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

• More on this later

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

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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?