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An Introduction to Networking

An Introduction to Networking. Chapter 1. Part I: Basic Networks Concepts. Concepts we will see throughout the book. Figure 1-1: Basic Networking Concepts. What Is a Network? A network is a transmission system that connects two or more applications running on different computers. Network.

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An Introduction to Networking

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  1. An Introductionto Networking Chapter 1

  2. Part I: Basic Networks Concepts Concepts we will seethroughout the book

  3. Figure 1-1: Basic Networking Concepts • What Is a Network? • A network is a transmission system that connects two or more applications running on different computers. Network

  4. Figure 1-1: Basic Networking Concepts • Client/Server Applications • Most Internet applications are client/server applications • Clients receive service from servers • The client is often a browser Client Program Server Program Services Client Computer Server Computer

  5. Part II: The Nine Elements of a Network Although the idea of “network”is simple, you must understand the nine elements found in most networks

  6. Figure 1-3: Elements of a Network Client Application Server Application Message (Frame) Switch 2 Access Line 1. Networks connect applications on different computers. Client Computer Server Computer Switch 1 Switch 3 Networks connect computers: 2. Clients (fixed and mobile) and 3. Servers Trunk Line Mobile Client Outside World Wireless Access Point Router

  7. Figure 1-3: Elements of a Network Client Application Server Application Message (Frame) Client Computer Server Computer 4. Computers (and routers) usually communicate by sending messages called frames Switch 1 Switch 3 Trunk Line Mobile Client Outside World Wireless Access Point Router

  8. Figure 1-3: Elements of a Network Client Application Server Application Message (Frame) Client Sends Frame to Sw1 Sw2 Sends Frame To Sw3 Sw1 Sends Frame to Sw2 Switch 2 Client Computer Server Computer Sw3 Sends Frame to Server Switch 1 Switch 3 Trunk Line 5. Switches Forward Frames Sequentially Mobile Client Outside World Switch 4 Wireless Access Point Router

  9. Switching Table PortHost 10 A1-44-D5-1F-AA-4C 13 B2-CD-13-5B-E4-65 15 C3-2D-55-3B-A9-4F 16 D4-47-55-C4-B6-F9 15 C3-2D-55-3B-A9-4F Figure 1-5: Ethernet Switch Operation C3- is out Port 15 D4-47-55-C4-B6-F9 Switch 2 Port 15 3 Frame to C3… Frame to C3… 1 C3-2D-55-3B-A9-4F A1-44-D5-1F-AA-4C B2-CD-13-5B-E4-65 Switch sends frame to C3- A1- sends a frame to C3-

  10. Figure 1-3: Elements of a Network Client Application Server Application Message (Frame) Switch 2 Access Line Client Computer Server Computer 6. Wireless Access Points Connect Wireless Stations to Switches Switch 1 Switch 3 Trunk Line Mobile Client Outside World Switch 4 Wireless Access Point Router

  11. Figure 1-3: Elements of a Network Client Application Server Application Message (Frame) Switch 2 Access Line Client Computer Server Computer 7. Routers connect networks to the outside world; Treated just like computers in single networks Switch 1 Switch 3 Trunk Line Mobile Client Outside World Switch 4 Yes, single networks can contain routers Wireless Access Point Router

  12. Figure 1-3: Elements of a Network 8. Access Lines Connect Computers to Switches Client Application Server Application Message (Frame) Access Line Switch 2 Client Computer Server Computer Switch 1 Switch 3 Trunk Line Mobile Client Outside World 9. Trunk Lines Connect Switches to Switches and Switches to Routers Switch 4 Wireless Access Point Router

  13. Figure 1-4: Packet Switching and Multiplexing Breaking Communications into Small Messages is Called Packet Switching, even if the Messages are Frames AC AC Server Computer C AC Client Computer A AC AC BD AC Trunk Line Multiplexed Packets Share Trunk Lines So Packet Switching Reduces the Cost of Trunk Lines BD Access Line BD BD Router D Mobile Client Computer B

  14. Part III: Transmission Speed

  15. Figure 1-6: Transmission Speed • Measuring Transmission Speed • Measured in bits per second (bps) • In metric notation: • Increasing factors of 1,000 … • Not factors of 1,024 • Kilobits per second (kbps)-note the lowercase k • Megabits per second (Mbps) • Gigabits per second (Gbps) • Terabits per second (Tbps)

  16. Figure 1-6: Transmission Speed • Measuring Transmission Speed • What is 23,000 bps in metric notation? • What is 3,000,000,000 in metric notation? • What is 15,100,000 bps in metric notation? • Occasionally measured in bytes per second • If so, written as Bps • Usually seen in file download speeds

  17. Figure 1-6: Transmission Speed • Writing Transmission Speeds in Proper Form • The rule for writing speeds (and metric numbers in general) in proper form is that there should be 1 to 3 places before the decimal point • 23.72 Mbps is correct (2 places before the decimal point). • 2,300 Mbps has four places before the decimal point, so it should be rewritten as 2.3 Gbps (1 place). • 0.5 Mbps has zero places to the left of the decimal point. It should be written as 500 kbps (3 places).

  18. Figure 1-6: Transmission Speed • Writing Transmission Speeds in Proper Form • How to convert 1,200 Mbps to proper form • Divide the number 1,200 by 1000 • Move decimal point three places to the left: 1.200 • Multiply the metric suffix Mbps by 1,000 • Gbps • Result: • 1.2 Gbps

  19. Figure 1-6: Transmission Speed • Writing Transmission Speeds in Proper Form • How to convert 0.036 Mbps to proper form • Multiply the number 0.036 by 1000 • Move decimal point three places to the right: 36 • Divide the metric suffix Mbps by 1,000 • kbps • Result: • 36 kbps

  20. Figure 1-6: Transmission Speed • Writing Transmission Speeds in Proper Form • How should you write the following in proper form? • 549.73 kbps • 0.47 Gbps • 11,200 Mbps • .0021 Gbps

  21. Figure 1-6: Transmission Speed • Rated Speed • The speed in bits per second that you should get (advertised or specified in the standard). • Throughput • The speed you actually get • Almost always lower than the rated speed • On Shared Transmission Lines • Aggregate throughput—total throughput for all users • Individual throughput—what individual users get

  22. Part IV: LANs and WANs

  23. Characteristics LANs WANs Scope For transmission within a site. Campus, building, and SOHO (Small Office or Home Office) LANs For transmission between sites Figure 1-8: LANs Versus WANs Campus LAN Building LAN Wide Area Network Home LAN

  24. Typical Speed Unshared 100 Mbps to a gigabit per second to each desktop. Even faster trunk line speeds. Shared 128 kbps to several megabits per second trunk line speeds Figure 1-8: LANs Versus WANs Characteristics LANs WANs Cost per bit Transmitted Low High It’s simple economics. If the cost per unit is higher, the number of units demanded will be lower. Corporations cannot afford high-speed for most of their WAN transmission

  25. Choices Unlimited Only those offered by carrier Figure 1-8: LANs Versus WANs Characteristics LANs WANs Management On own premises, so firm builds and manages its own LAN or outsources the Work Must use a carrier with rights of way for transmission in public Area. Carrier handles most work but Charges a high price.

  26. Figure 1-9: Local Area Network (LAN) in a Large Building Wall Jack Workgroup Switch 2 Client Server Workgroup Switch 1 Wall Jack To WAN Core Switch Router Frames from the client to the server go through Workgroup Switch 2, through the Core Switch, through Workgroup Switch 1, and then to the server

  27. Part V: Internets

  28. Router Router Figure 1-11: Internets • Single LANs Versus Internets • In single networks (LANs and WANs), all devices connect to one another by switches—our focus so far. • In contrast, an internet is a group of networks connected by routers so that any application on any host on any single network can communicate with any application on any other host on any other network in the internet. Application Application WAN LAN LAN

  29. PDA (Host) Client PC (Host) VoIP Phone (Host) Server (Host) Cellphone (Host) Figure 1-11: Internets Host • Internet Components • All computers in an internet are called hosts • Clients as well as servers Internet Cat (Ignores Internet)

  30. Figure 1-11: Internets • Hosts Have Two Addresses • IP Address • This is the host’s official address on its internet • 32 bits long • Expressed for people in dotted decimal notation (e.g., 128.171.17.13) • Single-Network Addresses • This is the host’s address on its single network • Ethernet addresses, for instance, are 48 bits long • Expressed in hexadecimal notation (e.g., AF-23-9B-E8-67-47)

  31. Figure 1-11: Internets • Networks are connected by devices called routers • Switches provide connections within networks, while routers provide connections between networks in an internet. • Frames and Packets • In single networks, message are called frames • In internets, messages are called packets

  32. Router Router Figure 1-11: Internets Packet Frame • Packets are carried within frames • One packet is transmitted from the source host to the destination host across the internet • Its IP destination address is that of the destination host WAN LAN LAN

  33. Router Router Figure 1-11: Internets Packet Frame • Packets are carried within frames • In each network, the packet is carried in (encapsulated in) a frame • If there are N networks between the source and destination hosts, there will be one packet and N networks between the source and destination hosts, there will be one packet and N frames for a transmission WAN LAN LAN

  34. Figure 1-12: Internet with Three Networks Host A R1 Packet Network X A packet goes all the way across the internet; It’s path is its route Network Y Route A-B Network Z R2 Host B

  35. Figure 1-12: Internet with Three Networks In Network X, the Packet is Placed in Frame X Frame X Details in Network X Packet Switch Host A 10.0.0.23 AB-23-D1-A8-34-DD Switch Server Host Data link A-R1 A data Link is a frame’s path through its single network Switch X1 A route is a packet’s path through the internet Mobile Client Host Switch X2 Router R1 D6-EE-92-5F-C1-56 Route A-B Network X

  36. Figure 1-12: Internet with Three Networks Details in Network Y To Network X Route A-B Router R1 Frame Y Data Link R1-R2 Packet Router R2 AF-3B-E7-39-12-B5 Network Y To Network Z

  37. Figure 1-12: Internet with Three Networks Network Z Details in Network Z Frame Z Packet Data Link R2-B Switch Z1 Switch Host B www.pukanui.com 1.3.45.111 55-6B-CC-D4-A7-56 Router R2 Switch Z2 Switch Router Mobile Client Host Mobile Client Computer

  38. Figure 1-12: Internet with Three Networks • In this internet with three networks, in a transmission, • There is one packet • There are three frames (one in each network) • If a packet in an internet must pass through 10 networks, • How many packets will be sent? • How many frames must carry the packet?

  39. Figure 1-13: Converting IP Addresses into Dotted Decimal Notation IP Address (32 bits long) 10000000101010110001000100001101 Divided into 4 bytes. These are segments. 10000000 10101011 00010001 00001101 Convert each byte to decimal (result will be between 0 and 255)* 128 171 17 13 Dotted decimal notation (4 segments separated by dots) 128.171.17.13 *The conversion process is described in the Hands On section at the end of the chapter.

  40. Figure 1-17: The Internet 1. Webserver Host Computer 1. User PC Host Computer 3. Internet Backbone (Multiple ISP Carriers) Access Line Access Line Router NAP NAP ISP ISP ISP NAP ISP 2. Webserver’s Internet Service Provider 2. User PC’s Internet Service Provider 4. NAPs = Network Access Points Connect ISPs

  41. Figure 1-18: Subnets in an Internet LAN 2 LAN 1 LAN Subnet 60.4.3.x Router R1 LAN Subnet 10.1.x.x Router R4 LAN Subnet 60.4.15.x LAN Subnet 10.2.x.x LAN Subnet 60.4.7.x WAN Subnet 123.x.x.x LAN Subnet 10.3.x.x LAN Subnet 60.4.131.x Router R3 Router R2 Note: Subnets are single networks (collections of switches, transmission lines) Often drawn as simple lines to focus on routers for internetworking

  42. Figure 1-19: Terminology Differences for Single-Network and Internet Professionals By Single-Network Professionals By Internet Professionals Single Networks Are Called Networks Subnets Internets Are Called Internets Networks • In this book, we will usually call internets “internets” • and subnets “single networks”

  43. Figure 1-14: The Internet, internets, Intranets, and Extranets • Lower-case internet • Any internet • Upper-case Internet • The global Internet • Intranet • An internet restricted to users within a single company • Extranet • A group of resources that can be accessed by authorized people in a group of companies

  44. Figure 1-20: IP Address Management • Every Host Must Have a Unique IP address • Server hosts are given static IP addresses (unchanging) • Clients get dynamic (temporary) IP addresses that may be different each time they use an internet • Dynamic Host Configuration Protocol (DHCP) (Figure 1-21) • Clients get these dynamic IP addresses from Dynamic Host Configuration Protocol (DHCP) servers (Figure 1-21)

  45. Figure 1-21: Dynamic Host Configuration Protocol (DHCP) 1. DHCP Request Message: “My 48-bit Ethernet address is A3-4E-CD-59-28-7F”. Please give me a 32-bit IP address.” 2. Pool of IP Addresses Client PC A3-4E-CD-59-28-7F DHCP Server 3. DHCP Response Message: “Computer at A3-4E-CD-59-28-7F, your 32-bit IP address is 11010000101111101010101100000010”. (Usually other configuration parameters as well.)

  46. Figure 1-20: IP Address Management • Domain Name System (DNS) (Figure 1-22) • IP addresses are official addresses on the Internet and other internets • Hosts can also have host names (e.g., cnn.com) • Not official—like nicknames • If you only know the host name of a host that you want to reach, your computer must learn its IP address • DNS servers tell our computer the IP address of a target host whose name you know. (Figure 1-22)

  47. 2. Sends DNS Request Message “The host name is Voyager.cba.hawaii.edu” Figure 1-22: The Domain Name System (DNS) 1. Client Host wishes to reach Voyager.cba.hawaii.edu; Needs to know its IP Address DNS Table Host Name IP Address … … … … Voyager.cba.hawaii.edu 128.171.17.13 … … Local DNS Host Voyager.cba.hawaii.edu 128.171.17.13

  48. Figure 1-22: The Domain Name System (DNS) DNS Table 3. DNS Host looks up the target host’s IP address Host Name IP Address … … … … Voyager.cba.hawaii.edu 128.171.17.13 … … DNS Host 4. DNS Response Message “The IP address is 128.171.17.13” 5. Client sends packets to 128.171.17.13 Voyager.cba.hawaii.edu 128.171.17.13

  49. Figure 1-22: The Domain Name System (DNS) The local DNS host sends back the response; the user is unaware that other DNS hosts were involved DNS Table Host Name IP Address … … … … Voyager.cba.hawaii.edu 128.171.17.13 … … Client Host Local DNS Host 1. DNS Request Message 3. DNS Response Message 2. Request & Response If local DNS host does not have the target host’s IP address, it contacts other DNS hosts to get the IP address Anther DNS Host

  50. Part VI: Security

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