Post on 20-Jan-2016
transcript
Networking
An overview of the major components
Issues
• How will each computer be identified? How will you control who talks and when?
• What kind of wire? How many wires in cable? What type of connectors?
• When two PCs access one file, what happens?
• How can access to data and peripherals be controlled?
The parts
• We need a client; a PC that is requesting information or services
• We need a Network Interface Card (NIC)to identify client; a way to break files into packets for transmission and reassemble packets
• We need wire/cables or some method to get data from point A to point B
• PC Operating System has to understand and communicate over the network
• We need a server
Topologies
Packets and NICs
• Data is moved in packets or frames, much as you would move your belongings in boxes between apartments
• Every NIC has a Media Access Control address (MAC) that is unique; 48-bits long as 12 hex characters
Frame
MACto
MACfrom
Data CRC
Hardware ProtocolNetwork Technology
• Defines the packet type
• Defines cabling and connectors used
• Defines everything necessary to get data from one computer to another
• We have two: Ethernet and Token Ring
Ethernet
• Mid-70’s by Digital Equipment, Intel and Xerox
• Dominant standard, thanks to Internet
• Three versions: coaxial, unshielded twisted pair and fiber optic
• Because frame type is constant, versions can be mixed on the network
Token Ring
• Developed by IBM
• Centered on communication with mainframe systems
• Completely incompatible with Ethernet
• Used to connect to IBM’s “Big Iron” systems and thus is far from dead
UTP Ethernet
• 10BaseT, or 100BaseT, or 1000BaseT• 10-, 100-, 1000Mbps (1 Gbps)• Uses a star bus topology, typically• Use Unshielded Twisted Pair (UTP) cable
(4 pairs = 8 wires)• Connect to Hub (or Switch) which contains
the bus• One PC per segment; 100 meters per
segment
CAT levels
What Mike does not tell you is that the number of twists per inch/footOf cable increase as the CAT level increases
Wiring Standards
EZ-RJ-45 has holes here so wires stick out
during assembly
1 8
More on cabling
• The space up in the false ceiling, in walls and under a raised floor is called a plenum space
• You should run plenum (non-toxic) cable in a plenum space
• It is 3x to 5x more expensive than PVC cable
Hubs and Switches• In a star network, all devices connect to a
central hub or switch (now that prices have come down). Max 1024 devices to a hub.
• When a wire breaks, only that device looses the network connection – the rest of the network remains functional
• Hubs act as repeaters, amplifying the signals – can use them to extend cable runs past 100 meters (~360 feet)
• They need electrical power…or PoE• Hubs rebroadcast signal to all ports; switch tries
to be selective
Crossover Cable
• Connect two PCs without hub
• 1-3, 2-6, 3-1 and 6-2 or “A” on one end and “B” on the other
• Be sure to mark these cables!
• Note that only 4 wires are required
Duplex
• Full-duplex: can both send and receive at the same time
• Half-duplex: either send or receive – like “push to talk” phones
Link Lights
• Should be solid on indicating good connection at both ends.
• Activity LED should flicker as data packets happen on the network.
• Both are first steps when troubleshooting network problems.
Token Ring
• Set of standards developed by IBM• Completely incompatible with Ethernet• Uses a ring topology• A token gets passed from NIC to NIC around the
ring• Can only send a packet when you have token –
thus no collisions• 4- or 16 Mbps rings• Originally built with two-pair shielded (STP)
cable; can be UTP today
Connectors
• Unique, hermaphroditic connector called IBM-type Data Connector (IDC) or Universal Data Connector (UDC)
• They can plug to each other
• “Standard” cable has IDC on one end and 9-pin connector on the other (at network card end)
Hermaphroditic Connector
Connections, cont.
• Can use a Token Ring Hub (Mulitstation Access Unit (MAU)) – not interchangeable with hub for Ethernet
• Can use RJ-45 connectors and Cat5e cable with MAU
Wire PCs/MAU Seg Ln MAU dist w/repeater
STP 260 100 m 720 m
UTP 72 45 m 360 m
Serial/Parallel
• When all else fails
• Only for two PCs
• Need crossover versions of 1284 (Parallel) or RS-232 (Serial)
• Really, really slow by comparison to Ethernet or Token Ring
• FireWire can be used; so can USB
Network Operating System
• We have NICs to assemble and disassemble packets (1)
• We have wire to transmit packets (2)• We need an OS that can communicate with the
hardware and other PCs (3)• We need a server, or resource, on our network
(4)• Every Windows version is a NOS – thanks to
Apple for starting the idea – but we need to configure it
The Three Parts
• Need to install a network protocol to communicate with hardware
• Enable server software to share resources
• Install client software to enable the PC to access shared resources
• Windows is capable of all three
NOS Organization
• Client/Server– Take one machine and dedicate it to server function(s)– Dedicated OS, not used as workstation– Everybody else is a client– Novell Netware
Server
Client Client Client
Peer-to-Peer
• Everybody is equal – all share resources and use resources
• All are workstations• Great for small networks with 10 or less systems• Each system maintains its own security; Win 9x:
– Read-Only– Full access– Depends on password
* NT family allows NTFS permissions on NTFS volumes• Need a local account on every system for each user that
will access resources
Workgroup(s)
• A nice way to organize the network into functional groups
• No security value – can’t limit access
• Designed for small networks – up to 15 computers
Multiple Servers
• With C/S and P2P, you have to log in to each server independently
Domain-Based
• Use a directory service to store user and computer account information (security database)
• This is stored (and accessed) at only one place on network; can have mirrors too
• Novell (ver. 5+) uses NetWare Directory Service (NDS)
• Windows 2000 and 2003 use Active Directory• Lightweight Directory Access Protocol, or
LDAP
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Administrator Account
• Windows 2000, XP and Vista
• Absolute power – can do anything: add, modify, remove anything
• Single account
• Loose password for this account and have to reinstall the OS
Protocols
• The “language” of the network – “above” the MAC address of the NIC
• Keeps track of machine names and addresses and organizes frames
• We need client software on each PC that can “speak” the protocol
• All networks use at least one protocol
NetBEUI
• NetBIOS Extended User Interface
• Great for small networks
• Very “chatty” protocol, but also very fast
• Won’t route, so constrained to small networks – 200 nodes
• Not directly supported in XP – but you can add it if necessary
IPX/SPX
• Novell’s idea; Internetwork Packet Exchange/Sequential Packet Exchange
• Can use it without a Netware server
• Client is called NWLink for Windows nodes
• Works well with routers, quick
TCP/IP
• From our UNIX brethren
• XP, OS X, Novell (version 5) all use it now
• Best for larger networks
• Not very speedy, takes up large amount of memory
AppleTalk
• Gets honorable mention
• Used on pre-OS X Mac systems
• Been around since 1984
• Quick, but “chatty”
• Does not have a PC version
Client Software
• Need client software for every kind of server you want to access
• Windows installs Client for Microsoft Networks
• You can add File and Printer sharing to make your system a server on the network
Installing and Configuring a Wired Network
• Network Interface Card, with driver(s) or USB and virtual NIC
• Protocol decision• Network client for that protocol
– Client (Service) for Microsoft Networks– Client Service for NetWare– Client Service for the protocol
• (Have to enable File (and Printer) Sharing to share resources from your machine)
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Installing a NIC
• Put it in available slot – usually PCI – if it is a separate device
• Plan on providing the driver files. You may be pleasantly surprised if Windows figures out the NIC without any help
• If you have to force the Add Hardware Wizard, you have done something very wrong
Configuring the Protocol
• NetBEUI – nothing to configure; just computer name (< 15 characters)
• NWLink – might have to set frame type (Auto Detect; 802.2, 802.3, 802.5); Netware File and Print Services requires additional software from Microsoft
• TCP/IP – Need to set IP address, subnet mask and default gateway. A+ exam will assume someone gives you this information
More TCP/IP
• Dotted Decimal Notation
• Classes of addresses:– Class A 1-126 (first bit is zero)– Class B 128-191 (first bit is one)– Class C 192-223 (first two bits are one)
• Subnet mask – what is network and what is host
255.255.0.0
Network Number
Host number
IP addresses
• 131.190.4.121 is Class B; subnet mask would be 255.255.0.0
• 131.190 is network address
• 4.121 is host, or computer, number
• 192.168.1.108 is Class C; subnet mask is 255.255.255.0
• 192.168.1 is Network address
• .108 is host, or computer, number
Default Gateway
• Where to send packets if destination is not on the local network
• Often, this is the router on your network
Gateway
Domain Name Service (DNS)
• Database of Internet names and IP addresses
• Internet names are controlled and restricted and cost money each year
• Top Level Domains: .COM,.EDU,.GOV, .ORG, .NET, .MIL and now we have a few more: .INFO, .BIZ, .NAME, .TV
.
.NET .MIL .COM
Dot
Aiconline.net Hbo.com
DNS Servers
DHCP
• Dynamic Host Configuration Protocol• Automatically assigns IP addresses on request• Rather like rooms in a hotel• Address can change from time to time – reboots
and shutdowns• Static IP, in contrast, does not change• Cuts way down on the hassle of IP addressing
and remembering what address goes where
WINS
• Windows Internet Name Server
• Enables Windows network names like Server1 to be correlated to IP addresses
• Going away; used by Win ME and earlier
• Being replaced with expanded DNS ability to resolve both Internet and Windows network names
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TCP/IP tools
• Run from a command prompt window
• PING – can you reach an IP address?
• IPCONFIG – what’s going on here?
• (NSLOOKUP – for DNS server names and addresses)
• TRACERT – Shows the route a packet takes from you to another IP address
Automatic Private IP Addressing
• If a computer can not access a valid DHCP server, will give itself an address
• 169.254.X.X – Last two numbers are random
• If IPCONFIG shows this type of number, you know something is wrong with network
Sharing Drive(s) or Folders
• First, turn on File/Printer Sharing• Right-click resource and select Sharing, or
Properties and then Sharing tab• Provide a name for the resource – name
will be used by others to access the resource
• Set access restrictions – if any• Sharing a printer follows same path (will
need a printer driver on accessing system)
Sharing Backup Drive
• Buy the drive
• Attach to one computer
• Share the drive (right click; sharing)
• Go to another PC on network; Map Network Drive (to get local name/letter)
• “Point” backup software to that drive letter and a folder unique to the PC
Mapping a Drive
• Source can be a networked hard disk drive or a folder on a drive
• You can assign a drive letter to that resource
• Within applications, you can refer to the network resource by that drive letter
• Will show up in My Computer
Sharing Printer(s)
• Make sure File and Printer sharing is turned on!
• Right click the printer – choose sharing, set the share name
• (For Win98, have to load printer driver files on system attaching to shared printer)
• Win XP/Vista: if sharing PC is XP, will automatically share driver also
Wander the Network
• My Network Places to “see” available resources on the network
• Can “map” a network resource to a drive letter
• UNC – Universal (to Microsoft only!) Naming convention: \\server\resource
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Set up a Network
InternetDSL or Cable
ModemRouter
PC 1
PC 2
PC 3 DHCP functionFirewall Function
SPI – Stateful Packet InspectionWireless access
Verify the Symptom
• Walk through the process with the user to get to the error/problem/issue as best you can
• Did it ever work? And then what changed?
• Can you isolate the symptom by using known good parts?
More Questions
• When did it (start to) happen?
• What has changed?
• Who did the changing?
• Can you reproduce the problem?
• What can you do to isolate the problem?
• Once fixed, have you tested the fix?
Mike’s Layers
• Check the NIC first, to see if it lights up
• Then check switches, hubs, routers for lights – or lack of them. My trip to SB.
• Check protocol used. Is it the right one?
• Are you trying to access something that is actually shared? Properly shared?
• Is laptop’s wireless turned on?