circuit switching network

7/31/2019 Circuit Switching Network

1/60

Chapter 2d


2/60

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)


3/60

Analog and Digital Services

over the Telephone Network

To reduce cost and improve performance, thetelephone companies gradually add digital technologies(digital switching and transmission)


4/60

Digital vs. Analog Switching (1)

digital data

time-slot-interchange can be

applied for switching the voicesignals (bits stream) to

appropriate outgoing trunks


5/60

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


6/60

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.


7/60

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


8/60

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


9/60

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.


10/60

ISDN System Architecture This architecture

will support

various ISDN

services


11/60

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


12/60

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


13/60

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.


14/60

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


15/60

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


16/60

PRI


17/60

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


18/60

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.


19/60

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


20/60


21/60

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


22/60

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


23/60

Part 3: ISDN Protocol Architecture

it complies to OSI 7layers model


24/60

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).


25/60

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


26/60

Framerelay


27/60

N-ISDN Framing & Multiplexing

2B1D: 2 B channels (labeled as B1 and B2) + 1D channel


28/60

Multidrop configurationsMultidrop configurations

With the

basic accessinterface , it is

possible to

than one TEdevice in a

passive-bus

configuration


29/60

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.


30/60

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.


31/60



Multiplexing


Transport Network

Circuit Switches



Traffic Management




Asymmetric Digital Subscriber Line (ADSL), Very High Bit Rate Digital Subscriber Line (VDSL)


32/60

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.


33/60

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


34/60

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


35/60

B-ISDN Reference Protocol Model


36/60

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


37/60

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.


38/60

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.


39/60



Multiplexing


Transport Network

Circuit Switches



Traffic Management




Asymmetric Digital Subscriber Line (ADSL), Very High Bit Rate Digital Subscriber Line (VDSL)


40/60

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


41/60

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


42/60

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.


43/60

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


44/60

ADSL Channel Configuration


45/60

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).


46/60

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


47/60

ADSL Reference Model


48/60

DSL Access Multiplexer


49/60

DSL Voice and Data Separation

DSLAM - Digital subscriber line access multiplexer


50/60

ADSL Configuration


51/60

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


52/60

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


53/60

HDSL Configuration


54/60

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


55/60

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


56/60

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


57/60

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


58/60

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


59/60

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


60/60

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

circuit switching network

Documents