4-BITS

4-BITS

8-BITS

8-BITS

GFI

LGN

LCN

PACKET
TYPE

CALL REQUEST

0B

4-BITS

4-BITS

VARIABLE

VARIABLE

8-BITS

63-BYTE MAX.

4-BYTES

12-BYTES

CALLING
ADDR. LGH.

CALLED
ADDR. LGH.

CALLED ADDR.

CALLED ADDR.

FACILITIES
LGH:

FACILITIES

P.I.D.

USER DATA

CALL ACCEPT

0F

CALLING
ADDR. LGH.

CALLED
ADDR. LGH.

CALLED ADDR.

CALLING ADDR.

FACILITIES
LGH:

FACILITIES

DATA

876

5

432

1

(UP TO 128 BYTES U.S.A.) 256 DATAPAC

P(R)

M

P(S)

0

USER DATA

RESET REQUEST

1B

8-BITS

8-BITS

RESET CAUSE

DIAGNOSTIC CODE OPTIONAL

RESTART REQUEST

FB

RESTART CAUSE

DIAGNOSTIC CODE OPTIONAL

CLEAR REQUEST

13

CLEARING CAUSE

DIAGNOSTIC CODE OPTIONAL

DIAGNOSTIC

F1

DIAGNOSTIC CODE

DIAGNOSTIC EXPLANATION

INTERRUPT

23

INTERRUPT USER DATA

RECEIVE READY

P(R)

0

000

1

RECEIVE NOT READY

P(R)

0

010

1

REJECT

P(R)

0

100

1

INTERRUPT CONFIRMATION

27

CLEAR CONFIRMATION

17

RESTART CONFIRMATION

FF

RESET CONFIRMATION

1F

HEX. VALUE

REASON

CLR

00

DTE Originated

DTE

01

Out of Order (PVC)

DER

03

Remote Procedure Error

RPE

05

Local Procedure Error

ERR

07

Network Congestion

NC

9

Remote DTE Operational (PVC)

DTO

OF

Network Operational (PVC)

NO

11

Incompatable Destination

ICD

HEX. VALUE

REASON

CLR

00

DTE Originated

DTE

01

Number Busy

OCC

03

Invalid Facility Request

INV

05

Network Congestion

NC

09

Out of Order

DER

0B

Access Barred

NA

0D

Not Obtainable

NP

11

Remote Procedure Error

RPE

13

Local Procedure Error

ERR

15

RPOA Out of Order

RP

19

Collect Call Refused

NRC

21

Incompatable Destination

ICD

29

Fast Select Not Subscribed

NFS

41

Buffer Overflow (Dynapac)

OVF

HEX. VALUE

REASON

00

DTE Originated

01

Local Procedure Error

03

Network Congestion

07

Network Up

HEX. VALUE

REASON

00

No Specific Code

0X

Invalid P(S) or P(R)

1X

Invalid Packet Type

2X

Packet Not Allowed

3X

Timer Expired

4X

Call Setup Problem

50 to 7F

Not Assigned

80 to FF

Network Specified

Refer to CCITT X.25 For Values of the X Variable.

GFI (General Format Identifier)

BIT 8

Q BIT (Data Qualifier) DATA PKTS ONLY
Q = 0: DATA PACKET contains user data
Q = 1: DATA PACKET contains control data

BIT 7

D BIT (Delivery Confirmation)
D = 0: End Ack not required
D = 1: End to End Ack required

BIT 6

When Set, P(S) and P(R) counters in the
DATA Packets are modulo 128

BIT 5

When Set, P(S) and P(R) counters in the
DATA packets are modulo 8

CLASS

FACILITY
CODE

HEX
VALUE

PARM.
LENGTH

PARAMETER
FIELD

A

1 BYTE

00

___

1 BYTE

B

1 BYTE

01

___

2 BYTES

C

1 BYTE

10

___

3 BYTES

D

1 BYTE

11

MORE THAN 3 BYTES

FACILITY FIELD

CLASS
IDENT.

FACILITY TYPE

LEADING OCTETS

1

2

3

CODE

VALUE

VALUE

A

Closed User Group

03

XX

___

A


A

National Options Marker
(Calling Network Facilities)

National Options Marker
(Called Network Facilities)

00


00

00


FF

A
A
A

Reverse Charging
Fast Select
Reverse Charge and Fast Select

01
01
01

01
X0
X0

A

Datapac Priority

01

02

A
B
B

Throughput Class
Window Size
Packet Size

02
43
42

01
0X
0X

0X
0X

D

Call Duration

C1

LGH. 04

XX

Refer to CCITT X.25 For Values of the X Variable and Other Facilities.

Bits 8,7

Recommended Use

0 0

CCITT Recommendations (ex. X.29)

0 1

CCG (DATAPAC)

1 0

Res. for International Users (ISO)

1 1

User Defined