fundamental networking(final)

7/29/2019 Fundamental Networking(Final)

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Networking Basic Concepts



Network Terms

• Network

• Client

• Server

• Simplex: information flows in only one direction

• Half-duplex: information flows in two directions,but only in one direction at a time.

• Full-duplex: information flows in two directions a

the same time



Key Network Terminology Explained (2)

• Node: anything connected to the network,

usually a computer, but it could be a printer or ascanner

• Segment: any portion of a network that isseparated by a switch, bridge or a router fromanother part of a network.

• Backbone: the main cabling of a network that alof the segment connect to. Usually, thebackbone is capable of carrying moreinformation than the individual segments.

• Topology: The way each node is physicallyconnected to the network

Network architecture



• Networking Topologies

• Bus

• Ring

• Star

• Star bus (Hybrid)



Common Topologies - Bus

• Bus: each node is daisy-chained (connected one rightafter the other) along the same backbone. Information

sent from a node travels along the backbone until itreaches its destination node. Each end of a bus network

must be terminated with a resistor to keep the



Common Topologies - Ring

• Ring: Similar to a bus network, ringshave nodes daisy chained, but the end

of the network in a ring topology comeback around to the first node, creatinga complete circuit. Each node takes aturn sending and receiving informationthrough the use of a token. The tokenalong with any data is sent from the

first node to the second node whichextracts the data addressed to it andadds any data it wishes to send. Thensecond node passes the token anddata to the third node, etc. until itcomes back around to the first nodeagain. Only the node with the token is

allowed to send data . All other nodesmust wait for the token to come tothem.



Common Topologies - Star

• In a star network, each node is connected to a

central device called a hub. The hub takes asignal that comes from any node and passes italong to all the other nodes in the network.

•A hub does not perform any type of filtering or routing of the data.

•A hub is a junction that joins all the different nodes together.



Common Topologies - Star

• In a star network, each node is connected to a

central device called a hub. The hub takes asignal that comes from any node and passes italong to all the other nodes in the network.



Common Topologies – Star Bus

• Prob. Most common topology used today.

Combines elements of the star and bustopologies to create a versatile networkenvironment.

• Nodes in particular areas are connected to hubs(and create star topology), and hubs are

connected together along the networkbackbone (like a bus network).

• Often you have stars nested within stars.



• Transmission Media



Basic transmission medium concepts

• Medium is the physical path betweentransmitter and receiver in a data transmissionsystem

• Guided Medium: waves are guided along asolid medium path (twisted pair, coaxial cable,and optical fiber).

• Unguided medium: waves are propagatedthrough the atmosphere and inner/outerspace(satellite, laser, and wireless transmissions).



Coaxial cable (1)

• Widely installed for use in business andcorporation ethernet and other types of LANs.

• Consists of inter copper insulator covered bycladding material, and then covered by an outer jacket

• Physical Descriptions:

Covered by sheath material

Outer conductor is braided shielded (ground)

Separated by insulating material

Inner conductor is solid copper metal



Coaxial cable (2)

• Applications:

– TV distribution (cable tv); long distance telephone

transmission; short run computer system links – Local area networks

• Transmission characteristics:

– Can transmit analog and digital signals – Usable spectrum for analog signaling is about 400 Mhz

– Amplifier needed for analog signals for less than 1 Km andless distance for higher frequency

– Repeater needed for digital signals every Km or lessdistance for higher data rates

– Operation of 100’s Mb/s over 1 Km.



Twisted Pair Cables

• Physical description:

– Each wire with copper conductor

– Separately insulated wires

– Twisted together to reduce cross talk

– Often bundled into cables of two or four twisted pairs

– If enclosed in a sheath then is shielded twisted pair (STP)otherwise often for home usage unshielded twisted pair(UTP). Must be shield from voltage lines

• Application:

– Common in building for digital signaling used at speed of10’s Mb/s (CAT3) and 100Mb/s (CAT5) over 100s meters.

– Common for telephone interconnection at home and officebuildings

– Less expensive medium; limited in distance, bandwidth, anddata rate.



Categories of Twisted Pairs Cabling Syste

Category Maximum datarate

CAT 1 Less than 1Mbps

CAT 2 4 Mbps

CAT 3 16 Mbps

CAT 4 20 Mbps

CAT 5 100 Mbps



Optical Fibers (1)

• Physical Description: – Glass or plastic core of optical fiber = 2to125 µm

– Cladding is an insulating material

– Jacket is a protective cover

– Laser or light emitting diode provides transmissionlight source

• Applications:

– Long distance telecommunication – Greater capacity; 2 Gb/s over 10’s of Km

– Smaller size and lighter weight

– Lower attenuation (reduction in strength of signal)

– Electromagnetic isolation – not effected by externalelectromagnetic environment. Aka more privacy

– Greater repeater spacing – fewer repeaters, reducesline regeneration cost

Repeaters



Network Devices



Hubs

• A hub is the place where data converges fromone or more directions and is forwarded out inone or more directions.

• Seen in local area networks

G



Gateways

• A gateway is a network point that acts as anentrance to another network. On the internet, interms of routing, the network consists ofgateway nodes and host nodes.

• Host nodes are computer of network users andthe computers that serve contents (such as

Web pages).• Gateway nodes are computers that control

traffic within your company’s network or at your

local internet service provider (ISP)

R



Routers

• A router is a device or a software in a computerthat determines the next network point to which

a packet should be forwarded toward itsdestination.

• Allow different networks to communicate witheach other

• A router creates and maintain a table of the

available routes and their conditions and usesthis information along with distance and costalgorithms to determine the best route for agiven packet.

• A packet will travel through a number of

network points with routers before arriving at itsdestination.

B id



Bridge

• a bridge is a product that connects a local areanetwork (LAN) to another local area networkthat uses the same protocol (for example,Ethernet or token ring).

• A bridge examines each message on a LAN,"passing" those known to be within the same

LAN, and forwarding those known to be on theother interconnected LAN (or LANs).

HUBS



HUBS

The original Ethernet LANs relied on certain physicalcharacteristics of the cable carrying the network data (usuallycoaxial cable). New Ethernet technologies introduced newcable types that we unable to fulfill the original physicalrequirements. New devices - hubs - were introduced tosimulate those characteristics.

Simply put, the hub's major function is to replicate data itreceives from one device attached to it to all others.

Networks for Beginners: http://compnetworking.about.com/

REPEATERS



REPEATERS

An illustration of a repeater at work The electrical signal entering the repeater at one end is weakened.The repeater amplifies the electrical signals and resends the data.

A common problem in the networking world is that of weakening electrical

signals. Electrical signals traveling through wires (such as copper wires used inmost networks), weaken due to the wire's electrical resistance. This effect limitsthe lengths of the cable that can be used. A repeater will overcome this limit,when there is a need to connect two computers at a larger distance.

A repeater is connected to two cable segments. Any electrical signal reachingthe repeater from one segment, will be amplified and retransmitted to the other

segment.




ROUTERS

• Routers connect two or more networks and forward data packets

between them. When data arrives from one of the segments, therouter decides, according to it's routing table, to which segmentto forward that data.




GATEWAY

• "Gateway" is a term that was once used to refer to a routing device. Today, inthe TCP/IP world, the term "router" is used to describe such a device.

The term gateway now refers to special-purpose devices, that perform protocolconversions. Gateways implement application layer conversions of informationreceived from various protocols.

• Examples of gateways found on today's markets are: – VocalTec Gateway: A gateway that converts human speech traveling on analog

phone lines into local area network protocol data, and visa-versa.

– RadVision Gateway: Converts video from digital phone lines into local area networkprotocol data, and visa-versa.


What is the difference between?

http://www.vocaltec.com/

http://www.radvision.com/

http://www.radvision.com/

http://www.vocaltec.com/



What is the difference between?

• Bridge: device to interconnect two LANs thatuse the SAME logical link control protocol butmay use different medium access controlprotocols.

• Router: device to interconnect SIMILARnetworks, e.g. similar protocols and

workstations and servers• Gateway: device to interconnect DISSIMILAR

protocols and servers, and Macintosh and IBMLANs and equipment

Switches



Switches

• Allow different nodes of a network tocommunicate directly with each other.

• Allow several users to send information over anetwork at the same time without slowing eachother down.

fundamental networking(final)

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