circuit switching network
TRANSCRIPT
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Chapter 2d
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Circuit Switching Networks
Chapter2a Circuit switches
Multiplexing
Chapter2b Synchronous Optical NETwork (SONET)
Transport Network
Circuit Switches
Chapter2c Telephone network: subscriber lines, digital subscriber lines (DSL)
Signaling: telephone & SS7
Traffic Management
Chapter2d Broadband circuit-based access networks:
Integrated Services Digital Network (ISDN)
Broadband Integrated Services Digital Network (B-ISDN)
Asymmetric Digital Subscriber Line (ADSL),
Very High Bit Rate Digital Subscriber Line (VDSL)
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Analog and Digital Services
over the Telephone Network
To reduce cost and improve performance, thetelephone companies gradually add digital technologies(digital switching and transmission)
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Digital vs. Analog Switching (1)
digital data
time-slot-interchange can be
applied for switching the voicesignals (bits stream) to
appropriate outgoing trunks
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Digital vs. Analog Switching (2)
the incoming 6 FDM channels of data must be demodulated and demultiplexed and feed
each of the voice channel to the input lines of the SDS
after switching, for transmission purpose, A, B, E (or C, D, F) must be modulated and
multiplexed for FDM transmission on their respective trunks
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Advantage of digital transmission In analog switching
system,
demodulation anddemultiplexing are
required before
switching and
mo u a on an
multiplexing are
required after
switching process
The digital transmission of voice signals enable
integration of switching and transmission by usingdigital switch.
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Figure 16-5
IDN
IDN (Integrated Digital Network) is referred to the telecommunicationnetwork which integrates transmission and switching through the useof digital switching techniques.
Advantages as compared to analog switching :
there is no accumulation of noise due to multiple modem
lower cost as saving in a large number of modem and multiplexer and
demultiplexer
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Figure 16-6
Conceptual view of ISDNConceptual view of ISDN The overall objective of ISDN is to provide a small set of user and
network interfaces that allows users with standard access to a variety of
network services. ISDN can integrate virtually all forms of communication,
including voice, data and video.
Channel type:BRI & PRI
service type:voice &non-voice
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Principles of ISDN [CCITT
Recommendation I.120(1993)]
support of voice and nonvoice applications
support of switched (circuit and packet) and nonswitched (dedicated line) applications. compatible with 64kbps switched digital connections intelligent in the network
able to provide sophisticated services, network management and maintenance capabilities
layered protocol architecture and can be mapped into the OSI model. Advantages :
existing standard for OSI can be extended/ used on ISDN
new ISDN-related standards can be used on existing standards reducing the cost of new implementation
standard can be developed and implemented independently for various layers and various functions within
layer
more than one physical configuration is possible for implementing ISDN according to
specific national situation.
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ISDN System Architecture This architecture
will support
various ISDN
services
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B Channel
B for Bearer.
64 Kbps channels.
64 kpbs channels that may be used to carry voice, data, facsimile, or image
Used to carry digitized voice and digital data.
ay e use to prov e access to a var ety o erent commun cat on mo essuch as circuit or packet switched
Possible Connections set up:
Circuit Switched
Packet Switched Frame Mode ~ frame relay
Semi permanent ~ leased line
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D Channel
D for Data/Demand.
Either 16 or 64 kbps depending on specific interfaces.
Mainl intended f r carr in i nalin inf rmati n t c ntr l I DN ervice
May also carry other information such as packet-switched data in addition tosignaling
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H Channel
H for Hybrid.
Data rate: 384 (H0), 1536 (H11) or 1920 (H12) Kbps.
Used for high data rates application such as video and teleconferencing.
Also for fast facsimile, high-speed data, and high-quality audio
Provided for user information at the primary rate interfaces (higher bit rates)
May be used as high-speed trunk or subdivide the channel according to user ownsTDM scheme
H0 = 384 KBPS Two H1 ~ H11 = 1.536 Mbps, H12 = 192 Mbps
These channels types are grouped into transmission structures that are
offered as a package to the user. Each package is suited to a differentlevel of customer needs.
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Types of logical channels 3 types of logical channels (time-slots) carried by the digital pipe between an end
office and an ISDN subscriber:
D (data),
B (bearer),
H (hybrid)
Type of channel
D B H
kbps 16 or 64 64 384(H0), 1536(H11),1920(H12)
function i) signaling
ii) low-speed data
videotex terminaliii) telemetry emergency services energy management
i) digital voice
64kbps PCMii) high speed data
circuit-switched packet-switched semipermanentiii) other
facsimile slow-scan video
i) high-speed data
fast facsimile video high-quality audioii) multiplexed
information streams at
lower data rates
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Transmission structures (ISDN Packages)Transmission structures (ISDN Packages)Transmission structures (ISDN Packages)Transmission structures (ISDN Packages) Transmission structure refers to the way in which logical channels providing
basic data transportation services are organized for transmission over the local
loop.
These channel types of D, B and H are grouped into 2
transmission structures that are offered as a package to
the user Basic rate interface, BRI
Primary rate interface, PRI
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PRI
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Basic Rate Interface (BRI)
Basic channel structure.
Intended for individual users (residential and small offices).
Consist of:
2B + D interface(a single physical interface).
Two full-duplex 64 Kbps B channels and one full-duplex 16 Kbps D channel.
Total bit rate = 144 Kbps.
With framing, synchronization, overhead bits total bit rate = 192 Kbps.
that it can be used to handle digital transmission. Intended for individual users (residential and small offices)
Allows simultaneous use of voice and data applications such as packet-switchedaccess, link to central alarm, facsimile, videotex, etc.
Should be accessed through a single physical multifunction interface or severalseparate terminals
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Primary Rate Interface (PRI)
Primary channel structure.
Intended for greater capacity requirements Offices with digital PABX or local network.
Due to differences in digital hierarchies used in different countries: USA, Canada, Japan use transmission structure based on 1.544 MbpsT1 transmission
facility. - .
23B + D Europe and most Asia use transmission structure based on 2.048 Mbps E1 transmission
facility. Channel structure: 30 B channels plus one 64-kbps D channel.
30B + D
User may lower requirements using: nB + D (n is from 1~30)
The channels structure for the 1.544 Mbps and 2.048 Mbps primary rates may be
structured using B, H0, H1, or combined B and H0 channel interface, with 64-kbps
D channel for signaling.
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Comparison of BRI & PRIBasic access or
Basic channel structure
Primary access or
Primary channel structure
all countries US, Canada, Japan Europetransmission
rate /bps
192k 1.544M 2.048M
. .
composition 2B + D (16kbps) +
synchronization +
framing
i) 23B + D (64) + ..
ii) 4H0
iii) H11
iv) 3H0 + 5B + Dv) 3H0 + 6B
vi) etc
i) 30B + D (64) + ..
ii) 5H0 + D
iii) H12 + D
iv) etc
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Functional Groups:
NT1, NT2, TE1,
TE2, TA
User-network Interface Configurations
ITU-T defines functional grouping and reference points in orderprotocol standards can be developed at each reference points, i.e.,
interface between functional groupsOnce stable interface standards exist,
technical improvements on either side of an interface can be made
equipment from different suppliers will be compatible
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Figure 16-10
Reference Points
U: interface between the customer
premise and the end officeU interface side carries full duplex
information on the pair.
The S Interface is
R: interface between a non-ISDN terminal
(TE2) and an ISDN terminal adaptor (TA)
T: separates the network providers
equipment from users equipment
S: Interface
between an ISDNterminal (TE1) or
an ISDN TA and
the ISDN NT2.
a 4 Wire interface
which runs at
192Kbps
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Part 3: ISDN Protocol Architecture
it complies to OSI 7layers model
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Figure 16-12 Simplified Layers of ISDN
Note that only layers 1, 2, and 3 are involved from the network point of view
(just make sure the data arrives at the destination safely and in order).
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ISDN Connections 6 types of services for end-to-end communication
Over B or H channel
circuit switched calls
serviced by an NT using only layer 1 functions
packet switched calls
serviced by an NT using only layer 1, 2 and 3 functions
rame re ay ca s using ayer &
semipermanent calls
arrangement with network provider to provide service for an agreed fixed period of
time
serviced by an NT using only layer 1 functions
over a D channel packet switched calls
serviced by an NT using only layer 1, 2 and 3 functions
frame relay calls
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Framerelay
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N-ISDN Framing & Multiplexing
2B1D: 2 B channels (labeled as B1 and B2) + 1D channel
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Multidrop configurationsMultidrop configurations
With the
basic accessinterface , it is
possible to
than one TEdevice in a
passive-bus
configuration
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when a TE does not want to transmit
LAPD frame, the TE transmits a series ofbinary one(means no line signal under
pseudoternary encoding scheme) on the
D channel
the NT, on receipt of a D channel bit,reflects back the latest received Dchannel bit, called E (echo) bit
when a TE wants to transmit a LAPD
Contention resolution Algorithm
,
it listens to the stream of incoming D channelecho bits
if it detects a string of 1-bits of length equal toa threshold value Xi, where i = priority classfor this LAPD frame
then it may transmitelse the terminal must wait
each of the transmitting TEwill continuously monitorthe echo bit and comparewith its recent transmittedbit.
a collision happens when adiscrepancy is detected, theterminal ceases to transmitand returns to a listen state.
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ISDN Contention resolution to make sure that all TE terminals, who share a single
physical line, can transmit signal successfully by taking
turn. only outgoing D channel traffic needs contention
resolution since all TE terminals ma tr to
transmit at the same time. each of the B channel is dedicated to a particular TE at any given time
address within each incoming D channel frame ensures that all TEs at the
subscriber site can read this address and determine whether the frame ofdata is for them.
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Circuit Switching Networks
Chapter2a Circuit switches
Multiplexing
Chapter2b Synchronous Optical NETwork (SONET)
Transport Network
Circuit Switches
Chapter2c Telephone network: subscriber lines, digital subscriber lines (DSL)
Signaling: telephone & SS7
Traffic Management
Chapter2d Broadband circuit-based access networks:
Integrated Services Digital Network (ISDN)
Broadband Integrated Services Digital Network (B-ISDN)
Asymmetric Digital Subscriber Line (ADSL), Very High Bit Rate Digital Subscriber Line (VDSL)
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Features
Data rates: in the range of 600 Mbps About 300 times faster than PRI rate
Medium: Fully fiber optic cable at all level of telecommunicationsnetwork
Broadband ISDN
.
Switching: Fast packet switching facility to be able of handling a widerange of different bit rates and traffic parameters. It is difficult to handle the large and diverse B-ISDN with circuit-switching
technology.
Services: Interactive and Distributive Interactive Service: require two-way exchanges between either two subscribersor between a subscriber and a service provider.
Distributive Service: Unidirectional services sent from a provider to subscriberswithout a subscriber having to transmit a request each time a service is desired.
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Figure A.6 BFigure A.6 B--ISDNISDN
ArchitectureArchitecture
User-Network InterfaceThe reference configuration
is shown in Figure A.7
(almost identical to A.4)
The broadband functional
groups are equivalent to the
functional groups defined for
narrowband ISDN
Figure A.7 BFigure A.7 B--ISDN Reference Points and Functional GroupingsISDN Reference Points and Functional Groupings
Transmission Structure
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Transmission Structure
Three new transmission services are defined:
First service: Full-duplex 155.52-Mbps
Can support all narrowband ISDN services & basic/primary rate
interfaces
Support most of the B-ISDN services
Example: supports one/more video channels
depends oncoding and video resolution
Most common B-ISDN service
It is asymmetrical:From subscriber to network 155.52-Mbps
From network to subscriber 622.08-MbpsExample: business conducts multiple simultaneous
videoconference
From provider to user need upper 622.08 MbpsFrom user to provider no initiation of distribution, so only
need lower 155.52 Mbps
Third service: Full duplex 622.08-Mbps
Appropriate for video distribution provider
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B-ISDN Reference Protocol Model
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Applications: Telephony
Video conferencing Data transfer
Mail (voice, data, video)
Broadcasting (TV, Radio) Access Method
Symmetrical 155.520 Mbps
Asymmetrical 155.520 /622.080 Mbps
Symmetrical 622.080 Mbps
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Several reasons why ISDN is considered a goodsolution: ISDN can be brought to the subscriber premise with
minimum cost.New equipment has appeared on the market that allows a
subscriber to use the entire bandwidth of the ISDN line.The protocol is flexible enough to be upgraded to higher
data rates using new technology and new transmissionmedia.N-ISDN can be used as a forerunner for B-ISDN, the data
rate of which is sufficient for several years to come.
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Broadband: A service or a system requiring transmission channels capable of
supporting rates greater than primary rate.
The term B-ISDN is sued for convenience in order to refer to and emphasize thebroadband aspects of ISDN. The intent, however, is that there be one
comprehensive notion of an ISDN, which provides broadband and other ISDNservices.
Asynchronous transfer mode (ATM) is the transfer mode for implementing B-ISDN and is independent of the means of transport at the Physical Layer
refer to OSI model.
B-ISDN will be based on the concepts developed for ISDN and may evolve byprogressively incorporating directly into the network additional B-ISDNfunctions enabling new and advanced services.
Since the B-ISDN is based on overall ISDN concepts, the ISDN accessreference configuration is also the basis for the B-ISDN referenceconfiguration.
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Circuit Switching Networks
Chapter2a Circuit switches
Multiplexing
Chapter2b Synchronous Optical NETwork (SONET)
Transport Network
Circuit Switches
Chapter2c Telephone network: subscriber lines, digital subscriber lines (DSL)
Signaling: telephone & SS7
Traffic Management
Chapter2d Broadband circuit-based access networks:
Integrated Services Digital Network (ISDN)
Broadband Integrated Services Digital Network (B-ISDN)
Asymmetric Digital Subscriber Line (ADSL), Very High Bit Rate Digital Subscriber Line (VDSL)
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Broadband Modems Support additional services to plain old telephone services (POTS) Example: low bit rate data application such as fax are supported by means of low bit rate
less than 56kbps modems
Also, twisted-pair lines in PSTN are used as the access lines for an ISDN
Basic rate (144kbps) and Primary rate (1.544/2.048 Mbps) over several kilometersare obtained using baseband transmission
It is known as digital subscriber line (DSL)
Primary rate line high-speed DSL (HSDL) IDSL using single pair and HDSL using two pairs. In addition simpler HDSL
operates with single pair is called single-pair DSL (SDSL)
Both are symmetric: they operate with equal bit rate in both direction
ADSL (Asymmetric DSL) and VDSL (very-high-speed DSL) uses asymmetricmethods Example: V.90 modem provides 33.6 kbps upstream and 56 kbps downstream
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DSL technologies
The line length limitations from telephone exchange to subscriber are morerestrictive for higher data transmission rates. Technologies such as VDSL provide veryhigh speed, short-range links as a method of delivering "triple play" services(typically implemented in fiber to the curb network architectures).
Example DSL technologies (sometimes called xDSL) include:
High-bit-rate Digital Subscriber Line (HDSL)
,
Asymmetric Digital Subscriber Line (ADSL), a version of DSL with a slower uploadspeed
Rate-Adaptive Digital Subscriber Line (RADSL)
Very-high-bit-rate Digital Subscriber Line (VDSL)
Very-high-bit-rate Digital Subscriber Line 2 (VDSL2), an improved version of VDSL
G. Symmetric High-speed Digital Subscriber Line (G.SHDSL), a standardisedreplacement for early proprietary SDSL by the International TelecommunicationUnion Telecommunication Standardization Sector
ADSL
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ADSL
Asymmetric Digital Subscriber Line
Higher bit rates in the downstream direction (from the telephone central office tosubscribers site) than the upstream direction (from the subscribers site to telephone
central office). Basically that is what the subscriber wants.
ADSL divides the bandwidth of the twisted pair cable (1MHz) into threebands.
First band (0 to 25KHz) used for telephone service. (POTS usually use4KHz, the rest are band guards to separate voice from data channels).
Second band (25 to 200KHz) Upstream communication.
Third band (250KHz to 1MHz) Downstream Communication.
Local Application: Malaysias TMNET Streamyx broadband Internet service.
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ADSL Design Asymmetric
Greater capacity downstream than upstream
Frequency division multiplexing
Lowest 25kHz for voice
Use echo cancellation or FDM to give two bands Use FDM within bands
Range 5.5km
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ADSL Channel Configuration
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Limitations of TMNET Streamyx:
Subscribers site must be within 5 km from the local exchange that provides theservice.
Subscribers site must have a direct copper connection from the local exchange thatprovides the service.
Transmission rate is based on Best Effort and are not guaranteed.
Advantages of TMNET Streamyx:
Separate data traffic from voice traffic ~ this allows uninterrupted telephonyservices even if ADSL fails.
Always on connection ~ ADSL is continuously available unlike regular dial uptelephone service.
Service rates are cheaper than the conventional 56Kbps dial up services provided bythe ISP (1 sen/min compared to 2.5 sen/min).
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ADSL Work along with POTS
Refer to service that differ in downstream and upstream
bandwidth using DSL technology Data rate downstream is up to 6.1Mbps
Data rata upstream is up to 640kbps
Major elements: ADSL Transceiver Unit Central Office (ATU-C)
ADSL Transceiver Unit Remote (ATU-R)
HPF
Passes data signal to broadband networks
LPF
Passes the voice signal to PSTN/POTS
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ADSL Reference Model
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DSL Access Multiplexer
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DSL Voice and Data Separation
DSLAM - Digital subscriber line access multiplexer
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ADSL Configuration
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ADSL Configuration Used over local analog loop
Uses FDM with three elements:
Reserve lowest 25kHz for POTS Two FDM bandwidth for upstream and downstream FDM within upstream BW and downstream BW
ay use c o ance a on to a ocate two
bandwidth for upstream and downstream: Better spectrum for downstream bandwidth as echo
cancellation reduce attenuation in higher frequency Offer flexibility in changing upstream capacity / no overlap
between upstream FDM and downstream FDM
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High bit rate DSL (HDSL) Used for wideband digital transmission
Symmetrical
Cost effective as compare to T1 Reliably transmit 2.048Mbps
Advantage: Tolerant of local loop modification made by telephone system
Moving data between HDSL and T1 is straight forward
Use two twisted pairs cable, if one fail HDSL operate with half bandwidth
Limitation:
Short distance
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HDSL Configuration
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Symmetric Digital Subscriber Line (SDSL) Operate on single pair of twisted pair cable, as opposed
to HDSL
Allow easy implementation of application that requires
symmetrical data rates
T1 and E1 speed with max distance 3 km
2B1Q and echo cancellation is used
768kbps data rate in both directions
Suited to run web server application
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Very high-data rate DSL (VDSL) Asymmetrical very high bandwidth
May operates on top Fiber To The Curb (FTTC) and Fiber To TheNeighborhood (FTTN)
Downstream data rates 12.9Mbps to 52.8Mbps
Upstream data rates 1.5Mbps to 2.3Mbps
.
Requires Fiber Optics and ATM
Echo cancellation is not used
Provides Separate Bandwidths: POTS: 0 to 4kHz
ISDN: 4 to 80kHz Upstream 300 to 700kHz Downstream >1MHz
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Rate Adaptive DSL (RADSL) Similar function with SDSL
Speed depending on local loop length and quality of transmission
medium More suited to application that requires more data flow
in one direction as compare to the other
e co may set speci ic rate or eac su scri er
Telco may dynamically adjust data rate for each subscriber
Popular combination: 6.1Mbps downstream and 640kbpsupstream
ANSI standard T1.413 Issues 2
Summary Chapter 2
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Summary Chapter 2
Circuit switches
What is circuit switch?
Setup procedure?
Advantages and Disadvantages?
Multiplexing Definition?
Advantages and Disadvantages?
Type of multiplexing
Working description of each multiplexing types
Calculation
Summary Chapter 2
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Summary Chapter 2
Synchronous Optical NETwork (SONET) Definition
Comparison with SDH
Signal rate and how it support lower data rate?
Calculation Frame structure
SONET Network
Definition Advantages
Linear and Ring network
Circuit Switches Blocking issue
Space and Time Division Switches
Multistage switches designed
Summary Chapter 2
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Summary Chapter 2
Telephone network: subscriber lines, digital subscriber lines
(DSL) Not important
Signaling: telephone & SS7 mportant o s gna ng
Signaling techniques
Traffic Management
Not important
Summary Chapter 2
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Summary Chapter 2
Integrated Services Digital Network (ISDN) BRI & PRI?
Basic frame structure
Broadband Integrated Services Digital Network (B-ISDN) Not im ortant
Asymmetric Digital Subscriber Line (ADSL) Implementation