Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Network tap wikipedia , lookup
Airborne Networking wikipedia , lookup
Wake-on-LAN wikipedia , lookup
Wireless security wikipedia , lookup
Piggybacking (Internet access) wikipedia , lookup
Dynamic Host Configuration Protocol wikipedia , lookup
Server Message Block wikipedia , lookup
Distributed firewall wikipedia , lookup
Cracking of wireless networks wikipedia , lookup
A Small PC Network Chapter 6 Copyright 2001 Prentice Hall Revision 2: July 2001 Small Peer-Peer PC Network No dedicated (fulltime) server User PCs supply services to each other So user PCs act both as clients and as servers 2 Small Peer-Peer PC Network 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 3 Small Peer-Peer PC Network Printer Sharing – Each PC can make one or more printers attached to it available to others 4 Small Peer-Peer PC Network Advantage – No dedicated server to purchase and maintain 5 Small Peer-Peer PC Network Disadvantages – If someone turns off their PC or crashes it, people using its files or printer are cut out 6 Small Peer-Peer PC Network Disadvantages – Users often set up security poorly giving access to unauthorized people New – Special problem if home network is connected to the Internet 7 8 Small Peer-Peer PC Network Overall – Beyond about 2-5 users, problems become too pronounced – Beyond about 10 users, very bad idea New Elements of a Simple PC Network with a Dedicated Server Hub or Switch Client PC Wiring Server Server Client PC 9 Elements of a Small PC Network 10 LAN Standards – We will focus on LANs that follow the Ethernet standard (80% do) Small Ethernet PC networks use only inexpensive UTP wiring 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) Elements of a Small PC Network Need a hub or switch to connect the PCs – Connector box with multiple plug-in jacks – Hubs and switches are described later Each PC needs a network interface card (NIC) – Implements physical and data link layer connection to the LAN Wire – Business-grade UTP telephone wiring 11 Elements of a Simple PC Network 12 Ethernet UTP Wiring – 4-pair bundle (8 wires) – Each pair is twisted – Terminates in RJ-45 connector Quality Level – Category 5 or Category 5e (enhanced) – Older categories (3 and 4) exist but are now fairly rare – New Category 6 is coming but will not be New necessary for Ethernet Elements of a Simple PC Network 13 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 Must test the wire after cutting it and attaching connectors! Elements of a Simple PC Network Plenum Wiring – For wiring run through airways; covering does not give off toxic fumes if it burns Required if wires are run through air conditioning ducts Needed – in false ceilings and false floors More expensive but required by law and concern for employee safety 14 15 Elements of a Small PC Network 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 Hub Bit Bit Elements of a Small PC Network Ethernet Hubs – Broadcasting is simple, so – Hubs are inexpensive 16 Elements of a Small PC Network 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 17 Elements of a Small PC Network 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 18 Elements of a Small PC Network 19 Ethernet Switches – One station transmits a frame to a switch (data link layer operation) – Switch only transmits frame out port of destination PC Switch – No broadcasting out all ports Switch Frame Frame Elements of a Small PC Network 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 20 Elements of a Simple PC Network 21 Client PCs – End user’s desktop or notebook PC – Add network interface card (NIC) – With Win95, Win98, Win ME, Win NT, or Win 2000 Professional, Win XP, and Macintosh, no extra software is needed – Networks have many client PCs Elements of a Simple PC Network 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 22 Elements of a Simple PC Network Server Operating System (SOS) – Servers need operating systems more reliable than client PC operating systems – Windows NT/2000 Server, Novell NetWare, UNIX, LINUX Application Software – Provides the services offered by the servers – E-mail, word processing, file sharing, etc. – More expensive than the SOS 23 Elements of a Simple PC Network 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 24 Elements of a Small PC Network 25 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 Versions New in order of increasing functionality: Windows 2000 Server, Advanced Server, DataCenter Server Elements of a Small PC Network 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 26 Elements of a Small PC Network UNIX – Powerful workstation servers run UNIX – Extremely reliable – Workstation servers running UNIX dominate the enterprise server market 27 Elements of a Small PC Network UNIX – Expensive to buy – Must retrain staff or hire UNIX staff – Many versions of UNIX exist Most run the same application software However, have different management utilities, etc., requiring training for each version used – Not for Small PC Networks 28 Elements of a Small PC Network LINUX – Version of UNIX – Runs on Intel PCs ( and compatibles); low cost – Available free 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 29 Elements of a Small PC Network 30 LINUX – Available in Distributions New A distribution has the LINUX kernel plus other programs Available on CD-ROM or by downloading Distributions from different LINUX vendors differ in the specific programs included Differences make selection, implementation difficult Elements of a Small PC Network 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 31 Servers Options – Put all services on one server, or – One server per service, or – In-Between solutions 32 Servers Option: Put All Services on One Server – Cheapest for small organizations 33 Servers 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 34 Servers Option: Hybrid with Some Servers Offering One Service, Others Offering Several – Distribute services in ways that make sense for the services, organization size, etc. 35 Servers 36 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 Server Application Software 37 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 Access Rights File Server No Access Rights Server Application Software File Service – For sharing application program files also – No need to install applications on each PC Greatly reduces installation labor File Server 38 Server Application Software File Server Program Access – Program is STORED on the file server File Server 39 Server Application Software 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 40 Server Application Software 41 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! Print Server File Server Client PC Shared Printer Server Application Software 42 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 Print Server File Server Shared Printer Server Application Software 43 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 Print Server File Server Server Application Software 44 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 RJ-45 Port Print Server UTP Parallel Cable 45 Server Application Software Print Server Location New – 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 RJ-45 Port UTP (up to 100 m) Parallel Cable (1-2 m only) 46 Server Application Software Typical Application Software – Word processing, e-mail, etc. – Must buy multiuser versions, not just a single copy from a retail store New – License will limit the number of users – Will cost more than the SOS New Server Application Software 47 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 RAS Client RAS Internal Software Server Dial-Up Telephone Line Dial-In LAN Client Server Application Software Internet Access for a Simple PC LAN – Serial Router – Simple, inexpensive router – One RJ-45 port for LAN, one suitable port for ISP Connection Access Line Serial Router 48 Server Application Software Serial Routers – May provide security to stop outside hackers Network address translation (NAT) hides addresses of internal machines Only serial router’s IP address appears in outgoing packets Serial Router Access Line IP Packet with Serial Router’s IP Address 49 Server Application Software Serial Routers – Provide security to stop outside hackers May provide a firewall (discussed in Chapter 10) to prevent unauthorized access from Internet hackers Serial Router Access Line 50 Server Application Software Directory Servers – Problem: Most networks have many servers – To use a resource, must know the server To send e-mail, address is user@server Files must be accessed on particular servers 51 Server Application Software Directory Servers – Directory server knows all resources on all servers – Can send mail to user (without @server) – Can search for a specific file across servers Directory Server 52 53 Server Application Software 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 File Server Systems Administration 54 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 File Server Systems Administration 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 55 File Server Systems Administration 56 Automatic Inheritance of Access Rights – – – Assign rights to individual or group in a directory Rights automatically inherited in lower directories Simplifies rights assignment Assigned Browse And Read Rights Application Word Processing Inherits Browse And Read Rights Inherits Browse And Read Rights Database Oracle QuickDB File Server Systems Administration 57 Blocking of Inheritance – – If assign rights explicitly in subdirectory, inheritance is blocked Only assigned rights are effective Assigned Browse And Read Rights Application Word Processing Assigned Browse And Execute Rights Inherit Browse And Read Rights Database Oracle QuickDB (Browse and Execute Only) File Server Systems Administration 58 The Assignment of Rights: Recap – Rights can be assigned to individuals or group Group members receive all rights assigned to the group – Rights are automatically inherited in lowerlevel 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 File Server Systems Administration Omnibus Rights – Administrator normally has omnibus rights – Can read, delete, etc. any file in any directory – Serious security concern 59 Setting Up a Client PC for Windows Physically install a NIC Set Up Microsoft Windows for Networking – Adapter (installed with NIC) – Protocol – Client 60 61 Client PC Setup for Windows 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 NIC Mother Board Slot Client PC Setup for Windows 62 Install NIC – Types of Slots – ISA for up lower speeds – PCI for higher speeds (longer slot) – NIC must be compatible with slot NIC Mother Board Slot Client PC Setup for Windows 63 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 Client PC Setup for Windows Set Up Microsoft Networking 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 64 Client PC Setup for Windows 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 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 65 Client PC Setup for Microsoft Windows 66 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 Client PC Setup for Microsoft Windows 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 67 Client PC Setup for Microsoft Windows 68 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 69 Setting Up a Peer-to-Peer Network New For Each PC – Install the Client for Microsoft Networks – This supports peer-peer networking 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 70 Setting Up a Peer-Peer Network New 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 71 Setting Up a Peer-Peer Network New 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 In (name of item selected) Sharing Dialog Box – Click Shared As radio button Give shared name (how others will refer to it) Add a comment if desired Setting Up a Peer-Peer Network 72 New In (name of items selected) Sharing Dialog Box – Select an Access Type Radio Button Read-Only – – Anyone can read but cannot change Can give password Full – – (can do anything) Can do anything Can give password Depends – on Password Can give different passwords for read-only, full 73 Using a Shared Resource New Using a Shared printer – In application, choose Print – Select printer as usual – May need to give password Using a Shared File or Directory – Choose Network Neighborhood – Select the desired file or directory – May need to give password