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Technical Guide to DataPac Brought

Found at: 0x1bi.net:70/textfiles/file?internet/datapac.inf


 ----------------------------------

 --- Technical Guide to DataPac ---

 --- Brought to you by the      ---

 --- NEW Dark Council (1990)    ---

 ----------------------------------

 --- If you can stand reading   ---

 --- through this entire        ---

 --- document, you are a boring ---

 --- person.  Go out and get    ---

 --- laid!                      ---

 ----------------------------------


  Here is the technical "About DataPac" document so efficiently stolen

from the DataPac information service. (Data


  It probably won't teach you much, but it might be nice to have around

f you ever need to do something out of the ordinary.

DATAPAC FAMILY OF SERVICES

--------------------------


DATAPAC 3000

------------

DATAPAC 3000 IS A SYNCHRONOUS, APPLICATION INDEPENDENT SERVICE THAT

ALLOWS DATA TERMINALS (DTE'S) AND DATA COMMUNICATING EQUIPMENT (DCE)

TO EXCHANGE DATA IN A PACKET-MODE OVER A PUBLIC OR PRIVATE PACKET

SWITCHING NETWORK.


THE DTE/DCE INTERFACE CONNECTION, DISCONNECTION AND TRANS

MISSION RULES

ARE DEFINED IN A PACKET SWITCHING PROTOCOL CALLED X.25 RECOMMENDATION

WHICH IS DEVELOPED AND GOVERNED BY THE INTERNATIONAL TELEPHONE AND

TELEGRAPH CONSULTATIVE COMMITTEE (CCITT).


HIGH LEVEL DATA LINK CONTROL (HDLC).  THE CCITT RECOMMENDATIONS

FOR X.25 ARE DIVIDED INTO THREE LEVELS, NAMELY:


THE PHYSICAL  INTERFACE (LEVEL 1);


THE FRAME LEVEL LOGICAL INTERFACE  (LEVEL 2);


THE PACKET LEVEL LOGICAL INTERFACE (LEVEL 3).


LEVEL 1


SPE

CIFIES THE USE OF FOUR-WIRE, POINT-TO-POINT SYNCHRONOUS

CIRCUIT BETWEEN THE DTE AND THE NETWORK (DCE). THIS CIRCUIT

THE OTHER CONNECTED TO THE NETWORK).


TYPICAL CHARACTERISTICS ARE:


- 4-WIRE POINT-TO-POINT OR DIAL VIA A V.22 BIS MODEM;


- FULL DUPLEX ;


- EIA RS232 CONVENTION.



MODEM/DATASET

LEVEL 2 - DEFINES THE FRAME LEVEL LINK PROCEDURES USED TO SYNCHRONIZE

          TRANSMISSION, INITIATE THE "HANDSHAKING" NECESSARY TO

          ESTABLISH

THE 'R-U-THERE'/YES-I-AM SEQUENCE, FLOW CONTROL

          MECHANISM AND PERFORM ERROR CHECKING OF DATA EXCHANGE

          ACROSS THE DTE/DCE INTERFACE (LINK).  THE DTE IS

          USUALLY LOCATED AT THE CUSTOMER PREMISES AND IS CALLED

          HOST WHILE THE DCE IS LOCATED IN THE NETWORK. THE PROCEDURES

          USED TO CONTROL THE LINK ARE DEFINED AS COMMANDS AND RESPONSES.


          CHARACTERISTICS ARE:


                            - HDLC;


                            - LINK ACCESS PROCEDURE -BALANCED

 (LAPB)


                            - X.25(80) OR X.25(84).




LEVEL 3 - DEFINES THE PACKET FORMATS AND CONTROL PROCEDURES REQUIRED

          TO ESTABLISH A LOGICAL PATH (CALL REQUEST), EXCHANGE

          INFORMATION (DATA PACKETS) AND FOR REMOVING THE LOGICAL

          PATH (CLEAR REQUEST) BETWEEN THE DTE AND DCE.


          CHARACTERISTICS ARE:

                           - LOGICAL CHANNELS (LCN`S)


                           - PACKET SIZE


                           - WINDOW SIZE



    - THROUGHPUT CLASS


                           - ETC



HOW IT WORKS

------------


THE CUSTOMER'S TERMINAL (HOST) IS CONNECTED TO A LOCAL MODEM

WHICH IN TURN, IS CONNECTED TO A SECOND MODEM (REMOTE) IN THE

CENTRAL OFFICE VIA BY 4 WIRES WHICH IN TURN, IS CONNECTED

TO A LINE PROCESSING MODULE IN THE DATAPAC NETWORK. THIS

CONFIGURATION IS CALLED THE DTE/DCE LINK AND CAN BE

ASSIGNED SPEEDS OF 1200 BPS THROUGH 19200 BPS.


THIS DTE/DCE LINK IS ASSIGNED A UNIQUE DATAPAC NETWORK ADDRESS

(DNA) AND OTHER LINK PARA

METERS SUCH AS LINE SPEED, MODEM TYPE,

FLOW CONTROL AND SECURITY BY TELECOM CANADA.


WHEN THE ELECTRICAL SIGNALS ARE IN THE CORRECT STATE AS

SPECIFIED IN LEVEL 1, THE DATAPAC LINE PROCESSING MODULE

CONTINUOUSLY TRANSMITS A CCITT COMMAND CALLED SABM (SET

ASYNCHRONOUS BALANCED MODE) TO THE CUSTOMERS'S TERMINAL

(HOST) EVERY THREE SECONDS.  IF THE HOST IS READY, IT

RESPONDS TO THE SABM WITH A CCITT RESPONSE UA (UNNUMBERED

ACKNOWLEDGEMENT).  WHEN THIS OCCURS, THE LINK IS INITIALIZED

(LEVEL 2 READY), THE HOST AND

 DATAPAC MODULE EXCHANGE

RESTARTS OR RESTART/RESTART CONFIRMATION COMMANDS.

WHEN THIS OCCURS, THE DTE/DCE LINK GENERATES A TRANSITION

TO THE NEXT X.25 LEVEL. LEVEL 3.


THE DTE THEN SIGNALS THE ADDRESS IT WISHES TO COMMUNICATE

WITH IN A CCITT DEFINED CALL REQUEST FORMAT (8 DIGITS ), 10

DIGITS IF USING 9TH AND 10TH DIGIT SUBADDRESSING ON A LOGICAL

CHANNEL (LCN)DATAPAC THEN ROUTES THE CALL REQUEST TO THE APPROPRIATE

DESTINATION (NATIONAL OR INTERNATIONAL) AND AWAITS A CCITT

DEFINED CALL ACCEPT PACKET. IF THIS

OCCURS, THE ACCEPT PACKET IS

TRANSMITTED BACK TO THE ORIGINATING HOST AND BOTH HOSTS MAY NOW

EXCHANGE CCITT DEFINED DATA PACKETS.  THIS IS CALLED A SWITCHED

VIRTUAL CALL (SVC); PERMANENT VIRTUAL CALLS (PVC'S) ARE ALSO

OFFERED.  AT THE END OF THE SESSION, EITHER HOST CAN TERMINATE THE SVC

BY TRANSMITTING A CCITT DEFINED CLEAR REQUEST PACKET.  UP TO 255 SVC'S

MAY BE SUPPORTED SIMULTANEOUSLY.



DIAL ACCESS SERVICE IS ALSO OFFERED AT 2400BPS WITH

A MAXIMUM OF EIGHT LCN'S OVER THE PUBLIC TELEPHONE NETWORK



BENE

FITS

========


DATAPAC 3000 PROVIDES CUSTOMERS WITH A COST EFFECTIVE SERVICE

DERIVED FROM PACKET SWITCHING TECHNOLOGY AND X.25 PROTOCOL.

SOME BENEFITS ARE:


DEDICATED OR DIAL-IN ACCESS


 - SIMULTANEOUS COMMUNICATION WITH MANY (UP TO 255) DIFFERENT

   LOCATIONS - NATIONAL AND INTERNATIONAL;


 - ERROR FREE TRANSMISSION;


 - SYSTEM EXPANSION FLEXIBILITY;


COMMUNICATION UNIVERSALITY

- COST CONTAINMENT THROUGH REDUCED HOST PORT CONNECTIONS;


- 24 HOURS 7 DAYS-A-WEEK SERVICE



- LOWER COMMUNICATION COSTS;


- CALL

 PARAMATER SELECTION TO SUIT PARTICULAR APPLICATIONS.



CALL OUR TELEMARKETING STAFF AT 1-800-268-9102 FOR MORE

________-


DATAPAC FAMILY OF SERVICES

==========================


DATAPAC 3101

------------


DATAPAC 3101 IS A NETWORK ACCESS SERVICE WHICH ENABLES TELETYPEWRITER

COMPATIBLE DEVICES, SUCH AS TIME-SHARING TERMINALS, TO ACCESS THE

DATAPAC NETWORK.


LOW SPEED, ASYNCHRONOUS DEVICES ARE SUPPORTED THROUGH AN INTERACTIVE

TERMINAL INTERFACE (I

TI) IN A PACKET ASSEMBLER/DISASSEMBLER (PAD),

WHICH ALLOWS THE DEVICES TO ACCESS THE NETWORK OVER DIAL-UP (DDD)

OR DEDICATED ACCESS LINES.


RECOMMENDATIONS X.3, X.28 AND X.29 AND SUPPORTS ACCESS TO THE

DATAPAC NETWORK FOR ASYNCHRONOUS, START-STOP CHARACTER MODE TERMINALS.


FOR THE TWELVE INTERNATIONAL PARAMETERS AND THEIR OPERATION.  ADDITIONAL

DOMESTIC PARAMETERS ARE A

LSO IN PLACE TO MEET CANADIAN MARKET REQUIREMENTS.


THE DATA TRANSFER MODE.


ACCESS AND MODIFY THE PARAMETERS IN THE PAD AS WELL AS THE DATA

TRANSFER PROCEDURE.


THE USER NEEDS NO SPECIAL HARDWARE OR SOFTWARE TO INTERFACE A

TERMINAL TO THE DATAPAC NETWORK.  A KNOWLEDGE OF THE ITI PROCEDURES

NT AT THE TERMINAL END.


THE DATAPAC 3101 SERVICE PROVIDES FOR TERMINAL TO HOST (USER'S

COMPUTER) AND TERMINAL TO TERMINAL COMMUNICATION.  THE HOST ACCESS

SHOULD CONFORM WITH THE X.25 PROTOCOL, USING THE DATAPAC 3000 ACCESS

SERVICE, AND ALSO SUPPORT THE HIGHER LEVEL PROTOCOL CONVENTIONS OF ITI.

HOST ACCESS MAY ALSO BE PROVIDED VIA THE DATAPAC 3101 SERVICE FOR SOME

APPLICATIONS.  THE DATAPAC 3101 SERVICE ALSO PROVIDES BLOCK MODE AND TAPE

SUPPORT.

____


DATAPAC FAMILY OF SERVICES

==========================


D

ATAPAC 3201

------------



NETWORK ACCESS SERVICE WHICH ENABLES VARIOUS TERMINALS

THAT ARE BUFFERED, POLLABLE AND OPERATE ASYNCHRONOUSLY TO COMMUNICATE WITH

HOST COMPUTERS THROUGH THE DATAPAC NETWORK.


APPLICATIONS

------------


THE DATAPAC 3201 SERVICE IS TYPICALLY USED BY THE GENERAL MERCHANDISE AND

SPECIALITY SECTORS OF THE RETAIL INDUSTRY IN CANADA.  IT PROVIDES A COST

EFFECTIVE COMMUNICATION SOLUTION WHENEVER THERE IS A REQUIREMENT FOR

SENDING SMALL AMOUNTS OF INFORMATION TO A HOST COMPUTER AND OBTAINI

NG A

SHORT RESPONSE.  THE PRIMARY APPLICATIONS ARE ON-LINE COMPILATION OF

SALES DATA TO HELP IN INVENTORY CONTROL, AND ON-LINE CREDIT VERIFICATION

TO DETECT FRAUDULENT CREDIT CARDS.  OTHER EMERGING APPLICATIONS INVOLVE

TRUST COMPANIES, CREDIT UNIONS, BANKS AND SERVICE STATIONS.


ACCESS ARRANGEMENTS

-------------------


DATAPAC 3201 PROVIDES SUPPORT AT THE CUSTOMERS' TERMINAL END (FOR EXAMPLE

A RETAIL STORE) BY MEANS OF A PACKET ASSEMBLER/DISASSEMBLER (PAD) WHICH IS

LOCATED IN A TELECOM CANADA MEMBER COMPANY

 CENTRAL OFFICE.  THE PAD

ENVIRONMENT.


DEVICES MAY COMMUNICATE TO THE PAD VIA TWO OPTIONS:


----------------


COMMUNICATION BETWEEN THE PAD AND THE TERMINAL CONFORMS TO THE ANSI

(AMERICAN NATIONAL STANDARDS INSTITUTE) X3.28-1976 ISO (INTERNATIONAL

STANDARDS ORGANIZATION) POLL/SELECT ASYNCHRONOUS PROTOCOL.  TELECOM CANADA

UNDERTAKES T

O TEST TERMINALS WHICH SUPPORT THIS PROTOCOL, PRIOR TO

CONNECTING THEM TO THE DATAPAC 3201 NETWORK.  FOR MORE INFORMATION REFER 

TO THE "RAPID TERMINAL COMMUNICATION PROTOCOL" SPECIFICATION.


COMMUNICATION BETWEEN THE CUSTOMERS HOST COMPUTER LOCATION AND THE

DATAPAC NETWORK IS ACCOMPLISHED BY THE USE OF A X.25 (DATAPAC 3000)

(POS) END TO END PROTOCOL" SPECIFICATION.


COMMUNICATION RESPONSE TIME

---------------------------


- DATA COLLECTIO

N:  AVERAGE 1.7 TO 2.3 SECONDS IN THE PEAK PERIODS.


- INQUIRY-RESPONSE (CREDIT CHECK):  AVERAGE 2.7 TO 4.2 SECONDS IN

  THE PEAK PERIODS.


MESSAGE SIZE

------------


A TYPICAL RETAIL DATAPAC 3201 APPLICATION USES SHORT INPUT AND OUTPUT

MESSAGES.  (FOR EXAMPLE AN AVERAGE OF 50 CHARACTERS).  ONE KILOPACKET

(1,000 PACKETS OR 256,000 BYTES) IS EQUAL TO APPROXIMATELY 1,000 SALES

TRANSACTIONS OR 500 CREDIT AUTHORIZATIONS.  AVERAGE TRANSACTION VOLUME 

WOULD BE LESS THAN 5000 PACKETS PER DAY.


OPTIONAL DATAPAC NET

WORK FEATURES:

---------------------------------


CLOSED USER GROUP (CUG):  ALLOWS DEVICES WITHIN ONE GROUP TO COMMUNICATE

                          ONLY WITH ACCREDITED DEVICES OF THE SAME GROUP,

                          RESULTING IN A HIGH DEGREE OF DATA SECURITY.

                          ADDITIONAL OPTIONS ARE AVAILABLE TO LIMIT CALL

                          ATTEMPTS BETWEEN CLOSED USER GROUPS OR WITHIN A

                          CLOSED USER GROUP.


REVERSE CHARGE CALL:      ALLOWS A USER TO CHARGE A

 CALL TO THE DESTINATION

                          ADDRESS


REVERSE CHARGE CALL

BLOCKING:                 REVERSE CHARGED CALLS DESTINED TO A DATAPAC 3201

                          ADDRESS WILL BE BLOCKED BY THE NETWORK.


 Whew!  I probably didn't get all of it, but hey, I'm lazy, and I am not

about to read through it all too see if it makes sense! 


Your Phriend,


Lithium

__________________________________________________________________________


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