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

Rick Graziani What is networking? Communication! An interconnection of computers and other devices including: –Client computers –Servers (computers) –Network Devices Hubs and Switches Routers Firewall

Rick Graziani Most successful networking applications?

Rick Graziani What is in a network?

Rick Graziani What is a network? A computer network is a series of computers and other devices interconnected by communication paths. Computer networks include: LANs and WANs

Rick Graziani Ethernet LANs

Rick Graziani LAN – Local Area Network LAN (Local Area Network) - A network connecting computers at a single site

Rick Graziani 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

Rick Graziani 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)

Rick Graziani 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.

Rick Graziani Creating an Ethernet Network Hubs and Switches are used to connect computers, printers and other devices in the Ethernet LAN.

Rick Graziani Creating an Ethernet Network 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.

Rick Graziani Creating an Ethernet Network

Rick Graziani Configuring IP (Internet Protocol)

Rick Graziani 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 instead of IP addresses you need to properly configure: –DNS (Domain Name System) Server IP Address

Rick Graziani 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 network!

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

Rick Graziani IP Configuration: Default Gateway 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

Rick Graziani IP Configuration: Default Gateway Any information that needs to be sent to IP Addresses outside your network is sent to the Default Gateway or Router. To the Internet

Rick Graziani IP Configuration: DNS To be able to use domain names, like instead of IP addresses you need to properly configure: –DNS (Domain Name System) Server IP Address

Rick Graziani IP Configuration: DNS You could use IP Addresses when accessing other computers, but we would rather use names (domain names).

Rick Graziani IP Configuration: DNS Computer networks only understand IP Addresses such as: – Computer networks do not understand domain names such as: – –A domain name is a name that is entered into a computer (e.g. as part of a website or other URL, or an 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: – ing a friend: DNS (Domain Name System) servers (computers) are used to translate domain names to IP Addresses.

Rick Graziani IP Configuration: DNS Hey, , what is the IP Address for It is Yahoo Web Server Hey, , please send me your web page. Here, , here is my web page.

Rick Graziani IP Configuration: DNS The details of how DNS works. If your DNS server does not know the answer, it will find out for you.

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

Rick Graziani How do I view/edit this information on my computer? 1. Right click 2. Right click 3. TCP/IP, Properties Left click

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

Rick Graziani Setting the IP Configuration Information IP information can be configured: –Statically –Dynamically Using a DHCP (Dynamic Host Configuration Protocol) Server

Rick Graziani 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.

Rick Graziani 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.

Rick Graziani 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!

Rick Graziani The Internet and TCP/IP

Rick Graziani 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.

Rick Graziani 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.

Rick Graziani What is TCP/IP? What is a protocol? Protocol: An agreed form of communications.

Rick Graziani 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: Destination IP Address This is known as an “IP Packet”

Rick Graziani Yahoo Web Server Source IP Address: Destination IP Address: Destination IP Address: Source IP Address: Inside envelope: Request for web page Inside envelope: Web page

Rick Graziani Pinging another computer (FYI)

Rick Graziani 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 Graziani 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?”

Rick Graziani Connecting Networks with Routers

Rick Graziani DSL or Cable Modem: No Router 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.

Rick Graziani 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

Rick Graziani When using NAT (Network Address Translation, the Router helps hide your network from attackers Public Address Private Address Hackers can only get to public addresses and not private addresses DSL or Cable Modem: With a Router Internet

Rick Graziani Networks: Bandwidth and Connections Local Area Networks DSL Cable Modem Leased Lines Modems

Rick Graziani 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

Rick Graziani 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: Mbps

Rick Graziani Connection to ISP: DSL DSL (digital subscriber line) is a very high-speed connection that uses the same wires as a regular telephone line.

Rick Graziani 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.

Rick Graziani 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.

Rick Graziani Connection to ISP: Cable Modem From 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.

Rick Graziani 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

Rick Graziani 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: Mbps

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