notes on computer networking

8/9/2019 Notes on Computer Networking

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Computer NetworkWednesday, November 25, 20096:38 PM



Types of Network: According to ScopeWednesday, November 25, 20097:02 PM

1. LAN (Local Area Network) - a connection of computers confined in a smallgeographical area, e.g. a single room or building.

2. CAN (Campus Area Network) - a connection of computers within a vicinity orcompound. 3. MAN (Metropolitan Area Network) - a connection of computers in a town orcity. 4. WAN (Wide Area Network) - a connection of computers in a largergeographical area.

a. From one region to anotherb. From one country to anotherc. From one continent to anothero Intranet - privately-owned network.

5. Wireless Network - data is sent via "radio frequency" or "radiotransceiver."

o WLAN (Wireless LAN) - IEEE 802.11o WWAN (Wireless WAN) - IEEE 802.16

Classification of NetworksWednesday, November 25, 20097:14 PM

1.Peer-to-Peer Network a. Computers can share data/communicate with each otherb. There is no hierarchy among computers (each computer can both actas client and server).

2.Client/Server Network a. Hierarchical:

i.Main/File Server - shares files and resources. It controls the clientcomputers.

ii.Client Computer - accesses files from the Main/File Server.

TYPES OF SERVERS 1. File and Print Servers

a. Provide file and printer resources from a centralized location.b. When a client sends a request for data to the file and print server, theentire database or file is downloaded to the computer making the request.

2. Database Servers



a. Store large amounts of data in a centralized location and make thisdata available to users so that they do not need to download the entiredatabase.b. The entire database stays on the server and only the results of arequest are downloaded to the computer making the request.

3. Mail Serversa. Manage the e-mail services for the network.

4. Fax Serversa. Manage fax traffic into and out of the network by sharing one or morefax modems.

5. Directory Services Serversa. Provide a central location to store information about the network,including the identity of the users accessing the network and the names of the resources available in the network.b. Network security is administered centrally.c. An administrator can define a resource, e.g. a printer, and the type of

access that users have to that resource. Then, users can locate theresource and use it, depending on the type of access assigned to them.

LAN Card / Ethernet LAN / NIC (Network Interface Card)/ Network Adapter

Brand Name: Realtek, RICOMM, CNET PING - (Ping referred as Packet Internet Grouper ) - is a computer networktool used to test whether a particular host is reachable across an IP network; itis also used to self test the network interface card of the computer, or as aspeed test.

OSI LayersWednesday, November 25, 20097:28 PM

Open System Interconnection Model/Layer was proposed by InternationalOrganization for Standardization’s (ISO) SC16 committee (July 1979).

o It is responsible to processing (receiving and sending) data.



• Layer I: Physical Layero Defines the specifications for peripherals

• e.g. layouts of pins,cable specs, voltages, hubs,repeaters, network adapters,

Host Bus Adapters (HBAs)o Converts data into bits • Layer II: Data Link Layer

o Controls the flow of datao Converts data into frames

• Layer III: Network Layer

o Transfers variable length of data to a networko e.g. routerso Internet Protocol (IP)

manages the transfer of data • Layer IV: Transport Layer

o Keeps track of the segmentsand retransmits those that failo Protocols• TCP (Transmission Control

Protocol) - a standard formatfor transmitting data in Packets (1 packet = 64 bits) from one computer to another on the network.

• UDP (User Datagram Protocol) - provides port numbers to helpdistinguish different user requests and, optionally, a checksum

capability to verify that the data arrived intact.

• Layer V: Session Layero Controls the dialogues (connections) between layerso responsible for graceful close of sessions, session checkpointing and

recoveryo Mail Servers:

• POP (Post Office Protocol) - transfers data.• SMTP (Simple Mail Transfer Protocol) - a.k.a. postman - getsdata from POP.

• Layer VI: Presentation/Syntax Layer

o Transforms data into the form that the application layer can accepto Converts data into ASCII characters

• Layer VII: Application Layer

o Identifies communication partners (means of communication)o Determines the resource availabilityo Synchronizes communication



EXAMPLE:



IEEE (Institute of Electrical & Electronics Engineers)Wednesday, November 25, 200911:22 PM • The IEEE (read eye-triple-e) is an international non-profit, professional

organization for the advancement of technology related to electricity. It has themost members of any technical professional organization in the world, with more

than 365,000 members in around 150 countries. • The IEEE is incorporated in the State of New York, United States.

• It was formed in 1963 by the merger of the Institute of Radio Engineers(IRE, founded 1912) and the American Institute of Electrical Engineers(AIEE, founded 1884). • IEEE is one of the leading standards-making organizations in the world.

• IEEE performs its standards making and maintaining functions through theIEEE Standards Association (IEEE-SA).

o IEEE standards affect a wide range of industries including: power andenergy, biomedical and healthcare, Information Technology (IT),telecommunications, transportation, nanotechnology, informationassurance, and many more.o One of the more notable IEEE standards is the IEEE 802 LAN/MANgroup of standards which includes the IEEE 802.3 Ethernet standard andthe IEEE 802.11 Wireless Networking standard.

• IEEE 802.3 • IEEE 802.11

Network CablesWednesday, November 25, 20099:02 PM



Twisted Pair CablesWednesday, November 25, 20099:52 PM

• It was first used in telephone systems by Alexander Graham Bell, 1881• A type of cabling that is used for telephone communications and mostmodern Ethernet networks.

• A pair of wires forms a circuit that can transmit data.• The pairs are twisted to provide protection against crosstalk , the noisegenerated by adjacent pairs.

o When electrical current flows through a wire, it creates a small, circularmagnetic field around the wire. When two wires in an electrical circuit areplaced close together, their magnetic fields are the exact opposite of eachother. Thus, the two magnetic fields cancel each other out. They alsocancel out any outside magnetic fields. Twisting the wires can enhance thiscancellation effect .

1.Unshielded Twisted Pair (UTP) Wire

o Used in a variety of networks.o Found in many Ethernet networks and telephone system wires.o UTP cable relies solely on the cancellation effect produced by thetwisted wire pairs to limit signal degradation caused by electromagneticinterference (EMI) and radio frequency interference (RFI).

• Advantageso Flexible and light weighto Easy to string between wallso Easy to work with and install



o Costs less than LAN cables

• Disadvantageso Susceptibility to interference and noiseo Relatively low bandwidth (3000 Hz)o Limited Data Rates - the longer the cable, the slower the data istransferred

2.Shielded Twisted Pair (STP) Wire

o Combines the techniques of shielding, cancellation, and wire twisting.o 2 copper wires coated with insulating coating to ground wires.

• Twisted pair > Shield > Outer Jacket

• Connector: Registered Jack Connectors (RJ)o RJ-11 - 4 pair wires - standard for telephone wires and computermodem connectors.o RJ-45 - used as Ethernet connectors.

Coaxial CableWednesday, November 25, 20099:16 PM

Coaxial cable is used as a transmission line for radio frequency signals, inapplications such as connecting radio transmitters and receivers with theirantennas, computer network (Internet) connections, and distributing cabletelevision signals.

• Center core > Dielectric Insulator > MetallicShield > Plastic Jacket• Usually used for Bus Topologies

• The design provides a special advantage:electrical interference is reduced because the twoconductors are shielded and confined separately.• The coaxial cable has a greater capacity thanthe copper wire; it has the potential to also carrytelevision signals

• CONNECTOR:o BNC (British Naval Connector or Bayonet Neill-

Concelman) - is used for RF signal connections, for analog and



Serial Digital Interface video signals, amateur radio antenna connections,aviation electronics (avionics) and many other types of electronic testequipment.

• EXAMPLES

Fiber OpticsWednesday, November 25, 200910:01 PM

Fibre optic cable "is particularly useful where interference-free communication is necessary, and a single fiber-optic cable

has a large channel capacity and therefore permits multipleuses"

• An optical fiber (or fibre) is a glass or plastic fiber that useslight waves to transmit data.



• Optical fibers are widely used in fiber-optic communications, which permitstransmission over longer distances and at higher bandwidths (data rates)than other forms of communications.• Signals travel along them with less loss, and they are also immune toelectromagnetic interference.

• Core > Cladding > Sheath

• CONNECTORS

o Subscriber Channel (SC) Connector - for Cable TV.

o Straight Tip (ST) Connector - for computers.

o Mechanical Transfer Registered Jack (MT-RJ) - an alternative forRJ-45.

• TYPES (Mode - path from which light is propagated)

o Multi-mode Graded Fiber - is the most common. It has broadbandwidths and a diameter of fifty to sixty-three micrometres (less than thethickness of human hair).



o Multi-mode Step-index Fiber - has less bandwidth - about 50 MHz -and are mostly used for digital communication.

o Single Index (or Single Mode Fiber (SMF)) - is an optical fiberdesigned to carry only a single ray of light (mode). This ray of light oftencontains a variety of different wavelengths. It is about five micrometresthick. Because of their small diameter, they are mostly experimental andthey also create problem in installation and maintenance

• ADVANTAGESo It provides a higher transmission capacityo It provides broad bandwidtho It is easily transportableo Immune to electromagnetic interferenceo It provides capacity to transmit all forms of communication (voice, data

and video).

• DISADVANTAGESo Cost of installation/maintenanceo Fragility

How To Make A Crossover Cable using Cat5eWednesday, December 02, 20095:33 PM

Materials:RJ-45 connectorCat5 or Cat5e UTP cableCrimper Procedure:1. Remove 3/4 inch outer jacket.2. Untwist each pair of wire and straighten each one.



3. Place the wires in the order of the two diagrams as shown below. Each endof the cable should use a different diagram.

Notes for wiring diagrams above:o For patch cables, 568-B wiring is by far, the most common method.o There is no difference in connectivity between 568B and 568A cables.Either wiring should work fine on any system*. (*see notes below)o For a straight through cable, wire both ends identical.o For a crossover cable, wire one end 568A and the other end 568B.o Do not confuse pair numbers with pin numbers. A pair number is usedfor reference only (eg: 10BaseT Ethernet uses pairs 2 & 3). The pinnumbers indicate actual physical locations on the plug and jack.

4. Bring all of the wires together, until they touch. Hold the grouped (andsorted) wires together tightly, between the thumb, and the forefinger. At thispoint, recheck the wiring sequence with the diagram.5. Cut the wires at a perfectly straight line.6. Insert the connector onto the wires. Check the wiring sequence one moretime. Make sure that the tips of the wires are all touching the end of theconnector.7. Use the crimper for RJ-45. Push the connector all the way in and then squeezedown all the way on the crimper. Remove the connector from the crimper body.

Network Topologies: Physical Thursday, November 26, 20097:37 PM

• Network topology is the configuration of a computer network.• Topology - layout of connected devices in a network.

CATEGORIES OF A NETWORK



• Physical Topology - refers to the physical layout of connections/devices in anetwork.• Logical Topology - determined by network protocols, which controls theflow of data in a network.• Signal Topology - mapping or path that the data takes in the nodes.

o Optical, electromagnetic, electrical, and radio frequency.

CONSIDERATIONS WHEN CHOOSING A TOPOLOGY • Money. A linear bus network may be the least expensive way to install anetwork; you do not have to purchase concentrators.• Length of cable needed. The linear bus network uses shorter lengths of cable.• Future growth. With a star topology, expanding a network is easily done byadding another concentrator.• Cable type. The most common cable in schools is unshielded twisted pair,which is most often used with star topologies.

LINEAR BUS TOPOLOGY

• Nodes of the network are connected to a common transmission medium (orbus), which has two end points (terminator ). • Cable: Coaxial Cable • Advantages:

o Easy to connect computer or peripheralso Requires less cable length than a star topologyo Cheaper compared to others

• Disadvantages:

o Entire network shuts down if there is a break in the main cableo Terminators are required at both ends of the backbone cableo Difficult to identify the problem if the entire network shuts downo Not meant to be used as a stand-alone solution in a large building



STAR TOPOLOGY

• A star topology is designed with each node (file server, workstations, and

peripherals) connected directly to a central network hub or concentrator• Data passes through the hub or concentrator before continuing to itsdestination• The hub manages or controls all functions of the network (sends orreceives data)

o It also acts as a repeater for the data flow • Cable: UTP Cable • Advantages:

o Easy to install and wireo No disruptions to the network then connecting or removing deviceso

Easy to detect faults and to remove parts

• Disadvantages:o Requires more cable length than a linear topologyo If the hub or concentrator fails, connection is disabledo More expensive than linear bus topologies because of the cost of theconcentrators



STAR-WIRED RING TOPOLOGY (Ring Token)

• The network consists of a set of repeaters joined by point-to-point links in a

closed loop• Links are unidirectional

o Data are transmitted in one direction only and all are oriented in thesame wayo Data circulate around the ring in one direction (clockwise orcounterclockwise).

• CSMA/CD (Carrier Sense Multiple Access with Collision Detection) -workstations wait for a computer to finish sending a data before sending another

MESH TOPOLOGY (Point-to-PointTopology)

• Mesh Network is a network where all thenodes are connected to each other and is acomplete network. In a Mesh Network everynode is connected to other nodes on thenetwork through hops.• While the data is traveling on the network, itis automatically configured to reach thedestination by taking the shortest route whichmeans the least number of hops. Data travels

by hopping from one node to another and thenreaches the destination node.• Star-configured workstations connected to bus and star networks

• Internet is based on mesh topology.

• Routers plays important role in mesh topology, routers are responsible toroute the message to its destination address or computer. • Advantages:

o Fault toleranceo Guaranteed communications channel capacity



• Disadvantages:

o Installation and reconfigurationo Cost of maintaining redundant

TREE TOPOLOGY (Expanded Star Topology)

•

Tree topology is a combination of the bus and the Star Topology• The tree like structure allows you to have many servers on the network andyou can branch out the network in many ways• This is particularly helpful for colleges, universities and schools so that eachof the branches can identify the relevant systems in their own network and yetconnect to the big network in some way• There will be at least three levels of hierarchy in the Tree Network

Topology and they all work based on the root nodeo The higher levels in the hierarchy are expected to perform morefunctions than the lower levels in the network

• Advantages:

o A Tree Topology is supported by many network vendors ad evenhardware vendorso A point to point connection is possible for individual segmentso All the computers have access to the larger and their immediatenetworkso Best topology for branched out networks

• Disadvantages:o Length of the network depends on the type of cable that is being usedo If the backbone line breaks, the entire segment goes down



o More difficult to configure and wire than other topologies



TCP/IPSaturday, January 09, 20104:19 PM

Transmission - process of sending, propagating and receiving an analogue ordigital information signal over a physical point-to-point or point-to-multipointtransmission medium, either wired or wireless.

Protocol - set of standard rules for data representation, signaling,authentication and error detection required to send information over acommunications channel

TCP/IP (Transmission Control Protocol/Internet Protocol)• Basic communication language or protocol of the Internet.• Used as a communications protocol in a private network.• Describes a set of general design guidelines and implementations of specificnetworking protocols.• Provides an end-to-end connectivity specifying how data should be

formatted, addressed, transmitted, routed and received at the destination.

TCP/IP Program1. The Higher Layer - manages the assembling of a message or file intosmaller packets that are transmitted over the Internet and received by a TCPlayer that reassembles the packets into the original message.2. The Lower Layer - handles the address part of each packet so that it gets tothe right destination.

Model of Communication• Uses the client/server modelcommunication.• Point-to-point• Stateless• HTTP• FTP• Telnet• SMTP• SLIP• PPP

Development of TCP/IP• 1960’s and early 1970’s• Advanced Research Projects Agency (ARPA)• Build a network to connect a number of military sites. Key Requirements• It must continue to function during nuclear war.• It must be completely decentralized with no key central installation that couldbe destroyed and bring down the whole network.



• It must be fully redundant and able to continue communication between Aand B even though intermediate sites and links might stop functioning duringthe conversation.• The architecture must be flexible as the envisaged range of applications forthe network was wide.

Why TCP/IP?• TCP/IP was accepted as an industry standard protocol.• It is a routable suite• It is provided on almost all network operating systems, and therefore allowsconnectivity between dissimilar systems• The protocols are in the public domain and are freely available, which makesit a popular choice for software companies.• It is a well designed protocol.• It is an open standard where no single vendor has any control over theprotocol and anyone is allowed to use it and develop applications based on it.

Architectural Principles• End-to-End Principle

o This principle has evolved over time. Its original expression put themaintenance of state and overall intelligence at the edges, and assumedthe Internet that connected the edges retained no state and concentratedon speed and simplicity. Real-world needs for firewalls, network addresstranslators, web content caches and the like have forced changes in thisprinciple.

• Robustness Principleo In general, an implementation must be conservative in its sending

behavior, and liberal in its receiving behavior. That is, it must be careful tosend well-formed datagrams, but must accept any datagram that it caninterpret .o The second part of the principle is almost as important: software onother hosts may contain deficiencies that make it unwise to exploit legalbut obscure protocol features.

TCP/IP LayersSaturday, January 09, 20104:31 PM

TCP/IP Protocol Suite



IP SUITE FUNCTIONS:• Host addressing and identification: This is accomplished with ahierarchical addressing system.• Packet routing: This is the basic task of getting packets of data (datagrams)from source to destination by sending them to the next network node (router)

closer to the final destination.

APPLICATION LAYER• It refers to the higher-level protocols used by most applications for networkcommunication. Examples of application layer protocols include the FileTransfer Protocol (FTP) and the Simple Mail Transfer Protocol (SMTP)• Data coded according to application layer protocols are then encapsulatedinto one or (occasionally) more transport layer protocols (such as theTransmission Control Protocol (TCP) or User Datagram Protocol (UDP)),which in turn use lower layer protocols to effect actual data transfer.• Application Layer protocols generally treat the transport layer (and lower)

protocols as "black boxes" which provide a stable network connection acrosswhich to communicate, although the applications are usually aware of keyqualities of the transport layer connection such as the end point IP addressesand port numbers.

TRANSPORT LAYER• Its responsibilities include end-to-end message transfer capabilitiesindependent of the underlying network, along with error control, segmentation,flow control, congestion control, and application addressing (port numbers). Endto end message transmission or connecting applications at the transport layercan be categorized as either connection-oriented , implemented inTransmission Control Protocol (TCP), or connectionless, implemented inUser Datagram Protocol (UDP).• It can be thought of as a transport mechanism, e.g. a vehicle with theresponsibility to make sure that its contents (passengers/goods) reach theirdestination safely and soundly, unless another protocol layer is responsible forsafe delivery.• The Transport Layer provides this service of connecting applications throughthe use of service ports.



o For example, the Transmission Control Protocol (TCP) is a connection-oriented protocol that addresses numerous reliability issues to provide areliable byte stream:

• data arrives in-order• data has minimal error (i.e. correctness)• duplicate data is discarded• lost/discarded packets are resent•

includes traffic congestion control

INTERNET LAYER• Solves the problem of sending packets.• Internetworking requires sending data from the source network to thedestination network . This process is called routing. Internet Layer Protocols• Internet Control Message Protocol (ICMP) used to transmit diagnosticinformation about IP transmission• Internet Group Management Protocol (IGMP) used to manage IP

Multicast data.• Internet Protocol Security (IPsec) is a protocol suite for securing InternetProtocol (IP) communications by authenticating and encrypting each IP packet of a data stream.

NETWORK ACCESS LAYER / LINK LAYER• Used to move packets between the Internet Layer interfaces of two differenthosts on the same link.• Is concerned with all of the components, both physical and logical, that arerequired to make a physical link.• It provides error control for data delivered on the physical network.

Network Layer Protocols• Address Resolution Protocol (ARP) is for determining a network host'slink layer or hardware address when only its Internet Layer (IP) or Network Layeraddress is known.• Neighbor Discovery Protocol (NDP) is responsible for discovery of othernodes on the link, determining the link layer addresses of other nodes, findingavailable routers, and maintaining reachability information about the paths toother active neighbor nodes.• Point-to-Point Protocol , or PPP, is a data link protocol commonly used toestablish a direct connection between two networking nodes. It can provideconnection authentication, transmission encryption privacy, and compression.

• High-Level Data Link Control (HDLC) provides both connection-orientedand connectionless service.• Fiber distributed data interface (FDDI) provides a standard for datatransmission in a local area network that can extend in range up to 200kilometers (124 miles).• Asynchronous transfer mode (ATM) is a packet-oriented transfer methodthat uses asynchronous time division multiplexing (TDM) techniques. It encodesdata into small fixed-sized cells (cell relay) and provides data link layer services.

OSI Model vs. TCP/IP Model



Saturday, January 09, 20104:56 PM

FOCUS OF RELIABILITY CONTROL•

Implementation of the OSI model places emphasis on providing a reliabledata transfer service, while the TCP/IP model treats reliability as an end-to-endproblem.• Each layer of the OSI model detects and handles errors, all data transmittedincludes checksums. The transport layer of the OSI model checks source-to-destination reliability.• In the TCP/IP model, reliability control is concentrated at the transport layer.

The transport layer handles all error detection and recovery. The TCP/IPtransport layer uses checksums, acknowledgments, and timeouts to controltransmissions and provides end-to-end verification.

ROLES OF HOST SYSTEM• Hosts on OSI implementations do not handle network operations (simpleterminal), but TCP/IP hosts participate in most network protocols. TCP/IP hostscarry out such functions as end-to-end verification, routing, and network control.

The TCP/IP internet can be viewed as a data stream delivery system involvingintelligent hosts.

SIMILARITIES• Both have layers.• Both have application layers, though they include very different services.• The TCP/IP and OSI architecture models both employ all connection and

connectionless models at transport layer. DIFFERENCES• TCP/IP combines the presentation and session layer issues into its applicationlayer.• TCP/IP combines the OSI data link and physical layers into the network accesslayer.• TCP/IP appears simpler because it has fewer layers.• TCP/IP protocols are the standards around which the Internet developed, sothe TCP/IP model gains credibility just because of its protocols.



• In contrast, networks are not usually built on the OSI protocol, even thoughthe OSI model is used as a guide.



Network PeripheralsSaturday, January 09, 20105:09 PM

ROUTERS

MODEMHistory:

o Digital modems developed from the need to transmit data for NorthAmerican air defense during the 1950s.o Modems were used to communicate data over the public switchedtelephone network or PSTN.o Analog telephone circuits can only transmit signals that are within thefrequency range of voice communication.o A modem sends and receives data between two computers.o Modem stands for the modulate/demodulate.o 1962: the Bell 103, created by AT&T, the world's first commercialmodem was released.

• It had a sizzling speed of 300 bps (bits per second). Bits per second (abbreviated bps or bit/sec) is a common

measure of data speed for computer modems and transmissioncarriers.

As the term implies, the speed in bps is equal to the number of bits transmitted or received each second.

Larger units are sometimes used to denote high data speeds.• 1 Kbps (kilobit per second) = 1,000 bps• 1 Mbps(megabit per second) = 1,000,000 bps or 1,000Kbps

Computer modems for twisted pair telephone lines usuallyoperate at 57.6 Kbps or, with Digital Subscriber Line (DLS)

service, at 512 Kbps or faster. So-called "cable modems," designed for use with TV cable

networks, can operate at more than 1.5 Mbps. (coaxial cable) Fiber optic modems can send and receive data at many

Mbps. 1980: modem speeds reached 14.4 Kbps. It took 14 years to double the speed to 28.8 Kbps. 1996: Dr. Brent Townshend created the 56K modem.

• Modem is a contraction of the wordsmodulator-demodulator.• It is typically used to send digital dataover a phone line.• Telephone lines were designed totransmit the human voice, not electronicdata from computers.• Modems were invented to convert digitalcomputer signals into a form that allowsthem to travel over the phone lines.

o Handshake - those are scratchysounds you hear from a modem'sspeaker . A modem on the other end



of the line understands it and converts the sounds back to digitalinformation that the computer understands.

• The sending modem modulates the data into a signal that is compatiblewith the phone line, and the receiving modem demodulates the signal backinto digital data. Wireless modems convert digital data into radio signals and back. Types of Modem:• Internal Modem - is a computer card that is attached to the computerthrough a slot.• External Modem - is a module that is connected to the system by means of a physical port.

HUB•A network hub is a networking device thatconnects to one or more equipment.

o For example, a computer can connect to a

server, printer and another computer through anetwork hub.•It is useful in sharing of resources and broadcastingdata it receives.•It helps connect these devices together without

having to connect to each other directly. 3 Types of Network Hubs:• Passive Hub - is a pass-through that only broadcasts signals it receivesthrough its input port, then sends it out through the output port.

o It only functions as a connector of different wires in a topology; thus, itdoes not do anything to regenerate or process the signals.

•

Active Hub - a.k.a. multiport repeater - works more than just a connectorbut also regenerates the data bits to ensure the signals are strong.o It provides an active participation in the network aside from acting asan interface.o It participates in the data communication, e.g. storing signals receivedthrough the input ports, before forwarding them.o It can monitor the data it is forwarding and sometimes help improvesignals before forwarding them to other connections. (Such a featuremakes troubleshooting of network problems easier.)

• Intelligent hub - can perform everything that the passive hub and activehub do, and help manage the network resources effectively to ensure that theperformance of the network is highly efficient.

o An intelligent hub can help in troubleshooting by pinpointing the actuallocation of the problem and help identify the root cause and resolution.o It is very adaptable to different technologies without any need tochange its configuration.o It performs different functions, e.g. bridging, routing, switching andnetwork management.

Setting Up a Network Hub at Home• Get an internet connection from an Internet Service Provider (ISP).



• After your internet connections is installed, you can connect your networkhub into the modem by using a network cable (Cat5 or RJ-45).• Then you can connect one or more cable to the Network Interface Card(NIC) of your computer; doing the same with other computers or printers thatneed to be in your network.

SWITCH• A switch is more sophisticated than a hub, giving you more options fornetwork management, as well as greater potential to expand.• A switch filters the data packets, and only sends the packet to the portwhich is connected to the destination address of that packet.• The first Ethernet switch was introduced by Kalpana in 1990.• for LAN only. Switch Diagram

Advantages of a Switch over a Hub• A switch provides higher total throughput than a hub because it can supportmultiple simultaneous conversations.• Switches also run in full duplex mode, which allows data to be sent andreceived across the network at the same time.

o Switches can effectively double the speed of the network whencompared to a hub which only supports half duplex mode (one-wayreceiving and sending data).



Switches improve the performance and efficiency of a network andshould be used when you:• Need to make best use of the available bandwidth• Have multiple file servers• Require improved performance from file servers, web servers or workstations• Use high speed multi-media applications• Are adding a high speed workgroup to a 10Mbit/sec LAN•

Plan to upgrade from 10 to 100Mbit/sec or Gigabit network Managed Switches• It allows the ports on the switch to be configured , monitored, enabled anddisabled.• Switch management can also gather information on a variety of network

parameters, such as:o The number of packets that pass through each of its portso What types of packets they areo Whether the packets contain errorso The number of collisions that have occurred

• Features:o

Gigabit Ethernet supporto Simple Network Management Protocol (SNMP) management andremote control capabilitieso A management interface that can be accessed through an internetbrowsero Auto-negotiation support which auto-senses the speed and duplexcapabilities of connected deviceso Built-in expansion capability

REPEATERS

• Regenerate incoming electrical, wireless or optical signals. With physical

media like Ethernet or Wi-Fi, data transmissions can only span a limiteddistance before the quality of the signal degrades.• Repeaters attempt to preserve signal integrity and extend the distance overwhich data can safely travel.• a.k.a. Active Hubs or Multiport repeaters

o In Wi-Fi, access points function as repeaters only when operating in so-called "repeater mode."

• Repeaters are technically OSI physical layer devices.



IP AddressingSaturday, January 09, 20105:59 PM

Protocol is a set of rules which is used by the computers to communicate witheach other across a network.

Bit is the smallest unit/value of Binary notation. 8 bits = 1 byte

Converting Decimal toBinary Form Example: 192 = 1 1 00 0 0 0 0

192/2 = 96 0

96/2 = 48 0

48/2 = 24 0

24/2 = 12 0

12/2 = 6 0

6/2 = 3 0

3/2 = 1 R1 1

1/2 = 0.5 1

Converting Binary to Decimal Form

Example: 1 1 0 0 0 0 0 0

1 1 0 0 0 0 0 0

27 26 25 24 23 22 21 20

128 64 32 16 8 4 2 1

128 + 64 = 192

WHAT IS AN IP ADDRESS? • IP stands for Internet Protocol.• Logical Addressing - used to transport a packet from its source to itsdestination.• Similar to the street address or email address, each IP address on thenetwork is unique.• Two computers on the same network cannot share the same IP address.

IP ADDRESSING • IP address uses (dotted decimal notation) to divide the 32- bit IP address intofour 8-bit or(1-byte) fields, these fields can hold a number from 0-255 eachgroup of numbers are known as Octets.

o an IP address is a series of four numbers separated by decimal points,such as 192.168.0.1

• Addresses are assigned to each physical connection of a device to a network,therefore if a device (host) has more than one connection to a network ornetworks, then it will have more than one IP address.



Example:

192 . 168 . 0 . 1

↓ ↓ ↓ ↓

Octet Octet Octet Octet

↓ ↓ ↓ ↓

8 bits 8 bits 8 bits 8 bits = 32 bits

• The first set of numbers in the IP address are the most useful for HSI (HighSpeed Internet) troubleshooting purposes.• IP addresses are divided into two parts, a Network ID and a Host ID each of which can be of varying bit lengths but always making 32 bits altogether. Example:

162.

146 . 93.

14

(dotteddecimal)

10100010.

10010010.

01011101.

00001110

Network ID

Network ID Host ID Host ID

• INTERNET ASSIGNED NUMBERS AUTHORITY (IANA)o The entity that oversees the following:

• global IP address allocation• root zone management for the Domain Name System (DNS)• media types• other Internet Protocol related assignments

o IANA coordinates the global IP and AS number space, and allocatesthese to Regional Internet Registries.o It is operated by the Internet Corporation for Assigned Namesand Numbers, better known as ICANN.

DIFFERENT IP ADDRESSES and WHERE IT COMES FROM • ISP (Internet Service Provider) Comcast IP Address → Modem

o Will be received a Comcast IP address when connecting directly totheir cable modem, or directly through a HUB or SWITCH to the Cablemodem. (not a router )o It begins with any of the following numbers: 24, 67, 71, 76, 98



• Router Address → Cable Modem to Router o You will receive a router IP address when connecting through a routeror a gateway.o Always start with numbers 192o Example: 192.188.1.100

• 169 IP Address (Computer self-given/assigned)o You will receive a 169 IP addresses if your computer does not make agood connection to a modem or a router.o It means there’s a problem when trying to connect to the internet.o Example: 10.xxx.xxx.xxx.

• Reserved IP Addresso 0.0.0.0• Default IP address• Specifies a default route

o 127.0.0.0

• Reserved for internal loopback addresses.

o 127.0.0.1

• Commonly used as the internal loopback address on many

servers/devices.• Is it often used to refer to the local host.• Using this address, applications can address a local host as if itwere a remote host.

WHAT DOES IT MEAN TO HAVE AN IP ADDRESS? • A computer without an IP address or with an invalid IP address, is notproperly communicating with the attached modem and router.



o The computer is set to the static IP 192.168.0.100 and does notreceive the Comcast IP address.

• When a device has the correct IP address, it is usually a sign that it isphysically communicating with the attached modem or router.

o The computer is set to DHCP and receives the correct address.



IP Address ClassesSaturday, January 09, 20106:00 PM

ADDRESS CLASS

1ST OCTET VALUE RANGE

1ST OCTET’S

BINARY PATTERN

NETWOR

K IDENTIFIE

R

(NETWOR

KS AND HOSTS)

DEFAULT SUBNET

NUMBER OF HOSTS

PER NETWORK

NUMBER OF

NETWORK

S

Class A- for large

networks.

-commonly used inscientific

researchandmilitarypurposes.

1 to 127

1.0.0.0 to127.255.255.

255

00000000-01111111

N.H.H.H

255.0.0.016,777,2

14(224-2)

128(27)

Class B- for

mediumsizenetworks.

128 to 191

128.0.0.0 to191.255.255.

255

10000000-10111111

N.N.H.H

255.255.0.0

65,534(216-2)

16,384(214)

Class C

- forsmallernetworks.

-commonly usedforcommercial andprivatenetworks

.

192 to 223

192.0.0.0 to223.255.255.

255

11000000-11011111

N.N.N.H

255.255.255.0

254(28-2)

2,097,150

(221)

Class D(multicast)

224 to 239

224.0.0.0 to239.255.255.

255

11100000-11101111

NA



Class E(experimental)

240 to 255

240.0.0.0 to255.255.255.

255

11110000-11111111

NA

• Classes A, B, C – are used to identify workstations, routers, switches, and

other devices.• Classes D and E – are reserved for special use.

Multicast Addressing (Class D)• Multicast addressing is a network technology for the delivery of informationto a group of destinations simultaneously using the most efficient strategy todeliver the messages over each link of the network only one, creating copiesonly when the links to the multiple destinations split.• The word multicast is typically used to refer to IP multicast which is oftenemployed for streaming media and Internet television applications. Experimental Addressing (Class E)• Reserved for future use, or Research and Development Purposes.

SubnetSaturday, January 23, 201011:05 PM

Subnetting - the process of breaking down an IP network into smallersubnetworks called “subnets.”

Subnet - division within a computer network usually composed of a networkrouter, a switch or hub, and at least one host. Subnet Mask - allows to identify which part of an IP address is reserved for thenetwork, and which part is available for host use. • Subnetting an IP network allows for the flow of network traffic to besegregated based on a network configuration.• It essentially organizes the hosts into logical groups, and provides forimproving network security and performance.• The most common reason for subnetting IP networks is to controlnetwork traffic.

Classful IP Address

• When we use IP Addresses with their default subnet masks.

CLASS DEFAULT SUBNET MASK

NUMBER OF BITS

A 255.0.0.0 24

B 255.255.0.0 16

C 255.255.255.0 8



Subnet Mask Hierarchy:

Example:

IP Address: 192.168.0.10 (Class C)Default Subnet Mask: 255.255.255.0

To Obtain the Network Address• Bitwise method

Binary Equivalent of previous example:

IP Address:

11000000 . 10101000 . 00000000 .00001010

Subnet Mask :

11111111 . 11111111 . 11111111 .00000000

New Network Address :

11000000 . 10101000 . 00000000 .00000000

Network Address(decimal form):

192 . 168 . 0. 0

Network IDHost ID

Classless IP Address• Classless IP Addresses have their subnet mask modified in a way so thatthere is a "Subnet ID".• This Subnet ID is created by borrowing Bits from the Host ID portion.

o Bits are borrowed depending on the number of networks needed bythe network administrator.

• Always borrow bits that are greater than (nearest) or equal tothe number of networks needed.

Subnet Mask Hierarchy:

Example: Create 8 subnets using the given below.

IP Address: 192.168.0.5 (Class C = 8 decimals)Default Subnet Mask: 255.255.255.224

0 10 0 01 0 1



23 = 8 networks= 3 bits were borrowed

To Obtain the Number of Hosts: 2n - 2Where:

n = bits borrowed- 2 = 1 network + 1 broadcast Using the example above,

28 - 23 = 25

25 - 2 = 32 - 2 = 30 hosts per network

IP Range per Network • Use increment to determine the subnet.

From previous example: 30 hosts/network + 1 1st Network: 192.168.0.0 - 192.168.0.312nd Network: 192.168.0.32 - 192.168.0.633rd Network: 192.168.0.64 - 192.168.0.954th Network: 192.168.0.96 - 192.168.0.1275th Network: 192.168.0.128 - 192.168.0.1596th Network: 192.168.0.160 - 192.168.0.1917th Network: 192.168.0.192 - 192.168.0.2238th Network: 192.168.0.224 - 192.168.0.255

IP Address:

11000000 . 10101000 . 00000000 .000 00101

Subnet Mask :

11111111 . 11111111 . 11111111 .111 00000

Network ID Subnet

ID

Host

ID

notes on computer networking

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