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Ethernet and Wireless Local Area Networks. History of Ethernet Standards. Ethernet The dominant wired LAN technology today Only “competitor” is wireless LANs (which actually are supplementary) The IEEE 802 Committee

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history of ethernet standards
History of Ethernet Standards
  • Ethernet
    • The dominant wired LAN technology today
    • Only “competitor” is wireless LANs (which actually are supplementary)
  • The IEEE 802 Committee
    • LAN standards development is done primarily by the Institute for Electrical and Electronics Engineers (IEEE)
    • IEEE created the 802 LAN/MAN Standards Committee for LAN standards (the 802 Committee)
history of ethernet standards3
History of Ethernet Standards
  • The 802 Committee creates working groups for specific types of standards
    • 802.1 for general standards
    • 802.3 for Ethernet standards
      • The terms 802.3 and Ethernet are interchangeable
    • 802.11 for wireless LAN standards
    • 802.16 for WiMax wireless metropolitan area network standards
ethernet physical layer standards
Ethernet Physical Layer Standards

UTP Physical

Layer

Standards

Speed

Maximum

Run

Length

Medium

Required

10BASE-T

10 Mbps

100 meters

4-pair Category 3 or higher

100BASE-TX

100 Mbps

100 meters

4-pair Category 5 or higher

1000BASE-T

(Gigabit

Ethernet)

1,000 Mbps

100 meters

4-pair Category 5 or higher

100BASE-TX dominates access links today.

Although 1000BASE-T is growing in access links today

ethernet physical layer standards5
Ethernet Physical Layer Standards

Fiber Physical

Layer

Standards

Speed

Maximum

Run

Length

Medium

850 nm light (inexpensive)

Multimode fiber

1000BASE-SX

1 Gbps

220 m

62.5

microns

160

MHz-km

1000BASE-SX

1 Gbps

275 m

62.5

200

1000BASE-SX

1 Gbps

500 m

50

400

1000BASE-SX

1 Gbps

550 m

50

500

The 1000BASE-SX standard dominates trunk links today.

Carriers use 1310 and 1550 nm light and single-mode fiber.

gigabit ethernet
Gigabit Ethernet
  • 10 Gbps Ethernet usage is small but growing
  • Several 10 Gbps 10GBASE-x fiber standards are defined, but none is dominant
  • Copper is cheaper than fiber but cannot go as far
  • 100 Gbps has been selected as the next Ethernet speed
    • Chosen over 40 Gbps
  • 100 Gbps Ethernet standards development is just getting underway
data link using multiple switches
Data Link Using Multiple Switches

Received

Signal

Received

Signal

Original

Signal

Received

Signal

Regenerated

Signal

Regenerated

Signal

62.5/125

Multimode Fiber

UTP

UTP

100BASE-TX

(100 m maximum)

Physical Link

1000BASE-SX

(220 m maximum)

Physical Link

100BASE-TX

(100 m maximum)

Physical Link

Each trunk line along the way has a distance limit

multi switch ethernet lan architecture
Multi-Switch Ethernet LAN Architecture

Switch 2 (root switch)

Port 7 on Switch 2

to Port 4 on Switch 3

Port 5 on Switch 1

to Port 3 on Switch 2

Switch 1

Switch 3

C3-2D-55-3B-A9-4F

Switch 2, Port 5

B2-CD-13-5B-E4-65

Switch 1, Port 7

A1-44-D5-1F-AA-4C

Switch 1, Port 2

D4-55-C4-B6-9F

Switch 3, Port 2

E5-BB-47-21-D3-56

Switch 3, Port 6

single point of failure in a switch hierarchy
Single Point of Failure in a Switch Hierarchy

Switch Fails

Switch 2

No Communication

No Communication

C3-2D-55-3B-A9-4F

Switch 1

Switch 3

B2-CD-13-5B-E4-65

D4-47-55-C4-B6-9F

A1-44-D5-1F-AA-4C

E5-BB-47-21-D3-56

hierarchy implications
Hierarchy Implications
  • Single possible path between stations.
  • Makes switching tables very simple because there is only one possible row for each address. Find the row, send the frame out the indicated port. Very fast, so minimizes switching cost.
  • Creates the potential for single points of failure.
  • Low cost is responsible for Ethernet’s LAN dominance.

PortStation

2 A1-44-D5-1F-AA-4C

7 B2-CD-13-5B-E4-65

5 E5-BB-47-21-D3-56

switch operation in ethernet
Switch Operation in Ethernet
  • Today, Switches Dominate in Ethernet
    • A frame comes in one port
    • The switch looks up the frame’s destination MAC address in the switching table
    • The switch sends the frame out a single port
    • Only two ports are tied up
    • Other conversations can take place on other port pairs simultaneously
ethernet 802 3 10base2
Ethernet 802.3 10Base2
  • Ethernet 10Base2

NIC

To Next

Station

T-Connector to Link NIC to next segments

ethernet 802 3 10base213
Ethernet 802.3 10Base2
  • Ethernet 10Base2

To next

station

T-connector

BNC connector

virtual lan with ethernet switches

Server

broadcast

Client C

Client B

Client A

Server D

Server E

Virtual LAN with Ethernet Switches

Server broadcasting without VLANS

Frame is Broadcast

Goes to all other stations

Creates congestion

virtual lan with ethernet switches15
Virtual LAN with Ethernet Switches

Server multicasting with VLANS

With VLANs,

broadcasts go to a server’s VLAN clients; less latency

Multicasting (some), not Broadcasting (all)

Server

broadcast

NO

NO

Client C

on VLAN1

Client B

on VLAN2

Client A

on VLAN1

Server D

on VLAN2

Server E

on VLAN1

handling momentary traffic peaks with overprovisioning and priority
Handling Momentary Traffic Peaks with Overprovisioning and Priority

Momentary traffic peak:Congestion and latency

Traffic

Momentary traffic peak:

Congestion and latency

Network capacity

Momentary traffic peaks usually last fraction of a second;

They occasionally exceed the network’s capacity.

When they do, frames will be delayed, even dropped.

Time

handling momentary traffic peaks with overprovisioning and priority17
Handling Momentary Traffic Peaks with Overprovisioning and Priority

Overprovisioned traffic capacity in Ethernet

Traffic

Overprovisioned network capacity

Momentary peak:

No congestion

Overprovisioning:

Build high capacity than will rarely if ever be exceeded.

This wastes capacity. But cheaper than using priority.

Time

handling momentary traffic peaks with overprovisioning and priority18
Handling Momentary Traffic Peaks with Overprovisioning and Priority

Priority in Ethernet

Traffic

Momentary

peak

High-priority traffic goes

Low-priority waits

Network capacity

Priority: During momentary peaks, give priority to

traffic that is intolerant of delay, such as voice.

No need to overprovision, but expensive to implement.

Ongoing management is very expensive.

Time

routed lan with ethernet subnets
Routed LAN with Ethernet Subnets

If a routed LAN links multiple Ethernet switched

networks, the switched networks are called subnets

local wireless technologies
Local Wireless Technologies
  • 802.11 Wireless LANs (Wi-Fi)
    • Today, mostly speeds of tens of megabits per second with distances of 30 to 100 meters or more
      • Can serve many users in a home or office
    • Increasingly,100 Mbps to 600 Mbps with 802.11n
    • Organizations can provide coverage throughout a building or a university campus by installing many access points
802 11 wireless lans wlans
802.11 Wireless LANs (WLANs)

Wireless hosts connect

by radio to access points

Transmission speed: up to 300 Mbps but usually 10 Mbps to 100 Mbps.

Distances between station and access point: 300 to 100 meters.

typical 802 11 wireless lan operation with wireless access points
Typical 802.11 Wireless LAN Operation with Wireless Access Points

802.11 uses a different

frame format than 802.3

The access point translates

between the two frame formats

However, the packet goes all the

way between the two hosts

hosts and access points transmit in a single channel
Hosts and Access Points Transmit in a Single Channel

The access point and all the hosts it servers

transmit in a single channel

If two devices transmit at the same time,

their signals will collide, becoming unreasonable

Media access control (MAC) methods

govern when a device may transmit;

It only lets one device transmit at a time

media access control mac
Media Access Control (MAC)
  • MAC methods govern when devices transmit so that only one station or the access point can transmit at a time
  • To control access (transmission), two methods can be used
    • CSMA/CA+ACK (mandatory)
    • RTS/CTS (optional unless 802.11b and g stations share an 802.11g access point)
csma ca ack in 802 11 wireless lans
CSMA/CA+ACK in 802.11 Wireless LANs
  • CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance)
    • Sender listens for traffic
      • 1. If there is traffic, waits
      • 2. If there is no traffic:
        • 2a. If there has been no traffic for less than the critical time value, waits a random amount of time, then returns to Step 1.
        • 2b, If there has been no traffic for more than the critical value for time, sends without waiting
        • This avoids collision that would result if hosts could transmit as soon as one host finishes transmitting
csma ca ack in 802 11 wireless lans28
CSMA/CA + ACK in 802.11 Wireless LANs
  • ACK (Acknowledgement)
    • Receiver immediately sends back an acknowledgement; no waiting because ACKs have highest priority.
    • If sender does not receive the acknowledgement, retransmits the frame using CSMA/CA.
    • 802.11 with CSMA/CA+ACK is a reliable protocol!
specific 802 11 wireless lan standards32
Specific 802.11 Wireless LAN Standards
  • 802.11g
    • Most popular 802.11 standard today
    • 54 Mbps rated speed with much slower throughput
    • Generally sufficient for Web browsing
    • Inexpensive
    • All access points support it
802 11n
802.11n
  • Under development
    • Rated speeds of 100 Mbps to 600 Mbps
    • Will operate in both the 2.4 GHz and 5 GHz bands
    • May use twice current bandwidth per channel (~20 MHz) to roughly double speed
    • Currently a draft standard
    • A bit of overkill for most users
bluetooth personal area networks pans
Bluetooth Personal Area Networks (PANs)
  • Bluetooth is standardized by a consortium
  • Connect devices on or near a single user’s desk
    • PC, Printer, PDA, Laptop, Cellphone
  • Connect devices on or near a single user’s body
    • Laptop, Printer, PDA, Cellphone
  • The goal is cable elimination
bluetooth pans
Bluetooth PANs
  • There may be multiple PANs in an area
    • May overlap
    • PANs are called piconets
bluetooth pan operation
Bluetooth PAN Operation

Notebook

master

File synchronization

Client PC

slave

Printing

Printer slave

Note: Printer

is in both

piconets;

Slave has

two masters.

Piconet 1

Call through company

phone System

Cellphone

master

Telephone slave

Piconet 2

802 11 versus bluetooth pans
802.11 versus Bluetooth PANs

802.11

Bluetooth

Focus

Large WLANs

Personal Area Network

Speed

11 Mbps to 54 Mbps

In both directions

722 kbps with back

channel of 56 kbps.

May increase.

Distance

100 meters for 802.11b

(but shorter in reality)

Even shorter of 802.11a

10 meters.

May increase

Number

of devices in

an area

Only 10 piconets,

each with

8 devices

maximum

Limited in practice only

by bandwidth and traffic

802 11 versus bluetooth pans38
802.11 versus Bluetooth PANs

802.11

Bluetooth

Scalability

Good through having

multiple access points

Poor

(but may get

access points)

Cost

Probably higher

Probably Lower

Battery Drain

Higher

Lower

Profiles

No

Yes

Profiles allow specific products to work together. Different profiles for printing, cordless telephones, headsets, etc. Must be implemented on both master and slave.

bluetooth pans39
Bluetooth PANS
  • Trends
    • Bluetooth Alliance is enhancing Bluetooth
    • The next version of Bluetooth is likely to grow to use ultrawideband transmission
      • This should raise speed to 100 Mbps (or more)
      • Transmission distance will remain limited to 10 meters
      • Good for distributing television within a house
emerging local wireless technologies
Emerging Local Wireless Technologies

In mesh wireless networks, the access points do all routing

There is no need for a wired network

The 802.11s standard for mesh networking is under development

This P2P networking needs high density of devices

emerging local wireless technologies41
Emerging Local Wireless Technologies

Can be focused electronically to give better reception

emerging local wireless technologies42
Emerging Local Wireless Technologies
  • Ultrawideband (UWB)
    • Uses channels that are several gigahertz wide
      • Each UWB channel spans multiple frequency bands
    • Low power per hertz to avoid interference with other services
    • Wide bandwidth gives very high speeds
    • But limited to short distance and ideal for video networking at home
    • Wireless USB provides 480 Mbps up to 3 meters, 110 Mbps up to 10 meters
emerging local wireless technologies43
Emerging Local Wireless Technologies
  • ZigBee for almost-always-off sensor networks
    • Very low speeds (250 kbps maximum)
    • Very long battery life (months or years)
    • At the other end of the performance spectrum from UWB
emerging local wireless technologies44
Emerging Local Wireless Technologies
  • RFID (Radio Frequency Identification) Tags
    • Like UPC tags but readable remotely
    • In most cases, the radio signal from the reader provides power for the RFID tag
    • The RFID tag uses this power to send information about itself
    • Battery-operated RFID tags can send farther and send more information
    • 30-500 KHz, short distances, for supermarket scanning and inventory control
    • 850-950 MHz, large distances, higher speed, for automated toll collection
emerging local wireless technologies45
Emerging Local Wireless Technologies
  • Software-Defined Radio
    • Can implement multiple wireless protocols
    • No need to have separate radio circuits for each protocol
    • Reduces the cost of multi-protocol devices
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