An Introduction to Networking Chapter 1 Updated January 2007 Panko’s Business Data Networks and Telecommunications, 6th edition Copyright 2007 Prentice-Hall May only be used by adopters of the book Copyright 2005 Prentice-Hall

Builds Slides with the “mouse click” icon in the upper right hand corner are “build” slides Not everything on the slide will appear at once Each time the mouse click icon is clicked, more information on the slide will appear. <This is a note primarily for you. However, students should understand builds it if they are working from copies of slides; otherwise, they may be confused when everything doesn’t appear at once.> <Read the slide.> Copyright 2005 Prentice-Hall

Part I: Basic Networks Concepts Concepts we will see throughout the book Copyright 2005 Prentice-Hall

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 Copyright 2005 Prentice-Hall

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 Copyright 2005 Prentice-Hall

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 Copyright 2005 Prentice-Hall

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 Copyright 2005 Prentice-Hall

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 Mobile Client 5. Switches Forward Frames Sequentially Switch 4 Outside World Wireless Access Point Router Copyright 2005 Prentice-Hall

Figure 1-5: Ethernet Switch Operation C3- is out Port 15 D4-47-55-C4-B6-F9 Switching Table Port Host 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 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- Copyright 2005 Prentice-Hall

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 Switch 4 Outside World Wireless Access Point Router Copyright 2005 Prentice-Hall

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 Switch 4 Outside World Yes, single networks can contain routers Wireless Access Point Router Copyright 2005 Prentice-Hall

Figure 1-3: Elements of a Network Client Application 8. Access Lines Connect Computers to Switches Server Application Message (Frame) Access Line Switch 2 Client Computer Server Computer Switch 1 Switch 3 Trunk Line Mobile Client 9. Trunk Lines Connect Switches to Switches and Switches to Routers Switch 4 Outside World Wireless Access Point Router Copyright 2005 Prentice-Hall

Figure 1-4: Packet Switching and Multiplexing Breaking Communications into Small Messages is Called Packet Switching, even if the Messages are Frames AC AC Client Computer A AC Server Computer C 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 Copyright 2005 Prentice-Hall

Network Elements: Recap Name the 9 Elements of Single networks. Without looking back through your handout Never talk about an innovation “reducing cost,” “increasing speed,” etc. without specifying which element is cheaper or faster. For example, multiplexing only reduces the cost of trunk lines; other costs are not decreased Copyright 2005 Prentice-Hall

Part III: Transmission Speed Copyright 2005 Prentice-Hall

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) Copyright 2005 Prentice-Hall

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 Copyright 2005 Prentice-Hall

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). Copyright 2005 Prentice-Hall

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 Copyright 2005 Prentice-Hall

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 Copyright 2005 Prentice-Hall

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 Copyright 2005 Prentice-Hall

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 Copyright 2005 Prentice-Hall

Part IV: LANs and WANs Copyright 2005 Prentice-Hall

Figure 1-8: LANs Versus WANs Characteristics Scope LANs WANs For transmission within a site. Campus, building, and SOHO (Small Office or Home Office) LANs For transmission between sites Campus LAN Building LAN Wide Area Network Home LAN Copyright 2005 Prentice-Hall

Figure 1-8: LANs Versus WANs Characteristics LANs WANs Cost per bit Transmitted Low High 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 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 Copyright 2005 Prentice-Hall

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 Copyright 2005 Prentice-Hall

Part V: Internets Copyright 2005 Prentice-Hall

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 Router Copyright 2005 Prentice-Hall

Host Figure 1-11: Internets Internet Components All computers in an internet are called hosts Clients as well as servers Client PC (Host) Cellphone VoIP Phone PDA Server Internet Cat (Ignores Internet) Copyright 2005 Prentice-Hall

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) Copyright 2005 Prentice-Hall

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 Copyright 2005 Prentice-Hall

Figure 1-11: Internets 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 Router Copyright 2005 Prentice-Hall

Figure 1-11: Internets 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 Router Copyright 2005 Prentice-Hall

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 Copyright 2005 Prentice-Hall

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 Copyright 2005 Prentice-Hall

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 To Network Z Router R2 AF-3B-E7-39-12-B5 Network Y Copyright 2005 Prentice-Hall

Figure 1-12: Internet with Three Networks Network Z Details in Network Z Frame Z Packet Data Link R2-B Switch Z1 Host B www.pukanui.com 1.3.45.111 55-6B-CC-D4-A7-56 Switch Router R2 Switch Z2 Switch Router Mobile Client Host Mobile Client Computer Copyright 2005 Prentice-Hall

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? Copyright 2005 Prentice-Hall

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. Copyright 2005 Prentice-Hall

Figure 1-17: The Internet 1. Webserver Host Computer 1. User PC Host 3. Internet Backbone (Multiple ISP Carriers) Access Line Access Line Router NAP NAP ISP ISP ISP NAP ISP 2. User PC’s Internet Service Provider 2. Webserver’s Internet Service Provider 4. NAPs = Network Access Points Connect ISPs Copyright 2005 Prentice-Hall

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 Copyright 2005 Prentice-Hall

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) Copyright 2005 Prentice-Hall

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.) Copyright 2005 Prentice-Hall

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) Copyright 2005 Prentice-Hall

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 2. Sends DNS Request Message “The host name is Voyager.cba.hawaii.edu” Local DNS Host Voyager.cba.hawaii.edu 128.171.17.13 Copyright 2005 Prentice-Hall

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 Copyright 2005 Prentice-Hall

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 Copyright 2005 Prentice-Hall

Part VI: Security Copyright 2005 Prentice-Hall

Figure 1-23: Firewall and Hardened Hosts Allowed Legitimate Packet Border Firewall Attacker The Internet Hardened Server Border firewall should pass legitimate packets Legitimate Packet Hardened Client PC Legitimate Host Internal Corporate Network Log File Copyright 2005 Prentice-Hall

Figure 1-23: Firewall and Hardened Hosts Server Border firewall should deny (drop) and log attack packets Attack Packet Border Firewall Attacker The Internet Hardened Client PC Denied Attack Packet Legitimate Host Internal Corporate Network Log File Copyright 2005 Prentice-Hall

Figure 1-23: Firewall and Hardened Hosts Server Attack Packet Attack Packet Border Firewall Attacker The Internet Hosts should be hardened against attack packets that get through Attack Packet Denied Attack Packet Hardened Client PC Legitimate Host Internal Corporate Network Log File Copyright 2005 Prentice-Hall

Figure 1-24: Cryptographic Protections Cryptography The use of mathematical operations to thwart attacks on message dialogues between pairs of communicating parties (people, programs, or devices) Initial Authentication Determine the other party’s identity to thwart impostors Copyright 2005 Prentice-Hall

Figure 1-24: Cryptographic Protections Message-by-Message Protections Encryption to provide confidentiality so that an eavesdropper cannot reach intercepted messages Electronic signatures provide message-by-message authentication to prevent the insertion of messages by an impostor after initial authentication Electronic signatures usually also provide message integrity; this tells the receiver whether anyone has changed the message en route Copyright 2005 Prentice-Hall

Topics Covered Copyright 2005 Prentice-Hall

Network Elements: Recap Applications (the only element that users care about) Computers Clients Servers Switches and Routers Transmission Lines Trunk lines Access Lines Messages (Frames) Wireless Access Points Never talk about an innovation “reducing cost,” “increasing speed,” etc. without specifying which element is cheaper or faster. For example, multiplexing only reduces the cost of trunk lines; other costs are not decreased Copyright 2005 Prentice-Hall

Recap: LANs and WANs LANs transmit data within corporate sites WANs transmit data between corporate sites Each LAN or WAN is a single network LAN costs are low and speeds are high WAN costs are high and speeds are lower WAN Copyright 2005 Prentice-Hall

Recap: Internets Most firms have multiple LANs and WANs. They must create internets An internet is a collection 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 Router Router Copyright 2005 Prentice-Hall

Recap: Internets Elements of an Internet Computers connected to the internet are called hosts Both servers and client PCs are hosts Routers connect the networks of the internet together In contrast, switches forward frames within individual networks Router Router WAN LAN LAN Client PC Host Server Host Copyright 2005 Prentice-Hall

Recap: 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 Copyright 2005 Prentice-Hall

Recap: Internets Switches versus Routers Messages Switches move frames through a single network (LAN or WAN) Routers move packets through internets Messages Messages in single networks are called frames Messages in internets are called packets Packets are encapsulated within (carried inside) frames Copyright 2005 Prentice-Hall

Recap: Security Security Firewalls Hardened Hosts Cryptographic security for sensitive dialogues Initial authentication Encryption for confidentiality Electronic signatures for authentication and message integrity Copyright 2005 Prentice-Hall