KIS – Cvičenie #1
Technológie komunikačných sietí
Fyzická vrstva RM OSI
Marián Beszédeš, B506
beszedes@ktl.elf.stuba.sk
Kis - Program cvičení
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Úvod, technológie komunikačných sietí
Ethernet, MAC podvrstva
Analýza prevádzky na sieti Ethernet
Návrh LAN siete
IP konfigurácia v prostredí OS Windows (+zadanie referátov)
Sieťovanie LAN a WAN
CBT
Manažment IP sietí
Test, príprava referátu
WAN: ISDN
Prezentácia referátu
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 BNCT-connectors directly to the
network card installed in the
PC
Thin Ethernet (10base2)
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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 CAT5cabling is also able to handle
100 MHz networks.
Fast Ethernet (100baseT)
100Base-TX
• 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-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:
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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 / Hub
10Base2
10BaseT (TP/UTP)
Network Repeater / Hub Limitations
Repeaters / 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
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www.windowsnetworking.com
www.wikipedia.org
www.cisco.com
www.ethermanage.com