Transcript Basic Concepts - Mahmoud Youssef

Other LAN Technologies
Chapter 5
Copyright 2003 Prentice-Hall
Panko’s Business Data Networks and Telecommunications, 4th edition
Other LAN Technologies

Large Ethernet networks

Wireless LANs

ATM LANS and QoS

Legacy LANs

Token-Ring Networks

10 Mbps Ethernet co-axial cable LANs
2
Figure 5.1: Multi-Switch Ethernet LAN
Switch 2
Port 5 on Switch 1
to Port 3 on Switch 2
Port 7 on Switch 2
to Port 4 on Switch 3
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
3
Figure 5.1: Multi-Switch Ethernet LAN
Switch 2
Switch 1
Port 5 on Switch 1
to Port 3 on Switch 2
Switching Table Switch 1
Port Station
2 A1-44-D5-1F-AA-4C
7 B2-CD-13-5B-E4-65
5 C3-2D-55-3B-A9-4F
5 D4-47-55-C4-B6-9F
5 E5-BB-47-21-D3-56
B2-CD-13-5B-E4-65
Switch 1, Port 7
A1-44-D5-1F-AA-4C
Switch 1, Port 2
E5-BB-47-21-D3-56
Switch 3, Port 6
4
Figure 5.1: Multi-Switch Ethernet LAN
Switch 2
Port 5 on Switch 1
to Port 3 on Switch 2
Switch 1
C3-2D-55-3B-A9-4F
Switch 2, Port 5
Switching Table Switch 2
Port Station
3 A1-44-D5-1F-AA-4C
3 B2-CD-13-5B-E4-65
5 C3-2D-55-3B-A9-4F
7 D4-47-55-C4-B6-9F
7 E5-BB-47-21-D3-56
Port 7 on Switch 2
to Port 4 on Switch 3
Switch 3
E5-BB-47-21-D3-56
Switch 3, Port 6
5
Figure 5.1: Multi-Switch Ethernet LAN
Switch 2
Switching Table Switch 3
Port Station
4 A1-44-D5-1F-AA-4C
4 B2-CD-13-5B-E4-65
4 C3-2D-55-3B-A9-4F
2 D4-47-55-C4-B6-9F
6 E5-BB-47-21-D3-56
A1-44-D5-1F-AA-4C
Switch 1, Port 2
D4-55-C4-B6-9F
Switch 3, Port 2
Port 7 on Switch 2
to Port 4 on Switch 3
Switch 3
E5-BB-47-21-D3-56
Switch 3, Port 6
6
Figure 5.2: Hierarchical Ethernet LAN
Only One
Possible Path
Between
Any Two
Stations
Ethernet
Switch A
Ethernet
Switch B
Ethernet
Switch D
Ethernet
Switch C
PC Client 2
Ethernet Switch F
Ethernet
Switch E
Server X
Server Y
Client PC1
7
Figure 5.3: Single Point of Failure in a
Switch Hierarchy
Switch Fails
No Communication
Switch 1
C3-2D-55-3B-A9-4F
B2-CD-13-5B-E4-65
A1-44-D5-1F-AA-4C
Switch 2
No Communication
Switch 3
D4-47-55-C4-B6-9F
E5-BB-47-21-D3-56
8
Figure C.10: 802.1D Spanning Tree Protocol
Loop, but
Spanning Tree Protocol
Deactivates One Link
Switch 2
Activated
Switch 1
Activated
Deactivated
C3-2D-55-3B-A9-4F
B2-CD-13-5B-E4-65
A1-44-D5-1F-AA-4C
Module C
Normal Operation
Switch 3
D4-47-55-C4-B6-9F
E5-BB-47-21-D3-56
9
Figure C.10: 802.1D Spanning Tree Protocol
Switch 2 Fails
Switch 2
Deactivated
Module C
Deactivated
Activated
Switch 1
C3-2D-55-3B-A9-4F
B2-CD-13-5B-E4-65
A1-44-D5-1F-AA-4C
Switch 3
D4-47-55-C4-B6-9F
E5-BB-47-21-D3-56
10
Figure 5.2: Hierarchical Ethernet LAN
Core
Core
Ethernet
Switch A
Core Ethernet
Switch B
PC Client 2
Workgroup
Ethernet
Workgroup
Switch D
Ethernet
Switch E
Core Ethernet
Switch C
Workgroup
Ethernet Switch F
Server X
Server Y
Client PC1
11
Figure 5.4: Workgroup Switches versus
Core Switches
Connects
Typical Port
Speeds
Switching Matrix
Workgroup Switches Core Switches
Client or Server to the Ethernet Switches
Ethernet Network
to One Another
100 Mbps,
10/100 Mbps
Gigabit Ethernet,
10 Gbps Ethernet
Lower Percentage of
80% or More of
Nonblocking* Capacity Nonblocking* Capacity
12
Figure C.8: Switching Matrix with Queue
Module C
Switch Matrix
Input Queue
Port
1
Incoming
Signal
Port
2
Port
3
Port
4
Port
5
Port
6
Port
7
Port
8
Outgoing
Signal
13
Figure 5.4: Workgroup Switches versus
Core Switches

Ports = 4

Speed = 1 Gbps
Switching Matrix
4Gbps
Nonblocking
1 Gbps

Maximum input = 4 Gbps

Nonblocking switch
matrix capacity = 4 Gbps
1 Gbps
1 Gbps
1 Gbps
14
Figure 5.5: Virtual LAN with Ethernet
Switches
Server Broadcasting without VLANS
Frame is Broadcast
Goes to all stations
Creates congestion
Server
Broadcast
Client C
Client B
Client A
Server D
Server E
15
Figure 5.5: Virtual LAN with Ethernet
Switches
Server Multicasting with VLANS
Multicasting
(some), not
Broadcasting (all)
VLANs are
collections of
servers and their
clients
Server
Broadcast
Client C
on VLAN1
Client A
on VLAN1
Client B
on VLAN2
Server D
on VLAN2
Server E
on VLAN1
16
Figure 5.6: Tagged Ethernet Frame
Basic 802.3 MAC Frame
Tagged 802.3 MAC Frame
By looking
Preamble (7 octets)
Preamble (7 octets)
at the value
in the 2
Start of Frame Delimiter
Start of Frame Delimiter
octets after
(1 Octet)
(1 Octet)
the
Destination Address
Destination Address
addresses,
(6 Octets)
(6 Octets)
the switch
can tell if
Source Address (6 Octets)
Source Address (6 Octets)
this frame
is basic
Tag Protocol ID (2 Octets)
Length (2 Octets)
(value less
1000000100000000
Length of Data Field in
than 1,500) 81-00 hex; 33,024 decimal
Octets
or tagged
Larger than 1,500, So not
1,500 (Decimal) Maximum
(value is
A Length
33,024)
17
Figure 5.6: Tagged Ethernet Frame
Basic 802.3 MAC Frame
Data Field (variable)
Tagged 802.3 MAC Frame
Tag Control Information
(2 Octets) Priority Level (0-7)
(3 bits); VLAN ID (12 bits)
(1 other bit)
Length (2 Octets)
PAD (If Needed)
Frame Check Sequence
(4 Octets)
Data Field (variable)
PAD (If Needed)
Frame Check Sequence
(4 Octets)
18
Figure 5.7: Ethernet Physical Layer
Standards
Physical Layer
Standard
Speed
Maximum
Run Length
Medium
10Base-T
10 Mbps
100 meters
4-pair Category 3, 4, or 5
100Base-TX
100 Mbps
100 meters
4-pair Category 5
100 meters
4-pair Category 5, 4-pair
Enhanced Category 5 is
preferred
UTP
1000Base-T
1,000 Mbps
19
Figure 5.7: Ethernet Physical Layer
Standards
Physical Layer
Standard
Speed
Maximum
Run Length
Medium
10Base-F*
10 Mbps
UP to 2 km*
62.5/125 micron
multimode, 850 nm.
100Base-FX
100 Mbps
412 m
62.5/125 multimode,
1,300 nm, hub
100 Base-FX
100 Mbps
2 km
62.5/125 multimode,
1,300 nm, switch
Optical Fiber
* Several 10 Mbps fiber standards were defined in 10Base-F.
20
Figure 5.7: Ethernet Physical Layer
Standards
Physical Layer
Standard
Speed
Maximum
Run Length
Medium
1000Base-SX
1 Gbps
220-275 m
62.5/125 micron
multimode, 850 nm.
1000Base-LX
1 Gbps
550 m
62.5/125 micron
multimode, 1,300 nm.
1000Base-LX
1 Gbps
5 km
9/125 micron single
mode, 1,300 nm.
Optical Fiber
Longer wavelength, longer distance (850, 1300, 1550 nm)
Single mode signals travel farther, but single mode is more expensive
21
Figure 5.7: Ethernet Physical Layer
Standards
Physical Layer
Standard
Speed
Maximum
Run Length
10GBase-SR/SX
10 Gbps
65 m
10GBase-LX4
10 Gbps
300 m
10GBase-LR/LW
10 Gbps
10 km
Medium
Optical Fiber
LAN*** multimode
(850 nm)
LAN*** multimode
1310 nm, wave division
multiplexing
LAN*** Single-mode,
1310 nm
***These descriptions are preliminary. LAN versions transmit at 10 Gbps.
WAN versions transmit at 9.6 for carriage over SONET links (see
Chapter 6).
22
Figure 5.7: Ethernet Physical Layer
Standards
Physical Layer
Standard
Speed
Maximum
Run Length
Medium
10GBase-ER/EW
10 Gbps
40 km
LAN*** Single mode,
1550 nm
40 Gbps Ethernet
40 Gbps
?
Single-mode fiber.****
Optical Fiber
**** 40 Gbps Ethernet standards are still under preliminary development.
23
Figure 5.7: Ethernet Physical Layer
Standards
Physical Layer
Standard
Speed
Maximum
Run Length
Medium
10Base5
10 Mbps
500 meters
Thick co-axial cable
10Base2
10 Mbps
185 meters
Thin co-axial cable
Co-Axial Cable
These are Legacy technologies that only operate at 10 Mbps
However, you will still encounter them in the field
We will see them at the end of this chapter
24
Figure 5.8: Typical 802.11 Wireless LAN
Operation with Access Points
CSMA/CA+ACK
Switch
UTP
Radio Link
Access
Point A
Access
Point B
Client PC
Server
Large Wired LAN
Laptop
Handoff
If mobile computer
moves to another
access point,
it switches service
to that access point
25
Figure 5.8: Typical 802.11 Wireless LAN
Operation with Access Points
Access Point
Industry
Standard
Coffee
Cup
Wireless
Notebook
NIC
To Ethernet
Switch
26
Figure 5.8: Typical 802.11 Wireless LAN
Operation with Access Points
D-Link
Wireless
Access
Point
Using Two Antennas Reduces Multipath Interference (See Ch. 3)
27
Figure 5.8: Typical 802.11 Wireless LAN
Operation with Access Points
Linksys
Switch
With
Built-In
Wireless
Access
Point
Using Two Antennas Reduces Multipath Interference (See Ch. 3)
28
Figure 5.8: Typical 802.11 Wireless LAN
Operation with Access Points

The Wireless Station sends an 802.11 frame to a
server via the access point

The access point converts the 802.11 frame into an
802.3 Ethernet frame and sends the frame to the
server
802.11
Frame
Mobile
Station
802.3
Frame
Access
Point
Ethernet
Switch
Server
29
Figure 5.8: Typical 802.11 Wireless LAN
Operation with Access Points

The server responds, sending an 802.3 frame to the
access point

The access point converts the 802.3 frame into an
802.11 frame and sends the frame to the mobile station.
802.11
Frame
Mobile
Station
802.3
Frame
Access
Point
Ethernet
Switch
Server
30
802.11 Wireless LAN Speeds

802.11
2 Mbps (rare)
2.4 GHz band (limited in bandwidth)

802.11b
11 Mbps,
2.4 GHz
3 channels/access point

802.11a
54 Mbps,
5 GHz (greater bandwidth)
11 channels/access point

802.11g
54 Mbps,
2.4 GHz
limited bandwidth
31
Figure 5.9: CSMA/CA + ACK in 802.11
Wireless LANs
Correction

CSMA/CA (Carrier Sense Multiple Access with
Collision Avoidance)

Station or access point sender listens for traffic

If there is no traffic, can send if there has been
no traffic for a specified amount of time

If the specified amount of time has not been met,
must wait for the specified amount of time. Can
send if the line is still clear
32
Figure 5.9: CSMA/CA + ACK in 802.11
Wireless LANs

Correction
CSMA/CA (Carrier Sense Multiple Access with
Collision Avoidance)

Station or access point sender listens for traffic

If there is traffic, the sender must wait until traffic
stops

The sender must then set a random timer and
must wait while the timer is running

If there is no traffic when the station or access
point finishes the wait, it may send
33
Figure 5.9: 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 using CSMA/CA
34
Who Implements CSMA/CA?

Stations (when they send)

Access Points (when they send)
Mobile
Station
802.11
Frame
Access
Point
CSMA/CA+ACK
35
Ad Hoc 802.11 Networks

Module C
No Access Point

Stations broadcast to one another directly

Not scalable but can be useful for SOHO use

NICs automatically come up in ad hoc mode
36
Wired Core / Wireless to the Desktop
Module C

Normal Networks: Core & Workgroup
Switches
Core
Core
Ethernet
Switch A
Core Ethernet
Switch B
Workgroup
Ethernet
Switch D
Workgroup
Switches
Attach to
Stations
Core Ethernet
Switch C
Workgroup
Ethernet Switch F
37
Wired Core / Wireless to the Desktop
Module C

With High-Speed Wireless LANs, Replace
Workgroup Switches with Access Points
Core
Core
Ethernet
Switch A
Core Ethernet
Switch B
Access
Point 1
Access
Points
Serve
Stations
Core Ethernet
Switch C
Access
Point 2
38
Wired Core / Wireless to the Desktop
Module C

Avoids Cost of Running Wires to the Desktop

Avoids Costs of Subsequent Changes

Only Useful for 802.11a


802.11b and 802.1g lack the bandwidth to serve
many users
Still Uses a Wired Core

To connect to remaining wired desktop devices

Probably cheaper than a wireless core
39
Personal Area Networks (PANs)

Connect Devices On or Near a Single User’s
Desk

PC

Printer

PDA

Notebook Computer

Cellphone

The Goal is Cable Elimination
40
Personal Area Networks (PANs)

Connect Devices On or Near a Single User’s
Body

Notebook Computer

Printer

PDA

Cellphone

The Goal is Cable Elimination
41
Personal Area Networks (PANs)

There May be Multiple PANs in an Area

May overlap

Also called piconets
42
Figure 5.10: 802.11 versus Bluetooth
LANs
802.11
Bluetooth
Focus
Local Area Network
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)
10 meters
(may increase)
Number
of Devices
Limited in practice only 10 piconets, each with
up to 8 devices
by bandwidth and traffic
43
Figure 5.10: 802.11 versus Bluetooth
LANs
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
Discovery
No
Yes
Discovery allows devices to figure out how to work together
automatically
44
Figure 5.11: Bluetooth Operation
Notebook
Master
Printing
File Synchronization
Printer Slave
Client PC
Slave
Piconet 1
Cellphone
Telephone
45
Figure 5.11: Bluetooth Operation
Notebook
Client PC
Printing
Printer Slave
Call Through Company
Phone System
Cellphone
Master
Telephone Slave
Piconet 2
46
Figure 5.11: Bluetooth Operation
Notebook
Master
Printing
Piconet 1
File Synchronization
Printer Slave
Client PC
Slave
Call Through Company
Phone System
Cellphone
Master
Telephone Slave
Piconet 2
47
Figure 5.12: Normal Radio Transmission
and Spread Spectrum Transmission
Channel Bandwidth
Required for Signal
Normal Radio:
Actual Bandwidth Used
Note: Height of Box Indicates Bandwidth of Channel
48
Figure 5.12: Normal Radio Transmission
and Spread Spectrum Transmission
Channel Bandwidth
Required for Signal
Frequency Hopping
Spread Spectrum (FHSS)
802.11
Direct Sequence
Spread Spectrum (DSSS)
802.11b
Wideband but Low-Intensity Signal
Note: Height of Box Indicates Bandwidth of Channel
49
Figure 5.13: Code Division Multiple Access
(CDMA) Spread Spectrum Transmission
Radio Spectrum
Low-Density Orthogonal Signal 1
Client PC 1
Server A
Client PC 2
Low-Density Orthogonal Signal 2
Server B
Used in Some Cellular Telephone Systems
50
OFDM
New

Orthogonal Frequency Division Multiplexing

Divide a large channel into many subchannels

Send part of the signal in each channel

Do not use channels with impairment

802.11a, 802.11g at 54 Mbps
Subchannel
Channel
Unused
Subchannel
51
Spread Spectrum Methods
Spread Spectrum Techniques
DSSS
802.11
DSSS
FHSS
OFDM
CDMA
52
Ultrawideband (UWB)

New
Not in Book
Extreme spread spectrum transmission

Signal spread over 25% above and below the central
carrier frequency or at least 1.5 GHz

If carrier is at 1 GHz, signal spreads between 500
MHz and 1.5 GHz

Much wider than traditional spread spectrum
channels
53
Ultrawideband (UWB)

New
Not in Book
Why UWB?

High transmission rate despite very low power

Very low power makes signals difficult to detect for
security

Multipath interference and interference are
unimportant

Can travel through thick walls

In fact, used in ground-penetrating radar
54
Ultrawideband (UWB)

New
Not in Book
Problems

Bandwidth usually cuts across multiple licensed and
unlicensed service bands

Potential for interference with existing services

Power per hertz is so low that existing services
should only perceive a slight increase in noise when
USB is used

Still, concern over low-power services such as GPS,
so government approval is limited
55
ATM

Ethernet competitor for switched LANs

Quality of Service (QoS) for telephony and
multimedia transmissions

Highly scalable in size (number of stations)

Highly complex and expensive

Not selling well for LANs

Increasingly popular for WANs
56
Figure 5.14: ATM versus Ethernet LANs
Ethernet LANs
ATM LANs
Designed for
LANs
Worldwide Telephone
Network
Complexity
Low
High
Equipment Cost
Low
High
Management Cost Low
High
Scalable in Speed
High
QoS Guarantees
High
None, but
Overprovisioning and
Priority make Ethernet
competitive even for
latency-intolerant
applications
Excellent for Voice
Usually not good
for data
57
Figure 5.15: Handling Brief Traffic Peaks
Congestion and Latency
Traffic
Network Capacity
Peak Load:
Congestion and Latency
Time
58
Figure 5.15: Handling Brief Traffic Peaks
Quality of Service (QoS) Guarantees in ATM
Traffic
Peak Load
Network Capacity
Other Traffic Must Wait
(Data)
Traffic with Reserved
Capacity Always Goes
(Voice)
Time
59
Figure 5.15: Handling Brief Traffic Peaks
Overprovisioned Traffic Capacity in Ethernet
Traffic
Overprovisioned Network Capacity
Peak Load:
No Congestion
Time
60
Figure 5.15: Handling Brief Traffic Peaks
Priority in Ethernet
Traffic
Peak Load
Network Capacity
High-Priority Traffic First
Low-Priority Waits
Time
61
Figure 5.16: ATM Network with Virtual Circuits
Virtual
Circuit
Client PC
ATM Switch 2
ATM Switch 1
ATM
Switch 3
ATM Switch 4
Virtual
Circuit
ATM switches can be arranged in a
Hierarchy, so there are multiple
Alternative routes. This makes
Switching slow
ATM Switch 5
Server
62
Figure 5.16: ATM Network with Virtual Circuits
Virtual
Circuit
Client PC
ATM Switch 2
ATM Switch 1
ATM
Switch 3
ATM Switch 4
Virtual
Circuit
ATM selects a single route, called a
Virtual circuit, before two stations
ATM Switch 5
Begin transmitting. This simplifies
Switching and so lowers switching cost
Server
63
Figure 5.16: ATM Network with Virtual Circuits
Virtual
Circuit
ATM Switch 2
ATM Switch 1
ATM
Switch 3
Client PC
ATM Switch 4
Virtual
Circuit
Switch 4 Switching Table
Virtual Circuit
A...
B...
C...
D...
Port
1
2
3
4
ATM Switch 5
Server
ATM switching tables are as simple as
Ethernet switching tables
64
ATM Reduces Switching Costs

Virtual circuits simplify switching, reducing
switching costs.

ATM is unreliable, also reducing switching costs
65
Figure 5.17: Virtual Circuit with VPI and
VCI
Virtual
Channels
Virtual Path
Site 1
Site 2
ATM Backbone
Virtual Path is a Path to a Site
Virtual Channel is a Connection to a Particular Computer at the Site
Switches in Backbone Only Have to Look at the
Virtual Path Indicator (VPI)
66
Figure 5.17: ATM Cell
Bit 1
Bit 2
Bit 3
Bit 4
Bit 5
Bit 6
Bit 7
Bit 8
Virtual Path Identifier
Virtual Path Identifier
Virtual Channel Identifier
Virtual Channel Identifier
Call Loss
Virtual Channel Identifier
Payload Type Reserved
Priority
Header Error Check
Payload
(48 Octets)
VPI: Specifies a VC to site
VCI: Specifies a station at site
Switches between sites only look at VPI
5 octets of header
48 octets of payload
53 octets total
67
ATM Cells

ATM frames are short and fixed in length; called
cells




Only 53 octets long
5 octets of header
48 octets of data
Reduces latency at switches

Switch may have to wait until entire frame arrives
before sending it back out--faster with short cells

Fixed length gives predictability for faster processing
68
Token-Ring Networks
Legacy LAN Technologies
Token-Ring Networks

Ring Topology
Dual Ring; normally
only one is used
Inner Ring
Outer Ring
Frame
Normal
Operation
70
Token-Ring Networks

Ring is wrapped if there is a break

The wrapped ring is still a full ring
Wrapped Ring
Break
71
Token-Ring Networks

Special Frame Called Token


Circulates when no station is transmitting
For access control, station must have token to send
Inner Ring
Outer Ring
Token
72
Figure 5.19: 802.5 Token-Ring Network
Wrapped Ring
Break
STP or UTP
73
Figure 5.18: Major Legacy Networks

Token-Ring Networks

802.5 Token-Ring Networks

4 Mbps initially, soon reached 16 Mbps

More expensive than Ethernet; has largely died in
the market

Still seen in some legacy networks, especially
among IBM mainframe users

Uses 2-pair shielded twisted pair to reduce EMI


Metal mesh around each pair
Metal mesh around jacket
74
Figure 5.18: Major Legacy Networks

Token-Ring Networks

FDDI (Fiber Distributed Data Interface)
 100 Mbps
 200 km circumference is possible (MANs)
 Had niche in LAN cores (far and fast)
 Losing out to faster gigabit Ethernet
Campus Building
FDDI LAN Ring
(200 km maximum circumference)
75
Figure 5.18: Major Legacy Networks

Early Ethernet Standards

General
 Before switches and hubs
 Only 10 Mbps
 Used coaxial cable
76
Figure 5.18: Major Legacy Networks

Early Ethernet Standards

15-Hole
AUI Port
10Base5
 Multidrop topology
 Thick trunk cable uses coaxial cable
technology; 500-meter limit
 Drop cable has 15 wires
 15-hole Attachment Unit Interface (AUI)
connector
Drop Cable
Trunk Cable
77
Figure 5.18: Major Legacy Networks

Early Ethernet Standards

10Base2
 Daisy chain topology
 Thin coaxial cable between stations
 Circular BNC connector
78
Figure 5.18: Major Legacy Networks

Ethernet 10Base2
To Next
Station
79
Figure 5.18: Major Legacy Networks

Ethernet 10Base2: UTP vs BNC Connectors
Thin
Coax
UTP
RJ-45
UTP
Connectors
BNC Connector
10Base2
T-Connector
80
Figure 5.18: Major Legacy Networks

Ethernet 10Base2
T-Connector
To Next
Station
BNC Connector
81