Download - Data communication part2
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DATCOMMLocal Area Network
Technologies
Engr. Melvin K. Cabatuan, MsE
De La Salle University
February 2013
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Objectives
- To briefly discuss the technology of dominantwired LANs- Ethernet, and other LAN media.
- Describe Media Access Control (MAC) andCarrier Sense Multiple Access/CollisionDetection (CSMA/CD)
- Explain Address Resolution Protocol (ARP)and Bridges.
- Discuss Switched Ethernet andVirtual LAN (VLAN).
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Objectives
- To briefly discuss the technology of dominantwired LANs- Ethernet, and other LAN media.
- Describe Media Access Control (MAC) andCarrier Sense Multiple Access/CollisionDetection (CSMA/CD)
- Explain Address Resolution Protocol (ARP)and Bridges.
- Discuss Switched Ethernet andVirtual LAN (VLAN).
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Objectives
- To briefly discuss the technology of dominantwired LANs- Ethernet, and other LAN media.
- Describe Media Access Control (MAC) andCarrier Sense Multiple Access/CollisionDetection (CSMA/CD)
- Explain Address Resolution Protocol (ARP)and Bridges.
- Discuss Switched Ethernet andVirtual LAN (VLAN).
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Objectives
- To briefly discuss the technology of dominantwired LANs- Ethernet, and other LAN media.
- Describe Media Access Control (MAC) andCarrier Sense Multiple Access/CollisionDetection (CSMA/CD)
- Explain Address Resolution Protocol (ARP)and Bridges.
- Discuss Switched Ethernet andVirtual LAN (VLAN).
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Local Area NetworkLAN
- A computer network that is designed for alimited geographic area such as a building or acampus.
- LAN technologies: Ethernet, token ring, tokenbus, FDDI, and ATM LAN.
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Local Area NetworkLAN
- A computer network that is designed for alimited geographic area such as a building or acampus.
- LAN technologies: Ethernet, token ring, tokenbus, FDDI, and ATM LAN.
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IEEE Project 802IEEE standard for LANs
- specify functions of the physical and data linklayer of major LAN protocols.
- subdivided the data link layer into twosublayers: logical link control (LLC) and mediaaccess control (MAC).
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IEEE Project 802IEEE standard for LANs
- specify functions of the physical and data linklayer of major LAN protocols.
- subdivided the data link layer into twosublayers: logical link control (LLC) and mediaaccess control (MAC).
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Ethernet- was created in 1976 at Xerox’s Palo AltoResearch Center (PARC).
- de facto standard technology that is used forconnecting LANs.
- first implemented by a group called DIX(Digital, Intel, and Xerox).
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Ethernet- was created in 1976 at Xerox’s Palo AltoResearch Center (PARC).
- de facto standard technology that is used forconnecting LANs.
- first implemented by a group called DIX(Digital, Intel, and Xerox).
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Ethernet- was created in 1976 at Xerox’s Palo AltoResearch Center (PARC).
- de facto standard technology that is used forconnecting LANs.
- first implemented by a group called DIX(Digital, Intel, and Xerox).
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Ethernet (802.3) Frame
- Preamblecontains 7 bytes (56 bits) of alternating 0s and1s that alerts the receiving system to thecoming frame and enables it to synchronize itsinput timing.
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Ethernet (802.3) Frame
- Start frame delimiter (SFD)(1 byte: 10101011) signals the beginning of theframe; the last 2 bits are 11 and alert thereceiver that the next field is the destinationaddress.
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Ethernet (802.3) Frame- Destination address (DA)is 6 bytes and contains the physical address ofthe destination station/s to receive the packet.
- Source address (SA)is 6 bytes and contains the physical address ofthe sender of the packet.
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Ethernet (802.3) Frame- Destination address (DA)is 6 bytes and contains the physical address ofthe destination station/s to receive the packet.
- Source address (SA)is 6 bytes and contains the physical address ofthe sender of the packet.
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Ethernet (802.3) Frame
- Length or Type◦ 802.3: length field to define the number ofbytes in the data field or◦ Ethernet: type field to define the upper-layerprotocol using the MAC frame.
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Ethernet (802.3) Frame- Data◦ carries data encapsulated from theupper-layer protocols;◦ a minimum of 46 and a maximum of 1500bytes.
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Ethernet (802.3) Frame- Data◦ carries data encapsulated from theupper-layer protocols;◦ a minimum of 46 and a maximum of 1500bytes.
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� Understand
What if the upper-layer packet is less than theminimum 46 bytes?
- Padding is added to make up the difference.
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� Understand
What if the upper-layer packet is less than theminimum 46 bytes?
- Padding is added to make up the difference.
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Ethernet (802.3) Frame
- Cyclic Redundancy Check (CRC)verifies that the data that left the sourcecomputer did not change at all during thetransmission.
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� UnderstandThe 802.3 standard defines the maximum length ofa frame (without preamble and SFD field) as 1518bytes. Give the historical reasons for thisrestriction.
- Memory was very expensive when Ethernetwas designed: a maximum length restrictionhelped to reduce the size of the buffer.
- It prevents one station from monopolizing theshared medium, blocking other stations thathavedata to send.
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� UnderstandThe 802.3 standard defines the maximum length ofa frame (without preamble and SFD field) as 1518bytes. Give the historical reasons for thisrestriction.
- Memory was very expensive when Ethernetwas designed: a maximum length restrictionhelped to reduce the size of the buffer.
- It prevents one station from monopolizing theshared medium, blocking other stations thathavedata to send.
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� UnderstandThe 802.3 standard defines the maximum length ofa frame (without preamble and SFD field) as 1518bytes. Give the historical reasons for thisrestriction.
- Memory was very expensive when Ethernetwas designed: a maximum length restrictionhelped to reduce the size of the buffer.
- It prevents one station from monopolizing theshared medium, blocking other stations thathavedata to send.
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MAC Addressalso referred to as the data link address or physicaladdress
- a 6 bytes (48 bits) physical address applied tothe network interface card (NIC) by themanufacturer during production.
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MAC Address
- normally written in hexadecimal notation, witha colon between the bytes.
- Ex. Ethernet MAC address4A: 30 : 10 : 21 : 10 : 1A
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MAC Address
- normally written in hexadecimal notation, witha colon between the bytes.
- Ex. Ethernet MAC address4A: 30 : 10 : 21 : 10 : 1A
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Source and Destination AddressingModes
- Source address is always a unicast address - theframe comes from only one station.
- Destination address can be unicast, multicast,or broadcast.
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Source and Destination AddressingModes
- Source address is always a unicast address - theframe comes from only one station.
- Destination address can be unicast, multicast,or broadcast.
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� ExerciseDefine the type of the following destinationaddresses:
- 4A : 30 : 10 : 21 : 10 : 1A- 47 : 20 : 1B : 2E : 08 : EE- FF : FF : FF : FF : FF : FF
Solution: Refer to the second hexadecimal digitfrom the left:
even ==> unicast;odd ==> multicast;all F’s ==> Broadcast
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� ExerciseDefine the type of the following destinationaddresses:
- 4A : 30 : 10 : 21 : 10 : 1A
- 47 : 20 : 1B : 2E : 08 : EE- FF : FF : FF : FF : FF : FF
Solution: Refer to the second hexadecimal digitfrom the left:
even ==> unicast;odd ==> multicast;all F’s ==> Broadcast
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� ExerciseDefine the type of the following destinationaddresses:
- 4A : 30 : 10 : 21 : 10 : 1A- 47 : 20 : 1B : 2E : 08 : EE
- FF : FF : FF : FF : FF : FFSolution: Refer to the second hexadecimal digitfrom the left:
even ==> unicast;odd ==> multicast;all F’s ==> Broadcast
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� ExerciseDefine the type of the following destinationaddresses:
- 4A : 30 : 10 : 21 : 10 : 1A- 47 : 20 : 1B : 2E : 08 : EE- FF : FF : FF : FF : FF : FF
Solution: Refer to the second hexadecimal digitfrom the left:
even ==> unicast;odd ==> multicast;all F’s ==> Broadcast
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� ExerciseDefine the type of the following destinationaddresses:
- 4A : 30 : 10 : 21 : 10 : 1A- 47 : 20 : 1B : 2E : 08 : EE- FF : FF : FF : FF : FF : FF
Solution: Refer to the second hexadecimal digitfrom the left:
even ==> unicast;odd ==> multicast;all F’s ==> Broadcast
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Transmission of Addresses
- transmission is left-to-right, byte by byte;however, for each byte, the least significant bitis sent first and the most significant bit is sentlast.
- Ex. Show how the address47 : 20 : 1B : 2E : 08 : EE is sent out on line.
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Transmission of Addresses
- transmission is left-to-right, byte by byte;however, for each byte, the least significant bitis sent first and the most significant bit is sentlast.
- Ex. Show how the address47 : 20 : 1B : 2E : 08 : EE is sent out on line.
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Transmission of Addresses
- transmission is left-to-right, byte by byte;however, for each byte, the least significant bitis sent first and the most significant bit is sentlast.
- Ex. Show how the address47 : 20 : 1B : 2E : 08 : EE is sent out on line.
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CSMA/CDCarrier Sense Multiple Access with CollisionDetection
- access method for traditional Ethernet(10-Mbps) that senses the medium beforetrying to use it.
- Ethernet stations can be connected togetherusing a physical bus or star topology but itslogical topology is always a bus.
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CSMA/CDCarrier Sense Multiple Access with CollisionDetection
- access method for traditional Ethernet(10-Mbps) that senses the medium beforetrying to use it.
- Ethernet stations can be connected togetherusing a physical bus or star topology but itslogical topology is always a bus.
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CSMA Collision
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CSMA/CDCarrier Sense Multiple Access with CollisionDetection Algorithm
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CSMA/CDMinimum Frame Size
- a restriction on the frame size is required.
- before sending the last bit of the frame, thesending station must detect a collision andabort.
- thus, transmission time Tfr must be at leasttwo times the maximum propagation time Tp.
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CSMA/CDMinimum Frame Size
- a restriction on the frame size is required.- before sending the last bit of the frame, thesending station must detect a collision andabort.
- thus, transmission time Tfr must be at leasttwo times the maximum propagation time Tp.
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CSMA/CDMinimum Frame Size
- a restriction on the frame size is required.- before sending the last bit of the frame, thesending station must detect a collision andabort.
- thus, transmission time Tfr must be at leasttwo times the maximum propagation time Tp.
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� Exercise
In the standard Ethernet, if the maximumpropagation time is 25.6µs, what is the minimumsize of the frame?
Tfr = 2 × Tp = 51.2µs10 Mbps ×51.2µs = 512 bits or 64 bytes
- This is the minimum size of the frame forStandard Ethernet.
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� Exercise
In the standard Ethernet, if the maximumpropagation time is 25.6µs, what is the minimumsize of the frame?
Tfr = 2 × Tp = 51.2µs
10 Mbps ×51.2µs = 512 bits or 64 bytes- This is the minimum size of the frame forStandard Ethernet.
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� Exercise
In the standard Ethernet, if the maximumpropagation time is 25.6µs, what is the minimumsize of the frame?
Tfr = 2 × Tp = 51.2µs10 Mbps ×51.2µs = 512 bits or 64 bytes
- This is the minimum size of the frame forStandard Ethernet.
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� Exercise
In the standard Ethernet, if the maximumpropagation time is 25.6µs, what is the minimumsize of the frame?
Tfr = 2 × Tp = 51.2µs10 Mbps ×51.2µs = 512 bits or 64 bytes
- This is the minimum size of the frame forStandard Ethernet.
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CSMA/CDFlow Diagram
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Standard EthernetImplementation
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� Reading Assignment
- Report about the IEEE 802.3Standard, in your own words.
- Submit throughwww.turnitin.com.
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Cable Specifications
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Coaxial Cable
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Shielded Twisted Pair (STP)
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Unshielded Twisted Pair (UTP)
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� Readings
It is the standards body that creates the Physicallayer specifications for Ethernet.
- EIA/TIA (Electronic Industries Associationand the newer Telecommunications IndustryAssociation)
- EIA/TIA specifies that Ethernet use aregistered jack (RJ) connector with a 4 5wiring sequence on unshielded twisted-pair(UTP) cabling (RJ-45).
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� Readings
It is the standards body that creates the Physicallayer specifications for Ethernet.
- EIA/TIA (Electronic Industries Associationand the newer Telecommunications IndustryAssociation)
- EIA/TIA specifies that Ethernet use aregistered jack (RJ) connector with a 4 5wiring sequence on unshielded twisted-pair(UTP) cabling (RJ-45).
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� Readings
It is the standards body that creates the Physicallayer specifications for Ethernet.
- EIA/TIA (Electronic Industries Associationand the newer Telecommunications IndustryAssociation)
- EIA/TIA specifies that Ethernet use aregistered jack (RJ) connector with a 4 5wiring sequence on unshielded twisted-pair(UTP) cabling (RJ-45).
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UTP Connections (RJ-45)
- RJ-45 connector is clear so you can see theeight colored wires that connect to theconnector’s pins. These wires are twisted intofour pairs.
- Four wires (two pairs) carry the voltage andare considered tip. The other four wires aregrounded and are called ring.
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UTP Connections (RJ-45)
- RJ-45 connector is clear so you can see theeight colored wires that connect to theconnector’s pins. These wires are twisted intofour pairs.
- Four wires (two pairs) carry the voltage andare considered tip. The other four wires aregrounded and are called ring.
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UTP Connections (RJ-45)8-pin modular connector
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Ethernet Cabling
Straight-through cable: used to connect- Host to switch or hub.
- Router to switch or hub
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Ethernet Cabling
Straight-through cable: used to connect- Host to switch or hub.- Router to switch or hub
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Ethernet CablingStraight-through cable: wires on both cable endsare in the same order.
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Ethernet CablingCrossover Cable: used to connect
- Switch to switch
- Hub to hub- Host to host- Hub to switch- Router direct to host
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Ethernet CablingCrossover Cable: used to connect
- Switch to switch- Hub to hub
- Host to host- Hub to switch- Router direct to host
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Ethernet CablingCrossover Cable: used to connect
- Switch to switch- Hub to hub- Host to host
- Hub to switch- Router direct to host
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Ethernet CablingCrossover Cable: used to connect
- Switch to switch- Hub to hub- Host to host- Hub to switch
- Router direct to host
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Ethernet CablingCrossover Cable: used to connect
- Switch to switch- Hub to hub- Host to host- Hub to switch- Router direct to host
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Ethernet CablingCrossover Cable: wires on each end of the cableare crossed - Transmit to Receive and Receive toTransmit on each side, for both tip and ring.
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Ethernet CablingSummary
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Fast Ethernet (802.3u)
- designed to compete with LAN protocols suchas FDDI or Fiber Channel.
- upgrade the data rate to 100 Mbps.- backward-compatible with Standard Ethernet.- same frame format and 48-bit address.- same minimum and maximum frame lengths.
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Fast Ethernet (802.3u)
- designed to compete with LAN protocols suchas FDDI or Fiber Channel.
- upgrade the data rate to 100 Mbps.
- backward-compatible with Standard Ethernet.- same frame format and 48-bit address.- same minimum and maximum frame lengths.
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Fast Ethernet (802.3u)
- designed to compete with LAN protocols suchas FDDI or Fiber Channel.
- upgrade the data rate to 100 Mbps.- backward-compatible with Standard Ethernet.
- same frame format and 48-bit address.- same minimum and maximum frame lengths.
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Fast Ethernet (802.3u)
- designed to compete with LAN protocols suchas FDDI or Fiber Channel.
- upgrade the data rate to 100 Mbps.- backward-compatible with Standard Ethernet.- same frame format and 48-bit address.
- same minimum and maximum frame lengths.
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Fast Ethernet (802.3u)
- designed to compete with LAN protocols suchas FDDI or Fiber Channel.
- upgrade the data rate to 100 Mbps.- backward-compatible with Standard Ethernet.- same frame format and 48-bit address.- same minimum and maximum frame lengths.
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Fast Ethernet (802.3u)Implementation
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Fast Ethernet (802.3u)
- MAC sublayer was kept untouched
- star topology: half duplex and full duplex- access method is the same (CSMA/CD) for thehalf-duplex
- autonegotiation allows two devices to negotiatethe mode or data rate of operation.
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Fast Ethernet (802.3u)
- MAC sublayer was kept untouched- star topology: half duplex and full duplex
- access method is the same (CSMA/CD) for thehalf-duplex
- autonegotiation allows two devices to negotiatethe mode or data rate of operation.
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Fast Ethernet (802.3u)
- MAC sublayer was kept untouched- star topology: half duplex and full duplex- access method is the same (CSMA/CD) for thehalf-duplex
- autonegotiation allows two devices to negotiatethe mode or data rate of operation.
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Fast Ethernet (802.3u)
- MAC sublayer was kept untouched- star topology: half duplex and full duplex- access method is the same (CSMA/CD) for thehalf-duplex
- autonegotiation allows two devices to negotiatethe mode or data rate of operation.
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Address Resolution Protocol (ARP)
- accepts a logical address from the IP protocol,then, identify and place the source anddestination MAC address in the frame
- operates at the Internet layer, but the theMAC address is attached at the NetworkAccess layer.
- maps a logical address to its correspondingphysical address
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Address Resolution Protocol (ARP)
- accepts a logical address from the IP protocol,then, identify and place the source anddestination MAC address in the frame
- operates at the Internet layer, but the theMAC address is attached at the NetworkAccess layer.
- maps a logical address to its correspondingphysical address
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Address Resolution Protocol (ARP)
- accepts a logical address from the IP protocol,then, identify and place the source anddestination MAC address in the frame
- operates at the Internet layer, but the theMAC address is attached at the NetworkAccess layer.
- maps a logical address to its correspondingphysical address
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Address Resolution Protocol (ARP)Position of ARP in TCP/IP protocol suite
- Why do we need ARP?
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Address Resolution Protocol (ARP)Position of ARP in TCP/IP protocol suite
- Why do we need ARP?
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ARP OperationARP request is broadcast
} If this is your IP address, send me yourMAC address. ~
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ARP OperationARP reply is unicast
} This is my MAC address. ~
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ARP Packet Format
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ARP Packet Format- Hardware type16-bit field defining the type of the network onwhich ARP is running. Each LAN has beenassigned.
Ex. Ethernet: type 1
- Protocol type16-bit field defining the protocol.
Ex. IPv4 protocol: 080016
- Hardware length8-bit field defining the length of the physicaladdress in bytes.
Ex. Ethernet: 6 bytes
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ARP Packet Format- Hardware type16-bit field defining the type of the network onwhich ARP is running. Each LAN has beenassigned.
Ex. Ethernet: type 1- Protocol type16-bit field defining the protocol.
Ex. IPv4 protocol: 080016
- Hardware length8-bit field defining the length of the physicaladdress in bytes.
Ex. Ethernet: 6 bytes
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ARP Packet Format- Hardware type16-bit field defining the type of the network onwhich ARP is running. Each LAN has beenassigned.
Ex. Ethernet: type 1- Protocol type16-bit field defining the protocol.
Ex. IPv4 protocol: 080016
- Hardware length8-bit field defining the length of the physicaladdress in bytes.
Ex. Ethernet: 6 bytes
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ARP Packet Format- Protocol Length8-bit field defining the length of the logicaladdress in bytes.
Ex. IPv4 protocol: 4
- Operation16-bit field defining the type of packet
Ex. ARP request (1), ARP reply (2).- Sender hardware addressvariable-length field defining the physicaladdress of the sender.
Ex. Ethernet: 6 bytes
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ARP Packet Format- Protocol Length8-bit field defining the length of the logicaladdress in bytes.
Ex. IPv4 protocol: 4- Operation16-bit field defining the type of packet
Ex. ARP request (1), ARP reply (2).
- Sender hardware addressvariable-length field defining the physicaladdress of the sender.
Ex. Ethernet: 6 bytes
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ARP Packet Format- Protocol Length8-bit field defining the length of the logicaladdress in bytes.
Ex. IPv4 protocol: 4- Operation16-bit field defining the type of packet
Ex. ARP request (1), ARP reply (2).- Sender hardware addressvariable-length field defining the physicaladdress of the sender.
Ex. Ethernet: 6 bytes
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ARP Packet Format- Sender protocol addressvariable-length field defining the logical addressof the sender.
Ex. IPv4 protocol: 4 bytes
- Target hardware addressvariable-length field defining the physicaladdress of the target.
Ex. Ethernet: 6 bytes- Target protocol addressvariable-length field defining the logical addressof the target.
Ex. IPv4 protocol: 4bytes
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ARP Packet Format- Sender protocol addressvariable-length field defining the logical addressof the sender.
Ex. IPv4 protocol: 4 bytes- Target hardware addressvariable-length field defining the physicaladdress of the target.
Ex. Ethernet: 6 bytes
- Target protocol addressvariable-length field defining the logical addressof the target.
Ex. IPv4 protocol: 4bytes
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ARP Packet Format- Sender protocol addressvariable-length field defining the logical addressof the sender.
Ex. IPv4 protocol: 4 bytes- Target hardware addressvariable-length field defining the physicaladdress of the target.
Ex. Ethernet: 6 bytes- Target protocol addressvariable-length field defining the logical addressof the target.
Ex. IPv4 protocol: 4bytes
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Encapsulation of ARP packet
An ARP packet is encapsulated directly into adata link frame.
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ARP Usage Scenarios
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ARP Usage Scenarios
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� Exercise
A host with IP address 130.23.43.20 and physicaladdress B2 : 34 : 55 : 10 : 22 : 10 has a packet tosend to another host with IP address 130.23.43.25and physical address A4 : 6E : F4 : 59 : 83 : AB(which is unknown to the first host). The twohosts are on the same Ethernet network. Show theARP request and reply packets encapsulated inEthernet frames.
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ARP Exercise Request
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ARP Exercise Reply
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Proxy ARP Router
- acts on behalf of a set of hosts.
- whenever a router running a proxy ARPreceives an ARP request looking for the IPaddress of one of its hosts, the router sends anARP reply announcing its own hardware(physical) address.
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Proxy ARP Router
- acts on behalf of a set of hosts.- whenever a router running a proxy ARPreceives an ARP request looking for the IPaddress of one of its hosts, the router sends anARP reply announcing its own hardware(physical) address.
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Proxy ARP Router
After the router receives the actual IP packet, itsends the packet to the appropriate host or router.
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Connecting Devices
- To connect LANs and WANs together we useconnecting devices.
- Ex. Repeaters (or hubs), Bridges (or two-layerswitches), and Routers (or three-layerswitches).
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Connecting Devices
- To connect LANs and WANs together we useconnecting devices.
- Ex. Repeaters (or hubs), Bridges (or two-layerswitches), and Routers (or three-layerswitches).
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Repeater
A repeater forwards every bit; it has no filteringcapability.
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BridgeTwo-layer switch
- operates in both the physical and the data linklayers.
- PHY: regenerates the signal it receives.- DLL: check the MAC addresses (source anddestination) contained in the frame.
- has a table used in filtering decisions.
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BridgeTwo-layer switch
- operates in both the physical and the data linklayers.
- PHY: regenerates the signal it receives.
- DLL: check the MAC addresses (source anddestination) contained in the frame.
- has a table used in filtering decisions.
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BridgeTwo-layer switch
- operates in both the physical and the data linklayers.
- PHY: regenerates the signal it receives.- DLL: check the MAC addresses (source anddestination) contained in the frame.
- has a table used in filtering decisions.
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BridgeTwo-layer switch
- operates in both the physical and the data linklayers.
- PHY: regenerates the signal it receives.- DLL: check the MAC addresses (source anddestination) contained in the frame.
- has a table used in filtering decisions.
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BridgeExample
The bridge consults its table to find the departingport.
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Transparent Bridge
- a bridge in which the stations are completelyunaware of the bridge’s existence.
- reconfiguration of the stations is unnecessarywhen added or deleted.
- forwarding function with dynamic forwardingtable
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Transparent Bridge
- a bridge in which the stations are completelyunaware of the bridge’s existence.
- reconfiguration of the stations is unnecessarywhen added or deleted.
- forwarding function with dynamic forwardingtable
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Transparent Bridge
- a bridge in which the stations are completelyunaware of the bridge’s existence.
- reconfiguration of the stations is unnecessarywhen added or deleted.
- forwarding function with dynamic forwardingtable
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Bridge Learning
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Switched LANTraditional
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Switched LANContemporary
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Bridging vs. LAN Switching
- Bridges are software based, while switches arehardware based (ASIC for filtering)
- A switch can be viewed as a multiport bridge.- Switches have a higher number of ports thanmost bridges.
- Both bridges and switches forward layer 2broadcasts.
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Bridging vs. LAN Switching
- Bridges are software based, while switches arehardware based (ASIC for filtering)
- A switch can be viewed as a multiport bridge.
- Switches have a higher number of ports thanmost bridges.
- Both bridges and switches forward layer 2broadcasts.
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Bridging vs. LAN Switching
- Bridges are software based, while switches arehardware based (ASIC for filtering)
- A switch can be viewed as a multiport bridge.- Switches have a higher number of ports thanmost bridges.
- Both bridges and switches forward layer 2broadcasts.
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Bridging vs. LAN Switching
- Bridges are software based, while switches arehardware based (ASIC for filtering)
- A switch can be viewed as a multiport bridge.- Switches have a higher number of ports thanmost bridges.
- Both bridges and switches forward layer 2broadcasts.
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Layer 2 Switch Functions
- Address learningremember the source hardware address of eachframe received, and save in forward/filter table.
- Forward/filter decisionsWhen a frame is received, the switch looks atthe destination hardware address and finds theexit interface.
- Loop avoidancestop network loops while still permittingredundancy.
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Layer 2 Switch Functions
- Address learningremember the source hardware address of eachframe received, and save in forward/filter table.
- Forward/filter decisionsWhen a frame is received, the switch looks atthe destination hardware address and finds theexit interface.
- Loop avoidancestop network loops while still permittingredundancy.
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Layer 2 Switch Functions
- Address learningremember the source hardware address of eachframe received, and save in forward/filter table.
- Forward/filter decisionsWhen a frame is received, the switch looks atthe destination hardware address and finds theexit interface.
- Loop avoidancestop network loops while still permittingredundancy.
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Address Learning
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Forward/Filter Decisions
Host A sends a data frame to Host D. What will the switch dowhen it receives the frame from Host A?
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Network RedundancyImportance and Problem
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Loop AvoidanceSpanning Tree Protocol (STP)
" All root ports forward,All nonroot ports block ".
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Virtual Private NetworkVPN
- It enables a host computer to send and receivedata across shared or public networks as if itwere a private network with all thefunctionality
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Network Security Issue
- Ensure confidentiality through use of◦ User authentication◦ Data encryption
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Virtual Private Networks
- network connection that uses the Internet togive users or branch offices secure access to acompany’s network resources.
- use encryption technology to ensure thatcommunication is private and secure
- Privacy is achieved by creating a "tunnel"between the VPN client and VPN server.
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Virtual Private Networks
- network connection that uses the Internet togive users or branch offices secure access to acompany’s network resources.
- use encryption technology to ensure thatcommunication is private and secure
- Privacy is achieved by creating a "tunnel"between the VPN client and VPN server.
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Virtual Private Networks
- network connection that uses the Internet togive users or branch offices secure access to acompany’s network resources.
- use encryption technology to ensure thatcommunication is private and secure
- Privacy is achieved by creating a "tunnel"between the VPN client and VPN server.
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Virtual Private NetworkA tunnel is created by encapsulation, in which the inner packetcontaining the data is encrypted and the outer headers containthe unencapsulated addresses.
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VPN Types/ Benefits
- Remote access VPNsEnable mobile users to connect with corporatenetworks securely wherever an Internetconnection is available.
- Site-to-site VPNs or intranetAllow multiple sites to maintain permanentsecure connections via the Internet instead ofusing expensive WAN links.
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VPN Types/ Benefits
- Remote access VPNsEnable mobile users to connect with corporatenetworks securely wherever an Internetconnection is available.
- Site-to-site VPNs or intranetAllow multiple sites to maintain permanentsecure connections via the Internet instead ofusing expensive WAN links.
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VPN Types/ Benefits
- Reduce costs by using the ISP’s supportservices instead of paying for more expensiveWAN support.
- Eliminate the need to support dial-up remoteaccess, which is a higher-cost solution requiringmore personnel.
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VPN Types/ Benefits
- Reduce costs by using the ISP’s supportservices instead of paying for more expensiveWAN support.
- Eliminate the need to support dial-up remoteaccess, which is a higher-cost solution requiringmore personnel.
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IP SecurityIPSec
- a collection of protocols designed by theInternet Engineering Task Force (IETF) toprovide security for a packet at the networklevel..
- helps create authenticated and confidentialpackets for the IP layer.
- operates in one of two different modes:transport or tunnel mode.
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IP SecurityIPSec
- a collection of protocols designed by theInternet Engineering Task Force (IETF) toprovide security for a packet at the networklevel..
- helps create authenticated and confidentialpackets for the IP layer.
- operates in one of two different modes:transport or tunnel mode.
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IP SecurityIPSec
- a collection of protocols designed by theInternet Engineering Task Force (IETF) toprovide security for a packet at the networklevel..
- helps create authenticated and confidentialpackets for the IP layer.
- operates in one of two different modes:transport or tunnel mode.
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IPSec Transport ModeIPSec in transport mode does not protect the IPheader;it only protects the information coming from thetransport layer.
It is used when we need host-to-host (end-to-end)protection of data.
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IPSec Tunnel Mode
IPSec in tunnel mode protects the original IPheader.
It is used between two routers, between a host anda router, or between a router and a host.
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Tunnel vs. Transport Mode
◦ In transport mode, the IPSec layer comesbetween the transport layer and the network layer.◦ In tunnel mode, the flow is from the networklayer to the IPSec layer and then back to thenetwork layer again.
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Other Terms
- 1000BASE-CX, 1000BASE-LX, 1000BASE-SX,1000BASE-TThe IEEE 802.3 standards for Ethernet implementationwith 1-Gbps data rate.
- 100BASE-FX, 100BASE-T4, 100BASE-TX, 100BASE-XThe IEEE 802.3 standards for Fast Ethernetimplementation with 100-Mbps data rate.
- 10BASE2, 10BASE5, 10BASE-F, 10BASE-E, 10BASE-LThe IEEE 802.3 standard for Thin Ethernet with 10-Mbpsdata rate.
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Other Terms
- Address Resolution Protocol (ARP)In TCP/IP, a protocol for obtaining the physical address ofa node when the Internet address is known.
- Address spaceThe total number of addresses used by a protocol.
- BandwidthThe difference between the highest and lowest frequenciesavailable for network signals. The term is also used todescribe the rated throughput capacity of a given networkmedium or protocol.
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Other Terms
- BridgeA network device operating at the first two layers of theOSI model with filtering and forwarding capabilities.
- Broadcast addressAn address that allows transmission of a message to allnodes of a network.
- CongestionExcessive network or internetwork traffic causing a generaldegradation of service. This can be seen in slower responsetimes, longer file transfers and network users becoming lessproductive due to network delays.
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Other Terms- Carrier Sense Multiple Access with Collision Avoidance(CSMA/CA)An access method in wireless LANs that avoids collision byforcing the stations to send reservation messages when theyfind the channel is idle.
- Carrier Sense Multiple Access with Collision Detection(CSMA/CD)An access method in which stations transmit whenever thetransmission medium is available and retransmit whencollision occurs.
- CollisionThe event that occurs when two transmitters send at thesame time on a channel designed for only one transmissionat a time; data will be destroyed.
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Other Terms
- Consultative Committee for International Telegraphy andTelephony (CCITT)An international standards group now known as the ITU-T.
- Defense Advanced Research Projects Agency (DARPA)A government organization, which, under the name ofARPA, funded ARPANET and the Internet.
- EthernetA local area network using the CSMA/CD access method.
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Other Terms
- ExtranetA private network that uses the TCP/IP protocol suite thatallows authorized access from outside users.
- FloodingSaturation of a network with a message. intranet A privatenetwork that uses the TCP/IP protocol suite.
- IntranetA private network that uses the TCP/IP protocol suite.
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Other Terms
- Institute of Electrical and Electronics Engineers (IEEE)A group consisting of professional engineers that hasspecialized societies whose committees prepare standards inmembers’ areas of specialty.
- Logical tunnelThe encapsulation of a multicast packet inside a unicastpacket to enable multicast routing by non-multicast routers.
- Physical addressThe address of a device used at the data link layer (MACaddress).
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Other Terms
- Request for Comment (RFC)A formal Internet document concerning an Internet issue.
- Reverse Address Resolution Protocol (RARP)A TCP/IP protocol that allows a host to find its Internetaddress, given its physical address.
- SwitchA device connecting multiple communication lines together.
- Switched EthernetAn Ethernet in which a switch, replacing the hub, candirect a transmission to its destination.
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ReferencesTEXTBOOK:
- Data Communications and Networking,Behrouz Forouzan, 4th Edition, McGraw-Hill,2007
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ReferencesSECONDARY SOURCE:
- TCP/IP Protocol Suite, Behrouz Forouzan, 4thedition, 2010
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ReferencesSECONDARY SOURCE:
- Data and Computer Communications, WilliamStallings, 2007
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ReferencesSECONDARY SOURCE:
- CISCO Networking Essentials, Troy McMillan,2012
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ReferencesSECONDARY SOURCE:
- Network Fundamentals, Cisco NetworkingAcademy, 2007
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Thank you for your attention!