KIS – Cvičenie #1

Technológie komunikačných sietíFyzická vrstva RM OSI

Marián Beszédeš, B506beszedes@ktl.elf.stuba.sk

Kis - Program cvičení • 1. Úvod, technológie komunikačných sietí• 2. Ethernet, MAC podvrstva• 3. Analýza prevádzky na sieti Ethernet• 4. Návrh LAN siete • 5. IP konfigurácia v prostredí OS Windows (+zadanie

referátov)• 6. Sieťovanie LAN a WAN • 7. CBT • 8. Manažment IP sietí • 9. Test, príprava referátu• 10. WAN: ISDN• 11. Prezentácia referátu• 12. Prezentácia referátu, zápočet

KIS – Podmienky / Hodnotenie

• Podmienky získania zápočtu– aktívna účasť na cvičeniach– žiadna neospravedlnená absencia na cvičeniach– max. dve absencie s lekárskym potvrdením

o práceneschopnosti.

• Hodnotenie:– za cvičenia je možné získať max. 40 bodov,– na získanie zápočtu je potrebných min. 20 bodov,– body sú prideľované na základe kontrolného testu

(max. 15 bodov), referátu (max. 15 bodov) a aktivity (max. 10 bodov).

RM OSI = Reference Model Open Systems Interconnection

Physical Layer RMOSI

• This layer conveys the bit stream– electrical impulse– Light– radio signal

through the network at the electrical and mechanical level.

• It provides the hardware means of sending and receiving data on a carrier, including defining cables, cards and physical aspects.

Ethernet = Physical, Datalink Layer

• Ethernet is a frame-based computer networking technology for local area networks (LANs). (since 1976)

• Defines:– wiring and signaling for the physical layer– frame formats and protocols (MAC Media

access control, Logical Link Control) for the data link layer

The Ethernet Physical Layers

• Ethernet devices– implement only the bottom two layers of the OSI

Model– they are typically implemented as network interface

cards –NICs– plug into the host device's motherboard.

• Naming convention – 10Base-T = 10 Mbps, baseband, over two twisted-pair cables – 100Base-T2 = 100 Mbps, baseband, over two twisted-pair

cables – 100Base-T4 = 100 Mbps, baseband, over four-twisted pair

cables – 1000Base-LX = 100 Mbps, baseband, long wavelength over

optical fiber cable

Thin Ethernet (10base2)

• (Cheapernet) is based on using a coax-cable, which is specified as RG58 (50 Ohm)

• 50 Ohm terminator on each end• One terminator MUST be grounded, the other

NOT !

Thin Ethernet (10base2)

• cable is connected via BNC-T-connectors directly to the network card installed in the PC

Thin Ethernet (10base2)

• BUS Topology

• Each connection to an Thin-Ethernet RG-58 cable is called a "node„ (PC, UNIX-workstation, fileserver, network printers,...).

• Limitations– maximum 30 nodes on one Thin-Ethernet segment

– minimum 0.5 meter distance between nodes

– maximum total cable-length of 185 meter

Thick Ethernet (10base5)• cable (single central wire,

plastic insulation, In turn surrounded by four shields, outside jacket)

• 255 nodes • each node must be at

least 2.5 meters• up to 500 meters

Twisted Pair Ethernet (10baseT/UTP)

• UTP - Unshielded Twisted Pair cable is connected via an RJ-45 connectors to the network card installed in the PC

• UTP cables connect now each PC to the "hub„ - amplifies and distributes the signal to other connected systems

Cable types

UTP categories

Category 1 Voice Only (Telephone Wire)

Category 2 Data to 4 Mbps (LocalTalk)

Category 3 Data to 10 Mbps (Ethernet)

Category 4 Data to 20 Mbps (16 Mbps Token Ring)

Category 5 Data to 100 Mbps (Fast Ethernet)

RJ45 must be shielded too

Crossover 10baseT

• Crossover: – PC – PC– Hub – Hub

• Some hubs offer special connectors :– "Uplink" or something like "MDI/X„ =

Straight / Crossower

10BaseT - Network

• Star Topology• Limitations:

– Maximum segment length 100 meters– Minimum between computers 2.5 meters– 1024 nodes maximum on the LAN

– 4 repeater / 5 segment rule of 10Base5 is retained

10BaseT - Larger networks

Twisted Pair versus Coax:Reliability / Advantages

• What happens, when the cable breaks ?• What happens, when PC added to a network ?

Coax cable can only be used on 10 MHz networks, while Twisted-Pair using CAT5-cabling is also able to handle 100 MHz networks.

Fast Ethernet (100baseT)

• 100BASE-TX -- Similar star-shaped configuration to 10BASE-T. It also uses two pairs, but requires Cat-5 cable to achieve 100Mbit/s.

• 100BASE-T4 -- 100 Mbit/s Ethernet over Cat-3 cabling, 4 pairs (as used for 10BASE-T installations)

• 100BASE-FX: 2 fiber optic cables

10 Mhz or 100 Mhz : Dual-Speed Hubs

100Base-TX 100Base-T4

Gigabit Ethernet (1000BaseT)

• UTP Cat 5e ("Category 5 enhanced"), UTP Cat 6 Cable (No need to rewire network !!!)

• It uses all four cable pairs for simultaneous transmission in both directions (echo cancellation, …)

Gigabit Ethernet (1000BaseT)

Types of wiring:

• 1000BASE-SX (a short laser wavelength on multimode fiber optic cable for a maximum length of 550 meters)

• 1000BASE-LX/LH (a long wavelength for a "long haul" fiber optic cable for a maximum length of 10 kilometers)

• 1000BASE-ZX (an extended wavelength single-mode optical fiber for up to 100 kilometers)

• 1000BASE-CX (two pairs of 150-ohm shielded twisted pair cable for a maximum length of 25 meters)

• 1000BASE-T (four pairs of Category 5 Unshielded Twisted Pair cable for a maximum length of 100 meters (e.g. 90 m horizontal (inside the building), 9 m at the patch panel, and 1 m from the port to the computer or node))

Computer networking devices

Networks have the trend to grow :

• Repeater / Hub (Multiport repeater)/

• Switch / Bridge

• Router

Network Repeater / Hub10Base2

10BaseT (TP/UTP)

Network Repeater / Hub LimitationsRepeaters / Hubs are 'non-intelligent' devices• whatever comes in on one port, gets amplified and send out to ALL other ports• any network transmission 'fills up/flows into' ALL cable-segments of the network• only ONE network connection can be active at a time on the complete

network !

Network Repeater / Hub Limitations

Network Bridge

• more 'intelligent' device • viewed at the data inside the transmissions, to

find out based on the Network-card addresses (MAC), whether it is necessary to transmit the information to a different segment or not

• only 2 connectors, allowing to split large networks into 2 smaller sub-networks (collision domains).

Network Switch

• Even more 'intelligent‘ device

• able to handle more than 2 ports and are able to handle more than 2 communications at the same time

• When a transmission comes in on one port, the switch looks at the MAC addresses to determine, onto which port to send it out

Network Switch

Network Router

• A router is a computer networking device that forwards data packet across an internetwork toward their destinations, through a process known as routing.

• Divides network into broadcast domains:– A broadcast domain is a logical area in a

computer network where any computer connected to the computer network can directly transmit to any other in the domain without having to go through a routing device

Router-Switch and Neighborhood Analogy

References

• www.windowsnetworking.com

• www.wikipedia.org

• www.cisco.com

• www.ethermanage.com