RaRa��unarske mreunarske mrežže i e i komunikacijekomunikacije

(laboratorijske vje(laboratorijske vježžbe)be)

Dejan AbazoviDejan Abazovi��ee--Mail: dejoa@ac.meMail: dejoa@ac.me

Plan i program Plan i program

• Ukupno 24 školska �asa• 4 vježbe po 6 �asova• Zadnja dva �asa, u ciklusu od 6,

testiranje-samostalan rad• Prisustvovanje obavezno

RaRa��unarske mreunarske mrežžee-- Tipovi raTipovi ra��unarskih mreunarskih mrežžaa

�LAN - Local Area Network

(manji prostori, tipi�no zgrada i sl.)�MAN - Metropolitan Area Network

(više LAN-ova, npr. na teritoriji grada ili sl.)�WAN - Wide Area Network

(geografski udaljena podru�ja)

-- Kategorije raKategorije ra��unarskih mreunarskih mrežžaa�Server based �Peer-to-peer

Principi funkcionisanja Principi funkcionisanja rara��unarskih mrezaunarskih mreza

Circuit Switching Circuit Switching (komutacija kola) (komutacija kola) -- uspostavljanje fizi�kog kola sa rezervisanim propusnim opsegom (POTS - Plain Old Telephone Service ili Post Office Telephone System)In telecommunications, a circuit switching network is one that establishes a fixed bandwidth circuit (or channel) between nodes and terminals before the users may communicate, as if the nodes were physically connected with an electrical circuit. The bit delay is constant during the connection, as opposed to packet switching, where packet queues may cause varying delay.

Packet SwitchingPacket Switching (komutacija paketa)(komutacija paketa) -- nema fizi�ke trajne komunikacije izmedju krajeva i svaki paket može da ide i razli�itim putem (WAN)Packet switching is a communications paradigm in which packets (discrete blocks of data) are routed between nodes over data links shared with other traffic. In each network node, packets are queued or buffered, resulting in variable delay. This contrasts with the other principal paradigm, circuit switching, which sets up a limited number of constant bit rate and constant delay connections between nodes for their exclusive use for the duration of the communication.

MreMrežžne topologijane topologija

• Bus• Prsten i dvostruki prste (Dual Ring)• Star - topologija zvijezde• Extended star - proširena zvijezda• Topologija drveta• Mesh• Neregularna topologija• �elijska topologija

n(n-1)/2

OSI referentni modelOSI referentni model

Open System Interconnection

You should be familiar with the OSI model, because it is the most widely used method for talking about network communications.

The OSI model:• Provides a standard for hardwaredevelopment

• Allows for modular software development• Speeds development of new technology

Konektor RJKonektor RJ--45, uti45, uti��nice i nice i Patch panel (UTP i STP)Patch panel (UTP i STP)

Topology Physical topologies--bus, star, cascading starLogical topology--bus (physical bus, logical bus; physical star, logical bus), star (physical star, logical star)

Media Access Method

1.CSMA/CD--Carrier Sense, Multiple Access/Collision Detection (contention). Devices use the following process to send data. Because all devices have equal access to the transmission media (multiple access), a device with data to send first listens to the transmission medium to determine if it is free (carrier sense). 2.If it is not free, the device waits a random time and listens again to the transmission medium. When it is free, the device transmits its message. 3.If two devices transmit at the same time, a collision occurs. The sending devices detect the collision (collision detection) and send a jam signal. 4.Both devices wait a random length of time before attempting to resend the original message (called backoff).

Transmission Media

•Thick coaxial, thin coaxial, twisted-pair, fiber-opticThe most common Ethernet implementations use unshielded twisted-pair cables (UTP). Each cable consists of eight wires, twisted into four pairs. UTP cables are classified by categories: Cat3, rated up to 10 Mbps •Cat4, rated up to 16 Mbps •Cat5, rated up to 100 Mbps •Cat5e, rated up to 1,000 Mbps (gigabit) UTP cables are connected with RJ-45 connectors.

Frame Type

•Frame size = 64 to 1518 bytes (this is the same for all Ethernet standards)Four frame types are supported: Ethernet 802.3--This frame type is the original Ethernet frame type. •Ethernet 802.2--This frame type accommodates standards set by the IEEE 802.2 committee related to the logical link control (LLC) sublayer. It is a more current frame type than 802.3. •Ethernet II--This frame type provides the ability to use TCP/IP as a transport/network layer protocol. Other Ethernet frame types operate strictly with IPX/SPX as a transport/network layer protocol. •Ethernet SNAP--This frame type (SubNetwork Address Protocol) is an enhanced version of Ethernet 802.2 that allows for greater compatibility with other network architectures such as Token Ring. This frame type also supports TCP/IP.

Physical Address

The MAC address (also called the burned-in address) is used as the Data Link layer physical device address. The MAC address is a 12-digit hexadecimal number. Each digit ranges from 0-9 or A-F.The MAC address FFFFFFFFFFFF is the broadcast address. Packets addressed to the broadcast address will be processed by all devices.

Ethernet Architecture FactsEthernet Architecture Facts

Category Standard Bandwidth Cable Type Maximum Segment Length

EthernetEthernet

10Base5 10 Mbps Coaxial (thicknet) 500 meters10Base2 10 Mbps Coaxial (thinnet) 185 meters

10BaseT 10 Mbps (half duplex)20 Mbps (full duplex)

Twisted pair (Cat3, 4, or 5) 100 meters

Fast EthernetFast Ethernet

100BaseTX 100 Mbps (half duplex)200 Mbps (full duplex) Twisted pair (Cat5) 100 meters

100BaseT4 100 Mbps (half duplex)200 Mbps (full duplex) Twisted pair (Cat5) 100 meters

100BaseFX 100 Mbps (half duplex)200 Mbps (full duplex) Fiber optic

412 meters (half duplex multimode cable)2,000 meters (full duplex singlemode cable)

Gigabit Gigabit EthernetEthernet

1000BaseSX (short)

1,000 Mbps (half duplex)2,000 Mbps (full duplex) Fiber optic 220 to 550 meters depending on

cable quality

1000BaseLX (long) 1,000 Mbps (half duplex)2,000 Mbps (full duplex) Fiber optic 550 to 5,000 meters depending

on cable quality

1000BaseCX (short copper)

1,000 Mbps (half duplex)2,000 Mbps (full duplex) Special copper 25 meters, used within wiring

closets

1000BaseT 1,000 Mbps (half duplex)2,000 Mbps (full duplex) Twisted pair (Cat5e) 100 meters

Ethernet StandardsEthernet Standards Bandwidth - jedinica informacije (bit) u jedinici vremena sekunda), bps (brzina toka, širina propusnogopsega)

Bandwidth - jedinica informacije (bit) u jedinici vremena (sekunda), bps (brzina toka, širina propusnog opsega)

BandwidthBandwidth

Primjeri bPrimjeri bandwidthandwidth--aa i dui dužžineine za za rarazlizli��ite tipove medijumaite tipove medijuma

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ThroughputThroughput -- protokprotok

• Odnosi se na stvarni izmjereni bandwidth u odredjenom dobu dana i upotrebom odredjenih Internet ruta pri prenosu odredejnog fajla

• Glavni faktor u analizi mrežnih performansi

Bandwidth Bandwidth i i ThroughputThroughput

Faktori koji uti�u na širinu propusnog opsega i protoka:

• mrežni uredjaji• tip podataka koji se prenosi• topologija mreže• broj korisnika• korisni�ki ra�unar i tip servera• zagušenje mrežnog saobra�aja

MreMrežžni uredjajini uredjaji

�Host — mrežni uredjaj direktno povezan na mrežni segment

printer, ra�unar, server, FAX, razni tipovi mrežni komunikacionih uredjaja i sl.

• LAN adapter

• Komunicira sa mrežom preko serijske konekcije a sa ra�unarom preko paralelne konekcije

• Zahtjevaju IRQ i I/O adresu

MreMrežžni adapter ni adapter -- NIC NIC network interface cardnetwork interface card

LAN LAN uredjaji u razliuredjaji u razli��itim itim topologijamatopologijama

HubHub

� Regeneriše signal� Koristi se kao mjesto

koncetracije � Ne filtrira saobra�aj� Ne definiše put

podacima� Naziva se i multiport

repeater

SwitchSwitch

� Koriste se kao mjesto koncentracije

� Kombinuju konektivnost HUB-a i mogu�nost regulacije bridge-a

� Obezbjedjuju odvojene puteve za podatke

RuterRuterii

� Uredjaji za regulisanje toka saobra�aja u velikim mrežama

� Donose odluke na osnovu mrežnih adresa� Rade sa paketima (Layer 3 data), odabiraju

najpovoljniji put za podatke� Dvije glavne funkcija: odabir puta i

preusmjeravanje paketa ka najboljoj ruti

Tok podataka kroz LANTok podataka kroz LAN

• Gornja tri sloja pripremaju podatke za prenos kreiraju�i prikladan format za prenos

• Transportni sloj kreira upracljave jedinice podataka koje se zovu segmenti

• Identifikuje segmente sa brojem sekvence -sequencenumber.

• Mrežni sloj enkapsulira segmente u pakete. Mrežni sloj dodaje odredišnu i izvorišnu adresu, obi�no IP, svakom paketu.

• Data link sloj dalje enkapsulira pakete u okvir (frame) i identifikuje ih sa izvorišnom i odredišnom MAC adresom.

Tok podataka kroz LANTok podataka kroz LAN

• Fizi�ki sloj prenosi bitove.

Tok podataka kroz LANTok podataka kroz LAN

• Pasivni uredjaji - bitovi jednostavno prolaze kroz takve uredjaje.

• Aktivni uredjaji - obavlja se regeneracija

• Uredjaji sa fizi�kog nivoa ne analiziraju header-e enkapsuliranih podataka