special material 3
DESCRIPTION
TRANSCRIPT
Copyright 2001 Global Wireless Education Consortium 1
Copyright 2001 Global Wireless Education Consortium 1
BASIC DATA NETWORKS
Copyright 2001 Global Wireless Education Consortium 2
Bandwidth
Narrowband0 - 64 kbps
Wideband64 Kbps - 45 Mbps
Broadband45 Mbps and Beyond
X.25 Frame Relay ATMSMDS
Token Ring
FDDI
x xT-1,PRI
T- 3
SONET
LAN
Backbone
Network Access
Network Hierarchy and Protocols
IP
Ethernet
Copyright 2001 Global Wireless Education Consortium 3
Definition: Topology
The Physical and Logical Way theNetwork Elements are Connected
Copyright 2001 Global Wireless Education Consortium 4
Legend
Device on LAN=
Bus Star Ring
Local Area Network (LAN) Topologies
Copyright 2001 Global Wireless Education Consortium 5
LAN Topologies
Legend
Device on LAN=
BusExample: Ethernet
CSM/CD: Carrier Sense Multiple Access/Collision Detection
Send Data Units out unless you detect another data unit.
Copyright 2001 Global Wireless Education Consortium 6
LAN Topologies
RingExample: Token Ring
Send data units when youpossess the token
Token: Special Type of Data Unit
Copyright 2001 Global Wireless Education Consortium 7
LAN Standards
IEEE 802.1 INTERNETWORKING
lOG
ICA
LL
INK
CO
NT
RO
(LL
C)
OSILAYERS3-7
OSILAYER 2
OSILAYER 1
PH
YS
ICA
L
ME
DIU
MA
CC
ES
SC
ON
TR
OL
(MA
C)
IEEE 802.2TYPE 1 - UNACKNOWLEDGED CONNECTIONLESS SERVICETYPE 2 - CONNECTION MODE SERVICETYPE 3 - ACKNOWLEDGED CONNECTIONLESS SERVICE
802.3CSMA/CD(ETHERNET)
802.4TOKEN BUS
802.5 TOKEN RING
802.6DQDB(MAN)
BASEBANDCOAXIALAND UNSHIELDEDTWISTED PAIR
BROADBANDCOAXIAL
BROADBANDCOAXIAL
OPTICALFIBER
SHIELDED OR UNSHIELDEDTWISTED PAIR
OPTICALFIBERORCOAXIALCABLE
Copyright 2001 Global Wireless Education Consortium 8
Access Networks: Entry to Wide Area Network (WAN)
CustomerPremises
Bridge-Router
Access NetworkEnter via port on LAN router
Copyright 2001 Global Wireless Education Consortium 9
Data Flow in an X.25 Network
Protocol LayersInvolvedin DataTransfer
3
2
1
Switch A Switch CX.25 Network
Switch B
Copyright 2001 Global Wireless Education Consortium 10
Data Flow in a Frame Relay Network
Frame Relay Network
Protocol LayersInvolvedin DataTransfer
3
2
1
Switch A Switch CSwitch B
Copyright 2001 Global Wireless Education Consortium 11
Backbone Networks
High Speed Interconnection of Networks
Copyright 2001 Global Wireless Education Consortium 12
ATM Cell Structure
Header Payload
48 Octets5 Octets
1
2
3
4
5
Octet 8 7 6 5 4 3 2 1
Bit Position
GFC VPIVPI VCI
VCIVCI PTI
HEC
VCI = Virtual Channel IDVPI = Virtual Path IDPTI = Payload Type IdentifierGFC = Generic Flow ControlCLP = Cell Loss PriorityHEC = Header Error Control
CLP
Backbone Example: Asynchronous Transfer Mode (ATM)
Copyright 2001 Global Wireless Education Consortium 13
ATM Users Receive as Much Bandwidth as They Require
PYTHON WITHEXPANDABLE
SKIN (BANDWIDTH)
Copyright 2001 Global Wireless Education Consortium 14
User 1
User 2
User 3
125 sec 250 sec 375 sec 500 sec
Asynchronous means data units (cells) areplaced on the network as the application requires
User 1 User 1 User 1
User 2 User 2User 2
User 3
Copyright 2001 Global Wireless Education Consortium 15
OPEN SYSTEMS INTERFACE (OSI) MODEL
Application
Presentation
Session
Transport
Network
Data Link
Physical
Application
Presentation
Session
Transport
Network
Data Link
Physical
Network
Data Link Data Link
NetworkNode
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66
55
44
33
22
11
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66
55
44
33
22
11
Copyright 2001 Global Wireless Education Consortium 16
Wireless OSI Model
Application
Presentation
Session
Transport
Network
Data Link
Physical
Application
Presentation
Session
Transport
Network
Data Link
Physical
Network
Data Link Data Link
NetworkNode
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66
55
44
33
22
11
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66
55
44
33
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11
MESSAGES USE
BOTTOM 3 LAYERS
Copyright 2001 Global Wireless Education Consortium 17
OSI Protocol “Stack”
What are We Doing?7
Are We Speaking the Same Language (Code)?6
How Long Can Both Sides Talk?
How do We Control Info Flows andand Keep Messages in the Right Order?
5
4
How do We Put Together and Move Chunks of InformationAcross a Whole Network?
3
What Signals and Timing Are We Using?How Are We Going to Recognize Errors between Two Points?2
What Hardware Are We Using?1
Copyright 2001 Global Wireless Education Consortium 18
The OSI Model
Application
Presentation
Session
Transport
Network
Datalink
Physical Header
User Info
1
7
6
5
4
3
2
A Set of Rules
Copyright 2001 Global Wireless Education Consortium 19
Layer Details – Layer 1
Network
Data Link
Physical
Application
Presentation
Session
Transport
Transmits bits received from the Data Link layer across the transmission medium
Copyright 2001 Global Wireless Education Consortium 20
Layer Details – Layer 2
Data Link
Physical
Sequences messages and checks for errors between adjacent link stations
Transmits bits received from the Data Link layer across the transmission medium
Network
Application
Presentation
Session
Transport
Copyright 2001 Global Wireless Education Consortium 21
Layer Details – Layer 3
Network
Data Link
Physical
Fragments or “packetizes” messages, and routes them to the proper destination
Sequences messages and checks for errors between adjacent link stations
Transmits bits received from the Data Link layer across the transmission medium
Application
Presentation
Session
Transport
Copyright 2001 Global Wireless Education Consortium 22
Layer Details – Layer 4
Network
Data Link
Physical
Transport
Fragments or “packetizes” messages, and routes them to the proper destination
Sequences messages and checks for errors between adjacent link stations
Transmits bits received from the Data Link layer across the transmission medium
Provides multiplexing, network connection management, quality of service, etc.
Application
Presentation
Session
Copyright 2001 Global Wireless Education Consortium 23
Header Information
Packet Format
Copyright 2001 Global Wireless Education Consortium 24
•Header•User Data
•Perhaps a Trailer•Store and Forward
Packet Switched Routing
Copyright 2001 Global Wireless Education Consortium 25
Header Information
Packet Format
Layer 2 Info Layer 3-5 Info Layer 2 InfoFlag Flag
Message Format
Types of Protocol Data UnitBeing Sent Through a Packet Switched Network
Protocol Data Units
Copyright 2001 Global Wireless Education Consortium 26
Header TrailerUser Data
Protocol Data Unit
Routing Fields
Copyright 2001 Global Wireless Education Consortium 27
ROUTERNODE B
DATAC CDATAB C
NODE A NODE C
Destination NodeWon’t Change
Address of NextNode on Route
Router Stores Packet, Reads Destination Information And Forwards
To The Next Node
Routers Routing Packets
Final Path
Data Switch Routing Example
• Ethernet Switch
– Receives Ethernet frame
– Looks up 6-byte Destination Address in a
Forwarding Table
– Sends frame out only the port associated with
the Destination Address
Ethernet Switch
10Base-T Switch
MAC #11 MAC #14MAC #13MAC #12
10Base-T Hub
MAC #21 MAC #24MAC #23MAC #22
Address Port UpdateTime
# 11 D 6:05.1441 PM # 12 C 6:04.1523 PM # 13 B 6:04.8722 PM # 14 A 6:05.1422 PM # 21 E 6:04.6623 PM # 22 E 6:04.2355 PM # 23 E 6:05.0233 PM # 24 E 6:04.9722 PM
FORWARDING TABLE
AE D C B
Copyright 2001 Global Wireless Education Consortium 30
ROUTINGCONSIDERATION
WHAT’S INCLUDED
Performance Number of hops Cost Delay Throughput
Decision Time Packet (Datagram) Session (Virtual Circuit)
Decision Place Each node (Distributed) Central node (Centralized) Originating node
Source of Information onNetwork Status
None Local Adjacent Nodes Nodes along route All nodes
Routing Strategy Fixed Flooding Random Adaptive
Adaptive Routing UpdateTime
Continuous Periodic Major load change Topology change
Packet Switched Network Routing
Copyright 2001 Global Wireless Education Consortium 31
Data Network Devices & the OSI Reference Model
•Gateways•Routers•Switches•Hubs•Bridges•Repeaters
Copyright 2001 Global Wireless Education Consortium 32
REPEATER
• LAYER 1 PHYSICAL
• I PHYSICALLY REPEAT AND REGENERATE BITS FOR MY OWN LAN
Copyright 2001 Global Wireless Education Consortium 33
BRIDGE
• LAYER 2 DATA LINK LAYER
• I LINK DATA FRAMES BY BRIDGING BETWEEN ISLANDS.
LAN 1 LAN 2
Copyright 2001 Global Wireless Education Consortium 34
HUB
• LAYER 2 DATA LINK LAYER• I ROUTE PACKETS BETWEEN ISLANDS
WITH COMMON PROTOCOLS
USER
USER
USER
USER
Copyright 2001 Global Wireless Education Consortium 35
DATA SWITCH
• LAYER 2 DATA LINK LAYER• I ROUTE PACKETS BETWEEN PORTS• PACKETS ARE NOT SENT TO EVERY PORT
(ONLY TO THE DESTINATION PORT)
USER
USER
USER USER
Copyright 2001 Global Wireless Education Consortium 36
ROUTER
• LAYER 3 NETWORK LAYER• I ROUTE PACKETS BETWEEN ISLANDS
WITH COMMON PROTOCOLS
Copyright 2001 Global Wireless Education Consortium 37
GATEWAY
• LAYER 3+• I CONVERT PROTOCOLS BETWEEN ISLANDS • SYNCHRONOUS TO ASYNCHRONOUS
SYNC ASYNC
Copyright 2001 Global Wireless Education Consortium 38
Data Network Devices in Data Network Applications
Copyright 2001 Global Wireless Education Consortium 39
Router
Router
Router
Carrier Network
Router
ChicagoRouter
LAN Hub
Client
DetroitRouter
LAN Hub
Server
CustomerNetwork
CustomerNetwork
AccessLine
AccessLine
Typical Packet Data Services
Copyright 2001 Global Wireless Education Consortium 40
• Routers modify layer 2 frame headers & trailers so packet can travel end-to-end over many links. They provide Gateways into and out of the PSTN.
IP packets / TR frames
IP packets / PPP frames
Router or Gateway modifies frame
IP packets / TR frames
Router RouterCSU CSUC.O .
T1T1TokenRing
TokenRing
Packets, Routers and the PSTN
Copyright 2001 Global Wireless Education Consortium 41
Combined Network
CMTS
MSC TELCO
NIU NIU
HostDigital
Terminal
SS7 SS7
Internet
Intranet orPublic Data Network
Average ResidencePower ResidenceCorporate A Corporate B
Trunks toTelco
Switch
Gateway
Copyright 2001 Global Wireless Education Consortium 42
IP Telephony Using a Computer as the Terminal
PSTN Internet
CODEC
Gateway
Router Cable Modem
Microphone
Copyright 2001 Global Wireless Education Consortium 43
PSTN Internet
CODEC
Gateway
Router
IP TelephonyGenerates Mobile Like Traffic
Cable Modem
TelephoneAdapter
Copyright 2001 Global Wireless Education Consortium 44
•Committed Information Rate (CIR)
•Data Collisions
•Protocol Analyzers
Detecting and Fixing Errors
Copyright 2001 Global Wireless Education Consortium 45
0 1 0 0 1 1 0 1 11 1 1 0 0 1 0 0 10 0 0 1 0 0 1 1 01 1 0 1 0 1 1 0 00 1 0 1 1 0 0 1 11 1 0 1 0 1 1 1 10 0 0 1 0 1 1 0 00 0 0 0 1 0 1 1 0
Block Parity Bits
BitPosition
1234567
CharacterParity
BlockParityCharacter
Copyright 2001 Global Wireless Education Consortium 46
•Longitudinal Redundancy Check (LRC)
•Block Parity Character •Checksum
•XMODEM Checksum
New Terms
Copyright 2001 Global Wireless Education Consortium 47
DATACRCResult
Figure AA
Copyright 2001 Global Wireless Education Consortium 48
•Automatic Repeat Request (ARQ)
•Acceptance (ACK)
•Reject (NAK)
Copyright 2001 Global Wireless Education Consortium 49
Forward Error Correction (FEC)
Copyright 2001 Global Wireless Education Consortium 50
Types of Digital Error Measurement
•Bit Error Rate (BER)
•Block Error Rate (BLER)
Copyright 2001 Global Wireless Education Consortium 51
•Errored Seconds
•Severely Errored Seconds
Copyright 2001 Global Wireless Education Consortium 52
Bit Error Rate Tester
Shift Register
Clock
InterfaceCoder
Itemundertest
InterfaceDecoder
ErrorCounter
Shift Register
+
Illustration Courtesy of Hewlett PackardSource: Application Note 387
+
+data
Error
Copyright 2001 Global Wireless Education Consortium 53
Summary
•Types of Data Networks•OSI Reference Model•Packet Structures•Routing•Devices•Applications•Detecting And Fixing Errors