Introduction Chapter 1 Panko’s Business Data Networks and Telecommunications, 5th edition Copyright 2005 Prentice-Hall

Learning Objectives By the end of this session, you should be able to List the eight elements of networks. Explain the major types of networks in businesses: LANs, WANs, internets, intranets, and extranets. Discuss major concerns for network managers: staffing, network architecture, standards, security, wireless networking, efficiency, and quality of service (QoS). Explain the elements and operation of a small home PC network using a LAN

Definition A NETWORK is a system of hardware software and transmission components that allow applications to on different stations within the system communicate with each other

Figure 1-2: Elements of a Network Client Station Mobile Client Application Message (Frame) Server Station Switch Access Line Trunk Line Outside World Router Access lines connect stations to switches Trunk lines connect switches to switches (and routers) Networks connect stations: clients (fixed and mobile) and servers Stations (and routers) usually communicate by sending messages called frames The path a frame takes is called its data link Switches move frames to or closer to the destination station Switches handle a packet sequentially Routers connect networks to the outside world. Treated just like stations Networks connect applications on different stations. Applications are all users care about

Figures 1-6 and 1-7: Workgroup and Core Switches 19 inches (48 cm) wide 19 inches (48 cm) wide Small Switches (Stacked): Workgroup Switches To Link Stations To Network Central Core Switch

Figure 1-3: Multiplexing in a Packet-Switched Network Trunk line multiplexes the messages of different conversations AC AC Client Station A AC Server Station C AC AC BD AC Trunk Line This reduces trunk line costs through cost sharing by users BD Access Line BD BD Router D Mobile Client Station B

Figure 1-2: Elements of a Network (Recap) Applications (the only element that users care about) Stations Clients Servers Switches Routers Transmission Lines Trunk lines Access Lines Messages (Frames) 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

LANs and WANs LANs transmit data within corporate sites WANs transmit data between corporate sites Each LAN or WAN is a single network

Figure 1-5: Local Area Network (LAN) in a Large Building Multi-floor Office Building The bank has multiple LANs—one at each site

Figure 1-5: Local Area Network (LAN) in a Large Building, Continued Wall Jack Workgroup Switch Workgroup Switch To WAN Core Switch Router

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 LAN WAN LAN Router Router

Figure 1-8: 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

Figure 1-8: Internet with Three Networks, Continued Messages in single networks (LANs or WANs) are called frames Message in internets are called packets Travel from the source host to the destination host across the entire internet Within a single network, the packet is encapsulated in (carried in) the network’s frame Package (Packet) Truck (frame) Packet Frame

Figure 1-8: Internet with Three Networks, Continued Frame X Details in Network X Packet Data Link A-R1 Switch Host A Switch Server Host Switch X1 Mobile Client Host Switch X2 Route A-B Router R1 Network X

Figure 1-8: Internet with Three Networks, Continued Details in Network Y To Network X Route A-B Router R1 Frame Y Data Link R1-R2 Packet To Network Z Router R2 Network Y

Figure 1-8: Internet with Three Networks, Continued Details in Network Z Packet Data Link R2-B Frame Z Switch Z1 Host B Switch Router R2 Switch Z2 Mobile Client Hosts Switch Router Network Z

Figure 1-8: Internet with Three Networks, Continued 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 N networks, How many packets will be sent? How many frames must carry the packet?

Figure 1-8: Internet with Three Networks, Continued Lower-case internet is any internet Upper-case Internet is the global Internet

NAP = Network Access Point Figure 1-11: The Internet Webserver User PC The Internet Backbone (Multiple Carriers) Access Line Access Line Router NAP NAP ISP 2 NAP ISP 4 ISP 1 ISP 3 Internet Service Provider For User PC Internet Service Provider For Webserver NAP = Network Access Point

Figures 1-9 and 1-10: Routers 19 inches (48 cm) wide 19 inches (48 cm) wide Small Routers Stacked For Branch Offices Large Routers for Large Sites and ISPs

Figure 1-12: The Internet, internets, Intranets, and Extranets internets versus the Internet Intranets Internal internet for use within an organization Based on the TCP/IP standards created for the Internet Extranets Connect multiple firms Only some computers from each firm are on the extranet Use TCP/IP standards

Recap Switches versus Routers Messages Switches move frames through single networks (LANs or WANs) Routers move packets through internets Messages Messages in single networks are called frames Messages in internets are called packets Packets are encapsulated within frames

End Day 1

Day 2

Review List the 8 common elements of a network Explain difference between a message and a packet Explain difference between switch and router Difference between trunk and access lines Given an internet, indicate number of frames, packets, networks traversed for message from A to B Different types of addresses

Figure 1-23: Logical Functions of the Access Router Cable Modem Access Router Router Function DHCP Server Function NAT Function Switch Function

Figure 1-24: 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 UTP D4-47-55-C4-B6-9F UTP UTP UTP Frame To C3… Frame To C3… C3-2D-55-3B-A9-4F A1-44-D5-1F-AA-4C B2-CD-13-5B-E4-65

Figure 1-25: Frames and Packets A1-BD-33-6E-C7-BB IP address = 192.168.0.3 PC in Emily’s Room Cable Modem Packet in DOCIS Frame Internal Router Packet in Ethernet Frame Access Router Packet is always carried (encapsulated) in a frame B2-CD-13-5B-E4-65 IP address = 192.168.0.2 PC in Study

Figure 1-26: Dynamic Host Configuration Protocol (DHCP) A1-BD-33-6E-C7-BB PC in Emily’s Room Cable Modem 1. IP Address = 60.47.112.6 The ISP only Gives each home a Single IP address ISP DHCP Server B2-CD-13-5B-E4-65 PC in Study Access Router A DHCP Server provides User PCs with a temporary IP Address each time the user connects to the Internet

Figure 1-26: Dynamic Host Configuration Protocol (DHCP), Continued A1-BD-33-6E-C7-BB IP address = 192.168.0.3 PC in Emily’s Room Cable Modem 1. IP Address = 60.47.112.6 Internal DHCP Server ISP DHCP Server 2. IP Address = 192.168.0.3 Access Router 2. IP Address = 192.168.0.2 The access router’s Internal DHCP server Gives private IP Addresses to each PC B2-CD-13-5B-E4-65 IP address = 192.168.0.2 PC in Study

Figure 1-27: Network Address Translation (NAT) 2. Packet from 60.47.112.6 Cable Modem Internal NAT Module Webserver IP address= 123.7.86.285 1. Packet from 192.168.0.2 Access Router The access router’s NAT module translates between the private IP addresses and the single ISP-given IP address PC in Study 192.168.0.2

Figure 1-27: Network Address Translation (NAT), Continued 3. Packet to 60.47.112.6 Cable Modem Internal NAT Module Webserver IP address= 123.7.86.285 4. Packet to 192.168.0.2 Access Router PC in Study 192.168.0.2

Figure 1-28: The Domain Name System (DNS), Continued DNS Table Host Name IP Address … … Voyager.cba.hawaii.edu 128.171.17.13 Originating Host’s DNS Resolver DNS Request Message “The host name is Voyager.cba.hawaii.edu” DNS Response Message “The IP address is 128.171.17.13” DNS Host

Figure 1-29: Converting Binary IP Addresses to Dotted Decimal Notation 01111111101010110001000100001101 8-Bit Segments 01111111 10101011 00010001 00001101 Convert Segments to Decimal 127 171 17 13 Dotted Decimal Notation 127.171.17.13

Elements of a Network Message (Frame) Application Application Client Station Switch Server Station Switch Trunk Line Access Line Switch Trunk Line Outside World Mobile Client Station Switch Router Mobile Client Station

Figure 1-22: Home Network Access Router About 4 inches (10 cm) Wide Switch Ports UTP Cords Run to Stations Power Jack for External WAN Port UTP Cord Runs to Cable Modem

Figure 1-19: Network Interface Cards (NICs) (Photo) PC Card NIC. Installed in PC Card slot in notebook and some PDAs. Internal NIC. Installed inside systems unit. Plugged into expansion slot on the mother board.

Internal NIC RJ-45 Jack PCI Connector Pins

Computer Mother Board Mother Board PCI Slots for Expansion Boards (NICs, etc.) Slot for Microprocessor (Pentium 4) Slots for RAM

Mother Board and Expansion Boards (NIC) Connector Expansion Slots Mother Board

4-Pair Unshielded Twisted Pair (UTP) Figure 1-20: Unshielded Twisted Pair (UTP) Cord With RJ-45 Connector (Photo) 4-Pair Unshielded Twisted Pair (UTP) Industry Standard Pen 8-Pin RJ-45 Connector UTP Cord

Figure 1-21: UTP Cord RJ-45 Connector and Jack RJ-45 Jack On a Wall On a Switch or On a NIC UTP Cord --- About as thick as a pencil Rugged and Flexible RJ-45 Connector

Figure 1-13: Major Network Technical Concerns Architecture Standards Security Efficiency Wireless Communication QoS

Figure 1-13: Major Network Technical Concerns Network Architecture A broad plan for how the firm will connect all of its computers within buildings (local area networks), between sites (wide area networks), and to the Internet New systems must fit the rules of the architecture Scalability – ability to accommodate growth efficiently Undisciplined growth in the past No overall plan Legacy networks Use obsolete technologies that do not fit the long-term architecture Too expensive to replace quickly; must live with many for awhile

Figure 1-13: Major Network Technical Concerns, Continued Standards Standards govern message interactions between pairs of entities (Figure 1-14) For example, HTTP request and response messages for WWW access Standards create competition This reduces costs It also stimulates the development of new features Protects the business if the main vendors go out of business

Figure 1-13: Major Network Technical Concerns, Continued Security A Major Problem Many attacks Growing trend toward criminal attackers

Figure 1-15: Firewalls Allowed Legitimate Packet Border Firewall Attacker Hardened Server Border firewall should pass legitimate packets Legitimate Packet Hardened Client PC Legitimate Host Log File Internal Corporate Network

Figure 1-15: Firewalls, Continued Border Firewall Attack Packet Attacker Border firewall should deny (drop) and log attack packets Hardened Server Denied Attack Packet Hardened Client PC Legitimate Host Log File Internal Corporate Network Network Management Console

Figure 1-13: Major Network Technical Concerns, Continued Security Virtual Private Networks (VPNs) (Figure 1-16) Provide communication over the Internet with added security Cryptographic protection for confidentiality (eavesdroppers cannot read) Cryptographic authentication (confirms sender’s identity)

Figure 1-16: Virtual Private Networks (VPNs) Site-to-Site VPN Using Gateway VPN Gateway Client PC 1 VPN Gateway Remote Access VPN Using Gateway Corporate Site B Internal Server Internet Remote Client PC 2 Host-to-Host VPN Corporate Site A Remote Client PC 3

Figure 1-13: Major Network Management Concerns, Continued Wireless Communication To improve mobility Drive-by hackers can eavesdrop on internal communication Drive-by hackers can break into the network bypassing firewalls Drive-By Hacker

Figure 1-13: Major Network Technical Concerns, Continued QoS Quality of Service (QoS) Numerical objectives for performance Transmission speed in bits per second (bps) A bit is a single one or zero NOT bytes per second Increase by factors of 1000, not 1024 kilobits per second (kbps)—lower-case k Megabits per second (Mbps) Gigabits per second (Gbps) Terabits per second (Tbps)

Figure 1-13: Major Network Technical Concerns, Continued Quality of Service For Transmission Speed, have 1 to 3 places BEFORE the decimal point. Example .5 Mbps is wrong 500 kbps is correct 2,300 Mbps is wrong 2.3 Gbps is correct 473.2 Mbps is correct

Figure 1-13: Major Network Technical Concerns, Continued Quality of Service Typical transmission speeds in most firms: LANs: 100 Mbps to each desktop WANs: most site-to-site links only are 56 kbps to a few megabits per second because long-distance transmission is very expensive and so must be used more sparingly LANs: 100 Mbps WANs: 56 kbps to a few Mbps

Figure 1-13: Major Network Technical Concerns, Continued Quality of Service Congestion, Throughput, Latency, and Response Time Congestion: when there is too much traffic for the network’s capacity Throughput: The speed users actually see (often much less than rated speed) Individual throughput is less than total throughput on shared-speed links

Figure 1-13: Major Network Technical Concerns, Continued Quality of Service Congestion, Throughput, Latency, and Response Time Latency: delay (usually measured in milliseconds or ms) Within corporations, latency is typically under 60 ms 90% of the time On the Internet, typically 30 ms to 150 ms

Figure 1-13: Major Network Technical Concerns, Continued Quality of Service Congestion, Throughput, Latency, and Response Time Response Time The time to get a response after a user issues a command A quarter second or less is good

Figure 1-13: Major Network Technical Concerns, Continued Availability Availability is the percentage of time a network can be used Downtime: when the user cannot use the network Want 24x7 availability Telephone network gives 99.999% availability Typical networks reach 98% today

Figure 1-13: Major Network Technical Concerns, Continued Error Rate Measured as the percentage of messages damaged or lost Substantial error rates can disrupt applications Substantial error rates generate more network traffic because of retransmissions