Intro to Networking Philip Ashman Asst. Prof. Okanagan College Dept of Network & Telecommunications Engineering Technologies
Objective • A quick note of reference. The information contained in this presentation is all information that has been and can be readily found on the Internet. • You are free to use and borrow this material as I have borrowed from others. • The goal is to provide a basic understanding of common networking and security terminology, as well as some of the next generation internet services known as Web 2.0. • The scope of this presentation is far too wide to cover any one of the aforementioned topics in detail, but as usual our good friends at Google, Wikipedia, and Cisco can provide you with more information than you could possibly consume!
What is a Network “Computer networking is the scientific and engineering discipline concerned with communication between computer systems. Such networks involve at least two devices capable of being networked with at least one usually being a computer. The devices can be separated by a few meters (e.g. via Bluetooth) or thousands of kilometers (e.g. via the Internet). Computer networking is sometimes considered a sub-discipline of telecommunications.” Quoted from Wikipedia
Intro to Networking • Sharing hardware or software • E.g. print document • Centralize administration and support • E.g. Internet-based, so everyone can access the same administrative or support application from their PCs
Computer Networking Models • Models, or protocol stacks, are organized into layers. This organizes the process into modules simliar to breaking programming code into subroutines OSI (Open Systems Interconnection) mnemonic “All People Seem To Need Data Processing” If you ever take a test on networking, you’ll have to now this, otherwise it is best to stick to the simplified model.
Simplified 4/5 Layer Model • Data Link & Physical Layer (Layer 1 &2)Most common protocol and media is Ethernet over copper twisted pair or fiber optic cable.Usually referenced as 10Base, 100BaseT, 1000BaseT for 10/100/1000Mbit/s on “T”wisted pair, or 10BaseFX, 100BaseFL, 1000BaseSX/LX/ZX for 10/100/1000Mbit/s over Fiber optics.The max distance for a single 10/100/1000 BaseT connection is 90M + 10M for patch cables. • Transport/Network Layer (Layer 3 & 4)Most common protocol is TCP/IP. IP is used at layer 4 to control the addressing, TCP/UDP is used at layer 3 for flow control and connection management • Application Layer (Layer 5,6 & 7)Applications that use the Layer 3/4 protocols to communicate. Eg: our Web Browsers, network printing, file sharing, skype, msn messenger etc…
Intro to Networking • Depending on one’s perspective, we can classify networks in different ways • Based on transmission media: Wired (UTP, coaxial cables, fiber-optic cables) and Wireless • Based on network size: LAN and WAN (and MAN) • Based on management method: Peer-to-peer and Client/Server • Based on topology (connectivity): Bus, Star, Ring
Transmission Media • Two main categories: • Guided • Twisted-Pair cables: • Unshielded Twisted-Pair (UTP) cables • Shielded Twisted-Pair (STP) cables • Coaxial cables • Fiber-optic cables • UnGuided • Wireless transmission, e.g. radio, microwave, infrared, sound, sonar
Twisted-Pair Cables • By sending half the signal down one wire in a pair, negating half the signal and sending it down the other wire in the pair, a subtraction at the other end will bring the signal back to it’s original amplitude and cancel out the interference.
Unshielded Twisted-Pair (UTP) • Typically wrapped inside a plastic cover (for mechanical protection) • UTP consists of 8 Strands, 4 pairs. They are usually terminated with an RJ45 connector according to the EIA/TIA 568A/B specs which indicates the order of the pairs. 10/100BaseT uses pairs 2 & 3 on pins 1,2, 3 & 6 Insulator Metal 4 Pairs Plastic Cover
Shielded Twisted-Pair (STP) • STP cables are similar to UTP cables, except there is a metal foil or braided-metal-mesh cover that encases each pair of insulated wires
Categories of UTP Cables • EIA classifies UTP cables according to the quality Categories 1,2,4 used to exist, but you can’t buy them any more: Category 3At least 3 twists per foot, for up to 10 Mbps (common in phone networks in residential buildings) Category 5 (or 5e)Up to 100 Mbps (common for networks targeted for high-speed data communications) Category 6More twists than Cat 5, up to 1 Gbps and uses 23 Gauge wire. Also rated up to 10Gbps for 35m.
Coaxial Cables • In general, coaxial cables, or coax, carry signals of higher freq (100KHz–500MHz) than UTP cables • Outer metallic wrapping serves both as a shield against noise and as the second conductor that completes the circuit
Fiber-Optic Cables • Light travels at 3108 ms-1 in free space • Refraction occurs when light goes between mediums of different densities with light bending away from the normal when it enters a less dense medium • The critical angle is the point at which the light is reflected back. • Beyond the critical angle total internal reflection
Fiber-Optic Cables • An optical fiber consists of a glass core (denser material) and a plastic cladding (less dense material) • Light is transmitted through the core and bounces back and forth along the core (as a result of the refraction index between the core and cladding) at a specific angle called the mode. • Common light sources include LEDs and lasers, although lasers allow for longer distances.
Fiber Optic Cables • Fiber Optic cable usually falls into two major categories, either Multi-mode or Single-mode. • Multi-mode has a glass core with a diameter of about 62.5/50 and allows light to travel at ‘multiple’ angles (modes) down the core at a specific wavelength (Usually 850nm or 1300nm) • Single mode has a glass core with a diameter of about 9 and allows light to travel at a ‘single’ angle (mode) down the core at a specific wavelength (Usually 1550nm)
Fiber Optic Cables Advantages and Disadvantages • Noise resistanceExternal light is blocked by outer jacket • Less signal attenuationA signal can run for miles without regeneration (currently, the lowest measured loss is about ~4% or 0.16dB per km) • Higher bandwidthCurrently, limits on data rates come from the signal generation/reception technology, not the fiber itself • CostOptical fibers are more expensive than copper • Installation/maintenanceAny crack in the core will degrade the signal, and all connections must be perfectly aligned
Wireless • Protocols in the 2.4GHz range are susceptible to interference from microwave ovens, cordelss telephones and blue tooth. • These are unregulated frequencies, but hopefully one or the other is smart enough to hop frequencies and reduce interference • 802.11b and g devices can use the same access points, but 802.11a requres separate (or dual) antennae. (makes sense as it uses a different freq.)
Wireless • There are proprietary extensions to boost the speed (usually advertised as 108G), but MIMO (Multiple-in Multiple-out) will likely be used to expand the bandwidth of existing technologies. • MIMO is a multi-antenna communication systems where the transmitter has multiple antennas capable of transmitting independent signals and the receiver is equipped with multiple receive antennas. Ie send data in parallell.
Wireless Security • When setting up your wireless access point learn how to log in to it and change the default settings! • Create a unique password • Create a unique SSID • Turn off SSID Broadcast • Turn on WPA-2 Pre-Shared Key encryption (may have to upgrade firmware) • Turn on MAC address filtering • Turn down the power settings if you have a small area to cover.
Local Area Network • Small network, short distance • A room, a floor, a building • Limited by no. of computers and distance covered • Usually one kind of technology such as Ethernet throughout the LAN • Often server a single location within an organization • Examples: • Network inside a Student Computer Lab • Network inside Okanagan College • Network inside your home
Wide Area Network (WAN) • A network that uses long-range telecommunication links to connect 2 or more LANs/computers housed in different places far apart. • Towns, states, countries • Examples: • Inter/Intra-City Connections • Internet Your home Canada WAN Office
WAN • Example WAN technologies: • ISDN – Integrated Service Digital Network • BW: Basic Rate: 192 Kbps Primary rate: 1.544Mbps • T-Carriers ― basically digital phone lines • BW: T1: 1.544Mbps T3: 28T1=approx 45Mbps • Frame relay • BW: 56K to 1.544Mbps or even higher • SONET – Synchronous Optical Network • BW: Multiples of OC1: 51.84Mbps • Supports OC12 and up to OC192 (9953.28Mbps) or even higher in the future
Broadband Cable Network The connection is shared by a number of subscribers, hence may raise performance and security problems TV PC Fiber-optic cable Cable Drop Coaxial Cable Cable company
Shaw Cable • Shaw is also providing an asymmetrical service. • Downstream: max 25 Mbps • Upstream: max 1 Mbps • Need a special Cable modem Ethernet link to PC Terayon Cable Modem Coaxial link from cable TV socket
Telco Network • Example of WAN: Telco Carrier ADSL Network • Telco services have been in existance since the beginning of the telephone • Telco companies make use of the existing copper phone cable in homes to deliver broadband data services via Assymmetric Digital Subscriber Line Network • Telus are currently upgrading their infrastructure bring fiber optic cable closer to homes and neigbourhoods in order to be able to offer higher speed services such as IPTV and digital phone services.
Telco Network Each connection is shared by a number of subscribers, hence may raise performance and security problems Copper Cable Home Fiber-optic cable Local Telco Office Telco company Fiberoptic Business
Telus ADSL • Asymmetric Digital Subscriber Line (ADSL) is an asymmetrical technology • Downstream: max 36 Mbps • Upstream: max 10 Mbps • May be reduced to 3 – 10 Mbps downstream and 2 Mbps upstream, depending on no. of subscribers • Need a special ADSL modem
Telus ADSL • Depending on whether Telus have your ADSL signal come in on the same wires as your telephone, you may need to install a Microfilter to avoid poor phone quality. • Microfilter installation is simple and requires no tools or telephone rewiring. Just unplug the telephone device from the baseboard or wall mount and snap in a microfilter, then snap in the telephone device.
Peer-to-Peer Networks • Peer-to-peer network is also called workgroup • No hierarchy among computers all are equal • No administrator responsible for the network Peer-to-peer
Peer to Peer Networks • Advantagesof peer-to-peer networks: • Low cost • Simple to configure • User has full accessibility of the computer • Disadvantages of peer-to-peer networks: • May have duplication in resources • Difficult to uphold security policy • Difficult to handle uneven loading • Where peer-to-peer network is appropriate: • 10 or less users • No specialized services required • Security is not an issue • Only limited growth in the foreseeable future
Clients-Server Networks • Network Clients (Workstation) • Computers that request network resources or services • Network Servers • Computers that manage and provide network resources and services to clients • Usually have more processing power, memory and hard disk space than clients • Run Network Operating System that can centralize management of not only data, but also users, groups, security, and applications on the network • Servers often have a more stringent requirement on its performance and reliability
Client-Server Networks • Advantages of client/server networks • Facilitate resource sharing – centrally administrate and control • Facilitate system backup and improve fault tolerance • Enhance security – only administrator can have access to Server • Support more users – difficult to achieve with peer-to-peer networks • Disadvantages of client/server networks • High cost for Servers • Need expert to configure the network • Introduce a single point of failure to the system
Core Network Topology • 3 basic types? • Bus TopologyRing Topology • Star Topology
Network Topology • Bus Topology • Simple and low-cost • A single cable called a trunk (backbone, segment) • Only one computer can send messages at a time • Passive topology - computer only listen for, not regenerate data • Star Topology • Each computer has a cable connected to a single point • More cabling, hencehigher cost • All signals transmission through the center core;if down, entirenetwork down • Depending on the intelligence of core, two or more computers may send message at the same time
Network Topology • Bus Topology Coaxial cable • Star Topology BNC T-Connector Network Card
T T T T T T T data data Ack Ack data Ack data Ack data data T T T Topology • Ring Topology • Every computer serves as • a repeater to boost signals • Uses Token passing to senddata, where only the computerwho gets the token can senddata • Disadvantages • Difficult to add computers • More expensive • If one computer fails, whole network fails T T T
Ethernet Addressing (Layer 2) • Since there can be many users on an ethernet network, everyone has to have their own unique address. • This is called the Media Access Control (or MAC) address, or sometimes ethernet address, physical address, adaptor address, hardware addres, etc. • It’s a 12-digit (48 bit) hexadecimal address that is unique to that ethernet adaptor and no other in the world. It can be written as 00:30:65:83:fc:0a or 0030.6583.fc0a or 003065:83fc0a or 00-30-65-83-fc-0a but they all mean the same thing. • The first 6 digits are the Vendor code, (003065 belongs to Apple), the last 6 are the individual inteface’s own. Like a car’s VIN. See http://coffer.com/mac_find/ to look up some vendor codes.
Hubs vs. Switches • Hubs • Shared media devices • Everyone sees everyone’s packets but each device only pays attention to those specifically directed to it, or to broadcasts. • Not too secure, but cheap. Most wireless still qualifies as a “hub,” while actual wired ethernet hubs are becoming hard to find now.
Hubs vs. Switches • Switches • Not shared most of the time. • The switch pays attention to the packets and makes a table of the “sender” ethernet addresses (it removes old data after a while). • When a packet comes along whose destination address is in the table (because that host has recently “talked” and identified itself) the packet only goes to that port. • Unknown packets and broadcasts still go to all ports, but overall, there are nearly no collisions and is generally more secure. • Switches are now much more common than hubs.
Finding your Ethernet Address • On Windows 95/98, from the “run” menu type “winipcfg” • On Windows NT, 2000 and XP, open a command window and type “ipconfig /all” • On MacOS 9, open the TCP/IP control panel and select “Get info” • On MacOS X and most Unix or Unix-like systems, from a terminal, type “ifconfig –a”. • This address can be used for the MAC address filtering on a wirelss router and is also required by Telus in order for a device to connect to the Internet on their ADSL network. (This can be done online by going to https://radon.bc.tac.net/cgi-bin/oca2.cgi)