Computer Networking Part 1 CS 1 Rick Graziani Cabrillo College Fall 2005.

Computer NetworkingPart 1

CS 1

Rick Graziani

Cabrillo College

Fall 2005

Rick Graziani [email protected] 2

What is networking?

• Communication!

• An interconnection of computers and other devices including:– Client computers– Servers (computers)– Network Devices

• Hubs and Switches• Routers• Firewall


Most successful networking applications?


What is in a network?


What is a network?

• A computer network is a series of computers and other devices interconnected by communication paths.

• Computer networks include: LANs and WANshttp://www.albany.edu


Ethernet LANs


LAN – Local Area Network

• LAN (Local Area Network) - A network connecting computers at a single site


LAN – Local Area Network

• A LAN:– Operates within a limited geographical area– Controlled by local administration– Allows local users to:

• Share printers• Access local file servers with software and data• Access the Internet


Ethernet LANs

• The most common LAN technology is Ethernet.

• Ethernet allows computers, printers, and other devices, “in the same network”, to be able to communicate.

• For devices to be able to communicate with each other over an Ethernet network, they must be configured with:– IP Address and Subnet Mask on the same network– What??? (We will discuss this shortly)


Creating an Ethernet Network

• To start, your computer must have an Ethernet Network Interface Card (NIC).

• Ethernet NICs have an RJ-45 interface or port.



• Hubs and Switches are used to connect computers, printers and other devices in the Ethernet LAN.



• Ethernet cables, i.e. Cat-5 or Cat-6 cables (Category 5, Category 6) are used to connect computers to the hubs and switches.

• Cat-5 cable connects computer NIC to hub or switch.




Configuring IP (Internet Protocol)


IP Configuration

• To communicate with other computers on your network you need to properly configure:– IP Address (of your computer)– Subnet Mask (of your computer)

• To communicate with computers outside your network you need to properly configure:– Default Gateway IP Address

• To be able to use domain names, like www.cabrillo.edu, instead of IP addresses you need to properly configure:– DNS (Domain Name System)

Server IP Address


IP Configuration: IP Address & Mask

• To communicate with other computers on your network you need to properly configure:– IP Address (of your computer)– Subnet Mask (of your computer)

• IP – Internet Protocol• IP Address is the unique address of

your computer on your network.• Subnet Mask is used by your computer

to figure out what network it belongs to.• Analogy:

– Name: RICKGRAZIANI– Mask: FFFFLLLLLLLL– The Mask tells us which part of

RICKGRAZIANI is the first name (F) and which part is the last name (L).

I am part of the 192.168.1.0 network!


IP Configuration: Default Gateway

• To communicate with computers outside your network you need to properly configure:– Default Gateway IP Address



• Default Gateway or Router: This is the device that connects your network to other networks, including the Internet.

Switch ports that connect to computers on your LAN

DSL or Cable Modem port that connects to your Internet Service Provider



• Any information that needs to be sent to IP Addresses outside your network is sent to the Default Gateway or Router.

To the Internet192.168.1.10

192.168.1.1


IP Configuration: DNS

• To be able to use domain names, like www.cabrillo.edu, instead of IP addresses you need to properly configure:– DNS (Domain Name System)

Server IP Address

207.62.87.54


IP Configuration: DNS• You could use IP Addresses when accessing other computers, but we

would rather use names (domain names).



• Computer networks only understand IP Addresses such as: – 66.94.230.47

• Computer networks do not understand domain names such as:– www.yahoo.com– A domain name is a name that is entered into a computer (e.g. as

part of a website or other URL, or an email address) and then looked up in the global [Domain Name System] which informs the computer of the IP address(es) with that name. (Wikipedia.com)

• People are better with names than numbers, so we would rather use names when:– Accessing a web page: www.yahoo.com– Emailing a friend: [email protected]

• DNS (Domain Name System) servers (computers) are used to translate domain names to IP Addresses.



Hey, 207.62.87.54, what is the IP Address for www.yahoo.com?

It is 66.94.230.47

Yahoo Web Server

Hey, 66.94.230.47, please send me your web page.

Here, 192.168.1.10, here is my web page.



• The details of how DNS works.

• If your DNS server does not know the answer, it will find out for you.


How do I view/edit this information on my computer?



1. Right click

2. Right click

3. TCP/IP, Properties Left click




Setting the IP Configuration Information

• IP information can be configured:– Statically– Dynamically

• Using a DHCP (Dynamic Host Configuration Protocol) Server


IP Configuration: Static Configuration

• Static configuration is when the user or administrator of the computer configures the IP Address, Subnet Mask, Default Gateway and DNS Server information.


IP Configuration: Dynamic Configuration

• Dynamic configuration is when the IP Address, Subnet Mask, Default Gateway and DNS Server information is obtained automatically from a DHCP (Dynamic Host Configuration Protocol) Server.


IP Configuration: Dynamic Configuration

I’m booting up, if there is a DHCP Server out there, I need my IP Configuration Information!

DHCP Server

Here is your IP Address, Subnet Mask, IP Address for the Default Gateway (router), and IP Address for the DNS Server!


The Internet and TCP/IP


What is the Internet?

• The Internet was originally designed by DARPA (Defense Advanced Research Projects Agency) in response to the U.S.S.R. launching Sputnik, the first satellite.

• Out of this came the Internet, a way for computers to communicate from different parts of the world.

• These computers can be any type of computer using any type of operating system, as long as they are using the protocol TCP/IP.


What is TCP/IP? What is a protocol?

• A protocol is nothing more than an agreement or rules to govern a way of communicating.

• The sender and receiver, and everyone in between, must agree on the rules, the protocol.

The actual letter (data) is inside (encapsulated) the envelope.


What is TCP/IP? What is a protocol?

• Protocol: An agreed form of communications.


TCP/IP Transmission Control Protocol / Internet Protocol

• TCP/IP is a suite of protocols.• IP (Internet Protocol) is used for sender and receiver addressing.• Every computer on the Internet or a network must have an IP

address to communicate.

Source IP Address: 192.168.1.10

Destination IP Address 66.94.230.47

This is known as an “IP Packet”


Yahoo Web Server


Destination IP Address: 66.94.230.47

Destination IP Address: 192.168.1.10


192.168.1.1066.94.230.47

Inside envelope: Request for web page

Inside envelope: Web page


Pinging another computer (FYI)


Connecting Networks with Routers

• The Internet, or simply the Net, is the publicly accessible worldwide system of interconnected computer networks.

• Routers are network devices that connect two or more networks together.

• Routers connect networks.


Rick’s IP Packet Analogy…

• Routers only need to care about where they send the packet next.

• “What is the next-hop router I need to send this packet to?”


Connecting Networks with Routers

http://www.maricopa.edu/network/maps/internal/do/routerip.html


DSL or Cable Modem: No Router

204.180.205.1 Public Address

Hacker can only get to public address and not private address

DSL or Cable Modem

• Routers can help protect your DSL or Cable Modem Network.


DSL or Cable Modem: With a Router

• The router is between your computer (LAN) and your DSL Modem.

• The router is between you and the Internet.

Internet


When using NAT (Network Address Translation, the Router helps hide your network from attackers.

204.180.205.1 Public Address

192.168.1.10 Private Address

Hackers can only get to public addresses and not private addresses

DSL or Cable Modem: With a Router

Internet


Networks: Bandwidth and Connections

• Local Area Networks

• DSL

• Cable Modem

• Leased Lines

• Modems


Bandwidth

• Bandwidth - The amount of information that can flow through a network connection in a given period of time.

• Usually measured in bits per second (bps)– bps: bits per second– Kbps: thousands of bits per second– Mbps: millions of bits per second


Bandwidth

LANs: 10 Mbps or 100 Mbps (or more)

Connection to ISP (Internet Service Provider)Note: Bandwidth depends up provider, location, and service plan.• DSL:

– Download: 600 Kbps to 1.5 Mbps (or more)– Upload: 256 Kbps (or more)

• Cable Modem: – Download: 600 Kbps to 3.0 Mbps (or more)– Upload: 256 Kbps (or more)

• Telephone Modem:– Up to 53 Kbps

• Leased Lines– T1: 1.5 Mbps– T3: 44.736 Mbps


Connection to ISP: DSL

• DSL (digital subscriber line) is a very high-speed connection that uses the same wires as a regular telephone line.


DSL: From HowStuffWorks.com

• Advantages of DSL: – You can leave your Internet connection open and still use the

phone line for voice calls. – The speed is much higher than a regular modem – DSL doesn't necessarily require new wiring; it can use the phone

line you already have. – The company that offers DSL will usually provide the modem as

part of the installation.

• But there are disadvantages: – A DSL connection works better when you are closer to the

provider's central office. – The connection is faster for receiving data than it is for sending

data over the Internet. – The service is not available everywhere.


Connection to ISP: Cable Modem

• A cable modem is a special type of modem that is designed to modulate a data signal over cable television infrastructure.


Connection to ISP: Cable Modem

• From www.linuxports.com

• Cable Modem Advantages – Fast data transfers, up to 30 Mbps if using a 100BaseT NIC– Competitive pricing against competing technologies– Easy to install - home prewired

• Cable Modem Disadvantages – The available bandwidth depends on the number of users on the

local cable TV line segment.– There is an asymmetrical transfer rate. Upstream is slower than

downstream.– There can be a bottleneck at the communication server at the head

end.


Connection to ISP: Telephone Modem

• A telephone modem is used to modulate and demodulate (translate) between the digital signals of the computer and the analog signals over the telephone line.

• Maximum bandwidth is only 53 Kbps.

• Need separate phone line if you want to use the phone while connected to the Internet

GOLDMAN: DATACOMM FIG.02-14

DTE DCE

DTE DCE

Modulation

Demodulation

digital analog

digital analog

PSTN Dial-up network

PSTN Dial-up network


Connection to ISP: Leased Lines

• Many companies and schools use leased lines to connect to their ISP.

• These are dedicated circuits between the provider and the customer.

• These include: – T1: 1.5 Mbps– T3: 44.736 Mbps

Computer NetworkingPart 1

CS 1

Rick Graziani

Cabrillo College

Fall 2005

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Computer Networking Part 1 CS 1 Rick Graziani Cabrillo College Fall 2005.

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