Racunarske mreze
Racunarske mreze
Racunarske mreze
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Raunarske mreže e i<br />
komunikacije<br />
(laboratorijske vježbe)<br />
Dejan Abazovi<br />
e-Mail: dejoa@ac.me
Plan i program<br />
• Ukupno 24 školska asa<br />
• 4 vježbe po 6 asova<br />
• Zadnja dva asa, u ciklusu od 6,<br />
testiranje-samostalan rad<br />
• Prisustvovanje obavezno
Raunarske mreže<br />
- Tipovi raunarskih mreža<br />
LAN - Local Area Network<br />
(manji prostori, tipino zgrada i sl.)<br />
MAN - Metropolitan Area Network<br />
(više LAN-ova, npr. na teritoriji grada ili sl.)<br />
WAN - Wide Area Network<br />
(geografski udaljena podruja)<br />
- Kategorije raunarskih mreža<br />
Server based<br />
Peer-to-peer
Principi funkcionisanja<br />
raunarskih mreza<br />
Circuit Switching (komutacija kola) - uspostavljanje fizikog kola sa<br />
rezervisanim propusnim opsegom (POTS - Plain Old Telephone<br />
Service ili Post Office Telephone System)<br />
In telecommunications, a circuit switching network is one that establishes a fixed bandwidth<br />
circuit (or channel) between nodes and terminals before the users may communicate, as if the<br />
nodes were physically connected with an electrical circuit. The bit delay is constant during the<br />
connection, as opposed to packet switching, where packet queues may cause varying delay.<br />
Packet Switching (komutacija paketa) - nema fizike trajne komunikacije<br />
izmedju krajeva i svaki paket može da ide i razliitim putem (WAN)<br />
Packet switching is a communications paradigm in which packets (discrete blocks of data) are<br />
routed between nodes over data links shared with other traffic. In each network node, packets are<br />
queued or buffered, resulting in variable delay. This contrasts with the other principal paradigm,<br />
circuit switching, which sets up a limited number of constant bit rate and constant delay<br />
connections between nodes for their exclusive use for the duration of the communication.
Mrežne topologija<br />
• Bus<br />
• Prsten i dvostruki prste (Dual Ring)<br />
• Star - topologija zvijezde<br />
• Extended star - proširena zvijezda<br />
• Topologija drveta<br />
• Mesh<br />
• Neregularna topologija<br />
• elijska topologija
n(n-1)/2
OSI referentni model<br />
You should be familiar with the OSI model,<br />
because it is the most widely used method<br />
for talking about network communications.<br />
The OSI model:<br />
• Provides a standard for hardware<br />
development<br />
• Allows for modular software development<br />
• Speeds development of new technology<br />
Open System Interconnection
Konektor RJ-45, utinice i<br />
Patch panel (UTP i STP)
Ethernet Architecture Facts<br />
Topology<br />
Media<br />
Access<br />
Method<br />
Physical topologies--bus, star, cascading star<br />
Logical topology--bus (physical bus, logical bus; physical star, logical bus), star (physical star, logical star)<br />
1.CSMA/CD--Carrier Sense, Multiple Access/Collision Detection (contention). Devices use the following process to<br />
send data. Because all devices have equal access to the transmission media (multiple access), a device with data<br />
to send first listens to the transmission medium to determine if it is free (carrier sense).<br />
2.If it is not free, the device waits a random time and listens again to the transmission medium. When it is free, the<br />
device transmits its message.<br />
3.If two devices transmit at the same time, a collision occurs. The sending devices detect the collision (collision<br />
detection) and send a jam signal.<br />
4.Both devices wait a random length of time before attempting to resend the original message (called backoff).<br />
Transmissi<br />
on Media<br />
Frame<br />
Type<br />
Physical<br />
Address<br />
•Thick coaxial, thin coaxial, twisted-pair, fiber-optic<br />
The most common Ethernet implementations use unshielded twisted-pair cables (UTP). Each cable consists of<br />
eight wires, twisted into four pairs. UTP cables are classified by categories: Cat3, rated up to 10 Mbps<br />
•Cat4, rated up to 16 Mbps<br />
•Cat5, rated up to 100 Mbps<br />
•Cat5e, rated up to 1,000 Mbps (gigabit)<br />
UTP cables are connected with RJ-45 connectors.<br />
•Frame size = 64 to 1518 bytes (this is the same for all Ethernet standards)<br />
Four frame types are supported: Ethernet 802.3--This frame type is the original Ethernet frame type.<br />
•Ethernet 802.2--This frame type accommodates standards set by the IEEE 802.2 committee related to the logical<br />
link control (LLC) sublayer. It is a more current frame type than 802.3.<br />
•Ethernet II--This frame type provides the ability to use TCP/IP as a transport/network layer protocol. Other<br />
Ethernet frame types operate strictly with IPX/SPX as a transport/network layer protocol.<br />
•Ethernet SNAP--This frame type (SubNetwork Address Protocol) is an enhanced version of Ethernet 802.2 that<br />
allows for greater compatibility with other network architectures such as Token Ring. This frame type also supports<br />
TCP/IP.<br />
The MAC address (also called the burned-in address) is used as the Data Link layer physical device address. The<br />
MAC address is a 12-digit hexadecimal number. Each digit ranges from 0-9 or A-F.<br />
The MAC address FFFFFFFFFFFF is the broadcast address. Packets addressed to the broadcast address will be<br />
processed by all devices.
Ethernet Standards<br />
Category Standard Bandwidth Cable Type Maximum Segment Length<br />
Ethernet<br />
Fast Ethernet<br />
10Base5 10 Mbps Coaxial (thicknet) 500 meters<br />
10Base2 10 Mbps Coaxial (thinnet) 185 meters<br />
10BaseT<br />
100BaseTX<br />
100BaseT4<br />
100BaseFX<br />
Bandwidth - jedinica informacije (bit) u jedinici vremena<br />
sekunda), bps (brzina toka, širina propusnog<br />
opsega)<br />
10 Mbps (half duplex)<br />
20 Mbps (full duplex)<br />
100 Mbps (half duplex)<br />
200 Mbps (full duplex)<br />
100 Mbps (half duplex)<br />
200 Mbps (full duplex)<br />
100 Mbps (half duplex)<br />
200 Mbps (full duplex)<br />
Twisted pair (Cat3, 4, or<br />
5)<br />
Twisted pair (Cat5)<br />
Twisted pair (Cat5)<br />
Fiber optic<br />
100 meters<br />
100 meters<br />
100 meters<br />
412 meters (half duplex<br />
multimode cable)<br />
2,000 meters (full duplex<br />
singlemode cable)<br />
1000BaseSX<br />
(short)<br />
1,000 Mbps (half duplex)<br />
2,000 Mbps (full duplex)<br />
Fiber optic<br />
220 to 550 meters depending on<br />
cable quality<br />
Gigabit<br />
Ethernet<br />
1000BaseLX (long)<br />
1000BaseCX (short<br />
copper)<br />
1,000 Mbps (half duplex)<br />
2,000 Mbps (full duplex)<br />
1,000 Mbps (half duplex)<br />
2,000 Mbps (full duplex)<br />
Fiber optic<br />
Special copper<br />
550 to 5,000 meters depending<br />
on cable quality<br />
25 meters, used within wiring<br />
closets<br />
1000BaseT<br />
1,000 Mbps (half duplex)<br />
2,000 Mbps (full duplex)<br />
Twisted pair (Cat5e)<br />
100 meters
Bandwidth<br />
Bandwidth - jedinica informacije (bit) u jedinici<br />
vremena (sekunda), bps (brzina toka,<br />
propusnog opsega)<br />
širina
Primjeri bandwidthb<br />
andwidth-a i dužine<br />
za<br />
razli<br />
zliite ite tipove medijuma<br />
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Throughput - protok<br />
• Odnosi se na stvarni izmjereni bandwidth<br />
u odredjenom dobu dana i upotrebom<br />
odredjenih Internet ruta pri prenosu<br />
odredejnog fajla<br />
• Glavni faktor u analizi mrežnih<br />
performansi
Bandwidth i Throughput<br />
Faktori koji utiu na širinu propusnog opsega i protoka:<br />
• mrežni uredjaji<br />
• tip podataka koji se prenosi<br />
• topologija mreže<br />
• broj korisnika<br />
• korisniki raunar i tip servera<br />
• zagušenje mrežnog saobraaja
Mrežni uredjaji<br />
Host — mrežni uredjaj direktno povezan na<br />
mrežni segment<br />
printer, raunar, server, FAX, razni tipovi mrežni<br />
komunikacionih uredjaja i sl.
Mrežni adapter - NIC<br />
network interface card<br />
• LAN adapter<br />
• Komunicira sa<br />
mrežom preko serijske<br />
konekcije a sa<br />
raunarom preko<br />
paralelne konekcije<br />
• Zahtjevaju IRQ i I/O<br />
adresu
LAN uredjaji u razliitim<br />
itim<br />
topologijama
Hub<br />
<br />
<br />
<br />
<br />
<br />
Regeneriše signal<br />
Koristi se kao mjesto<br />
koncetracije<br />
Ne filtrira saobraaj<br />
Ne definiše put<br />
podacima<br />
Naziva se i multiport<br />
repeater
Switch<br />
<br />
<br />
<br />
Koriste se kao mjesto<br />
koncentracije<br />
Kombinuju konektivnost<br />
HUB-a i mogunost<br />
regulacije bridge-a<br />
Obezbjedjuju odvojene<br />
puteve za podatke
Ruteri<br />
<br />
<br />
<br />
<br />
Uredjaji za regulisanje toka saobraaja u velikim<br />
mrežama<br />
Donose odluke na osnovu mrežnih adresa<br />
Rade sa paketima (Layer 3 data), odabiraju<br />
najpovoljniji put za podatke<br />
Dvije glavne funkcija: odabir puta i<br />
preusmjeravanje paketa ka najboljoj ruti
Tok podataka kroz LAN<br />
• Gornja tri sloja pripremaju<br />
podatke za prenos kreirajui<br />
prikladan format za prenos<br />
• Transportni sloj kreira<br />
upracljave jedinice podataka<br />
koje se zovu segmenti<br />
• Identifikuje segmente sa<br />
brojem sekvence -sequence<br />
number.
Tok podataka kroz LAN<br />
• Mrežni sloj enkapsulira segmente<br />
u pakete. Mrežni sloj dodaje<br />
odredišnu i izvorišnu adresu,<br />
obino IP, svakom paketu.<br />
• Data link sloj dalje enkapsulira<br />
pakete u okvir (frame) i<br />
identifikuje ih sa izvorišnom i<br />
odredišnom MAC adresom.
Tok podataka kroz LAN<br />
• Fiziki sloj prenosi bitove.<br />
• Pasivni uredjaji - bitovi jednostavno prolaze kroz<br />
takve uredjaje.<br />
• Aktivni uredjaji - obavlja se regeneracija<br />
• Uredjaji sa fizikog nivoa ne analiziraju header-e<br />
enkapsuliranih podataka
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