ETSI ETS 300 467 ed.1 (1998-03)

Broadband Integrated Services Digital Network (B-ISDN); Support of Frame Relay Bearer Service (FRBS) in B-ISDN and frame relay interworking between B-ISDN and other networks

DE/NA-053204

Širokopasovno digitalno omrežje z integriranimi storitvami (B-ISDN) – Nosilna storitev blokovnega posredovanja (FRBS) v B-ISDN in meddelovanje sistema B-ISDN z drugimi omrežji

General Information

• Status: Published
• Publication Date: 08-Mar-1998
• Technical Committee: NA 5 - Broadband Networks
• Current Stage: 12 - Completion
• Due Date: 13-Mar-1998
• Completion Date: 09-Mar-1998
• Ref Project: SIST ETS 300 467 E1:2003 - Broadband Integrated Services Digital Network (B-ISDN); Support of Frame Relay Bearer Service (FRBS) in B-ISDN and frame relay interworking between B-ISDN and other networks

Standards Content (Sample)

SLOVENSKI STANDARD
SIST ETS 300 467 E1:2003
01-december-2003
Širokopasovno digitalno omrežje z integriranimi storitvami (B-ISDN) – Nosilna
storitev blokovnega posredovanja (FRBS) v B-ISDN in meddelovanje sistema B-
ISDN z drugimi omrežji
Broadband Integrated Services Digital Network (B-ISDN); Support of Frame Relay
Bearer Service (FRBS) in B-ISDN and frame relay interworking between B-ISDN and
other networks
Ta slovenski standard je istoveten z: ETS 300 467 Edition 1
ICS:
33.080 Digitalno omrežje z Integrated Services Digital
integriranimi storitvami Network (ISDN)
(ISDN)
SIST ETS 300 467 E1:2003 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST ETS 300 467 E1:2003
EUROPEAN ETS 300 467
TELECOMMUNICATION March 1998
STANDARD
Source: NA Reference: DE/NA-053204
ICS: 33.020
Key words: Broadband, frame relay, interworking, ISDN, B-ISDN, frame mode, Bearer
Broadband Integrated Services Digital Network (B-ISDN);
Support of Frame Relay Bearer Service (FRBS) in B-ISDN and
frame relay interworking between B-ISDN and other networks
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
Internet: [e-mail] - http://www.etsi.fr - http://www.etsi.org
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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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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Contents
Foreword .5
1 Scope .7
2 Normative references.7
3 Abbreviations.8
4 Service description.10
4.1 Functional architecture.10
4.1.1 FRBS provided by FRSF inside B-ISDN .10
4.1.2 FRBS provided by FRSF outside B-ISDN, accessed via ATM bearer
capabilities.11
4.1.3 Frame relay protocol support via ATM bearer capabilities.12
5 Interfaces and protocols.13
5.1 Frame Relay B-ISDN Access Interface (FR-BAI) .13
5.1.1 Physical Layer .14
5.1.2 ATM layer .14
5.1.3 AAL.14
5.1.3.1 AAL5 SAR and CPCS.14
5.1.3.2 FR-SSCS.14
5.2 Frame relay B-ISDN Network-to-Network Interface (FR-BNNI) .14
5.2.1 Physical Layer (PL) .15
5.2.2 ATM layer .15
5.2.3 AAL.15
5.2.3.1 AAL5 SAR and CPCS.15
5.2.3.2 FR-SSCS.15
5.3 FR-SSCS .15
5.3.1 Service provided by FR-SSCS .15
5.3.1.1 Primitives .16
5.3.1.2 Description of connections .17
5.3.2 Interaction with the management and control plane.17
5.3.3 Functions, structure and coding of FR-SSCS .17
5.3.3.1 Functions in FR-SSCS.17
5.3.3.2 FR-SSCS-PDU structure and coding .18
5.3.4 Procedures for the FR-SSCS.18
5.3.4.1 State variable.18
5.3.4.2 Procedures at the sender side.18
5.3.4.3 Procedures at the receiver side.19
5.3.4.4 Summary of parameters and values on the FR-SSCS
connections.21
5.3.5 Frame Relay Permanent Virtual Connection (FR-PVC) monitoring .21
5.4 Multiplexing of FRBS connections over B-ISDN.22
5.5 Congestion management strategy.23
Annex A (normative): Additional procedures for Frame Relay Permanent Virtual Connections
(FR PVCs) for the carriage on ATM using unnumbered information frame.24
History.25

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Foreword
This European Telecommunication Standard (ETS) has been produced by the Network Aspects (NA)
Technical Committee of the European Telecommunications Standards Institute (ETSI).
This European Telecommunication Standard (ETS) defines the B-ISDN architectural configuration for
providing the FRBS service.
Transposition dates
Date of adoption of this ETS: 20 February 1998
Date of latest announcement of this ETS (doa): 30 June 1998
Date of latest publication of new National Standard
or endorsement of this ETS (dop/e): 31 December 1998
Date of withdrawal of any conflicting National Standard (dow): 31 December 1998

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1 Scope
This ETS defines the Broadband Integrated Services Digital Network (B-ISDN) architectural configuration
for providing the Frame Relay Bearer Service (FRBS) service.
B-ISDN FRBS is defined in ETS 300 399-1 [5] and ETS 300 399-4 [8].
This ETS specifies service specific convergence sublayer of AAL type 5 and its use for B-ISDN FRBS.
The B-ISDN FRBS belongs is a connection-oriented, variable bit rate, non assured operation broadband
services with no timing relation between the sender and receiver.
This ETS also describes the network interworking between B-ISDNs supporting FRBS and other ISDNs
and Public Data Networks (PDNs) supporting FRBS as defined in ETS 300 399-1 [5], ETS 300 399-2 [6]
and ETS 300 399-3 [7].
It describes also access configurations to networks supporting FRBS or FRDTS.
This ETS defines only the U-plane procedures for FRBS supported on Permanent Virtual Connections
(PVCs).
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] ETS 300 298-2: "Broadband Integrated Services Digital Network (B-ISDN);
Asynchronous Transfer Mode (ATM); Part 2: B-ISDN ATM layer specification
[ITU-T Recommendation I.361 (1995)]".
[2] ETS 300 299: "Broadband Integrated Services Digital Network (B-ISDN); Cell
based user network access for 155 520 kbit/s and 622 080 kbit/s; Physical layer
interfaces for B-ISDN applications".
[3] ETS 300 300: "Broadband Integrated Services Digital Network (B-ISDN);
Synchronous Digital Hierarchy (SDH) based user network access; Physical layer
User Network Interfaces (UNI) for 155 520 kbit/s and 622 080 kbit/s
Asynchronous Transfer Mode (ATM) B-ISDN applications".
[4] ETS 300 337: "Transmission and Multiplexing (TM); Generic frame structures
for the transport of various signals (including Asynchronous Transfer Mode
(ATM) cells and Synchronous Digital Hierarchy (SDH) elements) at the
ITU-T Recommendation G.702 hierarchical rates of 2 048 kbit/s, 34 368 kbit/s
and 139 264 kbit/s".
[5] ETS 300 399-1: "Frame relay services; Part 1: General description".
[6] ETS 300 399-2: "Frame relay services; Part 2: Integrated Services Digital
Network (ISDN); Frame relay bearer service; Service definition".
[7] ETS 300 399-3: "Frame relay services; Part 3: Frame relay data transmission
service; Service definition".
[8] ETS 300 399-4: "Frame relay services; Part 4: Broadband Integrated Services
Digital Network (B-ISDN); Frame relay bearer service; Service definition".
[9] ETS 300 428: "Broadband Integrated Services Digital Network (B-ISDN);
Asynchronous Transfer Mode (ATM) Adaptation Layer (AAL) specification -
type 5".

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[10] ETS 300 455-1: "Broadband Integrated Services Digital Network (B-ISDN);
Broadband Virtual Path Service (BVPS); Part 1: BVPS for Permanent
communications (BVPS-P)".
[11] ETS 300 455-2: "Broadband Integrated Services Digital Network (B-ISDN);
Broadband Virtual Path Service (BVPS); Part 2: BVPS for Reserved
communications (BVPS-R)".
[12] ITU-T Recommendation F.811 (1993): "Broadband connection-oriented bearer
service".
[13] ITU-T Recommendation G.804 (1994): "ATM cell mapping into plesiochronous
digital hierarchy (PDH)".
[14] ITU-T Recommendation G.832 (1994): "Transport of SDH elements on PDH
networks - Frame and multiplexing structures".
[15] CCITT Recommendation I.233.1 (1992): "ISDN frame relaying bearer service".
[16] ITU-T Recommendation I.363 (1994): "B-ISDN ATM Adaptation Layer (AAL)
specification".
[17] ITU-T Recommendation I.365.1 (1994): "Frame relaying service specific
convergence sublayer (FR-SSCS)".
[18] CCITT Recommendation I.370 (1992): "Congestion management for the ISDN
frame relaying bearer service".
[19] ETS 300 301, Edition 2 (1997): "Broadband Integrated Services Digital Network
(B-ISDN); Traffic control and congestion control in B-ISDN [ITU-T
Recommendation I.371 (1996)]".
[20] ITU-T Recommendation I.372 (1993): "Frame relaying bearer service network-
to-network interface requirements".
[21] ITU-T Recommendation I.555 (1994): "Frame relaying bearer service
interworking".
[22] CCITT Recommendation Q.922 (1992): "ISDN data link layer specification for
frame mode bearer services".
[23] ITU-T Recommendation Q.933 (1994): "Digital Subscriber Signalling System
No.1 (DSS1) - Signalling specification for frame mode basic call control".
[24] ITU-T Recommendation I.327 (1993): "B-ISDN functional architecture".
3 Abbreviations
For the purposes of this ETS, the following abbreviations apply:
AAL ATM Adaptation Layer
AAL5 AAL type 5
ATM Asynchronous Transfer Mode
ATM-VCC Asynchronous Transfer Mode-Virtual Circuit Connection
B-ISDN Broadband Integrated Services Digital Network
B-TE B-ISDN Terminal
BECN Backward Explicit Congestion Notification
BVPS Broadband Virtual Path Service
C/R Command/Response bit
CBR Constant Bit Rate
CEB Congestion Encountered Backward
CEF Congestion Encountered Forward

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CI Congestion Indication
CPCS Common Part Convergence Sublayer
CPCS-CI CPCS - Congestion Indication
CPCS-LP CPCS - Loss Priority
CPCS-UU CPCS - User-to-User Indication
D/C DLCI or DL-CORE control indicator
DE Discard Eligibility
DLCI Data Link Connection Identifier
DSS1 Digital Subscriber Signalling N°1
DTE Data Terminal Equipment
EA Address Extension bit
FCS Frame Check Sequence
FECN Forward Explicit Congestion Notification
FR Frame Relay
FR-BNNI Frame Relay Broadband Network-to-Network Interface
FR-IWP Frame Relay Interworking Point
FR-SSCS Frame Relay Service Specific Convergence Sublayer
FR-BAI Frame Relay Broadband Access Interface
FR-IAI Frame Relay ISDN Access Interface
FR-INNI Frame Relay ISDN Network to Network Interface
FR-PAI Frame Relay Private Access Interface
FR-PNNI Frame Relay Private Network to Network Interface
FRBS Frame Relay Bearer Service
FRDTS Frame Relay Data Transmission Service
FRSF Frame Relay Service Function
ID Interface Data
ISDN Integrated Service Digital Network
IWF Interworking Function
LME Layer Management Entity
LSB Least Significant Bit
MSB Most Significant Bit
NNI Network Node Interface
PCI Protocol Control Information
PDH Plesiochronous Digital Hierarchy
PDN Public Data Network
PDU Protocol Data Unit
PHY Physical layer
PISN Private Integrated Service Network
PVC Permanent Virtual Connection
SAP Service Access Point
SAR Segmentation and Reassembly Sublayer
SDH Synchronous Digital Hierarchy
SDU Service Data Unit
SSCS Service Specific Convergence Sublayer
TE Terminal Equipment
UNI User Network Interface
UPC Usage Parameter Control
VBR Variable Bit Rate
VC Virtual Channel
VCC Virtual Channel Connection
VCI Virtual Channel Identifier
VP Virtual Path
VPC Virtual Path Connection
VPI Virtual Path Identifier

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4 Service description
This description of FRBS in B-ISDN is in accordance with:
- ITU-T Recommendation F.811 [12], which provides a service description of a broadband
connection oriented bearer service. ITU-T Recommendation F.811 [12] includes the following
service subcategories:
- sub-category A: Constant Bit Rate (CBR);
- sub-category B: Variable Bit Rate (VBR) with timing;
- sub-category C: VBR without timing:
C1: emulation of packet mode bearer services;
C2: emulation of frame mode bearer services;
C3: others.
- sub-category X: Asynchronous Transfer Mode (ATM) Adaptation Layer (AAL) defined by
user;
- ETS 300 399-2 [6], which defines ISDN FRBS;
- ETS 300 399-1 [5];
- ETS 300 399-4 [8].
4.1 Functional architecture
B-ISDN is capable of supporting data transfer between B-ISDN customers based on frame relay transfer
techniques. The B-ISDN configuration is in line with the functional architecture defined in
ITU-T Recommendation I.327 [24]. It need not directly imply frame relay methods implemented within
B-ISDN. In the B-ISDN, virtual channels are established at the ATM layer by means of the connection
oriented technique. The frame relay protocol can be supported in the U-plane using the B-ISDN in the
following three ways:
a) FRBS provided by Frame Relay Service Function (FRSF) inside B-ISDN;
b) FRBS provided by FRSF outside B-ISDN, accessed via ATM bearer capabilities;
c) frame relay protocol support via ATM bearer capabilities.
In all cases the protocol stack implemented in B-ISDN customer equipment is identical as shown in
figures 1, 2 and 3. The management and control plane functions which need to be provided in the network
in all cases are for further study. The three cases are outlined in the following paragraphs.
4.1.1 FRBS provided by FRSF inside B-ISDN
In this case the FRSF is provided within the B-ISDN. The FRSF handles frame relay protocols and routes
data according to routing information provided during frame relay connection establishment. This case is
illustrated in figures 1a and 1b.
ATM
switched
B-ISDN
capabilities
B-ISDN B-ISDN
customer
customer
S or T
P S or T
using VP or VC
connections
FRSF FRSF
ATM connection
FRSF
FRSF: Frame Relay Service Function
P , S, or T:
Reference points
Figure 1a: FRBS provided by FRSF inside B-ISDN

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ATM ATM TE
TE ATM FRSF FRSF
FR-SSCS
FR-SSCS FR-SSCS FR-SSCS
CPCS
CPCS
CPCS CPCS
(note) SAR
SAR SAR (note) SAR
(note)
ATM ATM
ATM ATM ATM ATM
ATM
PHY PHY
PHY PHY PHY
PHY PHY
NOTE: The ATM switching capabilities can be integrated with FRSF.
Figure 1 b: Protocol stack of FRBS provided by FRSF inside B-ISDN
The statistical multiplexing can be done at the frame level. In this case the bearer capabilities required
from the ATM network can be met by those provided by the Virtual Path (VP) bearer service already
defined in ETS 300 455 [11], with peak bandwidth allocation. Virtual Channel (VC) bearer capabilities may
also be deployed and the way of mapping the frame relay parameters into ATM transfer capabilities
(e.g. for statistical multiplexing at the ATM layer) is for further study.
4.1.2 FRBS provided by FRSF outside B-ISDN, accessed via ATM bearer capabilities
In this case a transparent connection of the ATM layer, is used between B-ISDN interfaces (at reference
points S /T or M). Frame relay protocols operating on and above the adaptation layer are transparent to
B B
the B-ISDN. The frame relay service and adaptation layer functions are implemented outside the B-ISDN.
This case is illustrated in figures 2a and 2b.
Specialized
service provider
fram e relay FRSF
S pecialized
service
service provider
FRSF
fram e relay
service
M
M
B-ISDN
ATM
customer
sw itched
S or T
B-ISDN
capabilities
customer
S or T
using VP or VC
connection s
B-ISDN
ATM connection
FRSF Frame Relay Service Function
M, S, or T Reference points
Figure 2a: FRBS provided by FRSF outside B-ISDN

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ATM
TE ATM FRSF FRSF ATM TE
FR-SSCS FR-SSCS
FR-SSCS FR-SSCS
CPCS CPCS
CPCS CPCS
SAR SAR
SAR SAR
ATM
ATM ATM ATM
ATM ATM ATM
PHY
PHY PHY
PHY PHY PHY PHY
Figure 2b: Protocol stack of FRBS provided by FRSF outside B-ISDN
The requirements on the ATM layer are the same as in subclause 4.1.1.
4.1.3 Frame relay protocol support via ATM bearer capabilities
A frame relay protocol may also be carried by ATM bearer capabilities as shown in figures 3a and 3b. In
this case a transparent connection of the ATM layer, is used between B-ISDN UNIs (at reference point
S /T ). Frame relay protocols operating on and above the adaptation layer are transparent to the B-ISDN
B B
and they are implemented in the Terminal Equipments (TEs) at B-ISDN UNIs.
B-ISDN
B-ISDN
ATM
customer customer
switched
S or T
S or T
capabilities
using VP o r VC
connections
ATM connection
S or T Reference points
B-ISDN
Figure 3a: A frame relay protocol carried by an ATM bearer service
TE
ATM ATM TE
FR-SSCS
FR-SSCS
CPCS CPCS
SAR SAR
ATM ATM ATM ATM
PHY
PHY PHY PHY
Figure 3b: Protocol stack of frame relay protocol carried by an ATM bearer service
The switching and statistical multiplexing is done at the ATM level. The preliminary list of requirements for
the used bearer service is as follows:
- Virtual Channel Identifier (VCI) based switching;
- isolation between connections: e.g. usage parameter control, network parameter control;
- delay and delay variation adapted to data applications;
- network congestion: the random discarding of cells can badly impact the frame loss rate. This
impact may be reduced by taking frame boundaries (reflected in the value of the AUU bit in the
ATM cell header) into account when taking discarding decisions;
- a minimum bandwidth requirement per connection has to be met.
NOTE: Optional multiplexing at the frame level is transparent to the B-ISDN.

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5 Interfaces and protocols
5.1 Frame Relay B-ISDN Access Interface (FR-BAI)
Frame relay direct provision is performed through the use of specialized network functions (FRSF). User
equipment may have direct access to the equipment realizing FRSF at the S /T reference points. The
B B
protocol stack includes the UNI physical and ATM layer both in the user equipment on one side of the
FR-BAI and in the network equipment realizing FRSF on the other side. Usage Parameter Control (UPC)
functions, as foreseen for ATM user access, are performed on the network side of the FR-BAI.
Indirect user access to the FRSF 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 equipment realizing the FRSF and the adjacent ATM node(s) is defined at
the P/M reference points.
At the S /T reference points, the physical and ATM layer of the FR-BAI stack are terminated in the user
B B
equipment and the ATM node(s). They are based on the ATM UNI. 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/M reference points, the physical and ATM layer of the FR-BAI stack are terminated in the
equipment realizing FRSF and the ATM node(s) and are based on the ATM Network Node
Interface (NNI).
The functions performed by the frame relay specific layer (AAL 5 SAR, CPCS and Frame Relay Service
Specific Convergence Sublayer (FR-SSCS)) are the same both in the direct and indirect access cases.
The protocol stack for the direct and indirect access is shown in figure 4. The FR-SSCS protocol functions
and elements are defined in subclause 5.3.
FRSF or IWF
FR-B-TE
FR-SSCS FR-SSCS
CPCS CPCS
SAR SAR
ATM (UNI) ATM (UNI)
PHY PHY
FR-BAI
a) direct access
FR-B-TE ATM node FRSF or IWF
FR-SSCS FR-SSCS
CPCS CPCS
SAR SAR
ATM (UNI) ATM (NNI)
ATM (UNI) ATM (NNI)
PHY PHY
PHY PHY
FR-BAI
FR-BAI
at S /T at P / M
bb
b) access via ATM nodes
Figure 4: Frame Relay Broadband Access Interface (FR-BAI) U-plane protocol
reference architecture

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5.1.1 Physical Layer
All B-ISDN physical layer specifications are applicable (including ETS 300 300 [3] and ETS 300 299 [2],
ETS 300 337 [4], ITU-T Recommendations G.804 [13] and G.832 [14]).
5.1.2 ATM layer
As defined in ETS 300 298-2 [1].
5.1.3 AAL
5.1.3.1 AAL5 SAR and CPCS
As defined in ETS 300 428 [9].
5.1.3.2 FR-SSCS
As defined in subclause 5.3.
5.2 Frame relay B-ISDN Network-to-Network Interface (FR-BNNI)
The FR-BNNI supports frame relay service provision, allowing transfer of frame relay service data units
within the ATM network.
The FR-BNNI protocol stack is based on the ATM Network Node Interface (NNI).
Equipment realizing the FR-BNNI stack may be connected directly. Indirect linking through one or more
ATM nodes is also possible.
The U-plane protocol reference architecture for the FR-BNNI is given in figure 5.
FRSF or IWF
FRSF or IWF
FR-SSCS FR-SSCS
CPCS CPCS
SAR SAR
ATM (NNI) ATM (NNI)
PHY PHY
FR-BNNI
a) direct access
ATM node FRSF or IWF
FRSF or IWF
FR-SSCS FR-SSCS
CPCS CPCS
SAR SAR
ATM (NNI)
ATM (NNI) ATM (NNI)
ATM (NNI)
PHY PHY
PHY PHY
FR-BNNI
FR-BNNI
at S / T
at P / M
bb
b) access via ATM nodes
Figure 5: FR-BNNI U-plane protocol reference architecture
AAL 5
AAL 5
AAL 5
AAL 5

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5.2.1 Physical Layer (PL)
All B-ISDN physical layer specifications are applicable (including ETS 300 300 [3] and ETS 300 299 [2],
ETS 300 337 [4], ITU-T Recommendations G.804 [13] and G.832 [14]).
5.2.2 ATM layer
As defined in ETS 300 298-2 [1].
5.2.3 AAL
5.2.3.1 AAL5 SAR and CPCS
As defined in ETS 300 428 [9].
5.2.3.2 FR-SSCS
As defined in subclause 5.3.
5.3 FR-SSCS
NOTE: This subclause is in line with ITU-T Recommendation I.365.1 [17], but they are not
exactly the same.
The FR-SSCS is located in the upper part of the AAL on top of the Common Part Convergence Sublayer
(CPCS) of AAL type 5, as specified ETS 300 428 [9], clause 6 and shown in figures 6 and 7. The
FR-SSCS is used at the B-TE to emulate the FRBS in B-ISDN. It is also used for interworking between a
B-ISDN and a frame relay network.
5.3.1 Service provided by FR-SSCS
At the DL-CORE-SAP the FR-SSCS provides the core service as described in ETS 300 399-1[5],
annex C. The core service primitives, exchanged between the core service user and the core service
provider (FR-SSCS) are summarized in table 1 according to the table contained in CCITT
Recommendation Q.922 [22], subclause A.4.2.2. The primitives and their parameters are described in
detail in [5], annex C (see figure 6).
DL-CORE-SAP
DL-CORE DATA.request
DL-CORE DATA.indication
FR-SSCS
CPCS-UNITDATA.invoke CPCS-UNITDATA.signal
CPCS
SAR
ATM-DATA.request ATM-DATA.indication
ATM-SAP
Figure 6: Location of the FR-SSCS in the B-ISDN protocol reference model for a B-TE

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The exchange of information at the Frame Relay Interworking Point (FR-IWP) is described by
IWF-DATA.indication and IWF-DATA.request primitives (see figure 7). The parameters of those primitives
are contained in table 2.
FR-IWP
IWF-DATA.indication
Q.922
FR-SSCS
CORE
IWF-DATA.request
CPCS-UNITDATA.invoke CPCS-UNITDATA.signal
CPCS
SAR
ATM-DATA.request ATM-DATA.indication
ATM-SAP
Figure 7: Location of the FR-SSCS in the B-ISDN protocol reference model for the IWF between a
frame relay network and a B-ISDN
In the case of a FRSF, figure 7 applies with the following modification: the FR-IWP does not lead to Q.222
core, but to the same protocol stack as shown at the right hand side of the figure.
The FR-SSCS preserves the FR-SSCS-SDU sequence integrity. It uses the CPCS message mode
service without the corrupted data delivery option.
5.3.1.1 Primitives
The primitives exchanged across the DL-CORE-SAP are described in table 1.
Table 1: Core service primitives and parameters at the DL-CORE-SAP
Primitive DL-CORE DL-CORE FR-SSCS-PDU field
Parameter (note) DATA. request DATA.
indication
DL-CORE user data X X Information field
Discard Eligibility (DE) X DE
CEB X BECN
CEF X FECN
DL-CORE-Service-User protocol control X X C/R bit
information
X: parameter is present
NOTE: Whether the DL-CORE control parameter and the DLCI or DL-CORE control indicator
parameter are included in the DL-CORE DATA primitives is for further study.

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SIST ETS 300 467 E1:2003
Page 17
ETS 300 467: March 1998
The primitives exchanged across the FR-IWP are described in table 2.
Table 2: Primitives and parameters at the FR-IWP
Primitive IWF-DATA. IWF DATA. FR-SSCS-PDU field
Parameter request indication
DL-CORE user data X X Information field
DEl X X DE
CEB X X BECN
CEF X X FECN
DL-CORE-Service-User protocol control X X C/R bit
information
DLCI or DL-CORE control indicator XXD/C
(note 1)
DL-CORE control (note 2) X X DL-CORE control
X: parameter is present
NOTE 1: If this parameter is set = C it indicates the existence of the DL-CORE control
parameter.
NOTE 2: This parameter only exists as indicated by the DLCI or DL-CORE control indicator
parameter.
The primitives exchanged across the boundary between the FR-SSCS and the CPCS of AAL type 5 are
described in ITU-T Recommendation ETS 300 428 [9].
5.3.1.2 Description of connections
Multiple FR-SSCS connections may be associated with a single CPCS connection (and with the
corresponding ATM connection), allowing multiplexing at the FR-SSCS. Within a CPCS connection the
FR-SSCS connections are uniquely identified by the Data Link Connection Identifiers (DLCIs).
5.3.2 Interaction with the management and control plane
For further study.
5.3.3 Functions, structure and coding of FR-SSCS
5.3.3.1 Functions in FR-SSCS
The functions provided by the FR-SSCS include:
a) Multiplexing/demultiplexing
This function provides the capability to multiplex multiple FR-SSCS connections into a single CPCS
connection.
b) Inspection of the FR-SSCS-PDU length
These functions inspect the FR-SSCS-PDU to ensure that it consists of an integral number of
octets and to ensure that it is neither too long nor too sh
...