1. Chapter 61 MIS 430 Part III Local Area Networks

2. Chapter 62 Background 95+% of LANs are Ethernet Traditional (802.3) Switched Wireless (802.11 etc)

3. Chapter 63 Use LANs for Information Sharing Data Files, Email, Web pages Resource Sharing Printers, access to specialty hardware Access to software applications We use Keyserver to “meter” software to users Beware illegal activities: SPA “software police” http://www.spa.org/piracy/default.asp SW Publishers Association http://www.spa.org/piracy/default.asp Gateway to other networks

4. Chapter 64 Types of LAN Dedicated Server File, Web, Email, Database, Print servers Remote access server (RAS) for ISP Sophisticated Network SW Peer to peer server Regular client PC serves files and printers Internet Connection Sharing (ICS) Limit to < 10 computers unless inactive

5. Chapter 65 Day in the Life: LAN Admin Arrive before others: check network Run routine diagnostics Check daily logs Do daily backup (incremental is short) Check for Windows critical security updates, anti- virus updates Respond to user emails about problems Plan for future upgrades, SW rollouts, security improvements

6. Chapter 66 I. Basic LAN Components NIC-network interface card Network cables Network hub (switch or router) Network operating system (client, server versions) Client computers Server (can be a client)

7. Chapter 67 Network Interface Card (NIC) Built into motherboard or as an add in card PCI bus versus ISA bus (expansion slot) PC Card – plugs into laptop PC Card slot on side and sticks out (remove when putting in the case) miniPCI card – fits inside a laptop (~wireless) Speed: 10 vs 10/100 vs 100 Mbps Connector: RJ-45 vs BNC or AUI Plug and Play – computer configures NIC vs. program via SW vs. set jumper switches Boot PROM – allows booting from server

8. Chapter 68 Network Cables Most use UTP – unshielded twisted pair Also have coax (BNC) and fiber optic See Tech Focus 6-1 p. 192 for cables Cat 5 and 5e: 100 Mbps twisted pair Cat 6: 250 up to 1000 Mbps (1 “gigabit”) RG-58 coax 802.2 (RG-59 is TV cable) RG-8 coax 802.5 (more expensive than RG-58) X3T9.5 fiber optic (FDDI) Price/foot in table; add cost of connectors Cat 5 wire: 123 6 (Bl, Bl/Wh, Or, Or/Wh)

9. Chapter 69 Cable Management, p. 193 Terry College of Bus, U of Georgia No cable plan; a mess! Nobody knew where the cables and hubs were: had to crawl around ceiling wires Found asbestos in ceiling! Had to fix it … …Univ spent $400K to install Cat 5 to every office; installed fiber-optic BN between network segments

10. Chapter 610 Network Hub: Fig 6.2 p. 193 Hub repeats signal to other nodes Dumb hub: only repeats Smart hub: managed (SNMP) and program Switching Hub: switches signal only to destination (aka switch) Measure: # of ports Hub speed: 10, 10/100, or 100 Mbps Router often combines switched hub

11. Chapter 611 Network Operating System NOS – controls the network One set runs on server (Novell Netware; Windows Server: NT, 2000, 2003; Unix) One set runs on client (Windows 9x, ME, 2000, XP, Mac, etc.) NOS (server) replaces regular server operating system Provides file sharing, print sharing, web service, FTP service, email service, etc. Windows 2003 looks remarkably like Windows XP

12. Chapter 612 Network Profiles Gives the resources that are shared on the network User profile for each person shows what resources can be accessed

13. Chapter 613 II. Ethernet (IEEE 802.3) Traditional (shared) Ethernet Topology – layout of network Logical versus physical topology Bus Star – most prevalent Loop or ring Hybrid

14. Chapter 614 Ethernet Media Access Control Contention: CSMA/CD – carrier sense multiple access with collision detection So long as nobody is broadcasting on network, a node can transmit If two packets collide, jamming occurs and the two parties wait a random time and redo

15. Chapter 615 Types of Ethernet See figure 6-5 p. 199 10Base-2 (10=10 Mbps, Base=baseband, and –2 is coaxial cable 10Base-T = 10 Mbps twisted pair 100Base-T= 100 Mbps UTP 1000Base-T = 1 Gbps Ethernet 40GbE = 40 Gbps fiber Some use 10/100 which switches to match speed

16. Chapter 616 III. Switched Ethernet Switch replaces hub – only transmits packet to desired node, not all nodes Greatly enhances the capacity of cable because switch buffers packets, allowing transmissions on all lines ~ simultaneously Helpful as #users increases 10/100 switch allows mixture of 10 and 100 Mbps Switch uses forwarding table (like routing table) which builds dynamically This is a layer-2 switch (at data link layer)

17. Chapter 617 Switching Modes For first few minutes, works like a hub until it identifies where clients connect Cut through switching Sends pack immediately before checking CRC Store and forward switching Process packet normally after CRC Fragment-free switching Send after reading 1 st 64 bytes

18. Chapter 618 V. Best Practice LAN Design Effective Data Rates depend on.. Nominal data rate in physical layer Error rate (# of retransmissions) Efficiency of data link layer protocols used Efficiency of media access control methods CSMA/CD work well in low-volume subnets (the elbow curve – fig 6.7 p. 205) Thus keep utilization < 50-60%! Switched ethernet works better than hub See Fig 6.8 p. 207 for effective data rates/user

19. Chapter 619 Recommendations Costs drop after new technology appears – 10BaseT and 100BaseT are now cheap! Very small networks: 10BaseT Switched 10BaseT over Cat 5e cable is fine unless high volume data (streaming) is done Hi vol: switched 100BaseT on Cat 5e or fiber optic cables

20. Chapter 620 VI. Improve Network Performance Software – Basically fine tune network settings in NOS: disk cache, buffer space, etc. Add a new protocol that is faster Hardware – Buy another (or faster) server Increase memory in server RAID drive or higher performance disk NIC: get server version NIC with high performance

21. Chapter 621 Improve Network Performance Improve circuit capacity Upgrade to 100 Mbps hub Upgrade to switched hub Split into 2 or more subnets and add a server NIC for each network segment Move high demand clients to different segments

22. Chapter 622 Improve Network Performance Reduce network demand Move files to client computers (e.g., heavily used applications) Use disk cache SW on clients to reduce need to access files on servers Adjust time when users work – busiest times are 9 AM and right after lunch: FlexTime is very popular in IT