High-Level Data Link Control (HDLC)

Description: OpenSS7 Project Manual Pages ISDN Stack

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HDLC

Section: OpenSS7 SS7 Stack Devices (4)
Updated: 2008-10-31
Index Return to Main Contents

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NAME

hdlc - High-Level Data Link Control

SYNOPSIS

#include <sys/stropts.h>
#include <sys/cdi.h>
#include <sys/cdi_hdlc.h>
#include <sys/hdlc_ioctl.h>

int ch_stream = open(ch_device, flags);

int retval = ioctl(ch_device, I_PUSH, ``hdlc'');

DESCRIPTION

HDLC
is an implementation of the High-Level Data Link Control (HDLC) Procedures as specified in IS0 3309[1] and ISO 4333[2]. HDLC is intended to be used with the lapb(4), lapd(4), lapf(4), multiplexing drivers.

HDLC is implemented as a pushable STREAMS(4) module. The HDLC mdoule can be pushed over a stream conforming to the Channel Interface (CHI) as described in chi(7). The HDLC module provides HDLC access to the bit stream from the channel provided by the chi(7) Stream below it, by performing HDLC functions on the raw bit stream. The upper interface provided by the HDLC module is the Communications Device Interface (CDI) as described in cdi(7).

HDLC streams can be linked under dl(4) drivers lapd(4), lapb(4), lapf(4), gr303(4), v52(4), using the I_LINK or I_PLINK commands of streamio(7), to provide a complete Data Link that can then be linked under an isdn(4), fr(4), idlc(4), dpnss(4), iua(4), gr303ua(4), v5ua(4) or dua(4) driver using the I_LINK or I_PLINK commands of streamio(7), to provide data link services to the Layer 3 protocol. This is normally performed, as required, by the ISDN Configuration Daemon, isdnconfd(8).

NOTICES

HDLC has been implemented as a pushable module to ease the development of ISDN Data Link drivers for various cards. All that is required is for the card to provide a Channel Interface (CHI), chi(7), and push the hdlc(4) and dl(4) modules to provide a complete and compliant Q.921[3] Data Link.

HDLC is implemented internally as a soft-HDLC using host-based table lookups. While this is fairly efficient, devices that are capable of performing this function in hardware should provide the Communications Device Interface (CDI), cdi(7), directly. An example of a device that does not include HDLC is the x400p(4) driver. An example of one that does, is the acb56(4) driver.

NOTICES

HDLC modules are not normally pushed or accessed directly by user-level programs. The HDLC module is used directly by some test and monitoring programs.

IOCTLS

The HDLC module responds to Local Management Interface (LMI), lmi_ioctl(4), IO controls as interpreted for HDLC operation as described in hdlc_ioctl(4).

FILES

<ss7/cdi.h>, <ss7/cdi_hdlc.h>, <ss7/hdlc_ioctl.h>.

MODULES

streams-hdlc.o

SEE ALSO

ISDN(4), cdi(7), dl(4), hdlc_ioctl(4), isdnconfd(8).

VERSIONS

The HDLC module conforms to the CDI Specification, Revision 1.0[4].

The HDLC module does not appear until strss7 release 0.8.4.

REFERENCES

[1]

ISO/IEC 3309:1988, Data Communication --- High-Level Data Link Control Procedures --- Frame Structure, 1988, (Geneva), ISO/IEC, International Organization for Standardization. <http://www.iso.org/>

[2]

ISO/IEC 4335:1988, Data Communication --- High-Level Data Link Control Procedures --- Consolidation of Elements of Procedures, 1988, (Geneva), ISO/IEC, International Organization for Standardization. <http://www.iso.org/>

[3]

ITU-T Recommendation Q.921, Digital Subscriber Signalling System No. 1 --- ISDN User-Network Interface --- Data Link Layer Specification, March 1993, (Geneva), ITU, ITU-T Telecommunication Standardization Sector of ITU. (Previously "CCITT Recommendation") <http://www.itu.int/rec/T-REC-Q.921/>

[4]

CDI-API, CDI --- Application Program Interface Guide, Original Edition, 1997, March 1999, (Savoy, IL), G. Gerrietts, D. Grothe, M. Matthews and D. Healy, GCOM. <http://www.gcom.com/>

TRADEMARKS

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is a trademark of OpenSS7 Corporation.

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is a registered trademark of The Open Group.

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Other trademarks are the property of their respective owners.

IDENTIFICATION

OpenSS7 SS7 Stack: Package strss7 version 0.9a.8 released 2008-10-31.

Copyright©1997-2008OpenSS7 Corp. All Rights Reserved.
(See roff source for permission notice.)

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Index

NAME

SYNOPSIS

DESCRIPTION

NOTICES

NOTICES

IOCTLS

FILES

MODULES

SEE ALSO

VERSIONS

REFERENCES

TRADEMARKS

IDENTIFICATION

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