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Basic Computer Network. Bandwidth Data rate measured in bits (not bytes) per seconds Kbps (Kilobits per seconds) 125 chars/sec Mbps (Megabits per seconds)

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Presentation on theme: "Basic Computer Network. Bandwidth Data rate measured in bits (not bytes) per seconds Kbps (Kilobits per seconds) 125 chars/sec Mbps (Megabits per seconds)"— Presentation transcript:

1 Basic Computer Network

2 Bandwidth Data rate measured in bits (not bytes) per seconds Kbps (Kilobits per seconds) 125 chars/sec Mbps (Megabits per seconds) 1,250 chars/sec Gbps (Gigabits per seconds) 12,500 chars/sec

3 Connecting to the Internet Requirement A computer or PDA or cell phone An account with an ISP (Internet Service Provider) A modem (modulator/demodulator) for dial-up services or a NIC (Network Interface Card) for DSL/Cable services

4 Home Network (single machine) USB/Ethernet Cable DSL/Cable Modem Wall Jack

5 Home Network (multiple machines) USB/Ethernet Cable DSL/Cable Modem Wall Jack Hub/Switch/Router

6 Home Network (multiple machines) Ethernet Cable DSL/Cable Modem Wall Jack Hub/Switch/Router

7 Home Wireless Network Ethernet Cable DSL/Cable Modem Wall Jack Hub/Switch/Router

8 Connection Types LAN WLAN Dial-up Services Broadband Services WAN

9 LAN (Local Area Network) A network of computers that are in the same physical location, such as home or building Usually connected using Ethernet A standard on how computers communicate over a shared media (cable) Old: BNC connector for coaxial cable New: RJ45 for twisted pair cable

10 LAN (Local Area Network) Ethernet Standard 10BaseT 10Mbps (Mega bits per second) 100BaseT 100Mbps 1000BaseT 1000Mbps or 1Gbps

11 11 Ethernet First network to provide CSMA/CD Developed in 1976 by Xerox PARC (Palo Alto Research Center) in cooperation with DEC and Intel Is a fast and reliable network solution One of the most widely implemented LAN standards Can provide speeds in the range of 10Mbps- 10 Gbps Used with a bus or star topology

12 12 Types of Ethernet LANs 10Base-T Operates at 10 Mbps IEEE standard Fast Ethernet (100Base-T) Operates at 100 Mbps Gigabit Ethernet Operates at 1 Gbps Uses fiber optic cable 10 Gbps Ethernet Latest development of ethernet Uses fiber optic cable Developed to meet the increasing bandwidth needs of the LAN market Wireless Ethernet IEEE standard Operates at around 2.4 Gbps

13 13 LAN basics LANs can be either wired or wireless. Twisted pair, coax or fiber optic cable can be used in wired LANs Nodes in a LAN are linked together with a certain topology. These topologies include: Bus Ring Star Branching tree A node is defined to be any device connected to the network. This could be a computer, a printer, a router, etc. A Hub is a networking device that connects multiple segments of the network together A Network Interface Card (NIC) is the circuit board that has the networking logic implemented, and provides a plug for the cable into the computer (unless wireless). In most cases, this is an Ethernet card inserted in a slot of the computers motherboard The Network Operating System (NOS) is the software (typically part of the operating system kernel) that communicates with the NIC, and enables users to share files and hardware and communicate with other computers. Examples of NOS include: Windows XP, Windows NT, Sun Solaris, Linux, etc..

14 14 Star Topology Each node is connected to a device in the center of the network called a hub The hub simply passes the signal arriving from any node to the other nodes in the network The hub does not route the data Hub

15 15 Ring Topology The ring network is like a bus network, but the end of the network is connected to the first node Nodes in the network use tokens to communicate with each other Backbone

16 16 Access Control Methods Two primary access control methods exist for computers to communicate with each other over the network Token based access Carrier Sense Multiple Access with Collision Detection (CSMA/CD)

17 17 Token based access Used in bus and ring network topologies (token ring) Each computer in the network can only send its data if it has the token. This prevents collisions that occur when data is sent at the same time over the network The token is a special pattern of bits/bit in a frame that is directly detectible by each node in the network A computer may only transmit information if it is in possession of the token The message is sent to all other computers in the network

18 18 Operation of token ring As an example, suppose node # 1 wants to send information to node # 4 over the network Initially, an empty frame (network packet) circulates in the network

19 19 When node # 1 receives the empty frame, it inserts a token in the token bit part of the frame. This operation may just be an insertion of a 1 bit The node then inserts the message it wants to send as well as the address of the receiving node in the frame The frame is then successively received and examined by each node in the network. First it is sent to node #2. Node #2 examines the frame and compares the address in the frame to its own address. Since addresses do not match, it passes the frame onto node #3, which does the same thing When the frame is received by node #4, the address of the node matches the destination address within the frame. The node copies the message and changes the token bit in the frame to 0 The frame is then sent over to node #5. This node also compares addresses and sends it to node #6 which does the same procedure When node #1 receives the frame, it examines the token bit and recognizes that it has been changed to 0. Node #1 then concludes that the message has been received by the intended node: node #4. Node #1 then empties the frame and releases the empty frame back into the network for circulation

20 20 Lets see an animation of the token ringanimation

21 21 CSMA/CD Usually used in a bus topology Used in Ethernet LANs Unlike the token ring, all nodes can send whenever they have data to transmit When a node wants to transmit information, it first listens to the network. If no one is transmitting over the network, the node begins transmission It is however possible for two nodes to transmit simultaneously thinking that the network is clear When two nodes transmit at the same time, a collision occurs The first station to detect the collision sends a jam signal into the network Both nodes back off, wait for a random period of time and then re-transmit

22 WLAN (Wireless LAN) Wi-Fi (Wireless Fidelity) A wireless technology that connects computers without cables Access Point (AP) A device (base station) that connects wireless devices together Usually connected to a wired-network ESSID (Extended Service Set ID) A name for the AP, eg. mobilenet Hotspot The area covered by wireless access points

23 WLAN (Wireless LAN) Standard b - 11Mbps g - 54Mbps a - 54Mbps Security WEP (Wired Equivalen Privacy) WPA (Wi-Fi Protected Access) 2.4G 5G

24 Dial-up Services Modem Modulator/demodulator A device that converts analog signal to digital (modulation) and vice versa (demodulation) Speed 1200/2400/9600 bps 14.4/28.8/33.6 Kbps 56 Kbps

25 Dial-up Services ISDN Integrated Services Digital Network 2 data channel (56K each) 1 voice channel

26 Broadband Services xDSL (Digital Subscriber Line) A technology that provides digital data transmission over unused frequencies on traditional telephone lines For example, ADSL (Asymmetric DSL): DL > UL Speed Downlink 128Kbps - 4Mbps Uplink 64Kbps - 800Kbps Need a DSL modem Splitters are needed to separate the voice and data signal

27 Broadband Services Cable A technology that provides digital data transmission over cable TV infrastructure Speed Downlink 128Kbps - 3~5Mbps Uplink 64Kbps - 128Kbps~1Mbps Need a cable modem

28 Broadband Services Satellite A technology that provide digital data transmission over satellites Speed Downlink 500Kbps - 1Mbps Uplink 50Kbps - 100Kbps Need a satellite dish

29 WAN (Wide Area Network) A LAN spans a large geographic area, such as connections between cities Usually connected using leased line T1 (1.5Mbps) T3 (45Mbps) OC3 (155Mbps) OC12 (622Mbps) OC48 (2.4Gbps) Fiber optic lines Telecommunication lines

30 Hub/Switch/Router To connect multiple segments of networks into a larger one Hub A multiport repeater to enhance signal within the same LAN Switch Like hub but with intelligent Better performance Router Forward packets from one LAN to another

31 Intranet vs. Internet Intranet A private network that is contained within an enterprise Could be LANs and WANs Internet A public network of networks Both are using TCP/IP

32 TCP/IP A family of protocols that makes the Internet works The Robustness Principle Be liberal in what you accept, and conservative in what you send - Jon Postel

33 TCP/IP (cont) Application Layer Eg. WWW, FTP, IRC, , telnet, … Transport Layer Eg. TCP, UDP Network Layer Eg. IP Link Layer Eg. Ethernet, WiFi Physical Layer Eg. Ethernet Cable, fiber-optics Segments Packets Frames Bits Data

34 Packets A small chunk of data transmitted over the Internet Alice The Internet Bob

35 VPN (Virtual Private Network) A secure tunnel to a private network through a public network Once established, local node appears to be a node in the private network in a secure manner

36 Host & IP Address A host is a computer connected directly to the Internet Each host needs an IP address IP address A 32-bit number, arranged in 4 numbers seperated by. Eg and 192. ranges of IP addresss are reserved for LANs

37 DNS (Domain Name System) Domain name to IP address conversion Eg. ??.???.??.?? Domain name or IP address lookup

38 Top-level Domains gTLDs (generic TLDs).com,.edu,.net,.org,.gov,,.biz,.coop,.info,.museum,.name,.pro ccTLDs (country code TLDs).au,.ca,.br,.de,.fi,.fr,.jp,.hk,.cn,.tw,.my, ….us

39 Second-level Domains Domains that are directly below a TLD Eg. Must apply to a registrar for the appropriate TLD

40 Domain Names & Registrars Profitable domain names - $2.75M – $3M - $7.5M Network Solutions, Inc used to monopolize the name registration Now, ~500 registrars

41 How To Register A Domain Name? Come up a new name 2 name servers IP addresses 1 administrative contact 1 technical contact Register the name to an Internet domain registrar Eg. Used to be done via or fax, now all web-based!

42 Policies AUP (Acceptable Use Policies) A legal document, written to protect the ISP from unlawful use of its service, and outlines prohibited uses of the service and possible consequences of misuse Privacy Policies A document describes an ISPs policy for protecting users information

43 Conclusion Described how to get connected to the Internet Talked about the related network technologies and components

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