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8/4/2019 Ethernet Wireless LAN MOH
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ALTTC/ DX Faculty 1
8/4/2019 Ethernet Wireless LAN MOH
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ALTTC/ DX Faculty 2
Background of Ethernet (First LAN)
Digital, Intel & Xerox (DIX) consortiumcreated original Ethernet 1980(originally known as Alto AlohaNetwork)
The first network to provide CarrierSense Multiple Access / CollisionDetection (CSMA/CD)
Ethernet_II to followed in 1984 (ver-2)
IEEE termed this as 802 projectInitially IEEE 802 Project divided intothree groups
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ALTTC/ DX Faculty 3
High level interface (HILI) became 802.1committee
Responsible for High level interworkingprotocols and management
LLC group became 802.2 committee,for end to end link connectivity betweenhigher layer and media access dependent
layers
DL & MAC (DLMAC) group becameresponsible medium access protocols
DL MAC has been split into three sub
committees
Initial IEEE 802 Project
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ALTTC/ DX Faculty 4
802.3 for Ethernet
Came of with Ethernet physical layerspec.
MAC addressing is same as Ethernet_IIbut length field replaced type filed
Bus topology LAN at 10 Mbps withcollision detection (CSMA/CD)
10base 2/ thinnet 185 meters segmentwithout repeater over RG58 coaxial cable at 50ohms
10base 5/ thicknet 500 meters segmentwithout repeater over RG8/11 coaxial cable at50 ohms
10base T/UTP cat 3 UTP(Unshielded TwistedPair) to support 10 Mbps
DL MAC committees 802.3
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ALTTC/ DX Faculty 5
802.4 for Token Bus
Burroughs, concord data systems,Honeywell, western digital, generalmotors & Boeing took over 802.4
802.5 for Token Ring
IBM worked on 802.5
DL MAC committees 802.4/802.5
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ALTTC/ DX Faculty 6
Ethernet Technology
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ALTTC/ DX Faculty 7
Ethernet Standards (802.3)
Ethernet (10 Mbps)Ethernet_II - (DIX- Ethernet)IEEE 802.3 - Ethernet
Fast Ethernet (100 Mbps)
IEEE 802.12 - 100VG AnyLANIEEE 802.3u - Fast Ethernet
Gigabit Ethernet (1000 Mbps or 1Gbps)
IEEE 802.3z - Gigabit EthernetIEEE 802.ab - Gigabit Ethernet
10 Gigabit Ethernet (10 Gbps)IEEE 802.3ae - 10 Gigabit Ethernet
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ALTTC/ DX Faculty 8
Ethernet_II vs. OSI Model
Upper
Layers
Network
Ethernet_II
Other
Layers
NetworkData Link
Physical
OSI model
Media Access Control
(MAC)
DIX-Ethernet Layers
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ALTTC/ DX Faculty 9
Ethernet_II- Frame
8B 6B 6B 2B 46~1500B 4B
SOURCE
HARDWAREADDRESS
CRCLAYER 3 DATA
TYPE
DESTINATION
HARDWAREADDRESS
PREAMBLE
64~1518B
72~1526B
Eg. Of Type Fields:
0800- IP 0806- ARP 8035- RARP
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ALTTC/ DX Faculty 10
Ethernet_II Frame - Details
Preamble: 8 bytes of alternating 0s and 1s
to synchronise the receiverDestination Address (DA): 6 bytes (48bits) unique physical address of destinationmachine encoded in NIC
Source Address (SA): 6 bytes (48 bits)unique physical address of source machineencoded in NIC
Type : 2 bytes (16 bits) indicates the type ofLayer 3 protocol being used Eg. IP, ARP orRARP (uses RFC 1700 Ethernet Type Values)
Layer 3 Data: Between 46-1500 bytes
CRC : 4bytes (32 bits) for error detectioninformation
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ALTTC/ DX Faculty 11
MAC Address structure (for all Ethernet)
Destination address : (LS Bit first and MS bit Last in each byte -
Little-Endian style)I/G Individual / group address:
0 - Individual address.
1 - Group address.
U/L Universal /local address:
0 - Universally administered.
1- Locally administered.
Source address(LS Bit first and MS bit Last in each byte -
Little-Endian style)
I/G bit is always 0. U/L Universal/local address may be 0/1
U/L I/G
Organisationally Unique Identifier (OUI)
(3 bytes)
LSB MSB LSB MSB LSB MSB LSB MSB LSB MSB LSB MSB
Vendor Assingned No. (Serial No.)
(3 bytes)
Most Significant Byte Least Significant Byte
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ALTTC/ DX Faculty 12
CSMA/CD
Ethernet Uses Carrier Sense Multiple Access
with Collision Detection (CSMA/CD) as accessmethod
Any station wishing to transmit must listen forCarrier on the line
If no carrier is detected, the line is idle andtransmission can be initiated
Two or more stations transmits at the sametime, when there was no carrier, results incollision which is indicated by high voltage on
the lineAfter collision retry is done at staggered timeby different devices
CSMA/CD reduces the number of collision butdoes not eliminate them
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ALTTC/ DX Faculty 13
Ethernet CSMA/CD algorithm
If adapter detects another transmissionwhile transmitting, aborts and sendsjamsignal
After aborting, adapter enters
exponential backoffafter mth collision
first collision: choose K from {0,1} i.e.{0, 22-1};delay is K x 512 bit transmission times
after second collision: choose K from{0,1,2,3}ie. {0,1,..22-1}
after ten collisions, choose K from{0,1,2,3,4,,1023}I.e. {0,1,..210-1}
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ALTTC/ DX Faculty 14
IEEE Project 802
IEEE Project 802 sets standard toenable interworking between devices ofvarious vendors.
Logical Link Control (LLC) sub-layerhas been added to achieve the aboveobjective
Other
Layers
Network
IEEE Project 802
Other
Layers
Network
Data Link
Physical
OSI model
Logical Link Control
Media Access Control
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ALTTC/ DX Faculty 15
Initial IEEE Project 802
Other Layers
Network
IEEE Project 802
802.2 - Logical Link Control
802.4
Token Bus
802.5
Token Ring
ANSI
FDDI
802.3
CSMA/CD
IEEE 802.2 LLC deals with logical address,control information and data
MAC sub layer resolves contention for shared
media
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ALTTC/ DX Faculty 16
802.3 MAC Frame/802.2 LLC without SNAP
802.2 LLC LAYER
ENCAPSULATION DATA
43~1497B3B
7B 1B 6B 6B 2B 46~1500B 4B
SOURCE
HARDWARE
ADDRESS
CRC802.2 PDU
LENGTH
DESTINATION
HARDWARE
ADDRESS
SF
D
PREAMBLE
64~1518B
72~1526B
DSAP SSAP Control
1B 1B 12 B
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ALTTC/ DX Faculty 17
802.3 MAC Frame
Preamble
7 bytes of alternating 0s and 1s that alertthe receiving system and enable it tosynchronise its input timing
Start Frame Delimiter (SFD)
One byte (10101011) signals thebeginning of the frame
Destination Address (DA)6 bytes (48 bits) unique physical address
of destination machine encoded in NICSource Address (SA)
6 bytes (48 bits) unique physical addressof source machine encoded in NIC
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ALTTC/ DX Faculty 18
802.3 MAC Frame
Length (2 bytes)Indicate number of bytes in the frame
802.2 PDU
Upper layer information between 46-1500 bytes
CRC (4 bytes)
For error detection information
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ALTTC/ DX Faculty 19
802.2 LLC Header
DSAP:Destination service access point structureI/G - Individual/group address
0 - Individual DSAP.
1 - Group DSAP.
SSAP:Source service access point structure
C/R - Command/response:
0 - Command.
1 - Response.
Control: The structure of the control field is same as HDLC .
For IP Network value is (03)
DSAP SSAP ControlI/G C/R
802.2 LLC Header
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ALTTC/ DX Faculty 20
802.3 MAC Frame/802.2 LLC with SNAP
802.2 LLC / SNAPENCAPSULATION
DATA
38~1492B8B
7B 1B 6B 6B 2B 46~1500B 4B
SOURCE
HARDWARE
ADDRESS
CRC802.2 PDU
LE
NGTH
DESTINATIO
NHARDWARE
ADDRESS
SFD
PREAMBLE
64~1518B
72~1526B
DSAP SSAP Control
1B 1B 12 B
OUI Ether Type
SNAP
5B
2B3B
OUI- Organisationally Unique Identifier
SNAP- Sub Network Access Point
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ALTTC/ DX Faculty 21
Ethernet (Cabling Spec.)
Three main Cabling specificationsare available in Ethernet:
10 Base 5
Uses Thick co-axial Cable
10 Base 2
Uses Thin Coaxial Cable
10 Base TUses Unshielded Twisted pair cable
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ALTTC/ DX Faculty 22
10Base5; Thick Ethernet; Thicknet
The nickname derives from the size of thecable
Each station on Ethernet network has itsown Network Interface Card (NIC) which
provides the station with a unique 6 bytesphysical address
Each frame is transmitted to every stationon the link but will be read only by the
station to which it is addressedTransceiver performs the CSMA/CD forchecking voltages and collisions on the line
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ALTTC/ DX Faculty 23
10Base5; Thick Ethernet; Thicknet
5 Segments; 2500 M; 1000 Stations
R RSegment 1
Segment 1
500 M; 200 Stations
2.5 M 50 M
1-NIC(Network Interface Card)
1
2-RG-8 Thick Coaxial Cable
2
3-Cable Terminator
3
5-Attachment Unit Interface (AUI);Transceiver Cable (15 Wires)
5
6-Media Attachment unit (MAU);commonly known as Transceiver
6
4
4-Transceiver Vampire Tap
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ALTTC/ DX Faculty 24
10Base2; Thin Ethernet; Thinnet
Also known as cheapnet or cheapernet
Provides same data rate as 10Base5but with distance limitation of 185meters and lesser number of workstations
Transceiver circuitry has moved into theNIC
Transceiver tap has been replaced by aconnector that splices the station
directly into the cableBNC-T connector is with 3 ports; onefor NIC, one each for input and outputends of the cable
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ALTTC/ DX Faculty 25
10Base2; Thin Ethernet; Thinnet
185 M
2-RG-58 Thin Coaxial Cable
2
4
4-Cable Terminator
1-NIC(Network Interface Card)
1
3-BNC-T Connector
3
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ALTTC/ DX Faculty 26
10BaseT
A star topology LANAll individual transceiver functions andnetworking operations are placed in anintelligent hub with a port for each
stationHub fans out any transmitted frame toall its connected stations
Frame will be read by all, but will onlybe processed by the station to which itis addressed
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ALTTC/ DX Faculty 27
10BaseT
100 M
10Base-T Hub
100 M
1-10 Base-T Hub
1
2-RJ-45 Connector Male
2 5
5-RJ-45; Four Pairs UTP (Unshielded Twisted Pair) Cable
4-Network Interface Card
4
3-RJ-45 Connector Female
3
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ALTTC/ DX Faculty 28
Fast Ethernet Standards
Two standards are approved byIEEE in June 1995
802.12
802.3u
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ALTTC/ DX Faculty 29
Fast Ethernet Standards- 802.12/802.3u
802.12Uses even efficient signaling techniquesthan CSMA/CD known as DemandPriority Access Method (DPAM)
Also known as 100VG-AnyLANNot popular and eventually disappearedfrom the market
802.3u
Most popular spec. in 100Mbps over cat5 UTP or cat 5 plus
Also known as Fast Ethernet
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ALTTC/ DX Faculty 30
Fast Ethernet (Cabling Spec.)
Fast Ethernet (100Base-T) isavailable in three different types ofcable technologies:
100Base-T4Utilizes four pairs of telephone-grade twisted-pairwire and is used for networks that need a low qualitytwisted-pair on a 100-Mbps Ethernet
100Base-TXDeveloped by ANSI 100Base-TX is also known as
100Base-X, 100Base-TX uses two wire data gradetwisted-pair wire
100Base-FXDeveloped by ANSI, 100Base-FX utilizes 2 stands offiber cable
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ALTTC/ DX Faculty 31
100 Base-TXUses 2 pairs (1 pair towards hub andother pair from hub) of CAT-5 UTP orSTP
Encoding used is 4B/5B
Distance between hub & station be