01 Tw2102eu01eg 0001 Introduction

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Introduction Siemens

1

Contents

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1 Introduction

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Siemens Introduction l

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1 ISDN Principles

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Communication means the exchange of information. The function of communications

technolog is to facilitate communication !et"een #eo#le.

The term communication can relate to $arious t#es of information. The follo"ing fourt#es of information can !e differentiated%

$oice&

text&

data&

image.

' num!er of different communications sstems exists for each of these ( informationt#es. )o"e$er& each communications sstem su##orts one information t#e onl.

)o"e$er& the need to transmit more than one information t#e in a commoncommunications sstem exists.

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Information types and communication systems

Information type Communications system

Voice Telephony

Text TelegraphTeletypewriting (telex, teletex)videotex

Data Data transfer

Image Facsimile

*ig. 1

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Gentex net"or+

'n inner-#ostal-sstem net"or+ for transmitting telegrams

Telex net"or+

' "ides#read #u!lic net"or+ used for telegra#hing at a maximum transmissionrate of ,0 characters #er second ,0 !aud

CS/ Circuit S"itched /u!lic ata et"or+

' #u!lic net"or+ a!le to transmit data at a rate !et"een 200 and (&000 !it3s. Thisnet"or+ is li+e"ise used to transmit telexes modern text transfer at 2(00 !it3s.The telex and CS/ net"or+s are lin+ed in order to allo" text transfer !et"eensu!scri!ers in the telex and teletex net"or+s.

/S/ /ac+et S"itched /u!lic ata et"or+

' #u!lic net"or+ used to transfer data at rates !et"een 200 and (&000 !it3s. The$ideotex information centers are lin+ed "ith the /S/& "hile the $ideotexsu!scri!ers are located in the /ST.

/ST /u!lic S"itched Tele#hone et"or+

' #u!lic net"or+ for transferring $oice. This net"or+ also allo"s the transfer ofdata or $ideotex ! modem or facsimile grou# 2 and 4.

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circuit-

s"itching

#ac+et -

s"itchingcircuit-s"itching

/ST/S/Gentex

net"or+

Telex

net"or+CS/

Telegram Telex Teletex ata 5ideotex *acsimile Tele#hon

Transmission of $oice& text& data& image

5oice& text& data& image

*ig. 2 Current state

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With the exce#tion of the /ST& all the net"or+s sho"n in the figure !elo" use digital

nodes and lines. The nodes and inter-node trun+s in the /ST ma !e either analogor digital& !ut su!scri!er lines are al"as analog.

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/ST1nodes

or

Tele#hone

orTelefax

0ata

transfer

5ideotex

Telex

Teletex

0ata transfer

0ata transfer

S I E 6 E 1 S

1 I 7 0 8 9 *

68-

0E6

68-

0E6

Telexnodes

/S/01

nodes

CS/01nodes

S I E 6 E 1 S

1 I 7 0 8 9 *

*ig. 4 Con$entional net"or+s

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The fundamental idea !ehind IS Integrated Ser$ices Digital Net"or+ is to offer a

uniform net"or+ su##orting all information t#es !asic ser$ices of the con$entionaltele#hone net"or+ as "ell as man of the information t#es handled ! the existingtext and data net"or+s.

The transmission routes ha$e to !e digital: other"ise the a##ro#riate transmission;ualities and rates cannot !e guaranteed. Thus& the a!!re$iation IS encom#assesthe follo"ing functions%

Integrated% Stands for the incor#oration in one net"or+ of se$eral ser$icesinformation t#es& i.e. $oice& text& data and images can !etransferred in a common net"or+.

Ser$ices% Stands for the ser$ices offered& the !asic transmission ser$icesand the


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Tele#hone&analog

Tele#hone&

IS0

Telefax&

IS0

Teletex&

IS0

5ideotex&

IS0

Con$entional

terminals

0ata

transfer&

IS0

digital net"or+

Digital

Su!scri!er

Signaling sstem

1no. 1

Common

Channel

Signaling sstem

7no. ?

IntegratedSer$ices

Digital

Net"or+

uniform net"or+ for$arious ser$ices

S IE 6 E 1 S

1 I 7 0 8 9 *

T'

0ata

transfer&

IS0

S I E M E N SCCS?

IS0

/ST

CS/0

/S/0

others

'0

E7T

0SS1

*ig. ( IS

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1.1 Basic AccessITU-T has s#ecified t"o IS su!scri!er access t#es%

the !asic access for single lines and #ri$ate !ranch exchanges& and

the #rimar rate access exclusi$el for #ri$ate !ranch exchanges.

The !asic access A' uses the existing t"o-"ire co##er line& "hich is terminated !a net"or+ termination T at the su!scri!er end. With suita!le transmissionmethods& the re;uired o$erall !it rate of 10 +!it3s is #ossi!le in !oth directions. This

!it rate encom#asses 2 user channels !asic channels& A channels "ith ( +!it3sres#ecti$el and one signaling channel delta channel& channel "ith 1 +!it3s. Theremaining 1 +!it3s ca#acit is used for snchroni=ation.

The !asic access "ith the 2AB channel structure is used to connect one or moreterminal e;ui#ments. ' single-terminal e;ui#ment configuration re;uires a #oint-to-#oint connection& "hile a multi#le-terminal e;ui#ment configuration re;uires a #oint-to-multi#oint connection.

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S I E M E N S

et"or+

termination

T

10 +!it3s

2 x ( +!it3s B 1 +!it3s B 1 +!it3s

2 circuits B 1 sig. ch. B snchr.

2 A channels B 1 channel B snchr.

2 x A( B 1 x 1 B snchr.

Aasic D9ate 'ccess A'

2-"ire

Exchange

E7

*ig. , Aasic access

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'da#terunit

@

?

4

2

1

S0 UF0

TE

TTE

T'

(-"ire !us

2-"ire line

A B A B 1

A'

a3! 37.2,

Exchange

IS

et"or+

termination

T

S I E M E N S

IS

su!scri!erinterface

*ig. /oint-to-multi#oint configuration

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S0

UF0T2 T1TE

2A B 1

A'1

Exchange

IS-

su!scri!er

interface

A'n

IS

#ri$ate

!ranchexchange UF0

2A B 1

S I E 6 E 1 S

1 I 7 0 8 9 *

S I E 6 E 1 S

1 I 7 0 8 9 *

/ A 7

IS

net"or+

termination

IS

net"or+

termination

S I E M E N S

*ig. ? /oint-to-#oint configuration

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1.2 Primary Rate AccessThe #rimar rate access /' uses a (-"ire line& i.e. t"o smmetrical "ire #airs of anaudio-fre;uenc ca!le& o#tical fi!er or radio-rela lin+. In structure the /'corres#onds to the 40-channel !asic sstem /C640& meaning a transmission rate of20(@ +!it3s is #ossi!le in !oth directions. This !it rate encom#asses 40 user channelsA channels "ith ( +!it3s res#ecti$el& one (-+!it3s signaling channel channeland one (-+!it3s snchroni=ation channel.

The #rimar rate access "ith the 40AB channel structure is used for the #oint-to-#oint connection of medium-si=e to large #ri$ate !ranch exchanges.

et"or+

termination

/ A 7

Exchange

20(@ +!it3s

40 x ( +!it3s B ( +!it3s B ( +!it3s

40 #aload ch. B 1 sig. ch. B snch.

40 A channels B 1 channel B snch.

40 x A( B 1 x ( B snch

/rimar D9ate 'ccess /'

(-"ire

S I E M E N S

*ig. @ /rimar rate access

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IS

net"or+

termination

for

/'

S0

UT2 T1TE

40A B (

/'1

Exchange

U

/'n

40A B (

IS

#ri$ate

!ranchexchange

/ A 7

IS

net"or+

termination

for

/'

IS

su!scri!erexchange

S I E 6 E 1 S

1 I 7 0 8 9 *

S I E 6 E 1 S

1 I 7 0 8 9 *

S I E M E N S

*ig. /rimar rate access

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2 Internetwork Interfaces

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's IS cannot ta+e the #lace of existing net"or+s o$ernight& communication must

still !e #ossi!le !et"een su!scri!ers to different net"or+s "ho ne$ertheless use thesame ser$ices& e.g. tele#hone or data transmission. Such internet"or+communication re;uires internet"or+ interfaces !et"een the existingcommunications net"or+s and IS. The follo"ing internet"or+ interfaces areim#lemented.

2.1 Internetwork Interface from ISDN to te Pu!lic

Switced "elepone Network #PS"N$8!$iousl& su!scri!ers to the IS net"or+ IS su!scri!ers can and docommunicate "ith su!scri!ers in the #u!lic tele#hone net"or+. Indeed& the samenum!ering scheme is used in either net"or+. The internet"or+ interface can !eim#lemented at different #oints in the net"or+ at this case& and al"as entailscon$ersion into digital information of the analog information as "ell as con$ersioninto the a##ro#riate common channel signaling either SS1 or CCS? "ith ISUser /art of the analog signaling.

*igure 10 on the next #age sho"s the #ossi!le locations for the internet"or+

interface.In the first case a terminal e;ui#ment in the /ST e.g. grou# 4 fax machine or ananalog tele#hone is re;uired to !e connected to an IS access line. Theinternet"or+ interface is im#lemented here ! a terminal e;ui#ment ada#ter T' a3!.

In the second case an analog trun+ is used as the lin+ to the next exchange. )erethe internet"or+ interface is im#lemented ! the exchange& "hich can ser$ice !othanalog and digital trun+s. The con$ersion of the different signaling methods is#erformed in this exchange li+e"ise.

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IS0

exchange

S IE M E N S

IS0

exchange1

'0

2

T'

a3!

T

T'a3!

S IE M E N S

*ig. 10 Internet"or+ interface to /ST

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2.2 Internetwork Interface !etween ISDN and CSPDN %"ele& Network

These internet"or+ interfaces are reall transitions !et"een net"or+s "ith differentnum!ering schemes& signaling #rotocols and transmission rates. These transitionsare accom#lished ! the usage of a su##lementar hard"are unit& the inter"or+ingsu##ort sstem. 'll calls !et"een su!scri!ers to the three net"or+s must no" !erouted o$er an inter"or+ing node of this t#e. Exactl ho" man inter"or+ing nodesare necessar to #ro$ide the re;uired net"or+ transitions de#ends on the net"or+structure of a s#ecific countr. The inter"or+ing node offers%

ser$ice con$ersion !et"een Telex and Teletex& and

internet"or+ interface !et"een IS and CS/ and3or Telex net"or+s.

The inter"or+ing also offers a range of su##lementar ser$ices such as%

multi-address ser$ice or delaed transmission&

#olling of Teletex messages stored in the inter"or+ing.

The functions listed can !e called onl ! dialing a director num!er access codeallo"ing access to such a inter"or+ing node and the re;uired function. *ollo"ing thisit is necessar to dial the director num!er of the su!scri!er in accordance "ith thenet"or+ num!ering scheme.

)o"e$er& the IS su!scri!er al"as re;uires a suita!le terminal in order to !e a!leto use these #ossi!ilities of communication "ith su!scri!ers to the CS/ or Telexnet"or+.

's *igure 11 sho"s& data transfer in the CS/ and IS is com#ati!le. Similarl&IS Teletex is com#ati!le "ith the CS/ Teletex and "ith Telex.

*urthermore& IS also su##orts the connection of the snchronous 7.21 interface.

)o"e$er& this re;uires a terminal ada#ter "hich con$erts the signaling and ada#tsthe transmission rate from 200 to (&000 !it3s.

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Inter"or+ingsu##ort sstem

-inter"or+ing

IS0exchange

7.21

CS/0

exchange

Telexexchange

S I E M E N S

'CCESS code

IS0director num!er

0ata transferSI E6 E1S

1 I70 89 *

SI E6 E1S

1 I70 89 *0ata transfer

SI E6 E1S

1 I70 89 *

Teletex

Telex

Teletex

Teletex

T

CS/03telexdirector num!er

'CCESS code

T'721

T'

721

E7

*ig. 11 Internet"or+ interface IS-CS/3telex

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2.' Internetwork Interface !etween ISDN and PSPDN'n inter"or+ing unit at the interface to the #ac+et-s"itched #u!lic data net"or+/S/ allo"s IS su!scri!ers to esta!lish data connections "ith su!scri!ers tothe /S/.

's an IS exchange can neither esta!lish an 72, call nor #erform the #ac+ets"itching re;uired su!se;uentl& such data connections re;uire su##lementarnodes that carr out these functions. These nodes are termed #ac+et handlers /).

The configuration sho"n in *igure 12 sho"s ho" the channel and A channel of theIS su!scri!er access the #ac+et-s"itched net"or+.

/S/ terminals can !e used as terminals in con>unction "ith a terminal ada#ter.)ere a distinction must !e made !et"een the follo"ing t"o ada#ter t#es% T' 7.2,Afor !it rates u# to ( +!it3s& and T' 7.2, for !it rates u# to . +!it3s. The T' 7.2,Asu##orts the #ac+et-data transfer ser$ice in the A channel& "hile the T' 7.2,su##orts the #ac+et-data transfer ser$ice in the channel.

The IS line leads from the net"or+ termination T to the IS exchange andcontinues u# to the #ac+et handler /). The /) is located !et"een IS and/S/. 'lthough logicall assigned to the IS& the /) ma #hsicall !e #art ofthe /S/.

Note:

If t"o 72, su!scri!ers "ho are !oth connected to an IS exchange "ish toesta!lish a #ac+et-data connection& this connection still has to !e routed $ia the /)&as onl the latter is a!le to #erform the call setu# and #ac+et s"itching.

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S I E M E N S

S I E M E N S

/S/01exchange

A 0

S I E 6 E 1 S

1 I 7 0 8 9 *

S IE 6 E 1 S

1 I7 0 8 9 *

7.2,

7.2,

7.2,

7.2,

T'

7.2,A

T'

7.2,0

1T

/ac+et

)andler

/)

IS01exchange

*ig. 12 Internet"or+ interface IS-/S/

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' Application to ISDN of te ()*ayer +odel

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The 8SI ?-laer model "as s#ecified ! the International Standards 8rgani=ation

IS8 to descri!e the communication !et"een t"o #rocessors com#uters. )o"e$er&the model can also !e a##lied to other communication modes e.g. the setu# oftele#hone calls. The model descri!es #rotocols and interfaces.

The interface !et"een exchange and su!scri!er is descri!ed ! the SS1 #rotocolSS1 igital Su!scri!er Signaling Sstem o. 1& "hich "as s#ecified ! ITU-T andis !ased on the 8SI ?-laer model. )o"e$er& the SS1 su##orts onl the functions ofHaers 1 to 4.

Layer model for the !ha""el

*or the exchange of user information $ia the A channel& circuit-s"itching

communications net"or+s #ro$ide onl a Haer 1 connection !et"een t"o terminals.The exchanges in$ol$ed s"itch trans#arent Haer 1 connections through theirs"itching net"or+s according to the signaling information recei$ed. The functions ofthe remaining laers 2 to ? are im#lemented in the terminals in accordance "ith theser$ice im#lemented in the gi$en case. Thus& the functions ha$e end-to-endsignificance onl.

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S I E M E N SS I E M E N S

Terminal

e;ui#ment

1 11

2

4

(

,

HaerHaer

A-channelA-channel

CCITT

9ecommen-

dation

I.(40 !asic

access

or I.(41

#rimar rate

access

IS

Haer

?

1

2

4

(

,

Haer

?

Terminal

e;ui#ment

E7 E7

*ig. 14 /rotocol architecture for transfer of user information in the A-channel

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Layer model for the D !ha""elITU-T has s#ecified the Haers 2 to 4 for the #rotected transmission of signaling inthe channel. *igure 1, !elo" sho"s the distri!ution of the laers for signalexchange !et"een t"o terminal e;ui#ments.

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S I E M E N S S I E M E N S

11

2

4

Haer

SS1

channel channel

CCITT recom-

mendations.G403I.(,0 and

.G413I.(,1.G203I.((0 and

.G213I.((1I.(40!asic accessor I.(41#rimar rate

access

Haer

IS

1

2

4

Haer

2

4

1

Haer

2

4

#erm$"al

e%&$'me"t

#erm$"al

e%&$'me"t

E7 E7

*ig. 1( /rotocol architecture for the transmission of signaling information in the - channel

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The functions of the laers are as follo"%

Layer 1 ('hy)$!al layer*

Haer 1 of the SS1 descri!es the #hsical and electrical attri!utes of thetransmission lin+. This includes the definition of the acti$ation and deacti$ation of thelin+ and the multi#lexing and demulti#lexing function i.e. assignment of the !its tothe a##ro#riate channels !it snchroni=ation. With this the Haer 1 offers asnchroni=ed lin+ that can !e used to transmit messages of the Haers 2 and 4.

Layer 2 (data l$"+ layer*

The Haer 2 connection must !e esta!lished !efore the exchange of Haer 4messages can !egin. This connection is +no"n as the ata Hin+ Connection. Haer 2allo"s se$eral data lin+ connections to !e esta!lished for the channel& and is alsores#onsi!le for flo" control . Haer 2 guarantees error-free message transmission:this function includes error detection and correction.

The #oints at "hich Haer 2 offers its ser$ices to Haer 4 are +no"n as Ser$ice'ccess /oints. These #oints are identified ! Ser$ice 'ccess /oint Identifiers S'/I.The terminal ha$ing to !e addressed is identified ! the Terminal End#oint IdentifierTEI. The TEI allo"s transmitted messages to !e sent to a s#ecific terminal.

T"o o#erating modes are defined for Haer 2 data lin+ laer. 8ne mode #rotectedtransmission o#erates "ith num!ered messages num!ered frames "hich must !eac+no"ledged. ' frame determined to !e fault or missing "ill !e retransmitted. Theother o#erating mode un#rotected transmission o#erates "ith unnum!eredmessages& meaning message loss or transmission errors cannot !e detected.

Layer 3 ("et,or+ layer*

Haer 4 is res#onsi!le for controlling the call setu# and cleardo"n. This functionincludes !oth the !asic call as "ell as the control of su##lementar su!scri!er

features. Haer 4 generates the messages necessar for its control tas+ and #assesthem to Haer 2 for trans#ortation. 't the recei$ing end Haer 4 is ca#a!le ofinter#reting the corres#onding messages.

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et"or+ laerentit

/hsical laer

entit

ata lin+ laerentit

/hsical laer

entit

ata lin+ laerentit

et"or+ laerentit

4

E-!ha".e

JSer$ice

#rimiti$esK

channel

HaerHaer

Haer 1 #rotocol

Haer 2 #rotocollogical connection

Haer 4 #rotocol

logical connection

2

1

4

JSer$ice

#rimiti$esK

2

1

#erm$"al e%&$'me"t

JSer$ice

#rimiti$esK

JSer$ice

#rimiti$esK

*ig. 1, Haers 1-4

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01 Tw2102eu01eg 0001 Introduction

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