ITP 140 Mobile Applications Technologies Networks
A First Look Under the Hood 2
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Communication Channels Mediums for transporting data from one system to another Physical Twisted Pair (CAT-3, CAT-5/6) Coaxial (Cable) Fiber-Optic Wireless Infrared Radio (802.11 a/b/g/n, Bluetooth) Microwave Satellite 4
Wireless Connections Technology WiFi or 802.11 2.4GHz radio band industrial, scientific, & medical (ISM) band Different standards for 802.11 802.11a 5GHz spectrum at 54Mbps 802.11b 2.4GHz spectrum at 11Mbps 802.11g 2.4GHz spectrum at 54Mbps 802.11n 2.4GHz or 5 GHz at 540Mbps Access point consists of a radio transmitter/receiver & interface to a wired network 5
Bluetooth Wireless technology to allow computers, telephone & other devices to communicate with one another Piconet connection of 2 or more Bluetooth devices Microchip that send/receive radio signals 2.4GHz radio band industrial, scientific, & medical (ISM) band Software in chip called a link controller Identifies other Bluetooth devices Sends/receives data Range Class 2 radios up to 10 meters or 30 feet 6
Network Hardware Computers need specific types of hardware to connect to other systems Modem Old piece of technology for communicating through telephone lines Convert digital data (0s and 1s) to analog It makes a funny sound J MOdulating/DEModulating Max speeds are ~56 Kbps (kilobits per second) Network Interface Card (NIC) Uses ethernet and CAT5 cables for communication Slowest speeds are ~10 Mbps (megabits per second) Today s speeds are ~100 or ~1000 Mbps 7
Bandwidth Measures the capacity of the communications channel How fast the data can travel 3 types Low bandwidth Voice data, telephones ~56 kbps (kilobits per second) Medium band not normally used Broadband DSL, cable, leased lines > 1.5 Mbps 8
Connection Services Dial-up Who uses this anymore??? Through normal telephone lines Slow Max speeds ~40-50 kbps Digital Subscriber Line (DSL) Delivered over Plain Old Telephone Service (POTS) Separates data from voice in a telephone line 3 channels receiving data, sending data & voice Max speeds ~20 Mbps Cable Modem Coaxial cable carries TV & computer signals simultaneously Node single local area network ~ 500 homes # of people using the Internet in your node affects speed Max speeds ~50 Mbps 9
Fiber Optic Connection Services Brings a fiber optic line to the business or residence Max speeds ~300 Mbps Leased Line T1, T3 From 1.5 to 400 Mbps Very expensive 10
Network Hardware Local area network (LAN) is the smallest kind of network 5 of the most important pieces of hardware Hubs link groups of computers together Bridges link local area networks (LANs) with one another & keep local data within own network Gateways similar to bridges & also translate data from one type of network to another Ethernet Ethernet Hub Bridge 11
CISCOSYSTEMS CISCOSYSTEMS CISCOSYSTEMS Network Hardware Repeaters amplify the data at intervals so the signal that s sending the data doesn t weaken Routers manage Internet traffic by examining packets to determine their destination & sending them to another router that is closer to the final destination Ethernet Routers Ethernet Tokenring 12
Routers Traffic cops of the Internet Open IP packet, read destination address, calculate best route & send packet IP packet carries a segment holding the maximum hops (routers or gateways on any given path) it can travel Have 2 or more physical ports: receiving (input) ports sending (output) ports 13
Network Protocols Language for computer communication Standard for the Internet is called TCP/IP (Transmission Control Protocol/Internet Protocol) Identifies the receiver and the sender Formats the data in a particular way to be understandable by both the sender and the receiver 14
Internet Protocol (IP) IP implements the network layer Provides mechanism for routing packets not only within a LAN, but also anywhere across the globe Foundation for this facility is a globally-unique computer identifier known as an IP address IP addresses are assigned in a carefully- and centrally-controlled manner IP addresses can be assigned statically or dynamically (DHCP) 15
IP Addresses (IPv4) IPv4 (version 4) allows 32 bits for an IP address Used since 1981 Identifies both the network and the host (computer) Consists of 4 8-bit fields 8 bits has 256 possibilities (0-255) Format: <0-255>.<0-255>.<0-255>.<0-255> Total IP addresses = 2 32 4.3 Billion 16
IP Addresses (IPv6) IPv6 was developed by the Internet Engineering Task Force (IETF) to deal with the long-anticipated problem of IPv4 address exhaustion IPv6 (version 6) provides 128-bit addresses Total IP addresses = 2 128 = 340,282,366,920,938,463,463,374,607,431,768,211,456 IPv6 addresses are represented as eight groups of four hexadecimal digits with the groups being separated by colons 17
Transmission Control Protocol (TCP) IP allows packets to be sent to a computer anywhere on the globe However, many applications can benefit from the illusion of a dedicated connection, over which data may be sent reliably to the remote host TCP (Transmission Control Protocol) provides this illusion Application can establish a connection with the remote host, write bytes to the connection, and the remote machine will receive those bytes in the proper order 18
Reliable vs. Unreliable Transports Reliable transport TCP is known as a reliable transport Connection-oriented Bytes are received in the same order they are sent No data is lost Packets are error-checked and re-sent if necessary Unreliable transport Connectionless Packets are received in an arbitrary order Some packets may be lost No error-checking or automatic re-send Example: User Datagram Protocol (UDP) 19
User Datagram Protocol (UDP) UDP (User Datagram Protocol) is really just a thin layer on top of IP itself IP is also an unreliable protocol UDP adds only application multiplexing / demultiplexing and check-summing to IP Useful for applications where delivery speed is more important than accuracy or the order packets are received Streaming media, multiplayer games, VoIP 20
Network Terminology Node any network device (computer, printer, server, etc.) Client typically a node that heavily utilizes the services of another node Server typically a node that shares its resources with another node Hub central location for connecting nodes 21
Network Sizes Local Area Network (LAN) Small network for sharing resources Typically confined to a room or building WLAN wireless LAN Metropolitan Area Network (MAN) Many LANs connected together Wide Area Network (WAN) Many MANs connected together The only difference between the three (and any other types of area networks) is geographic boundary Completely arbitrary 22
Warriors of the Net http://www.warriorsofthe.net/movie.html The movie is 12 minutes long It is about how IP packets journey through the Internet past routers, firewalls, and transatlantic cables 23