forms a closed ring • Transmits in only one direction • If one device fails, all those after the device cannot function • Spans larger distance than bus network • LANs and WANs

46. Network Topologies –Star and Other Networks • Star Network • Devices connect to a central computer • Hub • If one device fails, only that device is affected • Hub fails • Other Topologies • Mesh • Redundant interconnections between nodes • Tree • Star networks connected together via a bus

47. 45 With ______ topology, the devices on the network are connected together in a closed loop. • bus • ring • star • tree

48. Networks • Can be classified according to • Geography • Architecture • Topology • Protocol/Communications Technology– Standards that govern how data/instructions flow over the network • Ethernet • Token Ring • TCP/IP • WAP • Others

49. Networks –Network Communications Technologies • Communications Protocol • Set of rules and procedures for exchanging information among computers • Ethernet • Token ring • TCP/IP • WAP • Others

50. Network Communications Technologies –Ethernet • Ethernet • Widely used LAN standard • Developed by Xerox, DEC, Intel - 1976 • Fast Ethernet (100Base-T) - 100 Mbps • Gigabit Ethernet - 1000 Mbps • 10-Gigabit Ethernet – 10 Gbps • Bus or star topology • PCs in the network to contend for access • Collision