Transcript Broadband Networking Technology Overview

Broadband Networking
Technology Overview
An Overview of WAN and Broadband
Terminology and
Common Deployment
Objectives
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To review WAN/Broadband Technologies
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Transmission Services
(POTS, DSx, Tx and Ex, xDSL, Cable)
Data Services
(ISDN, X.25, Frame Relay, SMDS, ATM)
Interfaces and customer premise equipment
(multiplexers, inverse multiplexers,
access routers)
To learn how customers typically use these
technologies
Why Do We Care About WANs?
Why
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To interconnect LANs
Terminal to Host
Terminal To LAN
Remote Access
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do people need WANs?
Client-to-Server
Remote to LAN
Videoconferencing
Voice
Internet
Definitions
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Synchronous vs. Asynchronous
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Synchronous: signals sourced from the same timing
reference
Asynchronous: signals sourced from independent clocks
 Frames
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vs. Cells
Frames - structure for sending data in a serial stream
Cells - fixed frame size (typically smaller - e.g. ATM)
Transmission Services
Plain Old Telephone Service (POTS)
 Digital Transmission Services
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Plain Old Telephone Service
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Where is it deployed?
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Homes
Offices
Public
Packet
Network
Central
Office
Central
Office
How does it work?
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Uses a digital circuit from a Local Exchange Carrier
(LEC) Central Office (CO) to an analog “local loop”- the
local terminal box and twisted pair copper wires to the
customer site (“Customer Prem”)
The CO uses connection-oriented packet switching to
send voice/data to another CO
POTS (cont’d)
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Why is it used?
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Voice
Asynchronous data using a modem
Next Generation POTS:
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ISDN
xDSL - Digital Subscriber Line - boosts ability for POTS
twisted pair copper lines to transmit at higher speeds
(ASDL - 1.5 to 6Mbps)
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Flavors: asymmetrical, symmetrical, high speed, very high speed
Digital Transmission Services
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Dedicated/switched transmission service at selected
speeds
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Common names are T1, E1, T3, E3, DS0, DS1, DS3, 56/64K
DS0 - 64Kbps is the building block
Fractional services use group of DS0s
(FT1 typically 384kbps)
How does it work?
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LAN to multiplexer; to a router or bridge; to a DSU/CSU; to
a twisted copper pair in customer prem; to a conditioned line
Digital Transmission Services (cont’d)
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Where is it deployed?
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Telcos (LECs, IXCs) sell and use the
services (e.g. T3)
To the home or SOHO (Small Office/
Home Office)
Why is it used?
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Inter-LAN connectivity, voice/data
Switched Services
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Cost effective bandwidth
Private Line
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Security and guaranteed bandwidth
Digital Transmission Services (cont’d)
Service
Speed
DDS/FT1
FT1
T1
E1
E3
T3
56K/64K
typically 384K
1.544 Mbps
2.048 Mbps
34.368 Mbps
44.736 Mbps
Cable Services
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What is it?
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Multiple Service Operators (MSOs) use existing/upgraded
coaxial cable to the home for data/video transmission
Requires cable modems
Transmission rate = 500 Kbps - 40 Mbps
Issues
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Increasing shared bandwidth/two-way: FTTC, FTTH,
HFC
Cable companies - only good at TV?
No standards
Data Services
ISDN
 X.25
 Frame Relay
 SMDS
 ATM
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Integrated Services Digital Network (ISDN)
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What is it?
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Packet-switched digital service
Bearer channels 64K that contain user data
Delta channels for signaling
B
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BRI
Basic Rate Interface (BRI)
2B+D
2 Bearer channels,
1 Delta channel- 16K
Primary Rate Interface (PRI)
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23B+D (T1) or 30B+D (E1)
1 Delta channel - 64K
D
B
D
PRI
ISDN (cont’d)
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Why is it used?
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LAN-to-LAN connectivity
Fax traffic
Remote office/SOHO connectivity
Internet
Link to the access points of packet public networks
ISDN specification also identifies supplementary
services such as Caller ID and Multiple Site
Numbers
X.25
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What is it?
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X.25 is a packet-switching service
X.25 interface supports up to 64 Kbps
Dial-up or direct connection
Why is it used?
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Typically used to connect remote terminals to host systems
Good: Allows connection with many different sites, deployed
world-wide
Bad: Error checking at each node causes slow performance
Frame Relay
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What is it?
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A packet-oriented communication method for
connecting computer systems
Need a router, Frame Relay Access Device (FRAD),
and line from customer to Frame Relay network
Typical bandwidth ranges from 56Kbps to T1
Network relies on the upper layer protocols to perform
any error checking
Frame Relay (cont’d)
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Frame Relay vocabulary
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Access rate
Committed Information Rate (CIR)
Data Link Connection Identifier (DLCI)
Congestion control
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Forward/Backward Explicit Congestion Notification
(FECN/BECN)
Discard Eligibility (DE)
Switched Multimegabit Data Service (SMDS)
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What is it?
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LEC Service
Connectionless, any-to-any connection that
uses fixed cells like ATM (service sometimes
rides on top of telco ATM infrastructure)
Why is it used?
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To extend LANs to MANs
Provides usage based billing and
some management
Limited adoption due to Frame Relay and ATM
Asynchronous Transfer Mode (ATM)
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What is it?
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Connection-oriented service using Permanent Virtual
Circuits (PVCs) or Switched Virtual Circuits (SVCs) over
fiber or copper
Simultaneous voice, video and data
Virtual Path and Connection Identifiers (VP/VCs) used to
identify the connection
Uses 53-octet cells
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5 bytes header/descriptor, 48 bytes payload
Special protocols depending upon data type
ATM, cont’d
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How is it deployed?
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Today is mostly used as backbone or WAN
Transport is commonly
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OC-3 (155Mb fiber), OC-12 (622Mb fiber)
DS-3 (45Mb), E3 (34Mb)
LAN can be as slow as 25Mbps, or up to OC-48
Why is it used?
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Supports multiple, disparate applications
High speed
Worldwide standard
Fiber Optics
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Single Mode Fiber
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Small core
High bandwidth
Long distances
Lasers used to generate the signal
Expensive/hard to handle
Multimode Fiber
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Large core diameter
High dispersion
Short distances/LANs
LEDs used to generate the signal
Interfaces and Customer Premise Equipment
Multiplexers/Inverse Multiplexers
 Interface Devices
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DSU/CSU
FRADs
 Copper
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Interfaces
RJ connectors
Other connectors
Multiplexers (MUX) and Inverse Multiplexers
Multiplexers: Used to combine multiple,
disparate applications on one trunk
 Inverse Multiplexer: Used to break up single
trunk into multiple slower trunks
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WAN Side
LAN Side
Data
Voice
Video
LAN
Frame Relay
ISDN
ATM
ATM
T1 Mux
T1
T1
T1
T1
Inverse
Mux
Inverse Multiplexer - Take 2
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Data transmission through High Speed Serial
Interface (HSSI) and then through WAN via
multiple lower speed links
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HSSI - 1.536M to 48.896M speeds
HSSI
48.896M
HSSI
Multiple
T1/E1s
T3/E3s
48.896M
Interface Devices
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Data Service Unit/Channel Service Unit
(DSU/CSU)
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Used with Digital Data Service (DDS) (2.4K to 64K)
DSU/CSU used to terminate T1 line
RS-232 or V.35 interface
FRADs
 PADs
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RJ Interfaces
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RJ-11
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RJ-11
Basic telephone
Widespread deployment
RJ-45
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Originally designed for dialup modem
Ethernet, Digital
Transmission Services (Tx,
Ex, ISDN)
RJ-45