A Small PC Network Chapter 6 Revision 1: August 2000 Copyright 2001 Prentice Hall

2 Previous 5 chapters n Looked at accessing the Internet n Only part of data communications and networking – Accessing the Internet dealt with WAN – Only looked at subnet using PPP and modems – What about LAN’s – Are there other subnet protocols and technologies?

3 First Five Chapters Concepts n Layered Architectures n Protocols n Connection Oriented vs connectionless n Circuit and Packet Switching n Routing n Etc.

4 Why network? n Share resources – Data resources n Distributed data n Data on servers – Share programs n Network versions of programs – Site license – # of clients – Share peripherals n Printers, scanners etc.

5 LAN and Layered Architecture n What layers deal with getting frames from 1 host to another on the same network (subnet) – Answer – datalink and physical n Datalink protocols – PPP – Ethernet – Token ring – FDDI n Datalink – concerns itself with a single link n Network – concerns itself with link to link(end-to-end)

6 Data Link Protocols n Services – Framing – Delivery of frame n Send frame to all n Pass a token around n Flow control (limited amount of buffering) n Error detection

7 Real World Example n Travel agent – network layer – Travel from here to Florence Italy n 1 ST Link – Clarksville to Nashville – Use Clarksville limousine service n 2 nd Link – Nashville to New York – Plane (American Airlines) n 3 rd Link – New York to Rome – Plane (Air Italia) n 4 th Link – Rome to Florence – Train

8 Implementation of Data Link Layer n Hardware – Adapter n NIC – Ram – DSP Chips – Interface to bus of computer – Interface to network connection – PC handles upper layers

9 Implementation of Data Link Layer n Software – Network operating system n NIC and PC are somewhat autonomous – PC sends Ip packet to NIC that puts it into frames and sends it – Reads incoming frames and may pass them to PC

10 Small Peer-Peer PC Network n No dedicated (full- time) server n User PCs supply services to each other n So user PCs act both as clients and as servers

11 Small Peer-Peer PC Network n File Sharing – Each PC can make certain disk drives or directories available to to other user PCs – Can allow others read-only or full access to files there – Can require password for access

12 Small Peer-Peer PC Network n Printer Sharing – Each PC can make one or more printers attached to it available to others

13 Small Peer-Peer PC Network n Advantage – No dedicated server to purchase and maintain

14 Small Peer-Peer PC Network n Disadvantages – If someone turns off their PC or crashes it, people using its files or printer are cut out

15 Small Peer-Peer PC Network n Disadvantages – Users often set up security poorly giving access to unauthorized people – Special problem if home network is connected to the Internet New

16 Small Peer-Peer PC Network n Overall – Beyond about 2-5 users, problems become too pronounced – Beyond about 10 users, very bad idea New

17 Elements of a Simple PC Network with a Dedicated Server Hub or Switch Server Client PC Server Wiring

18 Elements of a Small PC Network n LAN Standards – We will focus on LANs that follow the Ethernet standard (80% do) n Small Ethernet PC networks use only inexpensive UTP wiring n Speeds for NICs and Hubs or Switches – 10Base-T (10 Mbps, baseband, UTP) – 100Base-TX (100 Mbps, baseband, UTP) – 1000Base-T (Gigabit Ethernet) (1 Gbps)

19 Elements of a Small PC Network n Need a hub or switch to connect the PCs – Connector box with multiple plug-in jacks – Hubs and switches are described later n Each PC needs a network interface card (NIC) – Implements physical and data link layer connection to the LAN n Wire – Business-grade UTP telephone wiring

20 Elements of a Simple PC Network n Ethernet UTP Wiring – 4-pair bundle (8 wires) – Each pair is twisted – Terminates in RJ-45 connector n Quality Level – Category 5 or Category 5e (enhanced) – Older categories (3 and 4) exist but are now fairly rare

21 Elements of a Simple PC Network n Ethernet UTP Wiring – Come pre-cut in many useful lengths (1 m, 2 m, 25 m, etc.) with connectors already added to both ends – Can also cut wire to precise lengths needed and then attach connectors n Must test the wire after cutting it and attaching connectors!

22 Elements of a Simple PC Network n Plenum Wiring – For wiring run through airways; covering does not give off toxic fumes if it burns n Required if wires are run through air conditioning ducts n Needed in false ceilings and false floors – More expensive but required by law and concern for employee safety

23 Elements of a Small PC Network n Ethernet Hub Operation – One station transmits a single bit to a hub (physical layer operation) – Hub broadcasts bit to all attached stations – All but the destination PC should ignore the message Hub Bit

24 Elements of a Small PC Network n Ethernet Hubs – Broadcasting is simple, so – Hubs are inexpensive

25 Elements of a Small PC Network n Ethernet Hubs Can Create Latency – Only one station may transmit at a time or the signals will collide and be unreadable – Other stations must wait (latency) Must Wait

26 Elements of a Small PC Network n Ethernet Hubs Can Create Latency – Becomes a problem with 100+ PCs and 10 Mbps hub – 200 PCs is upper limit for tolerable service with a 10 Mbps hub Must Wait

27 Elements of a Small PC Network n Ethernet Switches – One station transmits a frame to a switch (data link layer operation) – Switch only transmits frame out port of destination PC – No broadcasting out all ports Switch Frame

28 Elements of a Small PC Network n Ethernet Switches – Multiple conversations can take place simultaneously because there is no broadcasting, which ties up all ports – No wait to transmit; no Latency Switch

29 Elements of a Simple PC Network n Client PCs – End user’s desktop or notebook PC – Add network interface card (NIC) – With Win95, Win98, Win NT, or Win 2000 Professional, and Macintosh, no extra software is needed – Networks have many client PCs

30 Elements of a Simple PC Network n Servers – Provide services to client PCs – Usually PCs themselves – Most PC nets have multiple servers – Require a NIC – Require a server operating system (SOS) – Require application software

31 Elements of a Simple PC Network n Server Operating System (SOS) – Servers need operating systems more reliable than client PC operating systems – Windows NT/2000 Server, Novell NetWare, UNIX, LINUX n Application Software – Provides the services offered by the servers – , word processing, file sharing, etc. – More expensive than the SOS

32 Elements of a Simple PC Network n Novell NetWare SOS – Once dominant, but market share has shrunk – Excellent file and print service – Excellent directory service (later) – Until recently, was not sufficiently robust and scalable for servers other than file servers

33 Elements of a Small PC Network n Microsoft Windows Server Operating System – More robust than desktop Windows (Win 95, Win 98, Win 2000 Professional, etc.) – All 32-bit code – Microsoft Windows NT Server before 2000 – Newer Microsoft Windows 2000 Server n Versions in order of increasing functionality: Windows 2000 Server, Advanced Server, Data Center Server New

34 Elements of a Small PC Network n Microsoft Windows Server Operating System – Easy to install, learn, and use because resembles desktop Windows – Becoming dominant for small business and small department servers – Windows NT Server has had serious reliability and scalability problems – Windows 2000 Server versions promise to improve reliability and scalability

35 Elements of a Small PC Network n UNIX – Powerful workstation servers run UNIX – Extremely reliable – Workstation servers running UNIX dominate the enterprise server market

36 Elements of a Small PC Network n UNIX – Expensive to buy – Must retrain staff or hire UNIX staff – Many versions of UNIX exist n Most run the same application software n However, have different management utilities, etc., requiring training for each version used – Not for Small PC Networks

37 Elements of a Small PC Network n LINUX – Version of UNIX – Runs on Intel PCs ( and compatibles); low cost – Available free n But usually pay around $50 to $150 for packaged version – Reliable like other UNIX versions – Open Source: Many people are developing tools to add to the LINUX core

38 Elements of a Small PC Network n LINUX – Available in Distributions n A distribution has the LINUX kernel plus other programs n Available on CD-ROM or by downloading n Distributions from different LINUX vendors differ in the specific programs included n Differences make selection, implementation difficult New

39 Elements of a Small PC Network n LINUX – Requires Extensive Labor to Set Up, Maintain – Device driver software often is lacking for printers, disk drives, and other devices – Requires more training because it is UNIX – Better distributions and support coming? New

40 Servers n Options – Put all services on one server, or – One server per service, or – In-Between solutions

41 Servers n Option: Put All Services on One Server – Cheapest for small organizations

42 Servers n Option: One Service Application per Server – Can optimize hardware for application – More reliable, because a crashing service does not crash others – Security: users cannot log into one service, switch to another easily

43 Servers n Option: Hybrid with Some Servers Offering One Service, Others Offering Several – Distribute services in ways that make sense for the services, organization size, etc.

44 Servers n Cost (Which is Cheapest?) – Difficult to know – For small organization, most or all services on one usually is cheapest – For larger organizations, optimization through multiple servers often minimizes costs

45 Server Application Software n File Service Allows File Sharing – File server stores program and data files – Shared file be accessed by any user with access rights – Built into most SOSs File Server Access Rights No Access Rights

46 Server Application Software n File Service – For sharing application program files also – No need to install applications on each PC n Greatly reduces installation labor File Server

47 Server Application Software n File Server Program Access – Program is STORED on the file server File Server

48 Server Application Software n File Server Program Access – But program is EXECUTED on the client PC – Limited by power of client PCs, which do not get very large File Server

49 Server Application Software n Print Service – Also built into SOSs – Print jobs go to shared printers – But they first go to the file server – Not directly to the print server! File Server Print Server Shared Printer Client PC

50 Server Application Software n Print Service – File server stores print job in a print queue until print server is ready to print it – File server sends the print job to the print server File Server Print Server Shared Printer

51 Server Application Software n Print Server – Print server feeds the print job to the printer – Print servers are simple and inexpensive because the file server does most of the work – Low print server cost allows shared printers can be scattered throughout the office File Server Print Server

52 Server Application Software n Print Server – Connects to printer via parallel port on the print server; no special printer needed – Has NIC to connect to the hub or switch – Requires an RJ-45 port on the hub or switch Print Server Parallel Cable UTP RJ-45 Port

53 Server Application Software n Print Server Location – Parallel cable distance limitation requires print server to be within 1-2 meters of the printer – UTP allows print server to be up to 100 meters from the hub or switch Print Server Parallel Cable (1-2 m only) UTP (up to 100 m) RJ-45 Port New

54 Server Application Software n Typical Application Software – Word processing, , etc. – Must buy multiuser versions, not just a single copy from a retail store – License will limit the number of users – Will cost more than the SOS New

55 Server Application Software n Remote Access Service (RAS) – User dials into a remote access server – Server authenticates the user (user must prove identity) – If authenticated, user may use internal servers – Client PC needs RAS software LAN Internal Server RAS Dial-In Client Dial-Up Telephone Line RAS Client Software

56 Server Application Software n Internet Access for a Simple PC LAN – Serial Router – Simple, inexpensive router – One RJ-45 port for LAN, one suitable port for ISP Connection Serial Router Access Line

57 Server Application Software n Serial Routers – May provide security to stop outside hackers n Network address translation (NAT) hides addresses of internal machines n Only serial router’s IP address appears in outgoing packets Serial Router Access Line IP Packet with Serial Router’s IP Address

58 Server Application Software n Serial Routers – Provide security to stop outside hackers n May provide a firewall (discussed in Chapter 10) to prevent unauthorized access from Internet hackers Serial Router Access Line

59 Server Application Software n Directory Servers – Problem: Most networks have many servers – To use a resource, must know the server n To send , address is n Files must be accessed on particular servers

60 Server Application Software n Directory Servers – Directory server knows all resources on all servers – Can send mail to user – Can search for a specific file across servers Directory Server

61 Server Application Software n Directory Servers – Know user access rights on all servers – Single login to directory server – After that, get access to all other servers where user has access rights Directory Server Single Login

62 File Server Systems Administration n Set Access Rights for Each Directory, File – The ability to even see a directory or file (otherwise, it will be invisible) – The ability to get a read-only copy of a file in a directory (a copy that cannot be edited and then saved under the same name) – The ability to create, edit, and delete files and subdirectories – The ability to assign access rights in a directory to other users

63 File Server Systems Administration n Set Up Access Rights for Each Directory, File – Must be done for each individual in each directory! – Usually, however, assign individual to groups – Give access rights to groups – Members of groups then get those rights – Using groups greatly simplifies the assignment of access rights

64 File Server Systems Administration n Automatic Inheritance of Access Rights – Assign rights to individual or group in a directory – Rights automatically inherited in lower directories – Simplifies rights assignment Application Word ProcessingDatabase OracleQuickDB Assigned Browse And Read Rights Inherits Browse And Read Rights Inherits Browse And Read Rights

65 File Server Systems Administration n Blocking of Inheritance – If assign rights explicitly in subdirectory, inheritance is blocked – Only assigned rights are effective Application Word ProcessingDatabase Oracle (Browse and Execute Only) QuickDB Assigned Browse And Read Rights Inherit Browse And Read Rights Assigned Browse And Execute Rights

66 File Server Systems Administration n The Assignment of Rights: Recap – Rights can be assigned to individuals or group n Group members receive all rights assigned to the group – Rights are automatically inherited in lower- level directories, unless – Rights are explicitly assigned in a directory, in which case automatic inheritance is blocked and only explicitly assigned rights are in effect in that directory

67 File Server Systems Administration n Omnibus Rights – Administrator normally has omnibus rights – Can read, delete, etc. any file in any directory – Serious security concern

68 Setting Up a Client PC for Windows n Physically install a NIC n Set Up Microsoft Windows for Networking – Adapter (installed with NIC) – Protocol – Client

69 Client PC Setup for Windows n Install NIC – Physically open systems unit – Main printed circuit board is the mother board – Has slots for expansion boards – Press NIC expansion board into slot, use screw to hold in place Slot Mother Board NIC

70 Client PC Setup for Windows n Install NIC – Types of Slots – ISA for up lower speeds – PCI for higher speeds – NIC must be compatible with slot Slot Mother Board NIC

71 Client PC Setup for Windows n Install the NIC – Boot system after installation – Windows should recognize the new NIC – Setup will be fairly automatic, although you may be asked to provide a disk that came with the NIC – Some NICs have their own setup disks and should bypass automatic Windows setup. Check the NIC documentation

72 Client PC Setup for Windows n Set Up Microsoft Networking n In Windows 95 and Windows 98, – Go to the Start Button – Choose Settings – Choose Control Panel – Double click the Network icon – This opens the Network Dialog Box

73 Client PC Setup for Windows n Be sure the Configuration tab is selected in the Network Dialog Box – You will see adapters, protocols, clients, and services that have already been added n Operations – Add: To add an adapter, protocol, client, or service – Remove: To remove one – Properties: To see or change the properties of the selected adapter, protocol, client, or service

74 Client PC Setup for Microsoft Windows n Adding a Protocol – In the Network Dialog Box, clicking the “Add” button takes you to the Select Network Component Type dialog box – Choose Protocol, then hit Add – You then go to the Select Network Protocol dialog box – Choose the Manufacturer and Protocol your server requires

75 Client PC Setup for Microsoft Windows n Configuring a Protocol – In the Network Dialog Box, click on the protocol you installed – Click the Properties button takes you to the properties dialog box for that protocol – Set up the properties – Bind the protocol to your client and adapter

76 Client PC Setup for Microsoft Windows n Client – In the Network Dialog Box, clicking the “Add” button takes you to the Select Network Component Type dialog box – Choose Client, then hit Add – You then go to the Select Network Client dialog box – Choose the manufacturer and client your server requires

77 Setting Up a Peer-to-Peer Network n For Each PC – Install the Client for Microsoft Networks – This supports peer-peer networking n Implement Sharing – In the Network Dialog Box, – Click the File and Print Sharing button – Enable file and print sharing by clicking on the appropriate boxes New

78 Setting Up a Peer-Peer Network n To Share a Specific Printer – Choose Start, Settings, Printers – Right click on icon for printer to be shared – Choose Sharing in the pop-up menu – Select Shared As in the Properties Dialog Box and give the printer any name – Give a password if desired – Anyone can now use it if they have the password or if you set no password New

79 Setting Up a Peer-Peer Network n To share a disk or directory’s files – In Explorer or My Computer, right click on disk or directory to be shared – Select Sharing in the pop-up menu n In (name of item selected) Sharing Dialog Box – Click Shared As radio button n Give shared name (how others will refer to it) n Add a comment if desired New

80 Setting Up a Peer-Peer Network n In (name of items selected) Sharing Dialog Box – Select an Access Type Radio Button n Read-Only – Anyone can read but cannot change – Can give password n Full (can do anything) – Can do anything – Can give password n Depends on Password – Can give different passwords for read-only, full New

81 Using a Shared Resource n Using a Shared printer – In application, choose Print – Select printer as usual – May need to give password n Using a Shared File or Directory – Choose Network Neighborhood – Select the desired file or directory – May need to give password New