SIST ETS 300 478-1 E1:2003

Network Aspects (NA); Connectionless Broadband Data Service (CBDS) over Asynchronous Transfer Mode (ATM); Framework and protocol specification at the User-Network Interface (UNI); Part 1: Specification

Define on the basis of DTR/NA-53203  CBDS over ATM  the access to CBDS service.

Omrežni vidiki (NA) –Nepovezavna širokopasovna podatkovna storitev (CBDS) z asinhronim prenosnim načinom (ATM) – Okvir in specifikacija protokola vmesnika uporabnik-omrežje (UNI) – 1. del: Specifikacija

General Information

• Status: Published
• Publication Date: 30-Nov-2003
• ICS: 33.040.40 - Data communication networks
• 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 300 478-1 ed.1 (1998-02) - Network Aspects (NA); Connectionless Broadband Data Service (CBDS) over Asynchronous Transfer Mode (ATM); Framework and protocol specification at the User-Network Interface (UNI); Part 1: Specification

Standards Content (Sample)

SLOVENSKI STANDARD
01-december-2003
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DVLQKURQLPSUHQRVQLPQDþLQRP$70±2NYLULQVSHFLILNDFLMDSURWRNRODYPHVQLND
XSRUDEQLNRPUHåMH81,±GHO6SHFLILNDFLMD
Network Aspects (NA); Connectionless Broadband Data Service (CBDS) over
Asynchronous Transfer Mode (ATM); Framework and protocol specification at the User-
Network Interface (UNI); Part 1: Specification
Ta slovenski standard je istoveten z: ETS 300 478-1 Edition 1
ICS:
33.040.40 Podatkovna komunikacijska Data communication
omrežja networks
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN ETS 300 478-1
TELECOMMUNICATION February 1998
STANDARD
Source: NA Reference: DE/NA-053205
ICS: 33.020
Key words: Access, ATM, Broadband, CBDS, CL, Network, UNI
Network Aspects (NA);
Connectionless Broadband Data Service (CBDS)
over Asynchronous Transfer Mode (ATM);
Framework and protocol specification at the
User-Network Interface (UNI);
Part 1: Specification
ETSI
European Telecommunications Standards Institute
ETSI Secretariat
Postal address: F-06921 Sophia Antipolis CEDEX - FRANCE
Office address: 650 Route des Lucioles - Sophia Antipolis - Valbonne - FRANCE
X.400: c=fr, a=atlas, p=etsi, s=secretariat - Internet: [e-mail]
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 1998. All rights reserved.

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ETS 300 478-1: February 1998
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 300 478-1: February 1998
Contents
Foreword .5
1 Scope .7
2 Normative references.7
3 Abbreviations.8
4 Framework for the provision of CBDS.9
4.1 Group addressing .9
4.2 Functional architecture.10
4.3 Connectionless server functional description .11
4.4 Interfaces .13
4.4.1 CLAI .13
4.4.1.1 Access Termination Functions (ATF).15
4.4.1.1.1 ATM Access Termination Functions (AATF).15
4.4.1.1.2 CL Access Termination Functions (CLATF).15
4.4.2 Connectionless Network Interface (CLNI).16
4.4.2.1 Network Termination Functions (NTF) .17
4.4.2.1.1 ATM Network Termination Functions (ANTF) .18
4.4.2.1.2 CL Network Termination Functions (CLNTF).18
4.5 Connections.18
4.6 Protocols.19
4.7 Numbering and addressing.19
4.7.1 Individual Address (IA) .19
4.7.2 Group Address (GA).19
4.7.3 Nested Group Address (NGA) .19
4.8 Traffic aspects: access class enforcement.20
4.8.1 Maximum Information Rate (MIR).20
4.8.2 Sustained Information Rate (SIR) and PDUs Per Time Unit (PPTU).21
4.9 Operations and maintenance.21
4.9.1 Identification of OAM information flow.21
4.9.2 OAM supported functions.21
5 Layer service and functions provided by the connectionless layer.21
5.1 Layer service provided by the connectionless layer.22
5.1.1 Description of primitives .22
5.1.1.1 CLL-UNITDATA.request.22
5.1.1.2 CLL-UNITDATA.indication.22
5.1.1.3 MCL-UNITDATA.request.22
5.1.1.4 MCL-UNITDATA.indication.23
5.1.2 Definition of parameters .23
5.1.2.1 source_address .23
5.1.2.2 destination_address.23
5.1.2.3 QoS.23
5.1.2.4 Data .23
5.2 Connectionless layer functions for user data transport.23
5.3 Transit operator selection .23
6 Protocol for the support of the CBDS on B-ISDN at the UNI .24
6.1 Protocol stack .24
6.2 Layer service expected from the AAL.24
6.3 CLNAP protocol data unit structure and encoding.25
6.3.1 Destination-Address.25
6.3.2 Source-Address.25
6.3.3 Higher-Layer-Protocol-Identifier (HLPI).26
6.3.4 PAD-length .26

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ETS 300 478-1: February 1998
6.3.5 QoS. 26
6.3.6 CRC Indication Bit (CIB) . 26
6.3.7 Header Extension Length (HEL). 26
6.3.8 Reserved . 26
6.3.9 Header extension. 26
6.3.10 User-information . 27
6.3.11 PAD . 27
6.3.12 CRC . 27
6.4 Procedures. 27
6.4.1 Interaction between CLNAP entity and CLLR&R entity . 27
6.4.2 Primitives between CLNAP & CLLR&R entities. 27
Annex A (normative): Encodings of the destination address field and source address field. 29
Annex B (informative): CRC32 generation and checking. 30
Annex C (informative): Interworking conditions with Switched Multi-megabit Data Service (SMDS) . 31
C.1 Destination and source addresses . 31
C.2 Header Extension Length (HEL). 31
C.3 Header Extension (HE) field . 31
C.4 HLPI. 31
Annex D (informative): Additional requirements in case of address screening supplementary service . 32
Annex E (informative): Procedures. 33
E.1 Receiving procedures. 33
E.1.1 PDU checks . 33
E.1.2 Ingress error conditions. 33
E.2 Sending procedures. 34
E.2.1 PDU checks . 34
E.2.2 Egress error conditions . 34
Annex F (informative): Bibliography . 35
History. 36

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ETS 300 478-1: February 1998
Foreword
This European Telecommunication Standard (ETS) has been produced by the Network Aspects (NA)
Technical Committee of the European Telecommunications Standards Institute (ETSI).
The present document is part 1 of a multi-part ETS covering the framework and protocol specification at
the User-Network Interface (UNI) for the Connectionless Broadband Data Service (CBDS) over
Asynchronous Transfer Mode (ATM), as identified below:
Part 1: "Specification";
Part 2: "Connectionless Network Access Protocol (CLNAP); Protocol Implementation Conformance
Statement (PICS) proforma specification".
Transposition dates
Date of adoption of this ETS: 6 February 1998
Date of latest announcement of this ETS (doa): 31 May 1998
Date of latest publication of new National Standard
or endorsement of this ETS (dop/e): 30 November 1998
Date of withdrawal of any conflicting National Standard (dow): 30 November 1998

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ETS 300 478-1: February 1998
Blank page
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ETS 300 478-1: February 1998
1 Scope
This first part of ETS 300 478 describes the support of connectionless data service on Broadband
Integrated Services Digital Network (B-ISDN) in accordance with:
- ETS 300 217 [2], which details the stage 1 aspects for the Connectionless Broadband Data Service
(CBDS);
- ITU-T Recommendation I.113 [5], which defines connectionless service (vocabulary);
- CCITT Recommendation F.812 [4], which provides a service description of a CBDS. CCITT
Recommendation F.812 [4] generally describes the service to include:
- source address validation;
- addresses based on CCITT Recommendation E.164 [3] numbering;
- point-to-point and multicast information transfer;
- address screening for point-to-point and multicast information transfer;
- network capabilities for charging;
- interworking with other ConnectionLess and Connection oriented data services;
- Quality of Service (QoS) parameters.
- ITU-T Recommendation I.211 [6], which describes connectionless data service aspects. ITU-T
Recommendation I.211 [6] identifies two configurations, type (i) and type (ii) to support
connectionless data service. In type (i), a Connectionless Service Function (CLSF) is installed
outside the B-ISDN. In type (ii), a CLSF, which handles routeing of data to be transferred based on
connectionless techniques, is installed within the B-ISDN;
- ITU-T Recommendation I.327 [8], which describes "high layer capabilities" for the support of
services (e.g. connectionless service) and gives functional architectural models for the cases
mentioned in F.812 Recommendation [4];
- ITU-T Recommendation I.362 [9], which specifies the use of ATM Adaptation Layer (AAL) type 3/4
for connectionless data services (although I.362 recognizes that the use of other AAL types is for
further study) and identifies that routeing and addressing are provided by the layer located above
AAL type 3/4;
- ETS 300 349 [10], which specifies AAL type 3/4;
- ITU-T Recommendation I.364 [1], which specifies the support of Broadband Connectionless Data
Bearer Service (BCDBS) on B-ISDN.
This ETS relates to type (ii) (direct) provision of connectionless service, using B-ISDN connectionless
service. However, aspects of this ETS may be applied to some type (i) provision of connectionless
service. This ETS describes the framework for network support of CBDS and the protocol used to support
CBDS at the User Network Interface (UNI). The protocol used to support CBDS at the Network Node
Interface (NNI) is described in 300 479-1 [14].
2 Normative references
This ETS incorporates by dated and undated reference, provisions from other publications. These
normative references are cited at the appropriate places in the text and the publications are listed
hereafter. For dated references, subsequent amendments to or revisions of any of these publications
apply to this ETS only when incorporated in it by amendment or revision. For undated references the latest
edition of the publication referred to applies.
[1] ITU-T Recommendation I.364 (1993): "Support of broadband connectionless
data service on B-ISDN".
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ETS 300 478-1: February 1998
[2] ETS 300 217-2 (1992): "Network Aspects (NA); Connectionless Broadband Data
Service (CBDS) Part 2: Basic bearer service definition".
[3] CCITT Recommendation E.164 (1991): "Numbering plan for the ISDN era".
[4] CCITT Recommendation F.812 (1992): "Broadband connectionless data bearer
service".
[5] ITU-T Recommendation I.113 (1988): "Vocabulary of terms for broadband
aspects of ISDN".
[6] ITU-T Recommendation I.211 (1993): "B-ISDN Service Aspects".
[7] ITU-T Recommendation I.324 (1988): "ISDN network architecture".
[8] ITU-T Recommendation I.327 (1993): "B-ISDN Functional Architecture".
[9] ITU-T Recommendation I.362 (1993): "B-ISDN ATM Adaptation Layer (AAL)
Functional Description".
[10] ETS 300 349: "Broadband Integrated Services Digital Network (B-ISDN);
Asynchronous Transfer Mode (ATM) Adaptation Layer (AAL) specification -
type 3/4".
[11] ISO/IEC IS 8802-6: "Information processing systems - Local Area Networks
(LAN) - Part 6: Distributed Queue Dual Bus (DQDB) Subnetwork of a
Metropolitan Area Network (MAN)".
[12] ITU-T Recommendation I.371: "Traffic Control and Congestion Control in
B-ISDN".
[13] ISO/IEC IS 10039: "LAN MAC service definition".
[14] ETS 300 479-1: "Network Aspects (NA); Connectionless Broadband Data
Service (CBDS) over Asynchronous Transfer Mode (ATM); Protocol
specification at the Network Node Interface (NNI); Part 1: Specification".
3 Abbreviations
For the purposes of this ETS, the following abbreviations apply:
AAL ATM Adaptation Layer
AATF ATM Access Termination Functions
ANTF ATM Network Termination Functions
ATF Access Termination Functions
ATM Asynchronous Transfer Mode
BAsize Buffer Allocation Size
BCD Binary Coded Decimal
BCDBS Broadband Connectionless Data Bearer Service
B-ISDN Broadband Integrated Services Digital Network
BOM Beginning Of Message
CBDS Connectionless Broadband Data Service
CF Connection Functions
CIB CRC Indication Bit
CL Connectionless
CLAI Connectionless Access Interface
CLATF CL Access Termination Functions
CLHF Connectionless service Handling Functions
CLL Connectionless Layer
CLLR&R Connectionless Layer Routeing & Relaying
CLMF Connectionless Mapping Functions
CLNAP Connectionless Network Access Protocol

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ETS 300 478-1: February 1998
CLNI Connectionless Network Interface
CLNIP Connectionless Network Interface Protocol
CLNTF CL Network Termination Functions
CLS Connectionless Server
CLSF Connectionless Service Function
CPCS Common Part Convergence Sublayer
CPE Customer Premises Equipment
CRC Cyclic Redundancy Check
CTF Control Functions
DA Destination Address
DQDB Distributed Queue Dual Bus
EI Encapsulating Indicator
EOM End Of Message
GA Group Address
GAHF Group Address Handling Functions
GAP Group Addressed PDU
HE Header Extension
HEL Header Extension Length
IA Individual Address
IEC International Electrotechnical Commission
IM Initial MAC
IS International Standard
ISDN Integrated Services Digital Network
ISO International Organization for Standardization
LAN Local Area Network
MAC Media Access Control
MAN Metropolitan Area Network
MCL Connectionless Layer Management
MID Multiplexing Identification
MIR Maximum Information Rate
NA Network Aspects
NGA Nested Group Address
NNI Network Node Interface
NPC Network Parameter Control
NTF Network Termination Functions
OAM Operation And Maintenance
PCF Protocol Conversion Functions
PDU Protocol Data Unit
PPTU PDUs per Time Unit
QoS Quality of Service
SA Source Address
SAP Service Access Point
SAR Segmentation And Reassembly
SDU Service Data Unit
SIR Sustained Information Rate
SMDS Switched Multi-megabit Data Service
SSCS Service Specific Convergence Sublayer
SSM Single Segment Message
UNI User Network Interface
UPC Usage Parameter Control
VCI Virtual Channel Identifier
VPI Virtual Path Identifier
4 Framework for the provision of CBDS
This definition of CBDS is provided by ETS 300 217 [2] in conjunction with this ETS.
4.1 Group addressing
Group addressing is a mechanism used for multicast communication (CCITT Recommendation F.812 [4],
paragraph 2).
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ETS 300 478-1: February 1998
Multicast information transfer allows a subscriber to send an Connectionless Network Access Protocol-
Protocol Data Unit (CLNAP-PDU) to the network which delivers the same CLNAP-PDU to several
intended recipients. The network shall deliver one and only one copy of the Group Addressed CLNAP-
PDU (GAP) across each of the Connectionless Access Interface (CLAI) associated with the individual
addresses represented by the group address (i.e. each CLAI associated with multiple destination
addresses will receive a single copy from the network). The GAP shall not be copied back to the
originating CLAI. Any recipient of a GAP may make use of the destination Group Address carried by that
GAP to multicast to the other recipients of the GAP. Non members of a group identified by a group
address (GA) may send GAPs to that group.
As a result of address screening, it is possible that some of the copies of the GAP will not be delivered, all
other copies are delivered according to the QoS.
The service provider is responsible for assigning group addresses and ensuring that each GA identifies
uniquely only one set of individual addresses. GA can be distinguished from individual addresses by the
address type.
4.2 Functional architecture
The provision of the connectionless data service in B-ISDNs is realized by means of ATM switched
capabilities and Connectionless Service Functions (CLSF). The ATM switched capabilities support the
transport of connectionless data units in B-ISDNs between specific functional groups CLSF able to handle
the connectionless protocol and to realize the adaptation of the connectionless data units into ATM cells to
be transferred in a connection-oriented environment. The CLSF functional groups may be located outside
a B-ISDN, in a private connectionless network or in a specialized service provider, or inside a B-ISDN.
The relevant reference configuration for the provision of the connectionless data service in a B-ISDN is
depicted in figure 1.
B-ISDN
custom er
CLSF
Specialized
S /T
B B
service provider
M
CLSF
P
B-ISDN
ATM switched
capabilities
S /T
M
B B
CLSF
CLSF
Specialized
Private
service provider
connectionless
B-ISDN
network
custom er
CLSF: Connectionless Service Function.
M, P, S , T : Reference points.
B B
Figure 1: Reference configuration for the provision of the CL data service in B-ISDN
The ATM switched capabilities are performed by the ATM nodes (ATM switch/cross-connect) which
realize the ATM transport network. The CLSF functional group terminates the B-ISDN connectionless
protocol and includes functions for the adaptation of the connectionless protocol to the intrinsically
connection-oriented ATM layer protocol and functions for the adaptation of the CL protocols using up to
9 2766 octets (9 188 user information plus protocol control information), variable size PDUs to the fixed
size, 48 octet ATM-SDUs and to the specific error characteristics (possible cell loss, possible burst cell
loss) of the ATM networks. These latter functions are those performed by the ATM Adaptation layer
type 3/4 (AAL 3/4), while the former ones are those related to the layer directly above the AAL denoted
Connectionless Layer (CLL) and performed by the Connectionless Network Access Protocol (CLNAP),
Connectionless Network Interface Protocol (CLNIP) and related Connectionless Layer Routeing &
Relaying (CLLR&R) functions, respectively.

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ETS 300 478-1: February 1998
The CLL protocols include functions such as routeing, addressing, QoS selection. In order to perform the
routeing of CL data units, the CLSF has to interact with the control/management planes of the underlying
ATM network.
CLSF CLSF
P P or M
ATM ATM
switched switched
capabilities capabilities
Option A Option B
CLSF and ATM switched capabilities CLSF and ATM switched capabilities
implemented in the same equipm ent implemented in different equipment
Figure 2: Implementation of CLSF and ATM switched capabilities
The general protocol structure for the provision of ConnectionLess (CL) data service in B-ISDN is shown
in figure 3.
Custom er terminal ATM switched capabilities
ATM switched capabilities
equipm ent   plus transit C LSF
plus access CLSF
CLLR&R CLLR&R
CLNAP
CLNAP CLNIP CLNIP CLNIP
ATM node
ATM node
AAL 3/4 AAL 3/4 AAL 3/4 AAL 3/4 AAL 3/4
ATM ATM
ATM ATM ATM ATM ATM
Physical Physical
Physical Physical Physical Physical Physical
NOTE: A null (empty) Service Specific Convergence Sublayer (SSCS) is used.
Figure 3: General protocol structure for provision of CBDS in B-ISDN
The CLSF functional group can be considered implemented in the same equipment together with the ATM
switched capabilities as depicted in figure 2 (option A). In this case there is no need to define the interface
at the P reference point. CLSF functional group and ATM switched capabilities can be implemented also
in separate equipment (figure 2, option B). In this case interfaces shall be defined at the M or P Reference
Points (refer to ITU-T Recommendations I.324 [7] and I.327 [8]) depending on whether the CLSF is
located outside or inside the B-ISDN.
4.3 Connectionless server functional description
A Connectionless Server (CLS) is a network element which includes the CLSF. It interfaces ATM nodes or
other CLSs at the P/M reference points and B-ISDN customer equipment at S /T reference points. The
B B
CLS may perform among others the following functions (see also figure 4):
- Connection Functions (CF), which include all port-related functionalities for the termination of ATM
connections;
- Connectionless Handling Functions (CLHF), which include all the service-specific functions required
for the support of connectionless service provision in B-ISDN. In general they are related to the
network integrity issues (e.g. address validation/screening, access class enforcement) and to
relaying issues (e.g. routeing, group address handling);

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ETS 300 478-1: February 1998
- Control Functions (CTF) are related to connection/resource handling and service processing; the
information necessary to effect control over the communication resources in the server can be
exchanged with other network elements through signalling or management protocols;
- Operation And Maintenance (OAM) functions.
NOTE: Transit CLSs do not contain access termination functions and access connection
control functions.
Connection functions
ATF
NTF
ATF
NTF
ATF NTF
Connectionless service handling functions
Other service
CLMF
specific
functions
Control functions
Network
Access
Connection & resource
connection
connection
handling functions
control
control
Operation and m aintenance functions
Figure 4: Connectionless server functional model
The Access Termination Functions (ATF) blocks contain the functions required to receive/transmit
information from/to a B-ISDN user possibly through an ATM node. The block performs protocol
functionalities corresponding to physical, ATM, AAL type 3/4 protocols and CLNAP.
The Network Termination Functions (NTF) blocks include the functions required to receive/transmit
information from/to a CLS possibly through an ATM node. The block performs protocol functionalities
corresponding to physical, ATM, AAL type 3/4 protocols and CLNIP.
Both ATF and NTF blocks include functions for terminating ATM connections and some CL services
specific functions. The description of the functional architecture of the ATF and NTF blocks relevant to the
specification of CLAI and Connectionless Network Interface (CLNI), respectively, is given in
subclause 4.4.
The Connectionless Handling Functions (CLHF) are located partly in the ATF/NTF blocks and partly in the
Connectionless Mapping Functions (CLMF) block.
The CLMF block (see figure 5) performs routeing, protocol conversion between access and network
terminations and group address handling functions, i.e. CLLR&R functions. The CLMF block (as shown in
figure 5) is composed of the following functional blocks:
- Group Address Handling Functions (GAHF);
- Protocol Conversion Functions (PCF); and
- Routeing functions.
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ETS 300 478-1: February 1998
PCF (Protocol
GAHF (G roup Address
Conversion Functions)
Handling F unctions)
Routeing functions
CLMF
Figure 5: CLMF Block
The GAHF block handles both group-addressed CLNAP-PDUs and group-addressed CLNIP-PDUs whose
resolution is requested by this CLS. This functional block performs group-addressed data units handling,
resolving the group address into its associated individual addresses. The resolved individual addresses
may identify end users served either by this CLS or by a remote CLS.
The PCF block performs protocol conversion between the Access Termination Functions (ATF) and the
Network Termination Functions (NTF). In particular, it provides all the relevant information necessary to
properly create a CLNIP-PDU from a CLNAP-PDU or to recover a CLNAP-PDU from the received
CLNIP-PDU.
The functions denoted as routeing, on the basis of the destination address of the data unit to be forwarded
across a User Network Interface (UNI) or Network Node Interface (NNI), select the proper outgoing
physical link and Virtual Path Identifier/Virtual Channel Identifier (VPI/VCI) to reach that destination.
The Control Functions (CTF) include the following functional blocks: access connection control, network
connection control, connection/resource handling functions. These blocks perform functions related to
internal resource allocation (e.g. associated with CL message multiplexing, QoS preservation), connection
establishment/release, etc. In particular, if the CL service is provided on the basis of switched ATM
connections between the terminal equipment and the CLS or between CLSs, the access and network
connection control functions support user access and network signalling systems, respectively. The
access and network connection control functions are, instead, related to the management plane if the CL
service is provided on the basis of semi-permanent ATM connections between the terminal equipment
and the CLS or between CLSs.
The block in figure 5, labelled "Other service specific functions" includes in particular usage information
measurement, traffic observations.
The functions described in this clause do not imply any particular implementation.
4.4 Interfaces
In the following subclauses, the access and network interfaces for the support of the CBDS on B-ISDN are
described for the user plane. The description of the control and management planes for these interfaces is
out of the scope of this ETS.
4.4.1 CLAI
The CLAI supports user access to the CBDS as defined in ETS 300 217 [2] on an ATM network.
User access to the ATM network is provided at the S /T reference points.
B B
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ETS 300 478-1: February 1998
Direct service provision is performed through the use of specialized network elements (CL servers, CLS);
user equipment may have direct access to the CLS at the S /T reference points. The protocol stack
B B
includes the UNI physical and ATM layers both in the user equipment on one side of the CLAI and in the
CL Server on the other side. Policing functions, as foreseen for ATM user access, are performed on the
server side of the CLAI.
a) direct access
CLNAP
CLNAP
AAL3/4 AAL3/4
ATM (UNI) ATM (UNI)
Physical
Physical
Customer CL server
equipment
CLAI at T /S
BB
NOTE: A null (empty) SSCS is used.
b) access via ATM nodes
CLNAP
CLNAP
AAL3/4
AAL3/4
ATM (UNI)
ATM (UNI) ATM (NNI) ATM (NNI)
Physical
Physical
Physical Physical
Customer ATM node CL server
equipment
CLAI at T /S
B
B CLAI at P
NOTE: A null (empty) SSCS is used.
Figure 6: Protocol stack at the U-plane for CLAI
Indirect user access to the server through one or more ATM nodes is also possible. In this case the
interface between the user equipment and the adjacent ATM node is defined at the S /T reference
B B
points, while that between the server and the adjacent ATM node(s) is defined at the P/M reference
points.
At the S /T reference points, the physical and ATM layers of the CLAI protocol stack are terminated in
B B
the user equipment and the ATM node(s). They are based on the ATM UNI. Usage Parameter Control
(UPC) functions as foreseen for ATM user access are performed by the ATM network elements at the
network side of the UNI.
At the P reference point, the physical and ATM layers of the CLAI stack are terminated in the server and
the ATM node(s) and are based on the ATM NNI.
The functions performed by the CL specific protocols (AAL type 3/4 and CLNAP) are the same both in the
direct and indirect access cases. The CLAI protocol stack for the "direct" and "indirect" access is shown in
figure 6. The CLNAP protocol functions and elements are defined in clause 6 of this ETS.

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ETS 300 478-1: February 1998
4.4.1.1 Access Termination Functions (ATF)
The ATF functional block performs all termination functions associated with the CLAI protocol stack and
some service support functions. Figure 7 gives a functional decomposition of the ATF block.
ATF
CLATF
AATF
Figure 7: ATF Functional Decomposition
The description given in the following does not imply any particular implementation.
4.4.1.1.1 ATM Access Termination Functions (AATF)
The AATF perform the protocol functionalities of the physical and ATM layers of the B-ISDN protocol
reference model.
Moreover the AATF perform some of the functions needed for connection establishment and release to
support communication between the server and the users served by it.
Traffic monitoring and control functions based on UPC and/or Network Parameter Control (NPC), as
specification by ITU-T Recommendation I.371 [12], may also be performed by the AATF according to the
type of access.
4.4.1.1.2 CL Access Termination Functions (CLATF)
This subclause only describes the CL termination functions performed in the CLS. CL termination
functions that are performed in the customer equipment are out of the scope of this ETS.
The CLATF of the CLS perform the protocol functionalities of the AAL type 3/4 Segmentation And
Reassembly (SAR), Common Part Convergence Sublayer (CPCS) and the CLNAP.
Other functions performed include:
- Source address validation.
The source address of each CLNAP-PDU is checked by the CLNAP entity at the server side of the
CLAI to support the source address validation feature as specified in ETS 300 217 [2];
- Local traffic filtering.
The destination address of each CLNAP-PDU is checked by the CLNAP entity at the server side of
the CLAI to screen out non-OAM communications destined to the same CLAI (internal to the
Customer Premises Equipment (CPE));
- Destination address screening.
If the address screening supplementary service as defined in ETS 300 217 [2] is provided,
destination address screening is performed by the CLNAP entity at the server side of the CLAI on
both individual and group addresses, in accordance to the service specifications;

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- Source address screening.
If the source address screening supplementary service as defined in ETS 300 217 [2] is provided,
source address screening is performed by the CLNAP entity of the server before delivering a
CLNAP-PDU at the destination CLAI;
- Access class enforcement.
If the network offers access classes, the CLNAP entity on the server side of the CLAI performs
access class enforcement (see subclause 4.8);
- Control of the maximum number of concurrent PDUs.
PDUs in excess of this value are discarded in the user-to-network direction and stored up to a pre-
subscribed limit in the network-to-user direction (see note).
NOTE: In case the number of the maximum allowed concurrent PDUs corresponds to the
number of maximum allowed Multiplexing Identification (MID) in the AAL 3/4 entity, the
AAL 3/4 entity discards the PDUs exceeding the limit.
4.4.2 Connectionless Network Interface (CLNI)
The CLNI supports connectionless service provision, allowing for transparent transfer of connectionless
service data units between CL servers using the ATM switched capabilities of the B-ISDN.
The CLNI protocol stack is terminated in CL servers and is based on the ATM Network Node Interface
(NNI) protocols.
Servers may be interconnected directly. Indirect interconnection through one or more ATM nodes is also
possible. In both cases the AAL type 3/4 protocol and the CLNIP of the CLNI protocol stack are
terminated in CL servers.
The physical and ATM layers are terminated in adjacent servers or between servers and adjacent ATM
node(s). They are in both cases based on the ATM Network Node Interface (NNI) when servers are
attached at the P reference point.

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The protocol stack for the CLNI is shown in figure 8.
a) direct connection between servers
CLNIP
CLNIP
AAL3/4 AAL3/4
ATM (NNI) ATM (NNI)
Physical
Physical
CL server
CL server
CLNI at P
NOTE 1: A null (empty) SSCS is used.
b) servers connected via ATM nodes
CLNIP
CLNIP
AAL3/4
AAL3/4
ATM (NNI)
ATM (NNI) ATM (NNI)
ATM (NNI)
Physical
Physical
Physical Physical
ATM node CL server
CL server
CLNI at P
CLNI at P
NOTE 2: A null (empty) SSCS is used.
Figure 8: Protocol stack at the U-plane for CLNI
The protocol stack for the CLNI includes, on the user plane, the physical, ATM, AAL type 3/4 and
Connectionless Network Interface Protocol (CLNIP).
This protocol stack for the user plane applies both when the connected network elements belong to the
same network operator/service provider and when the network elements belong to different
operators/service providers.
The CLNIP protocol functions and elements are defined in 300 479-1 [14].
4.4.2.1 Network Termination Functions (NTF)
The NTF functional block performs all termination functions associated with the CLNI protocol stack.
Figure 9 gives a functional decomposition of the NTF block.

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NTF
CLNTF
ANTF
Figure 9: NTF functional decomposition
The description given in the following does not imply any particular implementation.
4.4.2.1.1 ATM Network Termination Functions (ANTF)
The ANTF perform the protocol functionalities of the physical and ATM layers of the B-ISDN protocol
reference model.
Moreover the ANTF perform some of the functions needed for connection establishment and release to
support communication between servers.
Traffic monitoring and control functions based on NPC, according to the specification of
ITU-T Recommendation I.371 [12], are also performed by the ANTF when required.
4.4.2.1.2 CL Network Termination Functions (CLNTF)
The CLNTF perform the protocol functionalities of the AAL type 3/4 (SAR and CPCS sublayers, using a
null SSCS) and the CLNIP.
4.5 Connections
CBDS over ATM networks will be supported by ATM connections provisioned on either permanent,
semi-permanent, or switched basis. The CL and AAL type 3/4 functions will be realized by the CL
server(s).
Assignment of the VCI/VPI values is a local matter at each CLAI; a VPC/VCC at a given CLAI supports all
the overall end to end CL communication that a subscriber needs.
Connectionless communications take place at the CLL. For simultaneous transmission of multiple
CLNAP/CLNIP-PDUs each of them is associated with one AAL type 3/4 connection. Multiple AAL type 3/4
connections each associated with one MID value can be mapped on a single ATM connection.
The maximum number of concurrent PDUs is agreed at subscription time.
For a given pair of source and individually addressed destination, at the CL layer the PDU sequence
integrity shall be preserved or, in other words, no PDU should be mis-sequenced (see note).
NOTE: Mis-sequencing occurs at a given receiving interface when the order of reception of
two PDUs issued from the same source interface is different from the sending order. A
PDU is considered as received when the EOM (End of Message) cell/SAR segment of
the PDU has been received. Similarly, a PDU is considered as having been sent when
its EOM (End of Message) has been sent. In the case of interleaving on a ATM
connection of CLNAP/CLNIP-PDUs with the same source and destination address the
AAL type 3/4 may not guarantee the order in which the PDUs are delivered to the CLL.

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4.6 Protocols
The protocol for the support of CBDS on B-ISDN at the UNI is described in clause 6.
The protocol for the support of CBDS at the NNI is described in 300 479-1 [14].
4.7 Numbering and addressing
The number structure of CCITT Recommendation E.164 [3] shall be supported. One or more CCITT
Recommendation E.164 [3] number(s) is (are) assigned to the individual interface at the T reference
B
point. The same number is used in the CLL protocol address fields to identify the CLL entity.
The subscriber, to which the service is offered by a given network operator, accesses the service via a
single CLAI. One or more of the numbers assigned to the T reference point are associated to the CLAI
B
through which the subscriber accesses the service offered to him. The association of CCITT
Recommendation E.164 [3] numbers with S reference point is outside the scope of this ETS.
B
Further information concerning Numbering and addressing for CBDS can be found in annex F,
reference 4).
4.7.1 Individual Address (IA)
An individual address represents the address of a particular interface at the T reference point. More than
B
one number may be assigned to a T reference point (and could be used as an address in a PDU).
B
An IA can be used either as a source or a destination address.
One or more of the CCITT Recommendation E.164 [3] numbers assigned to the T reference point are
B
associated with the CLAI through which the customer accesses the service.
4.7.2 Group Address (GA)
A group address is used as a destination address where a number of recipients is intended, each recipient
being accessed through the use of the "unique" group identity. Each GA identifies uniquely a set of
individual addresses.
The intended recipients of a GA may be served by more than one network.
A GA can only be used as a destination address.
More than one Group Address (GA) may be associated with a CLAI at the T reference point. An interface
B
at the T reference point is identified by a group address if one or more of the individual addresses
B
assigned to the interface at the T reference point is identified by the group address.
B
4.7.3 Nested Group Address (NGA)
A Nested Group Address (NGA) is related to a GA and identifies a subset of individual addresses
pertaining to that GA. The NGA represents a set of individual addresses of members of a GA that are
located inside a given network; this network can be different from the network where the GAP originated
and from the network resolving the GA. (The resolution function provides, for a given GA or NGA, the list
of addresses of all the members and/or NGAs in the case of a GA using NGAs). The type of address used
for a NGA is the same as the one defined for a GA.
A NGA is globally unique. A given NGA associated with a GA cannot be reused for another GA in order to
allow independent evolution of the two GAs. A NGA is not intended to be used in a CLNAP-PDU.

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4.8 Traffic aspects: access class enforcement
The access class enforcement applies between the CPE and the connectionless server (i.e. at the CLAI) it
is connected to in the direction from the user to the network. An access class is defined as a subscription
condition based on the maximum allowed sustained information rate (see note 1) across the CLAI. An
access class mechanism is defined as a set of functions limiting the information rate (
...