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Solstice X.25 9.2 Developer's Guide

6.3.3 extraformat--Define Standard X.25 Facilities

Standard X.25 facilities are defined by the extraformat structure:

Example 6-4 extraformat Structure

#define MAX_NUI_LEN   64
 #define MAX_RPOA_LEN  8
 #define MAX_CUG_LEN   2
 #define MAX_FAC_LEN   109
 #define MAX_TARIFFS   4
 #define MAX_CD_LEN    MAX_TARIFFS * 4
 #define MAX_SC_LEN    MAX_TARIFFS * 8
 #define MAX_MU_LEN    16

 struct extraformat {
 /* extraformat structure */
         unsigned char     fastselreq;
         unsigned char     restrictresponse;
         unsigned char     reversecharges
         unsigned char     pwoptions;
         unsigned char     locpacket, rempacket;
         unsigned char     locwsize , remwsize;
         int               nsdulimit;
         unsigned char     nui_len;
         unsigned char     nui_field[MAX_NUI_LEN];
         unsigned char     rpoa_len;
         unsigned char     rpoa_field[MAX_RPOA_LEN];
         unsigned char     cug_type;
         unsigned char     cug_field[MAX_CUG_LEN];
         unsigned char     reqcharging;
         unsigned char     chg_cd_len;
         unsigned char     chg_cd_field[MAX_CD_LEN];
         unsigned char     chg_sc_len;
         unsigned char     chg_sc_field[MAX_SC_LEN];
         unsigned char     chg_mu_len;
         unsigned char     chg_mu_field[MAX_MU_LEN];
         unsigned char     called_add_mod;
         unsigned char     call_redirect;
         struct lsapformat called;
         unsigned char     call_deflect;
         unsigned char     x_fac_len;
         unsigned char     cg_fac_len;
         unsigned char     cd_fac_len;
         unsigned char     fac_field[MAX_FAC_LEN];
 };

The members of this structure are defined as follows:

Table 6-6 Members of extraformat Structure

Member 

Description 

fastselreq

Applies only to non-OSI applications, for example X.29. A non-zero value means the X.25 facility fast select is to be requested or indicated.

restrictresponsee

Sets response to be a Clear Request. 

reversecharges

A non-zero value means that reverse charging is requested or indicated for this connection

pwoptions

Indicates per virtual-circuit options. The field is a bit map with the following interpretation: 

bit 0: 0 - Packet size negotiation NOT permitted.  

1 NEGOT_PKT - Packet size negotiation permitted.

bit 1: 0 - Window size negotiation NOT permitted.  

1 NEGOT_WIN - Window size negotiation permitted.

bit 2: 0 - No concatenation limit asserted.  

1 ASSERT_HWM - Assert concatenation limit.

This field is used for two reasons: 1) The X.25 software always indicates the values of the window and packet sizes operating on the virtual circuit. However, the field pwoptions for an incoming call indicates whether these values are negotiable. 2) In Call Requests and Call Responses the NLI user can set a limit value, nsdulimit, for packet concatenation by the X.25 level that differs from the limit in the subnetwork configuration database. It is not a negotiable option, so that whatever the user has requested is used.

locpacket

Contains the packet size for local-to-remote calls, using the following notation: the actual packet size is 2 to the power of the value specified. For example if the field locpacket is set to 7, the actual packet size is 27 or 128.

rempacket

Contains the packet size for remote-to-local calls, using the following notation: the actual packet size is 2 to the power of the value specified. For example if the field rempacket is set to 7, the actual packet size is 27 or 128.

locwsize

The window sizes for local-to-remote calls.  

remwsize

The window sizes for remote-to-local calls. 

nsdulimit

Specifies the packet concatenation limit. 

nui_len

The length of any Network User Identification used in Call Requests and Responses. 

nui_field

Network User Identification used in Call Requests and Responses. This is not available on X.25 (80) networks.

rpoa_len

The length of any RPOA DNIC information used in Call Requests. Valid values for rpoa_len are 0, 4, 8, 12 and 16.

rpoa_field

Any Recognized Private Operating Agency (RPOA) DNIC information. This is used in Call Requests only. It is stored as two BCD digits per byte, right justified. 

On X.25 (80) networks, this is restricted to one RPOA of 4 BCD digits. Basic format encoding is used.  

On X.25 (84) and X.25 (88) networks, there can be one or more RPOAs. Extended format encoding is used if there is more than one RPOA. The maximum number of RPOAs is 4.  

cug_type

Possible values are: 

CUG -- Closed User Group  

BCUG -- Bilateral CUG 

0--No CUG used 

cug_field

Any applicable CUG information, stored as two BCD digits per byte, right justified.

Note: Incoming Closed User Group facilities are assumed to have been validated by the network. No further checking is performed.  

reqcharging

Requests call charging in a Call Request or Connect Accept. 

chg_cd_len

Gives length of chg_cd_field.

chg_cd_field

Specifies duration of the call if call charging is in use. Used in a Disconnect Indication or Confirm. 

chg_sc_len

Gives length of chg_sc_field.

chg_sc_field

Specifies segment count if call charging is in use. Used in a Disconnect Indication or Confirm. 

chg_mu_len

Gives length of chg_mu_field.

chg_mu_field

Specifies monetary unit if call charging is in use. Used in a Disconnect Indication or Confirm. 

called_add_mod

A one byte field holding the reason for any address modification as defined in the X.25 Recommendation, encoded as follows: 

X0000001--Called DTE busy. Call redirected. X0000111--Call distribution within hunt group. X0001001--Called DTE out of order. Call redirected. X0001111--Called DTE has requested systematic redirection. 11000000--Called DTE deflected call.

11000001--Called DTE busy. Gateway redirected call. 11001001--Called DTE out of order. Gateway redirected call.

11001111--Called DTE has requested systematic redirection. Gateway redirected call.

X indicates that this bit is 0 if the address modification occurred in a public data network and 1 if it occurred in a private network.

call_redirect

A one byte field holding the reason for a call redirection as defined in the X.25 Recommendation, encoded as follows: 

00000001--Called DTE busy. Call redirected. 00000111--Call distribution within hunt group. 00001001--Called DTE out of order. Call redirected. 00001111--Called DTE has requested systematic redirection. 11000000--Called DTE deflected call.

11000001--Called DTE busy. Gateway redirected call. 11001001--Called DTE out of order. Gateway redirected call.

11001111--Called DTE has requested systematic redirection. Gateway redirected call.

called

Supplies the originally-called DTE address. 

call_deflect

A one byte field holding the reason for a call deflection as defined in the X.25 Recommendation, encoded as follows: 

11000000--Called DTE deflected call.

11000001--Called DTE busy. Gateway redirected call. 11001001--Called DTE out of order. Gateway redirected call.

11001111--Called DTE has requested systematic redirection. Gateway redirected call.

deflected

In a Clear Request, contains the DTE address, and if required, the NSAP that a call is to be deflected to. 

x_fac_len

Indicates the length of a fac_field relating to X.25 facilities.

cg_fac_len

Indicates the length of a fac_field relating to non-X.25 facilities for the calling network.

cd_fac_len

Indicates the length of a fac_field relating to non-X.25 facilities for the called network.

fac_field

This field is used in Call Requests and Connect Accepts only. It allows for the passing of explicit facility encoded strings for X.25 facilities, and non-X.25 facilities for calling and called networks.  

Note -

The contents of this field, are not validated or acted upon by the code. The X.25 facilities are inserted at the end of any other X.25 facilities which are passed in the Call Request/Accept (for example, packet/window sizes). If any non-X.25 facilities are supplied the appropriate marker is inserted before the supplied facilities. Take care not to duplicate any facilities.