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NAME

libngatm - "ATM signalling library"

CONTENTS

Library
Synopsis
Description
Library Configuration
Information Elements
Messages
Contexts
See Also
Standards
Authors

LIBRARY

Begemot ATM signalling library (libngatm, -lngatm)

SYNOPSIS


.In netnatm/msg/unistruct.h
.In netnatm/msg/unimsglib.h

DESCRIPTION

The libngatm library handles UNI 4.0 messages. For each information element and message type the header files contain a structure definition. Additionally there are a number of help structures and a global context structure for some of the library functions. This document only describes the common structures. For information element and message structures see the header files.

LIBRARY CONFIGURATION

When the library is compiled a number of constants are define in the file uni_config.h. They define certain limits. Because of the use of these definitions a change in any of them requires a complete recompilation of all library code and all code that uses the library. The following constants are defined (they value behind the name is the default value):
UNI_MAX_ERRIE( 50)
When decoding information elements and analyzing them the library fills an array in the context with the identifiers of IEs that had errors. This is the size of this array.
UNI_NUM_IE_GIT( 3)
A message is allowed to contain more than one General Identifier Transport information element. This is the maximum supported number of these IEs.
UNI_NUM_IE_BLLI( 3)
The maximum number of BLLI information elements in a SETUP message.
UNI_NUM_IE_CALLEDSUB( 2)
The maximum number of Called Subaddress information elements in a SETUP message.
UNI_NUM_IE_CALLINGSUB( 2)
The maximum number of Calling Subaddress information elements in a SETUP message.
UNI_NUM_IE_TNS( 4)
The maximum number of Transit Network Selection information elements in a SETUP message.
UNI_TNS_MAXLEN( 4)
The maximum size of a name in the TNS IE.
UNI_UU_MAXLEN( 128)
Maximum size of user data in the UU IE.
UNI_ADDR_MAXLEN( 20)
Maximum address size.
UNI_SUBADDR_MAXLEN( 20)
Maximum subaddress size.
UNI_NUM_IE_DTL( 10)
Maximum number of DTL information elements in a SETUP message.
UNI_DTL_MAXNUM( 20)
Maximum number of identifiers in one DTL information element.

INFORMATION ELEMENTS

Each information element structure starts with a field of type:
struct uni_iehdr {
enum uni_coding coding; /* coding standard */
enum uni_ieact act; /* action indicator */
u_int pass:1; /* PNNI pass along request */
u_int present;/* which optional elements are present */
};

The coding field is the coding standard of the information element and may be one of UNI_CODING_ITU or UNI_CODING_NET. The action indicator act is used for error processing and is one of:

UNI_IEACT_CLEAR
clear call
UNI_IEACT_IGNORE
ignore IE and proceed
UNI_IEACT_REPORT
ignore IE, report and proceed
UNI_IEACT_MSG_IGNORE
ignore message
UNI_IEACT_MSG_REPORT
ignore message and report
UNI_IEACT_DEFAULT
the use action indicator flag was not set.

For information elements in PNNI message the pass fields contains the pass along flag from the IE header.

The present field is a bit field, which contains four common bits describing the current state of the information element. The rest of the bits are used by the information elements to indicate which of the optional fields of the IE are present. Most of the IE header files contain definitions for those bits. The common bits are:
#define UNI_IE_EMPTY 0x80000000
#define UNI_IE_PRESENT 0x40000000
#define UNI_IE_ERROR 0x20000000
#define UNI_IE_XXX 0x10000000

The flag UNI_IE_EMPTY indicates that the information element is present, but empty (its length is zero). This is legal for all information elements. The flag UNI_IE_PRESENT indicates that the IE is present in the message and the flag UNI_IE_ERROR indicates that the IE had an error. The flag UNI_IE_XXX is currently not used.

The following macros may be used to test or change these flags:

IE_ISPRESENT
Check whether the IE is present and not empty. Returns true in this case.
IE_SETPRESENT
Set the IE to be present and not empty.
IE_ISEMPTY
Check whether the IE is present and empty. Returns true in this case.
IE_SETEMPTY
Set the IE to be present and empty.
IE_ISERROR
Check whether the IE is present and has an error. Returns true in this case.
IE_SETERROR
Sets the IE to be present and to have an error.
IE_ISGOOD
Checks whether the IE is present, not empty and without error. Returns true in this case.

For each IE type there is an
.Vt enum uni_ietype definition of the form UNI_IE_* in uni_hdr.h.

unistruct.h contains a
.Vt union uni_ieall that is the union of all IE structures and a
struct uni_ie {
enum uni_ietype ietype;
union uni_ieall u;
};

MESSAGES

Each message structure starts with a
struct uni_msghdr {
struct uni_cref cref;
enum uni_msgact act; /* action indicator */
u_int pass:1; /* PNNI pass along request */
};

The cref is the call reference:
struct uni_cref {
u_int flag;
u_int cref;
};

There are two special call references: CREF_GLOBAL and CREF_DUMMY. The act field is the message action indicator and has one of the following values:

UNI_MSGACT_CLEAR
clear call
UNI_MSGACT_IGNORE
ignore message
UNI_MSGACT_REPORT
send STATUS message
UNI_MSGACT_DEFAULT
default handling for this message type

The pass field is the pass along indicator in the case of PNNI messages.

For each message type there is a
.Vt enum uni_msgtype definition of the form UNI_* in uni_hdr.h. uni_struct.h contains a
.Vt union_msgall that is the union of all message structures and a
struct uni_all {
enum uni_msgtype mtype;
union uni_msgall u;
};

CONTEXTS

The header file unimsglib.h contains a definition of a
.Vt struct uni_context that is used to minimize the number of arguments passed to certain functions and to avoid the use of global variables. This structure has the following public fields (all other fields are used internally by the library):
err This is an array consisting of the following structures:
struct uni_ierr {
enum uni_ierr_type err; /* what error */
enum uni_ieact act; /* the action indicator */
u_int ie:8; /* the ie type */
u_int man:1; /* mandatory flag */
u_int epref:1;/* Q.2971 9.5.3.2.1 low-pri epref */
};

When decoding information elements the information about IEs with errors is stuffed into this array.
errcnt
The current number of IEs in err.
q2932 Enable the Q.2932.1 Generic Functional Protocol. Currently only message and IE decoding/encoding is supported. The signalling part is still missing.
pnni Enable PNNI extensions. Currently only message and IE decoding/encoding is supported. The signalling part is still missing.
git_hard
Do hard checking on GIT information elements.
bearer_hard
Do hard checking on Broadband Bearer IEs. This involves rejecting old bearer type values.
cause_hard
Do hard checking on Cause information elements.
multiline
This is used by the printing routines. Legal values are 0 to 4 and give different kinds of printout.
tabsiz
The size of tabulation to use in printing. 4 is a good value.

SEE ALSO

libunimsg(3)

STANDARDS

AUTHORS


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