01 - introduction to wan
TRANSCRIPT
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Introduction to WAN
Course objectives
Learn about WAN devices
Understand WAN norms
Create a hierarchical network
Learn about WAN networks
By completing this course, you will :
Introduction to WAN
Course topics
WAN Technology concepts
WAN Connection options
Course plan
Introduction to WAN
WAN Technology concepts
Introduction to WAN
Plan
Overview
Equipments and devices
Physical Layer Terminology
Norms
Physical Layer concepts
Data Link concepts
Chapters we will study:
WAN Technology concepts
OverviewWAN Technology concepts
Working primarily on Layers 1 & 2 of the OSI Model
Correlation between OSI Model and WAN Services
OSI Model WAN Services
Data Link Frame Relay, ATM, HDLC
Physical Link Electrical, mechanical, operational connections
OverviewWAN Technology concepts
Main characteristics of WAN networks:
Wide geographical areas
Internet providers services
Layers 1 & 2 of the OSI Model
OverviewWAN Technology concepts
Local loop = part between the customer’s POP and the service provider CO
Group of links linked to interconnected telecom providers
WAN Technology concepts
Router
Layer 3 equipment
Provides several services such as :
Path selection
LAN and/or WAN ports
Filtering
NAT Redirection
Equipments and devices
WAN Technology concepts
Communication server
Layer 7 equipment
Inbound and outbound concentrator for users communications
Example : DSLAM
Equipments and devices
WAN Switches
Layer 2 unit
Multi-port device that ensure WAN traffic switching
Examples : ATM switch, ISDN
WAN Technology concepts
Equipments and devices
WAN Technology concepts
Modem & CSU/DSU unit
Layer 1 unit
Converts a signal into another one
Exemples
Modem : Digital to analog converter using modulation and demodulation process
CSU/DSU unit : Digital Interface (TA, NT1, etc.)
Equipments and devices
WAN Technology concepts
Physical Layer Terminology
12
3
4
5
6
LAN1
CPE2
Demarcation line3
Local loop4
Central Office switch5
Service provider interurban network6
WAN Technology concepts
Physical Layer Terminology
CPE
Located at the customer premise
Belong to the customer or rented by the provider
Example : Modem, NT1
DCE:
Convert user’s data in a WAN format
WAN Technology concepts
Physical Layer Terminology
DTE
Provides the user’s data
Demarcation Line :
Demarcation between customer side and provider side
Line that separate responsibilities
WAN Technology concepts
Physical Layer Terminology
Local loop
Link between the demarcation line and the central office
Switch :
Nearest to the customer
Inter-Urban network :
Service provider “cloud” (Routers, switches, etc).
WAN Technology concepts
WAN norms
Describes :
Delivery ways of Physical layer
Configuration of Data-link layer
Addressing
Flow control
Encapsulation
WAN Technology concepts
WAN norms
Normalization organisations :
ITU (International Telecommunications Union
ISO (International Standards Organization)
IETF (Internet Engineering Task Force)
EIA (Electrical Industries Association)
TIA (Telecommunications Industry Association)
WAN Physical Layer conceptsWAN Technology concepts
Physical layer
Description of the interface between DCE and DTE
DTE DCE
Physical layer norms
WAN Physical Layer conceptsWAN Technology concepts
EIA/TIA-232 (similar to the V.24)
Asymmetrical circuits
Up to 64 Kbits/s
EIA/TIA-449
Faster version of EIA/TIA-232 (2 Mbits/s)
EIA/TIA-612/613
Describes HSSI interface (Pour E3, T3, SDH STM-0, etc.)
WAN Physical Layer conceptsWAN Technology concepts
V.35
Synchronous circuits
For packet networks
X.21
Synchronous digital lines
G.703
BNC connector
E1 throughputs (2.048 Mbits/s)
WAN Physical Layer conceptsWAN Technology concepts
V. EAI-530: Two electrical implementation of EIA/TIA-449
RS-422: Symmetrical transmission
RS-423: Asymmetrical transmission
WAN Data Link conceptsWAN Technology concepts
Data link layer
Definition of data encapsulation
WAN Encapulations (Layer 2)
WAN Data Link conceptsWAN Technology concepts
Frame Relay :
Lightweight simplified Encapsulation
No error correction
To be used with very-top digital equipment
Fast data transmission
2 variants :
Cisco
IETF
WAN Data Link conceptsWAN Technology concepts
PPP :
Contain a layer 3 protocol identification field
Link quality verification at the connection establishment
Possible authentication:
PAP
CHAP
ISDN :
Group of digital services for voice and data
WAN Data Link conceptsWAN Technology concepts
LAPB :
For X.25 networks
On packets switching network
Also on point-to-point link if bad reliability and/or important delay (Example: satellite link)
Reliability and flow control
WAN Data Link conceptsWAN Technology concepts
HDLC :
Can be incompatible between providers (several implementation of HDLC)
Support point-to-point and multipoint connection type
Based on and replacement to SDLC
Enable by default on WAN interfaces of Cisco router
Very simplified ( no windowing and no flow control)
HDLC is recommended for link between 2 IOS equipment (if not PPP is advised)
WAN Data Link conceptsWAN Technology concepts
Telecom providers supply end-to-end communications
Offer services such as:
Communication initiation (Signalization)
Data transit
Time-division multiplexing
Bandwith sharing
WAN Data Link conceptsWAN Technology concepts
WAN paths that interconnect DTE
Link
Circuit
Canal
Line
WAN Data Link conceptsWAN Technology concepts
DTE provides datas (router)
DCE converts and transports datas (Modem, CSU/DSU unit, TA, NT1)
DCE is the interface between DTE and service provider WAN link
WAN Data Link conceptsWAN Technology concepts
2 kinds of circuits
End-to-End : Dedicated circuits (POTS, ISDN)
Virtual : Logical circuit through a cloud (Frame Relay, X.25)
SVC
PVC
WAN Data Link conceptsWAN Technology concepts
SVC
Dynamically established on demand an closed at the end of the transmission
3 steps communication :
Establishment
Data transfert
Closing
Bandwidth consumption (because of steps)
Low costs (according to time)
WAN Data Link conceptsWAN Technology concepts
PVC
Permanently established
Used for constant transmission needs
Communication in 1 step
Transfert
Lower bandwidth consumption (less steps)
Higher costs (permanent services)
WAN Data Link conceptsWAN Technology concepts
Line Bandwith
T1
E1
E3
T3
1.544 Mbits/s
2.048 Mbits/s
34.064 Mbits/s
44.736 Mbits/s
Examples :
PauseWAN Technology concepts
At which layers of the OSI Model do WAN networks work?
Layers 1 & 2
PauseWAN Technology concepts
What is the difference between a modem and a CSU/DSU unit?
The first one is analog, the second one digital
PauseWAN Technology concepts
What kind of encapsulation is generally used on ADSL lines ?
PPP
WAN Connection Options
Introduction to WAN
Plan
Introduction
Dedicated connection link options
Switched connection options
Chapters we will study:
WAN Connection Options
WAN network
Dedicated Switched
Circuits switching
Packets/cells switching
T1/E1T3/E3
POTSISDN
56K,V90
X.25Frame Relay
ATMSMDS
IntroductionWAN Connection Options
Dedicated connection link optionsWAN Connection Options
Continuous service
Physical dedicated link between customer and provider
Point-to-point synchronous serial links
Physical link
Virtual link made of several physical links
Used for big quantities of informations and constant traffics
Dedicated connection link optionsWAN Connection Options
Switched Connection OptionsWAN Connection Options
Circuit switching :
Physical commutation of telephony central in order to get a point-to-point link
Packets /cells Switching:
“Logical” switching performed at the layer 2 of the OSI model
Switched Connection OptionsWAN Connection Options
Circuit switching :
Physical dedicated circuit using switching at central offices
Established, maintained and closed at each session
Established on demand
Can be used as backup link for main link
Dedicated bandwidth
Switched Connection OptionsWAN Connection Options
Switched Connection OptionsWAN Connection Options
Circuit switching disadvantages :
Low data rate
Relatively long connection time
Example of ISDN:
2 types: BRI and PRI
Switched Connection OptionsWAN Connection Options
Usage of a virtual point-to-point dedicated circuit (PVC or SVC)
Forwarding variable (packets) or fixed (cells) length frames
Flexible usage
Better use of the bandwith than circuits switching links
Switched Connection OptionsWAN Connection Options
WAN network
Switch
LAN
LA
N
LA
N
Provider network
DCE
DCE DCE
Switched Connection OptionsWAN Connection Options
Packet switching can be viewed as a mix between leased lines and circuit switching (low cost)
Frame Relay, ATM, and legacy X.25 are the most popular packet-switching technologies used today
PauseWAN Connection Options
ATM
POST
RNIS
Frame Relay
Circuits switching
Packet switching
Link peers up
QuizzWAN networks
At customer side
At provider side
Where is DCE located ?
WAN connection
Option
WAN connection
Option
Course summary
WAN technologies
concept
WAN technologies
concept
Introduction to WAN
Congratulations
You have successfully completed the SUPINFO course
Introduction to WAN
The EndIntroduction to WAN