SIST ETS 300 099 E1:2003

• Abstract:

  T/NA2(89)10

• Status: Published
• Publication Date: 30-Nov-2003
• ICS: 33.080 - Integrated Services Digital Network (ISDN)
• Technical Committee: SS EIT - Technical Board for the electrotechnical, information technology and telecommunications fields
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Dec-2003
• Due Date: 01-Dec-2003
• Completion Date: 01-Dec-2003
• Ref Project: ETSI ETS 300 099 ed.1 (1992-08) - Integrated Services Digital Network (ISDN); Specification of the Packet Handler access point Interface (PHI)

SIST ETS 300 099 E1:2003 is the Slovenian standard for Integrated Services Digital Network (ISDN) Packet Handler access point Interface (PHI). Published by SIST and identical to ETS 300 099 Edition 1, it specifies the network-internal interface between the Packet Handler (PH) and the local Connection Related Function (CRF) for public ISDN packet mode services. It is aimed at implementers and operators who need the PH and CRF to work together across local or remote access arrangements.

What does SIST ETS 300 099 E1:2003 specify?

SIST ETS 300 099 E1:2003 defines the PHI for public ISDN packet mode services. The standard is used when the Packet Handling Function is implemented separately from the local CRF, so that a manufacturer-independent interface is needed between the two functions.

The scope covers both Case A and Case B services, including B-channel and D-channel access, semipermanent and switched access, and Permanent Logical Link (PLL) operation. It is written for public networks; use in private networks and interworking between private and public networks is outside the PHI scope.

The document is organized as follows:

Annex	What it covers
A	Requirements on the common channel signalling system
B	PHI signalling diagrams
C	Additional information for Permanent Virtual Circuit (PVC) on switched B-channel access, case B
D	Multi-PRA configurations
E	Switch-over and concentration procedures
F	Reset procedures
G	Layer 2 SDL diagrams and state tables
H	Coding of the BC and LLC information element
J	SDL for management frame continuity check
K	Selection mechanism for incoming calls

Clauses 1 to 13 cover scope, references, definitions, functional models, supported services, interface structure, configuration, OA&M, frame multiplexing, signalling, provisioning, exception handling, and PHI-specific information element coding.

What are the key requirements of SIST ETS 300 099 E1:2003?

SIST ETS 300 099 E1:2003 focuses on how PHI shall carry packet mode services, how links are identified and managed, and how signalling and recovery are handled in normal and exceptional cases. For implementation, the important point is that the standard does not just define a physical interface - it defines the service behaviour, link management, and coding needed for interoperable operation.

Service coverage and access modes

• Clause 5 states that the PHI supports Case A and Case B services, with B-channel access and D-channel access. For the reader, this means one interface specification covers both packet mode bearer services and PSPDN-related services.
• Clause 5.1.2 defines D-channel Case B service as a 64 kbit/s channel using Link Access Procedure on the D-channel (LAPD) and X.25 Packet Layer Procedures (PLP). In practice, an implementation must handle multiple SAPI=16 logical links on one subscriber D-channel and respect the LAPD information field limit that drives the packet size.
• Clause 5 also allows semipermanent and switched access, and for D-channel access it distinguishes semipermanent access, PLL access, and switched access. This matters because provisioning and call control differ depending on whether the link is fixed, registered, or established on demand.

Interface structure and channel roles

• Clause 6 defines the PHI as a Primary Rate Access (PRA) structure with 30B+D, and reserves the D64-channel for call control signalling for the B-channels. In practice, this tells the designer which channel carries signalling and which channels carry traffic.
• Clause 6.3 separates Bb-channels and Bd-channels. Bb-channels carry user B-channel packet mode services, while Bd-channels carry user D-channel packet mode services, so channel assignment must follow the service type.
• Clause 6.3.3 states that one Bd-channel per CRF-S/PH pair can also carry signalling information for link layer management when switched D-channel access or dynamic provisioning is used. That means the signalling path has to be planned together with the data links, not treated as an afterthought.

Multiplexing, identifiers and timers

• Clause 9 defines a unique Data Link Connection Identifier (DLCI) on each Bd-channel, with a 4-octet structure that combines SAPI and Link Identification Code (LIC). For implementation, the DLCI is the key to keeping multiple links distinct on the same Bd-channel.
• Clause 9.2 makes the DLCI unique within a sub-bundle, and Clause 9.3 fixes subscriber data links to SAPI 16. This is what lets the PH map the Bd-channel frames back to the right subscriber-side D-channel links.
• Clause 9.7 requires Bd-channel continuity checking while the channel is operational, with HDLC flag continuity as the default method and a management-frame method as an agreed alternative. This gives operations staff a way to confirm whether a Bd-channel is still usable before selecting it for new links.
• Clause 9.9 and Clause 9.10 define peer busy handling and default timer values, including two T200 values and different timing for frame switching and frame relaying. In practice, implementers need to align retry and polling behaviour with the chosen FH technique.

Signalling, provisioning and OA&M

• Clause 10 defines the signalling messages and procedures for switched B-channel services, switched Bd-channels, switched D-channel services, and restart on the D64-channel. This is the operational core of the standard: it tells each side how to set up, clear, and recover the different channel types.
• Clause 11 covers static and dynamic provisioning for semipermanent services and PLLs, using REGISTER and RELEASE COMPLETE messages and the facility information element. For the reader, this is the part that governs how links are registered, deregistered, and kept consistent between the PH and CRF.
• Clause 8 groups Operations, Administration and Maintenance (OA&M) by layer. It includes provisioning of semipermanent Bb-channels and Bd-channels, establishment and release of switched Bd-channels for operational requirements, re-establishment of dynamically provisioned semipermanent Bd-channels after failure, and layer 3 support for X.25 PLP and PVCs on the D-channel.

Exception handling and coding

• Clause 12 specifies how to handle outgoing and incoming call problems, call collisions, unavailable channels, repeated identifiers, and data-link disconnections for B-channel, Bd-channel, PLL, and semipermanent D-channel cases. For practical use, this clause is what keeps the two ends aligned when a link setup or recovery does not go as planned.
• Clause 13 and Annex H define the extra information elements and coding used in PHI signalling, including DLCI value, Bd-channel reference number, FH reference number, additional subscriber information, type of service, called party number, and cause. Annex K adds the normative incoming-call selection mechanism, which is important when a network has to decide which B-channel path should take the call.

What terms does SIST ETS 300 099 E1:2003 define?

• ISDN packet mode services - The standard uses this term for both Case B ISDN packet mode bearer services and Case A PSPDN services.
• Local PHI access - The subscriber is directly connected to the CRF-P, so the PH and the access-side CRF are the same functional point.
• Remote PHI access - The subscriber reaches the PHI through a CRF-S, so the subscriber-side CRF and the PH-side CRF are different.
• PHI OA&M - These are the OA&M functions that need coordination across the PHI, not the purely local functions on either side of the interface.
• Bb-channel - A B-channel of the PRA used for user B-channel packet mode services.
• Bd-channel - A B-channel of the PRA used for user D-channel packet mode services.
• Bundle - All Bd-channels of a PHI leading to a particular CRF-S.
• Sub-bundle - All Bd-channels of a PHI leading to a particular Frame Handler (FH) within the CRF-S.

Who uses SIST ETS 300 099 E1:2003?

SIST ETS 300 099 E1:2003 is used by ISDN network operators, exchange and switching equipment vendors, Packet Handler and Frame Handler implementers, and system integrators working on public packet mode services. It is also relevant for OA&M teams, because the standard includes provisioning, recovery, continuity checking, and exception handling. Test laboratories and quality teams use it to check signalling behaviour, channel mapping, and conformance to the supported service set.

What changed in SIST ETS 300 099 E1:2003 from the previous edition?

SIST ETS 300 099 E1:2003 is identical to ETS 300 099 Edition 1.

Which standards are used with SIST ETS 300 099 E1:2003?

• CCITT Recommendation I.130 and CCITT Recommendation I.324 set the ISDN service-description model and the network architecture used to place the PHI.
• ETS 300 048, ETS 300 049, and ETS 300 007 define the packet mode bearer services that PHI supports for Case A and Case B.
• CCITT Recommendation Q.932 provides the generic ISDN supplementary-service procedures and the facility coding basis used in dynamic provisioning.
• CCITT Recommendation X.25 provides the packet layer procedures used for D-channel services and related packet-mode behaviour.
• CCITT Recommendation X.31/I.462 covers support of packet mode terminal equipment in ISDN.
• ETS 300 125 provides the user-network interface layer 2 specification that PHI reuses for LAPD behaviour.
• ETS 300 102 parts 1 and 2 provide the basic call control procedures used for the signalling exchange.
• CCITT Recommendation I.412 defines the ISDN user-network interface structures and access capabilities behind the PRA model.
• CCITT Recommendation X.75 covers packet-switched signalling between public networks and supports the interworking context described in the foreword.
• CCITT Recommendation X.32 and CCITT Recommendation X.121 contribute terminal access and numbering support for packet mode and data-network addressing.
• CCITT Recommendations E.164, E.165, E.166, and X.122 contribute numbering and interworking rules used for identification and routing.
• prETS 300 011 provides the primary rate user-network interface layer 1 specification and test principles used at the physical interface.

What does the SIST ETS 300 099 E1:2003 document contain?

SIST ETS 300 099 E1:2003 contains a reference configuration, functional models for local and remote access, and a service overview that cross-references the PHI procedures with the supported services. It then gives the basic interface structure, the PRA channel arrangement, the channel types, and the frame multiplexing rules for Bd-channels.

The document also includes signalling procedures, message sets, timer behaviour, and the extra information element coding needed for PHI-specific exchanges. Annexes B, G, and J provide diagrams and state tables for implementation work, while Annex H and Annex K provide normative coding and selection rules used for signalling and incoming-call handling.

SLOVENSKI STANDARD
01-december-2003
'LJLWDOQRRPUHåMH]LQWHJULUDQLPLVWRULWYDPL,6'1±6SHFLILNDFLMDYPHVQLND
GRVWRSRYQHWRþNHSDNHWQHJDVWUHåQLND3+,
Integrated Services Digital Network (ISDN); Specification of the Packet Handler access
point Interface (PHI)
Ta slovenski standard je istoveten z: ETS 300 099 Edition 1
ICS:
33.080 Digitalno omrežje z Integrated Services Digital
integriranimi storitvami Network (ISDN)
(ISDN)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN ETS 300 099
TELECOMMUNICATION August 1992
STANDARD
Source: ETSI TC-NA Reference: T/NA2(89)10
ICS: 33.080
ISDN, access, interface
Key words:
Integrated Services Digital Network (ISDN);
Specification of the
Packet Handler access point Interface (PHI)
ETSI
European Telecommunications Standards Institute
ETSI Secretariat
F-06921 Sophia Antipolis CEDEX - FRANCE
Postal address:
650 Route des Lucioles - Sophia Antipolis - Valbonne - FRANCE
Office address:
c=fr, a=atlas, p=etsi, s=secretariat - [e-mail]
X.400: Internet:
Tel.: [phone] - Fax: [phone]
Copyright Notification: No part may be reproduced except as authorized by written permission. The copyright and the
foregoing restriction extend to reproduction in all media.
© European Telecommunications Standards Institute 1992. All rights reserved.
New presentation - see History box

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ETS 300 099: August 1992
Whilst every care has been taken in the preparation and publication of this document, errors in content,
typographical or otherwise, may occur. If you have comments concerning its accuracy, please write to
"ETSI Editing and Committee Support Dept." at the address shown on the title page.

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ETS 300 099: August 1992
Contents
Foreword.11
1 Scope .13
1.1 Implementation alternatives for ISDN packet mode services and applicability of this
specification.13
1.2 ISDN packet mode services supported .13
1.3 Local and remote access to the PHI .13
2 Normative references .14
3 Definitions and abbreviations.16
3.1 Definitions.16
3.2 Abbreviations.18
4 Reference configuration and functional model .19
4.1 Reference configuration.19
4.2 Basic functional model.21
4.3 Functional model for remote access to the PHI.23
5 Services supported by the PHI specification .25
5.1 Basic services.25
5.1.1 Services provided on the B-channel .25
5.1.1.1 Semipermanent access.25
5.1.1.2 Switched access . 26
5.1.2 Services provided on the D-channel (case B).26
5.1.2.1 Semipermanent access.26
5.1.2.2 PLL access. 27
5.1.2.3 Switched access . 27
5.2 Detailed service aspects.27
5.2.1 Notification of incoming calls.27
5.2.1.1 No Notification Class.28
5.2.1.2 Conditional Notification Class.28
5.2.2 Mapping of information elements .28
5.2.3 Access connection clearing .28
5.2.4 Access collision.29
5.2.5 Cause mappings .29
5.3 Numbering, addressing and terminal selection .29
5.3.1 Numbering and addressing.29
5.3.2 Terminal selection and compatibility checking .30
5.3.3 Directory number and services association.31
5.4 Services cross-reference and conformance statement for the PHI .31
6 Basic interface structure .33
6.1 General.33
6.2 Interface architecture for single-PRA PHI.33
6.2.1 Local PHI access .33
6.2.2 Remote PHI access.33
6.3 PHI channel types .36
6.3.1 D64-channel.36
6.3.2 Bb-channels (case A and case B).39
6.3.3 Bd-channels.39
6.3.3.1 Data transfer. 41
6.3.3.2 Link layer management .41

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ETS 300 099: August 1992
7 Interface configuration .44
7.1 Frame handler function at the CRF-S .44
7.2 Multi-PRA PHI configuration .44
8 Operations, administration and maintenance (OA&M).44
8.1 General .44
8.1.1 Scope.44
8.1.2 Definitions.44
8.1.3 Principles.44
8.2 Layer 1 OA&M requirements.45
8.2.1 Administration .45
8.2.1.1 Provisioning of semi-permanent Bb-channels.45
8.2.1.2 Provisioning of semi-permanent Bd-channels.45
8.2.2 Operations and maintenance .45
8.2.2.1 Primary rate access.45
8.2.2.2 Establishment and release of switched Bd-channels due
to operational requirements .45
8.2.2.3 Re-establishment of dynamically provisioned
semi-permanent Bd-channels in case of failure.45
8.3 Layer 2 OA&M requirements.46
8.3.1 Bb-channels .46
8.3.2 Bd-channels .46
8.3.2.1 Administration.46
8.3.2.2 Operations .46
8.3.2.2.1 General status and performance
monitoring.46
8.3.2.2.2 Load sharing .47
8.3.2.3 Maintenance.47
8.3.3 D64-channel.47
8.4 Layer 3 OA&M requirements.47
8.4.1 Service support .47
8.4.1.1 CCITT Recommendation X.25 Packet Layer Procedures
(PLP).47
8.4.1.2 PVCs on the D-channel .47
8.4.2 Signalling (D64 and Bd-inband).48
8.4.2.1 Administration.48
8.4.2.2 Operations .48
8.4.2.2.1 D64-signalling.48
8.4.2.2.2 Bd-inband signalling .48
8.4.2.3 Maintenance.48
8.4.2.3.1 D64-signalling.48
8.4.2.3.2 Bd-inband signalling .48
9 Frame multiplexing on the Bd-channels.48
9.1 Principle .48
9.2 Address field layout.49
9.3 Subscriber data links .51
9.4 Signalling data link.51
9.4.1 The DLCI value of the signalling data link.51
9.4.2 Establishment of the signalling data link.52
9.4.3 Signalling data link failure .52
9.4.4 Recovery of the signalling data link .52
9.5 Switchover and concentration.53
9.6 Reset procedures.53
9.7 Bd-channel continuity check.53
9.7.1 HDLC Flag continuity check procedure.53
9.7.2 Management frame continuity check procedure.54
9.7.2.1 Both-way procedure description.54
9.7.2.2 One-way procedure description .54
9.7.2.3 Management frame layouts .55

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ETS 300 099: August 1992
9.7.2.4 Parameter set. 55
9.8 Connection verification procedure .56
9.9 Peer busy procedures .56
9.10 Default timer values.56
10 PHI signalling .57
10.1 General introduction .57
10.1.1 Signalling procedures.57
10.1.2 Signalling messages.57
10.1.3 Information Elements.57
10.2 B-channel services, switched, case A . 58
10.2.1 Signalling messages.58
10.2.1.1 Call proceeding .59
10.2.1.2 Connect . 59
10.2.1.3 Connect acknowledge.59
10.2.1.4 Disconnect.59
10.2.1.5 Release.60
10.2.1.6 Release complete.60
10.2.1.7 Setup.60
10.2.1.8 Status.61
10.2.1.9 Status enquiry .61
10.2.2 Case A, procedures for an outgoing call (CRF-P to PH) .61
10.2.3 Case A, procedures for an incoming call (PH to CRF-P).62
10.2.4 Case A, procedures for call clearing .63
10.3 B-channel services, switched, case B . 63
10.3.1 Signalling messages.63
10.3.1.1 Call proceeding .64
10.3.1.2 Connect . 64
10.3.1.3 Connect acknowledge.64
10.3.1.4 Disconnect.65
10.3.1.5 Release.65
10.3.1.6 Release complete.65
10.3.1.7 Setup.66
10.3.1.8 Status.66
10.3.1.9 Status enquiry .67
10.3.2 Case B, procedures for an outgoing call (CRF-P to PH) .67
10.3.3 Case B, procedures for an incoming call (PH to CRF-P).68
10.3.4 Case B, procedures for call clearing .69
10.4 Switched Bd-channels .69
10.4.1 Signalling messages for circuit mode procedures.69
10.4.1.1 Connect .70
10.4.1.2 Setup.70
10.4.2 Signalling messages for packet mode procedures.70
10.4.2.1 Connect . 70
10.4.2.2 Setup.71
10.4.3 Procedures for Bd-channels established by the CRF-S (CRF-P to PH).71
10.4.4 Procedures for Bd-channels established by the PH (PH to CRF-P).72
10.4.5 Procedures for Bd-channel access connection clearing.73
10.5 D-channel services, switched, case B. 73
10.5.1 Signalling messages.73
10.5.1.1 Connect .74
10.5.1.2 Release.74
10.5.1.3 Release complete.74
10.5.1.4 Setup.75
10.5.1.5 Status.76
10.5.2 Procedures for data link establishment by the CRF-S (CRF-S to PH) .76
10.5.3 Procedures for data link establishment by the PH (PH to CRF-S).77
10.5.4 Procedures for data link disconnection .79
10.5.5 Procedures after receipt of a STATUS message .80
10.6 Restart on the D64-channel. 80

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10.6.1 Signalling messages .80
10.6.1.1 Restart .81
10.6.1.2 Restart acknowledge .81
10.6.1.3 Status.81
10.6.2 Restart procedure .81
10.7 The timers T320, TPHI, TPH, and TCRF.82
11 Static and dynamic provisioning for PLL and semipermanent services.82
11.1 General Introduction.82
11.1.1 Signalling procedures.83
11.1.2 Signalling messages .83
11.1.3 Information elements .83
11.2 B-channel services, case A and case B, semipermanent .83
11.2.1 Static provisioning.83
11.2.2 Dynamic provisioning .83
11.3 Semipermanent Bd-channels.83
11.3.1 Static provisioning.83
11.3.2 Dynamic provisioning .83
11.3.3 De-registration of dynamically provisioned Bd-channels .84
11.4 D-channel services, PLL .84
11.4.1 PLL data link provisioning, static.84
11.4.2 Messages for dynamic provisioning of PLL data links .84
11.4.2.1 Register.85
11.4.2.2 Release complete.85
11.4.2.3 The linked identifier of the invoke component.85
11.4.2.4 The argument of the invoke component.86
11.4.2.5 The result of the return result component.86
11.4.2.6 The error value of the return error component.86
11.4.2.7 The parameter of the return error component.86
11.4.3 Procedures for PLL data link registration by the CRF-S (CRF-S to PH).86
11.4.4 Procedures for PLL data link registration by the PH (PH to CRF-S).87
11.4.5 Procedures for PLL data link de-registration.88
11.5 D-channel services, semipermanent.89
11.5.1 Semipermanent data link provisioning, static .89
11.5.2 Messages for dynamic provisioning of semipermanent data links.89
11.5.3 Procedures for semipermanent data link registration .89
11.5.4 Procedures for semipermanent data link de-registration .90
12 Exception handling.90
12.1 B-channel service (case A and B) .90
12.1.1 Outgoing call.90
12.1.2 Incoming call.90
12.1.2.1 Unsuccessful call .90
12.1.2.2 Premature clearing by remote terminal .90
12.1.2.3 No Bb-channel available .90
12.1.2.4 Data link disconnect.90
12.1.2.5 Acceptance of call on existing B-channel.91
12.1.3 Call collision .91
12.1.4 Data transfer phase.91
12.1.4.1 Subscriber disconnects data link .91
12.1.4.2 Bb-channel is cleared.91
12.1.4.3 Restart on PHI.91
12.2 Bd-channel establishment.91
12.2.1 Bd-channel establishment by the CRF-S.92
12.2.1.1 Corrupted "user-user" information element.92
12.2.2 Bd-channel establishment by the PH .92
12.2.2.1 Corrupted "user-user" information element.92
12.3 Switched D-channel service.92
12.3.1 Exception resolution using layer 2 procedures.92
12.3.1.1 Exception reporting on the user-network interface .92

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12.3.1.2 No exception reporting .93
12.3.1.3 DM-frame in the Bd-channel .93
12.3.2 Outgoing call.93
12.3.2.1 No Bd-channel available .93
12.3.2.2 Signalling data link disconnection.93
12.3.2.3 Data link establishment rejection.93
12.3.2.4 Repeated DLCI . 94
12.3.3 Incoming call.94
12.3.3.1 Unsuccessful call .94
12.3.3.2 Premature clearing by remote terminal .94
12.3.3.3 No Bd-channel available .95
12.3.3.4 Signalling data link disconnection.95
12.3.3.5 Acceptance of call on existing data link.95
12.3.3.6 Repeated "called party number".95
12.3.3.7 Repeated DLCI . 96
12.3.3.8 Data link disconnect.96
12.3.4 Call collision.96
12.3.5 Data transfer phase. 96
12.3.5.1 Subscriber disconnects data link .96
12.3.5.2 Bd-channel is cleared.96
12.3.5.3 Restart on PHI . 96
12.4 PLL or semipermanent D-channel service.96
12.4.1 Outgoing call.96
12.4.1.1 No Bd-channel available .96
12.4.1.2 SETUP with PLL (semipermanent) DLCI value.97
12.4.1.3 SABME with unknown DLCI.97
12.4.2 Incoming call.97
12.4.2.1 No Bd-channel available .97
12.4.2.2 SABME with unknown DLCI.97
12.4.3 Call collision.97
12.4.3.1 Call collision on network-user interface.97
12.4.3.2 Call collision on the Bd-channel .98
12.4.3.3 Exceeding the maximum number of data links .98
12.4.4 Data transfer phase. 98
12.5 PLL or semipermanent registration or de-registration.98
12.5.1 Registration and de-registration by the CRF-S.98
12.5.1.1 Data link disconnection.98
12.5.1.2 Repeated DLCI . 98
12.5.1.3 Unknown de-registration parameter.98
12.5.2 Registration or de-registration by the PH.99
12.5.2.1 Data link disconnection.99
12.5.2.2 Repeated "called party number".99
12.5.2.3 Repeated DLCI . 99
12.5.2.4 Unknown de-registration parameter.99
13 Additional information elements for PHI signalling.99
13.1 Coding rules .99
13.2 Coding of the additional information elements. 103
13.2.1 DLCI value. 103
13.2.2 Bd-channel reference number. 103
13.2.3 FH reference number. 104
13.2.4 Additional subscriber information . 104
13.2.5 Type of service . 105
13.2.6 Called party number . 105
13.2.7 Cause . 105
13.3 Coding of the facility Information Element. 106
13.3.1 Embedded information elements. 106
13.3.2 Operation value. 106
13.3.3 Error value. 107

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Annex A (informative): Requirements on the common channel signalling system .108
Annex B (informative): PHI signalling diagrams.108
B.1 Introduction.108
B.1.1 Conventions for the diagrams .108
B.2 B-channel services case A .111
B.2.1 B-channel establishment .111
B.2.2 B-channel disconnection.111
B.3 B-channel services case B .113
B.3.1 B-channel establishment .113
B.4 Dynamic Bd-channels.114
B.4.1 Bd-channel establishment.114
B.5 Data link establishment and release .117
B.5.1 D-channel data link establishment.117
B.5.2 D-channel link disconnection.119
B.6 Bd-channel establishment, semipermanent .120
B.7 Dynamic provisioning for D-channel PLL service.121
B.7.1 PLL data link registration .121
B.7.2 PLL data link de-registration.122
B.8 Dynamic provisioning for D-channel semi-permanent service .123
B.8.1 Semi-permanent data link registration .123
Annex C (informative): Additional information for PVCs on switched B-channel access (case B).124
C.1 Introduction.124
C.2 Procedure.124
C.2.1 Identification .124
C.2.2 B-channel establishment .124
C.2.3 Layer 2 and layer 3 establishment .124
C.2.4 Error procedures.124
C.2.5 Procedures for VCs on B-channels supporting PVCs.124
Annex D (informative): Multi-PRA configurations.125
D.1 Selection by using numbers.125
D.2 Selection by a hunting algorithm or a call deflection mechanism.125
D.3 Non-associated signalling.125
Annex E (informative): Switch-over and concentration procedures .126
E.1 Introduction.126
E.2 Applicability.126
E.3 Constraints .126
E.4 Procedures.126
E.4.1 Switchover procedures . 126
E.4.1.1 Switchover during link establishment .126

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E.4.1.2 Switchover of an established link . 127
E.4.2 Detailed procedure. 127
E.5 Traffic management considerations. 127
E.5.1 Bd-channel failure or malfunction . 127
E.5.2 Unexpected overload. 128
E.5.3 Concentration of under-loaded Bd-channels. 128
E.6 Modifications to the main part of the specification . 128
E.6.1 General interface architecture. 128
E.6.2 Data transfer . 128
E.6.3 Administration. 128
E.6.4 Load sharing. 128
E.6.5 Bd-inband signalling. 129
E.6.6 Switchover and concentration procedure. 129
E.6.7 Procedures for data link establishment by the CRF-S. 129
E.6.8 Bd-channel is cleared . 129
E.6.9 Call collision on the Bd-channel. 129
Annex F (informative): Reset procedures . 130
F.1 Procedure. 130
F.2 Coding. 130
Annex G (informative): Layer 2 SDL diagrams and state tables. 131
G.1 SDL diagrams. 131
G.2 Key to the state transition tables . 133
G.2.1 Definition of a cell of the state transition table. 133
G.2.2 Key to the contents of a cell. 133
G.3 State transition tables. 133
Annex H (normative): Coding of the BC and LLC information element. 135
H.1 BC information element for circuit switched bearer capability. 135
H.2 LCC information element for case A services. 135
H.3 BC information element for packet mode bearer capability . 137
H.4 BC information element in the Bd-channel signalling link. 137
Annex J (informative): SDL for management frame continuity check. 138
Annex K (normative): Selection mechanism for incoming calls. 142
History. 144

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Foreword
This European Telecommunication Standard (ETS) has been prepared by the Network Aspects (NA)
Technical Committee of the European Telecommunications Standards Institute (ETSI).
In accordance with CCITT Recommendation I.130 [1], the following three level structure is used to
describe the telecommunications services by European public telecommunications operators under the
pan-European Integrated Services Digital Network (ISDN):
- Stage 1: is an overall service description, from the user's standpoint;
- Stage 2: identifies the functional capabilities and information flows needed to support the service
described in stage 1; and
- Stage 3: defines the signalling system protocols and switching functions needed to implement the
service described in stage 1.
This ETS defines a network-internal interface for the provision of ISDN packet mode services as defined in
ETS 300 048 [7] (derived from CCITT Recommendation I.232 [16]), ETS 300 049 [8] (derived from CCITT
Recommendation I.232 [16]) (stage 1) and ETS 300 007 [20] (derived from CCITT Recommendation X.31)
(stage 3).
NOTE 1: The term ISDN packet mode services is used in a way as to include both case B (ISDN
packet mode bearer services, PMBS) and case A (PSPDN services), see
ETS 300 007 [20].
NOTE 2: No stage 2 service description existed at the time this standard was prepared.
NOTE 3: The PLL service described in ETS 300 049 [8] and supported by this standard is not
explicitly mentioned in ETS 300 007 [20].
NOTE 4: For case A services described in ETS 300 007 [20] and supported by this standard, no
stage 1 service description exists.

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1 Scope
1.1 Implementation alternatives for ISDN packet mode services and applicability of this
specification
This specification defines a network-internal interface for the provision of ISDN packet-mode services.
The term ISDN packet mode services is defined in such a way as to include both case B (ISDN Packet
Mode Bearer Services (PMBS)), and case A (PSPDN services), see ETS 300 007 [20].
This specification shall be used if a specific implementation alternative for the provision of these services is
used in an ISDN. The implementation alternatives and the exact location of the interface are described in
the following paragraphs.
In CCITT Recommendation I.324 [6], local Connection-Related Function (CRF) and Packet-Handling
Function (PHF) are defined as being involved in the provision of packet mode bearer services (PMBS).
The local CRF includes the Exchange Termination (ET). Two basic implementation alternatives are
mentioned in subclause 3.1.2 of CCITT Recommendation I.324 and in ETS 300 007 [20]:
1) the PHF is integrated in the local CRF; and
2) the PHF is not part of the local CRF. Local CRF and PHFs are implemented with different physical
equipment and in a multi-vendor environment. In addition, the PH, although logically belonging to the
ISDN, may be physically part of the PSPDN.
In the first case, the interface between ET and PHFs can be kept internal and proprietary. In the second
case, a standardised interface between local CRF and PHFs is required. This specification defines a
manufacturer-independent interface between the local CRF and PHFs. The interface is called the Packet
Handler access point Interface (PHI).
If the second implementation alternative is chosen for the provision of packet mode services in an ISDN,
this specification shall be used for the implementation of the PHI. The existence of this specification does,
however, not preclude the choice of the first implementation alternative in an ISDN.
Considerations for the use of the PHI in private networks and interworking between private and public
networks are outside the scope of this standard. The PHI is a network-internal interface to be used in
public networks.
1.2 ISDN packet mode services supported
The full scope of services defined in ETS 300 048 [7] and ETS 300 049 [8] (Case B) and in
ETS 300 007 [20] (Cases A and B) is supported by the PHI specification, see Clause 5 for details.
Subclause 5.4 contains a table giving an overview of the services, references to the relevant sections of
the PHI specification and a conformance statement.
The PHI specification uses the term Packet Handler (PH) in both Case A and Case B services. For Case
A services, the PH assumes the role of the Access Unit (AU), see ETS 300 007 [20].
No other services are supported by the PHI specification.
1.3 Local and remote access to the PHI
The PHI denotes the interface between the PH and the CRF it i
...