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An Introduction to Networking Chapter 1 Updated January 2009 Raymond Panko’s Business Data Networks and Telecommunications, 7th edition May only be used by adopters of the book © 2009 Pearson Education, Inc. Publishing as Prentice Hall Builds 2 • Slides with the blue mouse 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 • The number by the mouse icon gives the number of builds on the slide (the number of mouse clicks) © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-2 1-1: Black Box View of Networks • What Is a Network? – Preliminary definition: A network is a communication system that allows application programs on different hosts to work together Application 1 Application 2 Network Host A Host B © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-3 Hosts • Hosts – Any computer attached to a network is called a host – Including client PCs, servers, mobile phones, etc. Host Host Host Cat (Ignores Internet) © 2009 Pearson Education, Inc. Publishing as Prentice Hall Host 1-4 Networked Applications © 2009 Pearson Education, Inc. Publishing as Prentice Hall What are Networked Applications? • Applications that can only exist because of networking • E-Mail • The World Wide Web • Facebook • YouTube • Etc. © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-6 Application Standards • Application standards govern communication between application programs – Allow products from different vendors cannot talk to one another • For example, the Hypertext Transfer Protocol (HTTP) standardizes communication between any browser and any Web servers – Different applications use different standards • E-mail uses the Simple Mail Transfer Protocol (SMTP) and other standards •… © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-7 Application Standards • Application standards govern communication between application programs – Standards are also called protocols • Many standards have “protocol” in their names • Example: Hypertext Transfer Protocol – HTTP is an open standard (not controlled by any vendor) • Open standards drive down product costs – Vendor-controlled standards are called proprietary standards © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-8 1-2: Hypertext Transfer Protocol (HTTP) 1 • HTTP is a Client/Server Protocol – The client is the browser; it sends a request – The server is the Web server; it sends a response – Most application standards are client/server protocols Browser Client Host HTTP Request Message (Asks for File) Web server Program HTTP Response Message (Contains the Requested File) © 2009 Pearson Education, Inc. Publishing as Prentice Hall Web server 1-9 1-3: The ARPANET and the Internet • ARPANET – Some of the first networked applications were created for the ARPANET – Created by the Defense Advanced Research Projects Agency (DARPA) around 1970 • Served researchers doing business with DARPA • Connected many sites around the United States © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-10 1-3: The ARPANET and the Internet • Soon, Many Similar Networks Appeared – CSNET in computer science – BITNET in business and the social sciences – Tower of Babel situation—no interconnection – This was frustrating to users © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-11 1-3: The ARPANET and the Internet • Next, DARPA Created the Internet in 1980 to Connect Networks Together – Initially, commercial activity was forbidden – Became commercial in 1995 – Today, the Internet is almost entirely commercial – Almost no government money flowing in to run the Internet © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-12 1-4: Traditional Internet Applications • File Transfer Protocol (FTP) • E-Mail • The World Wide Web (WWW) • E-Commerce – Buying and selling on the Internet © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-13 1-5: The Internet Versus the World Wide Web (and Other Applications) World Wide Web E-Mail FTP (Application) (Application) (Application) Other Applications The Internet (Transmission System) The Internet is a global transmission system. The WWW, e-mail, etc., are applications that run over the Internet global transmission system © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-14 1-6: Newer Internet Applications 3 • Instant Messaging (IM) • Streaming Audio and Video – No need to wait until the entire file is downloaded before beginning to see or hear it • Voice over IP (VoIP) – Telephony over the Internet or other IP networks • Peer-to-Peer (P2P) Applications – Growing processing power of PCs allows PCs to serve other PCs directly © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-15 1-6: Newer Internet Applications • Web 2.0 – A hazy term that focuses on using the Internet to facilitate communication among people – Including the creation of communities – In addition, the users themselves typically generate the content – Blogs, wikis, podcasts – Examples: community building sites such as MySpace and Facebook, video sharing sites such as YouTube, virtual worlds such as Second Life, and specific information sharing sites, such as craigslist © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-16 1-7: Corporate Network Applications • Corporate Network Applications are Specific to Businesses – Can consume far more corporate network resources than traditional and new Internet applications combined • Transaction-Processing Applications – Simple, high-volume repetitive clerical transaction applications – Accounting, payroll, billing, manufacturing, etc. – Not all corporate network applications are transactionprocessing applications © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-17 1-7: Corporate Network Applications • Enterprise Resource Planning (ERP) Applications – Serve individual business functions while providing integration between functional modules Inter-Function Transaction Accounting Billing Sales Manufacturing Purchasing Inter-Function Transaction Warehousing Inter-Function Transaction © 2009 Pearson Education, Inc. Publishing as Prentice Hall Shipping 1-18 1-7: Corporate Network Applications • Organizational Communication Applications – E-mail, etc. – Groupware • Integrate multiple types of communication, organize communication for retrieval, and provide multiple ways to disseminate and retrieve information © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-19 1-7: Corporate Network Applications • Converged Networks – Voice and data traditionally have needed different networks – Convergence: Moving voice/video and data networks to a single network – Can save the corporation a great deal of money by only having a single network – Many technical issues remain © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-20 1-8: File Service 2 File Server 1. User saves data file to file server, which is backed up nightly 3. Others can retrieve the file and even edit it if they are given permission 2. Later, user can retrieve the data file from any other computer © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-21 1-8: File Service 2. A multiuser version of the program is required 1. A program is Installed on the file server; Less expensive than installing it on many individual PCs 3 File Server 3. For execution, a copy is downloaded from the file server 4. Note that the program is executed on the client PC, not on the file server! © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-22 Quality of Service (QoS) © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-9: Network Quality of Service (QoS) • Quality of Service (QoS) – Indicators of network performance – Speed, etc. • Metrics – Ways of measuring specific network quality-of-service variables – The metric for speed is bits per second © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-24 1-10: 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) © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-25 1-10: Transmission Speed • Measuring Transmission Speed – What is 23,000 bps in metric notation? – What is 3,000,000,000 bps in metric notation? – What is 15,100,000 bps in metric notation? • Occasionally measured in bytes per second – If so, written as Bps, rather than bps – Usually seen only in file downloads © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-26 1-10: Transmission Speed 3 • 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) • Leading zeros do not count © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-27 1-10: Transmission Speed • Writing Transmission Speeds in Proper Form – How to convert 1,200 Mbps to proper form, to 12.02 Gbps Number Suffix 12,020 Mbps Must divide number by 1,000 So must multiply suffix by 1,000 12,020 12.02 Mbps Gbps © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-28 1-10: Transmission Speed • Writing Transmission Speeds in Proper Form – How to convert .2346 Mbps to proper form, to 234.6 kbps Number Suffix 0.2346 Mbps Multiply by 1,000 Divide by 1,000 0.2346 234.6 Mbps kbps © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-29 1-10: 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 © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-30 1-10: 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—the individual user’s share of the aggregate throughput © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-31 1-11: Cost • Network Demand, Budgets, and Decisions – Figure 1-12 shows that network demand is growing explosively, while network budgets are growing slowly – This creates a cost squeeze that affects every decision – Overspending in one area will result in the inability to fund other projects Figure 1-12 © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-32 1-11: Cost • Systems Development Life Cycle Costs – Hardware: Full price: advertised base price plus necessary options – Software: Full price: advertised base price plus necessary options – Labor costs: Networking staff and user costs – Outsourcing development costs – Total development investment © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-33 1-11: Cost 1 • Systems Life Cycle (SLC) Costs – System development life cycle (SDLC) versus system life cycle (SLC) • SLC has ongoing costs after development – Total cost of ownership (TCO) • Total cost over entire life cycle • SLC includes carrier costs – Carrier pricing is complex and difficult to analyze – Must deal with leases, which lock the firm in for months or years © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-34 1-13: Other Quality-of-Service Metrics • We Have Already Seen Speed and Cost • Availability – The percentage of time a network is available for use – “Our availability last year was 99.9%” • Downtime is the amount of time a network is unavailable – Measured in minutes, hours, etc. – “In July, we had five minutes of downtime.” © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-35 1-13: Other Quality-of-Service Metrics • Error Rates – Packet error rate: the percentage of packets lost or damaged – Bit error rate: the percentage of bits lost or damaged © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-36 1-13: Other Quality-of-Service Metrics • Latency and Jitter – Latency • Delivery delay, measured in milliseconds – For instance, 250 ms is a quarter of a second • Bad for real-time applications – Voice and video – Network control messages © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-37 1-13: Other Quality-of-Service Metrics • Latency and Jitter – Jitter • Variation in latency between successive packets • Makes voice sound jittery Figure 1-14 © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-38 1-13: Other Quality-of-Service Metrics • Service Level Agreements – Customers want guarantees for performance – Provider pays penalties if the network does not meet its service metrics guarantees – Often specified on a percentage basis • At least 100 Mbps 99.5% of the time • To guarantee this speed 100% of the time would be impossible, and even 99.99% would be far more expensive © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-39 1-13: Other Quality-of-Service Metrics • Service Level Agreements – Specify a worst case – Speed SLAs • Low speed is the worst case • So an SLA would guarantee a lowest speed that would be delivered • E.g., no worse than 1 Mbps) • Customer would like higher speeds • But wants no less than 1 Mbps © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-40 1-13: Other Quality-of-Service Metrics • Service Level Agreements – Latency SLAs • Would an SLA specify a lowest latency or a highest latency? • Ask yourself, “Which is worse: large latency or small latency?” • The answer: Large latency is worse • So specify a maximum latency • No more than 100 ms 99% of the time © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-41 1-13: Other Quality-of-Service Metrics • Service Level Agreements – What would an SLA guarantee for availability? © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-42 1-13: Other Quality-of-Service Metrics • Service Level Agreements – What would an SLA guarantee for error rates? © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-43 1-15: Network Security • Security – Security attacks can be extremely expensive – Companies need to install defenses against attacks – Chapter 9 discusses network security in depth © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-44 1-15: Network Security • Authentication – Goal is to stop impostors – Supplicant attempts to prove its identity to a verifier – Example: user logging into a server is a supplicant; the server is a verifier – Proofs of identity are called credentials Supplicant: True User? Credentials: Password © 2009 Pearson Education, Inc. Publishing as Prentice Hall Verifier: Server 1-45 1-15: Network Security 2 • Cryptographic Protections – Eavesdroppers may intercept your messages • Read and even change messages • Send new messages impersonating the other side – Cryptography is the use of mathematics to protect information in storage or in transit – Encryption for confidentiality • An eavesdropper cannot read encrypted messages • The legitimate receiver, however, can decrypt the message © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-46 1-15: Network Security • Firewall – Examines each packet passing through it – Drops and logs provable attack packets – It lets other packets get through, even if suspicious Passes Other Packets Drops Arriving Packet Provable Attack Packet © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-47 1-15: Network Security • Host Hardening – Some attacks will inevitably get past safeguards and reach hosts – Hosts must be “hardened” to withstand attacks – Hardening is a set of protections we will see in Chapter 9 • Example: installing antivirus software on the host • Example: downloading security updates •… © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-48 Switched Networks © 2009 Pearson Education, Inc. Publishing as Prentice Hall Figure 1-16: Ethernet Switch Operation In switched networks, Messages are called frames Switch connectors are called ports Ethernet Switch Host A1-… wishes to send a frame to Host C3 The frame must pass Through the switch A1-44-D5-1F-AA-4C D4-47-55-C4-B6-9F C3-2D-55-3B-A9-4F B2-CD-13-5B-E4-65 © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-50 Figure 1-16: Ethernet Switch Operation Ethernet Switch UTP Host A1-… sends the frame to the switch D4-47-55-C4-B6-9F Frame To C3… A1-44-D5-1F-AA-4C C3-2D-55-3B-A9-4F B2-CD-13-5B-E4-65 © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-51 Figure 1-16: Ethernet Switch Operation 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-B6-9F Ethernet Switch Frame To C3… UTP D4-47-55-C4-B6-9F A1-44-D5-1F-AA-4C The switch reads the destination address in the frame. It looks up the address (C3-…) in the switching table. It reads the port number (15) C3-2D-55-3B-A9-4F B2-CD-13-5B-E4-65 © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-52 Figure 1-16: Ethernet Switch Operation 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-B6-9F The switch sends the Ethernet Switch D4-47-55-C4-B6-9F frame out Port 15, to the destination host. Frame To C3… A1-44-D5-1F-AA-4C C3-2D-55-3B-A9-4F B2-CD-13-5B-E4-65 © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-53 1-17: Switched Network in a Multistory Building On each floor, hosts connect to a workgroup switch via wire or wireless transmission A core switch connects the workgroup switches to each other © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-54 1-17: Switched Network in a Multistory Building 3 Client Wall Jack Server Workgroup Switch 2 Workgroup Switch 1 Wall Jack To WAN Router Core Switch 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 © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-55 Figure 1-18: Four-Pair Unshielded Twisted Pair (UTP) Copper Wiring © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-56 1-19: Packet Switching and Multiplexing In packet switching, the sending host breaks each message into many smaller packets Sends these packets out one at a time Packets are routed to the destination host © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-57 1-19: Packet Switching and Multiplexing Multiplexing reduces cost. Each conversation only has to pay for its share of the trunk lines it uses © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-58 Routed Networks (Internets) © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-20: Routed Networks • The 1980s: A Switched Tower of Babel – At first, there were only switched networks – Soon, there were many incompatible switched networks – Users on different switched networks could not communicate with each other Switched Network 1 SW SW SW Switched Network 2 SW SW SW © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-60 1-20: Routed Networks • Routers and Routed Networks – Routers were created connect different switched networks together – Routed networks are also called internets Routed Network (Internet) Switched Network 1 SW SW SW Router Switched Network 2 SW Router SW SW © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-61 1-20: Routed Networks • Routers and Routed Networks – Routers are more complex (and expensive) than switches • Designed to work no matter how complex the internet • Require more hands-on administration than switches Routed Network (Internet) Switched Network 1 SW SW SW Router Switched Network 2 SW Router © 2009 Pearson Education, Inc. Publishing as Prentice Hall SW SW 1-62 Terminology Internet • Capitalization of “Internet” – “Internet” with a capital “I” is used for the global Internet we all use each day – “internet” with a lower-case “i” is used when talking about a smaller internet or about internets in general – In all cases, capitalized at the beginning of a sentence internet © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-63 1-20: Routed Networks 1 • Originally, only switched network addresses existed – Different switched network technologies used different address schemes – A universal address scheme was necessary to represent any host on any network in the world. • Cerf and Kahn Created this Universal Address – These were called IP address – 32 bits long – Usually expressed in dotted decimal notation, such as 128.171.17.13. – Host IP addresses are globally unique © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-64 1-20: Routed Networks • So Hosts on an Internet Have Two Addresses • Example – The author’s computer has the Ethernet address AF-23-B9-C8-4E-38 • This is its address on its Ethernet switched network – The author’s computer also has the IP address 128.171.17.13 • This is its globally unique IP address © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-65 1-20: Routed Networks • Packets and Frames – Packets are called frames in switched networks – Packets are called packets in routed networks – A packet is carried in a frame within each switched network Packet Frame © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-66 Routers, Frames, and Packets • A frame arrives at a router – The frame contains a packet • The router takes the packet out of the frame – The router puts the packet into a new frame appropriate for the next network and sends it out – The packet continues; the frame does not Packet Frame 1 Packet Network 2 Frame 2 Router Packet Network 2 © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-67 1-21: Routed Network (Internet) 2 2. Packet travels through three switched networks 1. When a packet is sent, the packet travels all the way from the source host to the destination host 3. The packet travels in three frames—one in each switched network © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-68 1-21: Routed Network (Internet) • In this example, the internet has three networks – When a packet is sent, – That one packet goes all the way from the source host to the destination host – The packet travels in three different frames along the way, one in each network – A frame only travels through a single network © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-69 1-21: Routed Network (Internet) • Suppose that a packet has to travel through seven networks – When a packet was sent, – How many packets go from the source host to the destination host? – How many frames will there be along the way? © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-70 4 1-22: The Global Internet 1. Web server Host Computer 1. User PC Host Computer 4. Internet Backbone (Multiple ISP Carriers) Access Line Access Line Router NAP ISP ISP NAP NAP ISP ISP 2. User PC’s Internet Service Provider 5. NAPs = Network Access Points Connect ISPs © 2009 Pearson Education, Inc. Publishing as Prentice Hall 3. Web server’s Internet Service Provider 1-71 1-22: The Global Internet • How is the Internet Financed? – Through ISP subscriber payments • Residences typically pay $10 to $100 per month • Business typically pay thousands or tens of thousands of dollars per month – Like the telephone network • The telephone network is supported by customer payments to telephone carriers – Almost no government money involved © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-72 1-22: The Internet • The TCP/IP Standards – The set of protocols that governs the Internet – Standards for both applications and packet delivery – Created by the Internet Engineering Task Force (IETF) © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-73 1-23: Domain Name System (DNS) • Domain Name System (DNS) – 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 – Like looking up someone’s name in a telephone directory © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-74 1-23: Domain Name System (DNS) 1 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 © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-75 1-23: Domain Name System (DNS) 2 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 … … 4. DNS Response Message “The IP address is 128.171.17.13” 5. Client sends packets to 128.171.17.13 DNS Host Voyager.cba.hawaii.edu 128.171.17.13 © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-76 LANs and WANs © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-25: LANs and WANs (Study Figure) Category Local Area Networks Wide Area Networks Abbreviation LAN WAN Distance Span Customer premises (apartment, office, building, campus, etc.) Between sites within a corporation or between different corporations Wide Area Network Building LAN Campus LAN Home LAN © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-78 1-25: LANs and WANs Category Local Area Networks Wide Area Networks Can use switched network technology? Yes Yes Can use routed network Yes, especially in large technology? LANs Yes, in fact, that is what the Internet is Many students are surprised that LANs can be routed and that WANs can be switched © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-79 1-25: LANs and WANs Category Local Area Networks Wide Area Networks Implementation Do it yourself Must use a carrier with rights of way Ability to choose technologies High Low Need to manage technologies High Low © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-80 1-25: LANs and WANs Category Local Area Networks Cost per bit transmitted Low Therefore, typical transmission speed Wide Area Networks High with arbitrary Changes unrelated to costs Usually 100 Mbps to 10 About 256 kbps to 50 Gbps Mbps In economics, you learned that when unit price goes up, people will purchase less of the product Because WANs cost much more per bit, companies learn to live with fewer bits per second © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-81 Network Management © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-26: Network Management • Strategic Network Management – As far as possible, build a coherent roadmap – Pay special attention to decisions that lock you in for long periods of time – Legacy technologies are technologies selected previously that limit services today • For upgrading, service benefits must exceed update costs © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-83 1-26: Network Management • Product Selection with Multicriteria Decision Making – The entire systems development life cycle (SDLC) must be followed – For network products, corporations buy instead of make network elements • Must use multicriteria decision making (Figure 1-26) • Select purchasing criteria (speed, cost, etc.) • Give each criterion an importance weight • Rate each product on each purchasing criteria © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-84 1-27: Multicriteria Decision Making in Purchase Decisions Criterion Functionality Product A Product B Criterion Criterion Criterion Product Criterion Weight Rating Score Rating Score (Max: 5) (Max: (Max: 10) 10) 5 9 45 7 35 Availability 2 7 14 7 14 Cost Ease of Management Electrical Efficiency Total Score 5 4 20 9 45 4 8 32 6 24 1 9 9 8 8 120 © 2009 Pearson Education, Inc. Publishing as Prentice Hall 126 1-85 1-28: Network Management • Ongoing Management – After the SDLC ends – The most important (and expensive) part of the systems life cycle – Often discussed in terms of OAM&P – Operations, administration, maintenance, and provisioning © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-86 1-28: Network Management • Ongoing Management (OAM&P) – Operations • Moment-by-moment traffic management • Network operations center (NOC) using SNMP (see Figure 1-29) © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-87 1-28: Network Management • Ongoing Management (OAM&P) – Maintenance • Fixing things that go wrong • Conducting preventative maintenance • Should be separate from the operations staff © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-88 1-28: Network Management • Ongoing Management (OAM&P) – Provisioning (Providing Service) • Includes physical installation • Includes setting up user accounts and services • Reprovisioning when things change • Deprovisioning when accounts and services are no longer permitted • Collectively extremely expensive © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-89 1-28: Network Management • Ongoing Management (OAM&P) – Administration • High end: planning • Middle: analysis of operations to indicate needed changes • Low: paying bills, managing contracts, etc. © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-90 Simple Network Management Protocol (SNMP) © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-29: Simple Network Management Protocol (SNMP) Network Management Software (Manager) The manager manages multiple managed devices from a central location Collects information about each managed device Managed Device Managed Device Can sometimes reconfigure managed devices remotely © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-92 Figure 10-13: Simple Network Management Protocol (SNMP) Network Management Software (Manager) Network Management Agent (Agent), Objects Managed Device Manager talks to a network management agent on each managed device—not to the managed device directly © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-93 Figure 10-13: Simple Network Management Protocol (SNMP) Network Management Software (Manager) Data Management Information Base (MIB) Data Manager collects data about each device; stores the data in a Management Information Base (MIB) © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-94 Figure 10-13: Simple Network Management Protocol (SNMP) Network Management Software (Manager) 1. Command (Get, Set, etc.) 2. Response 3. Trap (Alarm) Initiated by a Managed Device Simple Network Management Protocol (SNMP) Messages Managed Device © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-95 1-29: Simple Network Management Protocol (SNMP) • Notes – Remote management can greatly reduce the TCO by reducing labor costs, despite the higher cost of managed devices Central Management No Central Management Device costs Higher Lower Labor costs Much Lower Much Higher TCO Lower Higher © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-96 Key Points • Perspective – Definition of a network – Networked applications – Quality of Service • Network Technology – Switched versus routed networks (internets) – The global Internet – LANs versus WANs • Network Management © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-97 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. Printed in the United States of America. Copyright © 2009 Pearson Education, Inc. Publishing as Prentice Hall © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-98