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AIXLink/X.25 1.1 for AIX: Guide and Reference

N_DISCON_REQ Primitive


Requests that an existing connection be disconnected.


This primitive consists of one M_PROTO message block with the following structure:

typedef struct {
   ulong PRIM_type;
   ulong DISCON_reason;
   ulong RES_length;
   ulong RES_offset;
   ulong SEQ_number;
} N_discon_req_t;

(Optionally followed by clear user data.)


The N_DISCON_REQ primitive requests that the network service (NS) provider either disconnect an existing connection or deny a request for a network connection. This primitive is user-originated.

The format of the message is one M_PROTO message block, followed by one or more M_DATA message blocks that indicate user data. Any integral number of octets of data, up to the network's clear user data limit, can be sent provided the length is even.


PRIM_type Specifies the N_DISCON_REQ primitive.
DlSCON_reason Not used since all calls are cleared with a diagnostic of 0 (zero).
RES_length Indicates the length of the responding address parameter. The responding address parameter is optional and is present if the primitive indicates rejection of an attempt by an NS user to establish a network connection. The responding address parameter conveys the network address of the NS user entity from which the N_DISCON_REQ primitive was issued. Under certain circumstances, such as call redirection and generic addressing, the value of the responding address parameter may be different from the destination address in the corresponding N_CONN_REQ primitive.
RES_offset Specifies where the responding address begins. The value of this parameter is the offset from the beginning of the M_PROTO message block.
SEQ_number Identifies the sequence number of an N_CONN_IND primitive. This parameter can have two types of values:
>0 Identifies the sequence number of the rejected N_CONN_IND message. NPI uses this number to associate the N_DISCON_REQ primitive with an unacknowledged N_CONN_IND primitive that is to be rejected.
0 Indicates the N_DISCON_REQ primitive is rejecting an established network connection (NC).


The NS provider should generate one of the following acknowledgments upon receipt of this primitive:

Successful Indicated by the N_OK_ACK primitive.
Unsuccessful Non-fatal errors are indicated by the N_ERROR_ACK primitive.

Error Codes

The applicable non-fatal errors are as follows:

NOUTSTATE Indicates the primitive was issued from an invalid state.
NBADDATA Indicates the amount of user data specified was outside the range supported by the NS provider.
NSYSERR Indicates a system error. The error is indicated in the primitive.
NBADSEQ Indicates one of the following conditions:
  • The specified sequence number referred to an invalid N_CONN_IND primitive.
  • The primitive attempted to reject an established NC, but the value of the sequence number was not 0.
  • The primitive attempted to reject an unconfirmed N_CONN_REQ primitive, but the value of the sequence number was not 0.

Implementation Specifics

The N_DISCON_REQ primitive is part of X.25 Licensed Program.

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