E# REHABILITACIÓN DE CASETAS DEL CONJUNTO DEL C.E.P.A.J

Liaison has the ability to connect and communicate to the host systems in

ATL via asynchronous means, or "dial-up". The protocol standard used is called X.28. A local telephone number is provided by SITA to dial into a Packet Assembler / Dis-Assembler (PAD), which is the direct entry point into the SITA network.

The PAD qualifies the incoming request by verifying the account information

(NUI/Network Password) issued to the caller by SITA. After passing the account

verification level, SITA network searches for the Destination Network Address

(DNA) and, when found, connects into the host systems. Other layers of security

must then be satisfied, such as User ID/Password and host Sign-In. This

completes the process of connecting, and normal host transactions may now

commence.

Special note should be taken when considering host User Group, or the amount

of functionality allowed. Since X.28 connectivity utilizes Dynamic PIDs, there is a

limitation to User Group 17 and higher. This is an intentional security feature,

designed to inhibit functionality over the easy access dial-up provides.

Dynamic PIDs also have several other limitations. A permanent ZZ address may

not be established for dynamic PIDs. With dynamic PIDs, the PID changes each

time you connect. Since a ZZ address is tied to a specific PID, you cannot

assign a ZZ address to a dynamic PID. Also, Ticketing cannot be used on

dynamic PIDs. Both these limitations may be overcome at some point, so

contact Atlanta for a status update.

Asynchronous modems provide the means for communication from a PC. There

are literally hundreds of manufacturers offering several models each in the

market today. Most conform to conventional standards, such as Hayes. There

will be some, however, which do not completely comply. Anomalies will occur

during the dialing/handshake process in such cases. When this happens, it is

advisable to consult the user manual from the modem manufacturer for a

recommended initialization string. In some remote cases, connectivity may not

be achieved at all. Be sure your modem is Hayes compatible to avoid these

problems.

X.28 dialup is often confused with dialup TCP-IP. X.28 dialup uses a standard PC

modem. Dialup IP uses a router.

Configuration for X.28

From Step 5 in the Liaison Configuration Wizard, the "Protocol" selection box appears. Be sure this has been highlighted for "DialUp" for X.28 to be defined.

Click on OK to continue.

The next box to appear will be "Dial Up Properties". The settings in the upper portion of the box define the interaction between the PC, modem, and telephone line. The lower portions are values the SITA network requires to satisfy account information and security levels. Where the drop-down arrows are seen, values may be chosen

Dial Up Properties Field Descriptions

Number

This is the telephone number of the local PAD. If a dialing prefix is needed, type this in first, followed by a comma (,) or a "W" for a pause, needed for the second dial tone

Port Select the COM port the PC uses to connect itself to the modem Baud

Rate

This is the speed of line transmission (Bits Per Second). Be sure not to exceed the speed rating for the modem

Data Bits Select between 7 and 8. This setting depends on the modem (SITA ATL default is 8).

Parity Generally, this setting depends on the modem. Use "E" for Even, "O" for Odd, and "N" for None. (SITA ATL default is N)

Stop Bits Always leave in the default value of "1". However, it may be set to either "1.5" or "2", if required. (SITA ATL default is 1)

Modem 1 The modem initialization string, using Hayes standard dialogue. The default value is "ATV1E1".

Modem 2

Some modems require a second initialization string, separate from the first. This field may also be used to enable such Hayes features like "speaker on". A minimum character string of "AT" must appear in this field.

Interval Number of seconds between modem initialization steps. Must be a whole number, not a decimal or fraction

Time Out

If a connection has not been established within this number of seconds, the session is terminated and must be re-initiated. Recommended length is between 20-40 seconds

Dial Type For rotary telephone service, select "Pulse". For touch-tone service, select "Tone"

PAD Prompt

A character string sent to the PAD when it answers a call. This is a means of telling the PAD to respond. DO NOT change the values

The Network NUI value is obtained from SITA once an X.28 account is established. Based upon your geographic location the Network NUI and Password may be obtained from your SITA Account Manager.

Network NUI

The NUI and Password are issued upon receipt of an X.28 request. The NUI will be 8 characters long. The first 4 characters are controlled by the Liaison registration key and will appear on this screen automatically. If they appear incorrectly on this screen, you must obtain a modified registration key from

Liaison [email protected]

Network Password

Also obtained from SITA with the NUI. Strictly used for security match PAD ID

(DNA)

This is the Destination Network Address for ATLIS. Note the default (9001031,PDX28M) is for PSA connections. For PSB access it should read 9001181,PDX28M

Click on OK when all values have been entered. The wizard will present the next and final parameters for X.28 in a box labeled "Dynamic PID Properties". This information is

packaged into the X.28 packet header. Then delivers CONLNK elements to the host system for dynamic PID definition.

Following are explanations for each input field

Destination

The host code is placed here. The default is "X28DEV", which is the test system in ATL. For production access, change to either "X28PSA" or

"X28PSB", depending on which mainframe the target host resides. Presently, these are the only access host codes.

MCC Message Characteristics Character always leave this field in the default value of "M".

Country Code

Determines origin country for the terminal session. Use a valid two-letter ISO country code. This a mandatory field.

IATA Number Optional; enter an eight-digit IATA number if this location is a travel agency. TLX Address Optional; input the Teletype/Type B address associated with this location.

City Determines origin city for the terminal session. Use a valid three-letter IATA City code. This is a mandatory field.

PALC

Primary Airline Code is extracted from the registration key, and cannot be changed in this step. This must be your Airline Code or your agent sign-in will not be accepted.

SALC Secondary Airline Code; also extracted from the registration key, and cannot be changed.

Version Version: For information purposes only. Editing is not possible for this field. Screen Size

Defines the dimensions of the emulator display. The default is 24 lines by 80 columns, which is standard. Unless host requirements are different, it is recommended to use the default.

Department Use for AIRFARE definition only.

Click on OK when finished, the wizard will return to Step 5. This concludes the X.28 configuration.

7.3

Appendix C - Slow/No Response Analysis for TCP-IP Liaison