Ethernet BasicsPhysical Layer Ethernet StandardsData Link Layer Ethernet StandardsEthernet Security 1 © 2013 Pearson

Characteristic Local Area Network (LAN) Wide Area Network (WAN) Location Located entirely on customer’s premises Must carry transmissions beyond customer’s premises Consequence of Location Owning company operates the LAN User must contract with a carrier that has rights of way to carry wires between premises 2 © 2013 Pearson

Characteristic Local Area Network (LAN) Wide Area Network (WAN) Technology and Service Consequence of Corporate versus Carrier Ownership Owner can use any technology and service options it wishes Customer is limited to technologies and service options offered by available carriers 3 © 2013 Pearson

Characteristic Local Area Network (LAN) Wide Area Network (WAN) Labor Consequences of Corporate versus Carrier Ownership Owner must do all operation and maintenance work Operational and maintenance work is done by the carrier 4 © 2013 Pearson

Characteristic Local Area Network (LAN) Wide Area Network (WAN) EconomicsTransmission distances are short, so the cost per bit carried is low Transmission distances are long, so the cost per bit carried is high 5 © 2013 Pearson

Characteristic Local Area Network (LAN) Wide Area Network (WAN) Speed Consequences of Economics Very high speeds are affordable Customers are content with lower speeds Design Consequences of Economics Optimization of transmission capacity is not pressing Optimization of transmission capacity is critical 6 © 2013 Pearson

Workgroup Switches Connect Hosts to the Network 7 © 2013 Pearson

Core Switches Connect Switches to Other Switches 8 © 2013 Pearson

Hosts Normally Connect to Workgroup Switches Through UTP Copper Wiring 9 © 2013 Pearson

Switches Often Connect to Other Switches Through Optical Fiber 10 © 2013 Pearson

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Characteristic Unshielded Twisted Pair Optical Fiber MediumCopper wireGlass SignalElectricalLight Maximum Distance in LANs Usually 100 meters Usually 200 to 500 meters SpeedSimilar CostLowerHigher 12 © 2013 Pearson

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Ethernet BasicsPhysical Layer Ethernet StandardsData Link Layer Ethernet StandardsEthernet Security 15 © 2013 Pearson

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22 NOT just 4 pairs! © 2013 Pearson

Propagation Effect(s) Impact Installation Discipline Attenuation Signal may become too low to be received properly. Limit cord distance to 100 m Noise Random electromagnet energy in the wire (noise) adds to the signal and may produce errors. Terminal crosstalk interference Interference by other wire pairs in the cord is crosstalk interference. Crosstalk interference at the two ends where the wires are untwisted is terminal crosstalk interference. Major problem Limit untwisting of the wires to 1.25 cm (0.5 in) 23 © 2013 Pearson

Ethernet Signaling Standard Transmission Speed UTP Quality Category Maximum Cord Length 100BASE-TX100 Mbps Category 5e, 6, or higher 100 meters 1000BASE-T1 Gbps Category 5e, 6, or higher 100 meters 10GBASE-T10 GbpsCategory 655 meters 10GBASE-T10 GbpsCategory 6A100 meters 24 Category is a measure of UTP QUALITY © 2013 Pearson

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 When modes arrive at different times, this is called modal dispersion.  If light rays from different clock cycles overlap, modal dispersion may make the signal unreadable. 27 © 2013 Pearson

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Wavelength Core Diameter Modal Bandwidth Maximum Propagation Distance 850 nm62.5 microns160 MHz-km220 m 850 nm62.5 microns200 MHz-km270 m 850 nm50 microns500 MHz-km500 m 29 © 2013 Pearson

UTPOptical Fiber  UTP wire quality is indicated by a cord’s category number (5e, 6, etc.).  Multimode optical fiber quality is indicated by a cord’s modal bandwidth. 30 © 2013 Pearson

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 Wavelength is the physical distance between comparable points on adjacent cycles.  Optical fiber transmission is described in terms of wavelength.  Wavelengths for optical fiber are measured in nanometers (nm).  For LANs, 850 nm light is used almost exclusively. 32 © 2013 Pearson

CharacteristicLAN Fiber Carrier WAN Fiber Required Distance Span 200 to 300 m1 to 40 m Light Wavelength850 nm 1,310 or 1,550 nm Type of Fiber Multimode (Thick Core) Single-Mode (Thin Core) Core Diameter50 or 62.5 microns 8.3 microns 33 © 2013 Pearson

CharacteristicLAN Fiber Carrier WAN Fiber Primary Distance Limitation Modal Dispersion Absorptive Attenuation Quality MetricModal Bandwidth (MHz-km) Not Applicable 34 © 2013 Pearson

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36 The first physical link is 100BASE-TX, so the maximum physical span is 100 meters. The first physical link is 100BASE-TX, so the maximum physical span is 100 meters.

© 2013 Pearson 37 The switch regenerates the received signal. On a 1000BASE-SX link, the clean new signal can travel up to another 220 meters. The switch regenerates the received signal. On a 1000BASE-SX link, the clean new signal can travel up to another 220 meters.

38 The second switch also regenerates the signal. The clean regenerated signal goes on. The second switch also regenerates the signal. The clean regenerated signal goes on. © 2013 Pearson

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Ethernet BasicsPhysical Layer Ethernet Standards Data Link Layer Ethernet Standards Ethernet Security 40 © 2013 Pearson

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43 4 BitsDecimal (Base 10) Hexadecimal (Base 16) hex hex hex hex hex hex hex hex What is 0101 in hex? What is 0000 in hex? © 2013 Pearson

44 What is 1001 in hex? What is 1111 in hex? 4 Bits* Decimal (Base 10) Hexadecimal (Base 16) hex hex A hex B hex C hex D hex E hex F hex © 2013 Pearson

 Converting a 48-bit MAC address to hex ◦ Write down the 48-bit address in 12 four-bit nibbles. ◦ Represent each nibble as a hex symbol. ◦ Pair the hex symbols and put a dash between the 6 pairs. ◦ Try these four nibbles: © 2013 Pearson

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51 A packet from A1… to E5… must pass through Switches 1, 2, and 3.

© 2013 Pearson 52 Switch 1 sees that it should send the frame to E5 out Port 5.

© 2013 Pearson 53 Switch 2 sees that it should send the frame to E5 out Port 7.

© 2013 Pearson 54 Switch 3 sees that it should send the frame to E5 out Port 6.

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57 Loops are not allowed in Ethernet. A strict hierarchy is required. Loops are not allowed in Ethernet. A strict hierarchy is required. © 2013 Pearson

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 Tag Control Information (TCI) Field ◦ There are 12 bits for VLAN addresses. ◦ There are 3 bits for frame priority. ◦ This permits 2 3 = 8 different priority values. 60 © 2013 Pearson

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Ethernet BasicsPhysical Layer Ethernet StandardsData Link Layer Ethernet StandardsEthernet Security 62 © 2013 Pearson

 Power over Ethernet (POE) ◦ Switches can supply power to devices via UTP. ◦ (Wired telephone systems and USB ports already do this.) ◦ Less expensive than supplying power separately. 63 © 2013 Pearson

 Latest POE Standard ◦ Provides up to 25 Watts to attached devices ◦ Sufficient for most wireless access points ◦ Sufficient for VoIP phones ◦ Sufficient for surveillance cameras ◦ Sufficient for tablets  Not sufficient for desktop or notebook PCs 64 © 2013 Pearson

 The Future ◦ Nonstandard products now supply 60 Watts of power. ◦ May become a future standard. ◦ Still will not be enough for desktop or notebook PCs.  POE switches ◦ New switches can be purchased with POE. ◦ Companies can also add POE equipment to an existing non-POE switch. 65 © 2013 Pearson

 The Problem ◦ Anyone can enter the building and plug their computer into a switch or into a wall RJ-45 port, which connects to a switch.  This usually gives the attacker access to the network without going through a firewall.  Solution: access control at switch ports. ◦ 802.1X Port Based Access Control can do this. ◦ Created by the WG, not the WG. ◦ WG creates general standards, such as security standards. 66 © 2013 Pearson

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 Advantages of a Central Authentication Server ◦ Consistency: Attacker cannot find a misconfigured switch. ◦ Rapid changes: When someone leaves, is hired, or needs credential changes. ◦ Switch cost: Authentication server does heavy work. ◦ Reduced management cost: Only one authentication database to maintain. 69 © 2013 Pearson

 802.3ba governs Ethernet for both 40 Gbps and 100 Gbps  Virtual Lane ◦ Entire 40 Gbps or 100 Gbps  Media Lane ◦ Physical connection ◦ There may be several per virtual lane ◦ Essentially, built-in bonding © 2013 Pearson 70 Box

 Example: 100GBASE-SR10 ◦ 100 Gbps virtual lane ◦ S = 850 nm light ◦ R = How bits are processed ◦ 10 = 10 Gbps media lane  Media Lanes ◦ 10 Mbps optical fiber pairs ◦ 2 extra pairs ◦ 24 optical fiber strands in total © 2013 Pearson 71 Box