Description: Manual Page

Keywords: ss7 ss7/ip ss7 over ip ss7 mtp ss7 sccp ss7 tcap sigtran mtp sccp tcap openss7 acb56 linux telephony pstn linux telephony linux nebs linux compactpci

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PLP

Section: OpenSS7 X.25 Networking Devices (4)
Updated: 2008-10-31
Index Return to Main Contents

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NAME

plp, x25-plp, x25_plp - X.25 Packet Layer Protocol

SYNOPSIS

#include <xti.h>
#include <xti_osi.h>

plp_stream = open( /dev/plp ,O_RDWR);

DESCRIPTION

The PLP multiplexing pseudo-device driver is an implementation of X.25 PLP[1].

USAGE

Streams providing LAPB, MLP, LLC2 or XOT/XOS data links conforming to the Data Link Provider Interface (DLPI)[2], dlpi(7), can be linked beneath this multiplexing driver to provide data link service to the driver.

Streams opened on the upper multiplex, present the Network Provider Interface (NPI)[3], npi(7), OSI conforming service interface.

 ----------------------------------------------------------NPI--
 Network +----------------------------------+                   
 Layer   |                CONS              |                   
         +--+--------+--------------+-------+                   
            |        |              | - NLI                     
            |        |   +----------+-------------------------+ 
            |        |   |              X.25 PLP              | 
            |        |   +----+-------+--------+---------+----+ 
            |        |        |       |        |         |      
 -----------|--------|--------|-------|--------|---------|-DLPI-
 Datalink   |        |        |       |        |         |      
 Layer  +---+--+ +---+--+ +---+--+ +--+--+ +---+--+ +----+----+ 
        | ISOT | | LLC1 | | LLC2 | | XOT | | LAPB | |   MLP   | 
        +---+--+ +---+--+ +--+---+ +--+--+ +---+--+ +-+-----+-+ 
            |        |       |        |        |    +-+-+ +-+-+ 
            +--------|-------|--------+        |    |SLP| |SLP| 
                     |       |        |        |    +-+-+ +-+-+ 
 --------------------|-------|--------|--CDI---|------|-----|---
 Communications      |       |        |        |      |     |   
 Device          +---+-------+---+ +--+--+  +--+------+-----+-+ 
 Layer           |      802      | | TCP |  |       WAN       | 
                 +---------------+ +-----+  +-----------------+ 
 ---------------------------------------------------------------

A user of the PLP network service opens the pseudo-device driver by opening the clone device /dev/plp. This yeilds a PLP Stream. When the user bind and connects the Stream from a local NSAP to a remote NSAP, the user Stream is associated with one or more data links at the lower multiplex. The user Stream is associated with data link streams in the following fashion:

*

When the PLP Stream is connected, using the N_CONN_REQ(7) primitive, the driver usese the NSAPs to determine whether an existing data link exists, and if it does, the Stream is associated with that data link. if a suitable data link does not exist, a request is issued to a connection manager daemon listening on the connection management Stream.

*

The connection manager satisfies requests by examining the NSAP contained in the N_CONN_REQ(7) primitive. The NSAP can be one of several forms:

1.

An X.121 address.

In this case the connection manager opens an X.25 LAPB stream on the X.25 LAPB device, binds and connects the Stream appropriately according to the information in the N_CONN_REQ(7) primitive and then links the connected Stream under the PLP multiplexing driver. It responds to the request indicating the multiplexer index of the linked Stream.

If binding or connecting the X.25 LAPB Stream fails, the connection manager response on the connection management Stream with a negative acknowledgement that the X.25 PLP driver tanslates into an N_ERROR_ACK(7) primitive to the PLP user.

2.

An LSAP address.

In this case the connection manager opens an X.25 LLC2 stream on the X.25 LLC2 device, binds and connects the Stream appropriately according to the information in the N_CONN_REQ(7) primitive and then links the connected Stream under the PLP multiplexing driver. It responds to the request indicating the multiplexer index of the linked Stream.

If binding or connecting the X.25 LLC2 Stream fails, the connection manager response on the connection management Stream with a negative acknowledgement that the X.25 PLP driver tanslates into an N_ERROR_ACK(7) primitive to the PLP user.

*

Data link Streams may also be linked under the PLP multiplexing driver at configuration time using static configuration information obtained from configuration files.

*

Data link Streams may also be linked under the PLP multiplexing driver using route discovery protocols.

INTERFACE

The interface for the X.25 PLP is the Network Provider Interface (NPI)[3], npi(7), the CONS subset.

ADDRESSES

The address format is a socket address of structure type sockaddr_x25. Allocation of addresses in the Internet is described in RFC 982[4], RFC 1237[5], RFC 1629[6].

OPTIONS

Quality of service options provided by the Network Provider Interface (NPI)[3], npi(7), for OSI conforming implementations npi_osi(7).

PRIMITIVES

Primitives used are the primitives of the Network Provider Interface (NPI)[3] npi(7), for OSI conforming implementations npi_osi(7).

IOCTLS

PLP does not provide any input-output controls of its own. The I_LINK(7), I_PLINK(7), I_UNLINK(7) and I_PUNLINK(7) input-output commands can be used to link Streams beneath this multiplexing driver that conform to the Data Link Provider Interface (DLPI)[2], dlpi(7), providing either X.25 LAPB[1], lapb(4), or ISO 8802 LLC2[7], xol(4), data links.

NOTICES

The X.25 PLP would typically be implemented according to X.25 standards over the LAPB data link protocol described in X.25[1], and implementing the Data Link Provider Interface (DLPI)[2], dlpi(7). The X.25 PLP can be used to provide the ISO CONS as described in X.223[8].

X.25 PLP is not very useful on its own except for WAN encapsulation over X.25 links using RFC 877[9], superseded by RFC 1356[10].

Alternatives include:

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X.25 PLP adapted for LANs, as described in ISO/IEC 8881[11], that implements the dlpi(7) using LLC2 instead of LAPB. This is described in more detail under iso-lan(4).

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X.25 PLP implemented directly over TCP ala RFC 1613[12], termed xot(4). Under this scheme, TCP replaces the lower layers of X.25 PLP[12]. This mechanism appears most useful for tunnelling X.25 SVC and PVCs over a TCP/IP internetwork.

Perhaps a better way of tunneling X.25 SVCs and PVCs over a TCP/IP internetwork nowadays would be to implement X.25 over SCTP (Stream Control Transmission Protocol) as described here under xos(4).

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Another way of providing X.25 CONS[8] for use by TP is utilizing TCP/IP as an X.25 CONS replacement as described in RFC 983[13], RFC 1006[14], This mechanism is described as providing the ISO TP0 and TP2 transport classes.

IMPLEMENTATION

This driver is incomplete.

DEVICES

/dev/plp

The X.25 Packet Layer Protocol device. This is a clone(4) device that opens user Streams.

SEE ALSO

ns-tcp(4), xol(4), xot(4), isot(4), itot(4), iso-ip(4), iso-tp4(4), ISO(4).

BUGS

As this driver is incomplete, the bug are being developed.

COMPATIBILITY

NPI[3], DLPI[2].

CONFORMANCE

X.25[1], NPI[3], DLPI[2].

HISTORY

The PLP device is new for OpenSS7 X.25 Networking.

REFERENCES

[1]

ITU-T Recommendation X.25, Interface between Data Terminal Equipment (DTE) and Data Circuit-terminating Equipment (DCE) for terminals operating in the packet mode and connected to the public data networks by dedicated circuit, October 1996, (Geneva), ITU, ITU-T Telecommunication Standardization Sector of ITU. (Previously "CCITT Recommendation") <http://www.itu.int/rec/T-REC-X.25/>

[2]

DLPI, Data Link Provider Interface (DLPI) Specification, Revision 2.0.0, Draft 2, August 20, 1991, (Parsippany, New Jersey), UNIX. International,Inc., UNIX International Press. <http://www.openss7.org/doc/dlpi.pdf>

[3]

NPI, Open Group CAE Specification: Network Provider Interface (NPI) Specification, Revision 2.0.0, Draft 2, August 17, 1992, (Parsippany, New Jersey), UNIXInternational,Inc., UNIX International Press. <http://www.openss7.org/docs/npi.pdf>

[4]

RFC 982, Guidelines for the Specification of the Structure of the Domain Specific Part (DSP) of the ISO Standard NSAP Address, April 1, 1986, H. W. Braun, The Internet Society. <http://www.ietf.org/rfc/rfc0982.txt>

[5]

RFC 1237, Guidelines for OSI NSAP Allocation in the Internet, July 1991, R. Colella, E. Gardner and R. Callon, The Internet Society. (Obsoleted by RFC 1629) (Status: PROPOSED STANDARD) <http://www.ietf.org/rfc/rfc1237.txt>

[6]

RFC 1629, Guidelines for OSI NSAP Allocation in the Internet, May 1994, R. Colella, R. Callon, E. Gardner and Y. Rekhter, The Internet Society. (Obsoletes RFC 1237) (Status: DRAFT STANDARD) <http://www.ietf.org/rfc/rfc1629.txt>

[7]

ANSI/IEEE Std. 802.2-1998 [ISO/IEC 8802-2:1998], IEEE Standard for Information Technology --- Telecommunications and Information Exchange Between Systems --- Local and Metropolitan Area Networks --- Specific Requirements --- Part 2: Logical Link Control, May 7, 1998, (New York), ANSI/IEEE, IEEE Computer Society. [ISBN 1-55937-959-6]

[8]

ITU-T Recommendation X.223 [ISO/IEC 8878], Use of X.25 to Provide the OSI Connection-mode Network Service for ITU-T Applications, November 1993, (Geneva), ITU, ITU-T Telecommunication Standardization Sector of ITU. (Previously "CCITT Recommendation") <http://www.itu.int/rec/T-REC-X.223/>

[9]

RFC 877, Standard for the Transmission of IP Datagrams over Public Data Networks, September 1983, J. T. Korb, The Internet Society. (Obsoleted by RFC 1356) (Status: UNKNOWN) <http://www.ietf.org/rfc/rfc0877.txt>

[10]

RFC 1356, Multiprotocol Interconnection on X.25 and ISDN in the Packet Mode., August 1992, A. Malis, ed., The Internet Society. (Obsoletes RFC 877) (Status: DRAFT STANDARD) <http://www.ietf.org/rfc/rfc1356.txt>

[11]

ISO/IEC 8881:1989, Information Processing Systems --- Data Communications --- Use of the X.25 Packet Level Protocol in Local Area Networks, 1989, (Geneva), ISO/IEC, International Organization for Standardization. <http://www.iso.org/>

[12]

RFC 1613, Cisco Systems X.25 over TCP (XOT), May 1994, J. Forster, G. Satz, G. Glick and R. Day, ed., The Internet Society. (Status: INFORMATIONAL) (Defines TCP port number 1998.) <http://www.ietf.org/rfc/rfc1613.txt>

[13]

RFC 983, ISO Transport Arrives on Top of the TCP, April 1, 1986, D. E. Cass, M. T. Rose, The Internet Society. (Obsoleted by RFC 1006) <http://www.ietf.org/rfc/rfc0983.txt>

[14]

STD 35/RFC 1006, ISO Transport Service on top of the TCP --- Version 3, May 1987, Marshall T. Rose, ed., The Internet Society. (Obsoletes RFC 983) (Updated by RFC 2126) (Also STD 35) <http://www.ietf.org/rfc/rfc1006.txt>

TRADEMARKS

OpenSS7tm

is a trademark of OpenSS7 Corporation.

Linux®

is a registered trademark of Linus Torvalds.

UNIX®

is a registered trademark of The Open Group.

Solaris®

is a registered trademark of Sun Microsystems.

Other trademarks are the property of their respective owners.

IDENTIFICATION

OpenSS7 X.25 Networking: Package strx25 version 0.9.2.1 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

USAGE

INTERFACE

ADDRESSES

OPTIONS

PRIMITIVES

IOCTLS

NOTICES

IMPLEMENTATION

DEVICES

SEE ALSO

BUGS

COMPATIBILITY

CONFORMANCE

HISTORY

REFERENCES

TRADEMARKS

IDENTIFICATION

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