Transcript No Slide Title

Chapter Objectives
After completing this chapter you will be able to:
 Describe in detail the following Local Area Network (LAN)
technologies:
- 802.3 Ethernet
- 802.5 Token Ring
- Fibre Distributed Data Interface (FDDI)
- Wireless LAN
LAN Protocols
Protocol
Media
Topology
Access
Method
Bandwidth/
% Usable
Robustness Relative
Cost
Ethernet 802.3 Coax/bus
UTP/star
STP/star
Fibre/ star
Token Ring/
UTP/star
802.5
STP/star
Contention
2 Mbit/s
10 Mbit/s
100/1000 Mbit/s
(40 –45%)
4 Mbit/s
16 Mbit/s (80%)
100/1000 Mbit/s
Little fault
tolerance, but
mature
technology
Some fault
tolerant
features, such
as ring wrap
FDDI
Fibre/ring, star
Token
passing
100 VGAnyLAN
UTP/star
STP/star
Fibre/star
Polling with 100 Mbit/s
demand
priority
New
technology is
expensive
Arcnet
Bus, star
Token
passing
Low cost,
mature
technology
Token
passing
100 Mbit/s (8085%)
2.5 Mbit/s
Little fault
20 Mbit/s
tolerance,
100 Mbit/s (80%) very robust
Low cost
widely
available
More than
Ethernet but it
provides more
Optical fibre
technology is
expensive
Ethernet
Ethernet is one of a family of network architectures
governed by a protocol called Carrier Sense
Multiple Access/Collision Detect (CSMA/CD). This
type of network follows the Institute of Electrical and
Electronic Engineers (IEEE) standard 802.3
CSMA/CD
Carrier Sense
Multiple Access
Collision Detect
Listen
Wait
Send & Listen
Access All Terminals
Detect
Calculate
Send
Ethernet Access Media
Name
Cable
Max. segment
length
Nodes per
segment
10Base5
Thick Coaxial
500m
100
10Base2
Thin Coaxial
185m
30
10BaseT
Twisted Pair
100m
1024
10BaseF
Optical Fibre
2km
1024
Ethernet Hubs
There are two kinds of hub:
Repeater hubs - Each port of a repeater hub links individual
Ethernet media segments together to create a larger network that
operates as a single Ethernet LAN.
Switching hubs - This kind of hub provides packet switching,
typically based on bridging ports. Each port of a packet switching
hub provides a connection to an Ethernet media system that
operates as a separate Ethernet LAN. Unlike a repeater hub
whose individual ports combine segments together to create a
single large LAN, a switching hub makes it possible to divide a set
of Ethernet media systems into multiple LANs that are linked
together by way of the packet switching electronics in the hub.
Components in an Ethernet System
Twisted-Pair Media System
Ethernet Frame Format
Number of bytes:
7
Preamble
1
6
6
S
O Destination Source
Address
Address
F
SOF = Start of frame
FCS = Frame check sequence
2
46-1500
4
Type
Data
FCS
Minimum frame size = 64 bytes
Maximum frame size = 1518 bytes
MAC Addressing
There are two, MAC Layer addresses in an Ethernet frame. The
first is the address of the source device and the second is the
intended destination device. Each address consists of 48 bits, or
12 hexadecimal digits, which are typically denoted by six, twodigit hexadecimal numbers:
00-80-2C-00-19-20
The first six digits (high order) identify the manufacture and the
last six digits (low order) are used for a serial number
Multicast
Octet Order
7
-
0 7
-
Bit Order
0 7
-
Manufacturer's Address
Multicast Bit
0 7
-
0 7
-
0 7
Serial Number
-
0
Fast Ethernet Transmission Medium
Name
Cable Type
Segment
length
100Base-TX
2 pair cable
(category 5 UTP or STP)
100m
100Base-T4
4 pair UTP cable
100m
100Base-FX
Optical fibre cable
200m
Gigabit Ethernet
 Latest extension to Ethernet
 1000 Mbit/s - 10 times faster than Fast Ethernet
 Compatible with existing Ethernet
Token Ring Network
Advantages of Token Ring
 High reliability, the ring can continue normal operation
despite any single fault
 Bypassing inactive stations
 Effective use, 95% in Token Ring only whilst 30-40% in
Ethernet
 Excellent traffic handling
 Large maximum frame length
 High bandwidth efficiency. 70% in Token Ring, 30% in
Ethernet
 Many media choices: UTP, STP, coaxial or optical fibre
 Supports transmission priority
Frame Formats
Token Ring Management
 Sending out a new token if one is lost
 Re-sending messages
 Ensuring that the token is passed in its proper sequence
 Managing congestion
 Automatically correcting network errors
Token Ring
PC
Token
MSAU
PC
PC
PC
FDDI Rings
Failed Station
Outer ring used for data
Inner ring unused
except during failure
Inner ring unused
except during failure
Workstation
Workstation
A
B
Station Types
Dual attached station (DAS), which is connected to both
rings
Single attached station (SAS), which is attached only to
the primary ring
Dual attached concentrator (DAC), which is connected to
both rings and provides connection for additional stations
and concentrators. It is actually the root of a tree
Single attached concentrator (SAC), which is connected
only to the primary ring (through a tree)
Main Steps in a Normal Frame Transmission
1. Sending station waits for token.
2. Sending station captures and strips token, and then transmits frames.
3. Sending station issues token at the end of transmission.
4. Destination station copies the transmitted frame and sets the A and C
bits (address recognised and frame copied indicators).
5. Sending station removes the data from the ring by stripping the sent
(and acknowledged) frame.
6. The first bytes of the frame are not stripped, and continue to circulate
on the ring (as a fragment). Each repeating station strips one byte from
the fragment, and a transmitting station completely strips it
Frame Formats
Wireless LAN
Peer-to-Peer