ETSI TS 148 016 V13.0.0 (2016-01)

ETSI TS 1148 016 V13.0.0 (201616-01)

TECHNICAL SPECIFICATIONION
Digital cellular telecocommunications system (Phahase 2+);
General Paackec t Radio Service (GPRS);
Base S Station System (BSS) -
Serving GPRS SSupport Node (SGSN) interfarface;
NNetwork service
(3GPP TS 48.0.016 version 13.0.0 Release 1313)

R
GLOBAL SYSTTEME FOR
MOBILE COMMUUNNICATIONS
3GPP TS 48.016 version 13.0.0 Release 13 1 ETSI TS 148 016 V13.0.0 (2016-01)

Reference
RTS/TSGG-0248016vd00
Keywords
GSM
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ETSI
3GPP TS 48.016 version 13.0.0 Release 13 2 ETSI TS 148 016 V13.0.0 (2016-01)
Intellectual Property Rights
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (https://ipr.etsi.org/).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Foreword
This Technical Specification (TS) has been produced by ETSI 3rd Generation Partnership Project (3GPP).
The present document may refer to technical specifications or reports using their 3GPP identities, UMTS identities or
GSM identities. These should be interpreted as being references to the corresponding ETSI deliverables.
The cross reference between GSM, UMTS, 3GPP and ETSI identities can be found under
http://webapp.etsi.org/key/queryform.asp.
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
ETSI
3GPP TS 48.016 version 13.0.0 Release 13 3 ETSI TS 148 016 V13.0.0 (2016-01)
Contents
Intellectual Property Rights . 2
Foreword . 2
Modal verbs terminology . 2
Foreword . 6
1 Scope . 7
2 References . 7
3 Definitions, symbols and abbreviations . 8
3.1 Definitions . 8
3.2 Symbols . 9
3.3 Abbreviations . 9
4 Network Service general description . 10
4.1 Overview . 10
4.2 Addressing . 11
4.2.1 Network Service Virtual Link (NS-VL) . 11
4.2.2 Network Service Virtual Connection (NS-VC) . 12
4.2.3 Network Service Virtual Connection Group . 13
4.2.4 BSSGP Virtual Connection (BVC) . 13
4.2.5 Use of Concepts on the Gb Interface when Intra Domain Connection of RAN Nodes to Multiple CN
Nodes applies in the BSS . 14
4.3 Sub-Network Service functions . 14
4.4 Load sharing function . 15
4.4.1 Load Sharing function for the Frame Relay Sub-Network . 15
4.4.1.1 Overview . 15
4.4.1.2 Requirements on load sharing function . 15
4.4.2 Load sharing function for the IP Sub-Network . 15
4.4.2.1 Overview . 15
4.4.2.2 Selection of the local IP endpoint . 16
4.4.2.3 Selection of the remote IP endpoint . 16
4.4.2.3.1 Selection of remote IP endpoint for data traffic . 16
4.4.2.3.2 Selection of remote IP endpoint for signalling traffic . 17
4.4a Resource distribution function . 17
4.4a.1 Requirements on resource distribution function . 17
4.5 NS-VC management function . 18
4.5.1 Blocking / unblocking of an NS-VC . 18
4.5.2 Reset of an NS-VC . 18
4.5.3 Test of an NS-VC . 19
5 Elements for layer-to-layer communication . 19
5.1 Service primitive model . 19
5.2 Service primitives and parameters . 19
5.2.1 Primitives . 20
5.2.1.1 NS-UNITDATA-Request . 20
5.2.1.2 NS-UNITDATA-Indication . 20
5.2.1.3 NS-CONGESTION-Indication . 20
5.2.1.4 NS-STATUS-Indication . 20
5.2.2 Parameters. 20
5.2.2.1 NS SDU . 20
5.2.2.2 Link Selector Parameter . 21
5.2.2.3 BVCI I and NSEI . 21
5.2.2.4 Congestion cause . 21
5.2.2.5 Transfer capability . 21
5.2.2.6 NS affecting cause. 21
5.2.2.7 NS change IP endpoint . 21
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6 Sub-Network Service protocol . 22
6.1 Frame Relay support of the Sub-Network Service protocol . 22
6.1.1 Overview . 22
6.1.2 Network configuration . 22
6.1.3 Services expected from layer 1 . 23
6.1.4 Options selected from FRF 1.1 . 23
6.1.4.1 Support of DL-CONTROL sub-layer. 23
6.1.4.2 Frame length . 23
6.1.4.3 Congestion control procedures . 23
6.1.4.3.1 DE bit usage . 23
6.1.4.3.2 FECN and BECN bit usage . 23
6.1.4.4 Signalling procedures . 24
6.1.4.5 C/R bit usage . 24
6.1.5 Abnormal conditions. 24
6.2 IP Support of the Sub-Network Service Protocol . 24
6.2.1 Overview . 24
6.2.1a Abnormal Conditions . 25
6.2.2 IP Fragmentation . 25
6.2.3 Services expected from layer 1 and layer 2 . 25
6.2.4 Size Procedure . 25
6.2.4.1 Abnormal Conditions . 26
6.2.5 Configuration Procedure . 26
6.2.5.1 Abnormal Conditions . 27
6.2.6 Add Procedure . 28
6.2.6.1 Abnormal Conditions . 28
6.2.7 Delete Procedure . 29
6.2.7.1 Abnormal Conditions . 29
6.2.8 ChangeWeight Procedure . 29
6.2.8.1 Abnormal Conditions . 30
7 Network Service Control protocol . 30
7.1 Procedures for the transmission of NS SDUs . 30
7.1.1 Abnormal Conditions . 30
7.2 Blocking / unblocking procedures . 30
7.2.1 Abnormal Conditions . 32
7.3 Reset procedure . 32
7.3.1 Abnormal conditions. 33
7.4 Test procedure for a Frame Relay Sub-network . 33
7.4.1 Abnormal conditions. 34
7.4b Test Procedure for an IP Sub-network . 34
7.4b.1 Abnormal Conditions . 34
7.4b.1.1 Abnormal Conditions for signalling endpoints . 34
7.4b.1.2 Abnormal Conditions for data endpoints . 35
7.5 Procedure for error reporting . 35
7.5.1 Abnormal conditions. 35
7.6 Resource Distribution Procedure . 35
7.6.1 Abnormal Conditions . 36
8 General protocol error handling . 36
8.1 General case . 36
8.1.1 Presence requirements of Information Elements . 36
8.1.2 Erroneous events . 37
8.1.3 Non-erroneous events . 37
8.1.4 Other events . 38
8.2 Special cases . 38
8.2.1 Deviations from the "General case" sub-clause . 38
8.2.2 Error reporting . 38
9 General PDU definitions and contents . 38
9.1 General structure of a PDU . 38
9.2 Network Service Control PDUs . 39
9.2.1 NS-ALIVE . 39
9.2.2 NS-ALIVE-ACK . 40
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9.2.3 NS-BLOCK . 40
9.2.4 NS-BLOCK-ACK . 40
9.2.5 NS-RESET . 41
9.2.6 NS-RESET-ACK . 41
9.2.7 NS-STATUS . 41
9.2.7.1 Static conditions for NS-VCI . 42
9.2.7.2 Static conditions for NS PDU . 42
9.2.7.3 Static conditions for BVCI . 42
9.2.7.4 Static conditions for List of IP4 Elements. 42
9.2.7.5 Static conditions for List of IP6 Elements. 42
9.2.8 NS-UNBLOCK . 43
9.2.9 NS-UNBLOCK-ACK . 43
9.2.10 NS-UNITDATA . 43
9.3 Sub-Network Service Control PDUs . 43
9.3.1 SNS-ACK . 43
9.3.2 SNS-ADD . 44
9.3.3 SNS-CHANGEWEIGHT . 44
9.3.4 SNS-CONFIG . 44
9.3.5 SNS-CONFIG-ACK . 45
9.3.6 SNS-DELETE . 45
9.3.7 SNS-SIZE . 45
9.3.8 SNS-SIZE-ACK . 46
10 General information elements coding . 46
10.1 General structure of the information elements . 46
10.1.1 Information Element Identifier . 47
10.1.2 Length indicator . 47
10.2 Information element description . 47
10.3 Information elements . 48
10.3.1 BVCI . 48
10.3.2 Cause . 48
10.3.2a End Flag . 49
10.3.2b IP Address . 49
10.3.2c List of IP4 Elements . 50
10.3.2d List of IP6 Elements . 50
10.3.2e Maximum Number of NS-VCs . 50
10.3.2f Number of IP4 Endpoints . 51
10.3.2g Number of IP6 Endpoints . 51
10.3.3 NS PDU . 51
10.3.4 NS SDU . 51
10.3.5 NS-VCI . 52
10.3.6 NSEI . 52
10.3.7 PDU type . 52
10.3.7a Reset Flag . 52
10.3.8 (void) . 53
10.3.9 NS SDU Control Bits . 53
10.3.10 Transaction ID . 53
11 List of system variables . 53
Annex A (informative): Recommended usage of BVCI and NSEI. 55
Annex B (informative): Recommended usage of Resource Distribution for IP . 56
Annex C (informative): Change History . 59
History . 60

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3GPP TS 48.016 version 13.0.0 Release 13 6 ETSI TS 148 016 V13.0.0 (2016-01)
Foreword
rd
This Technical Specification has been produced by the 3 Generation Partnership Project (3GPP).
The contents of the present document are subject to continuing work within the TSG and may change following formal
TSG approval. Should the TSG modify the contents of the present document, it will be re-released by the TSG with an
identifying change of release date and an increase in version number as follows:
Version x.y.z
where:
x the first digit:
1 presented to TSG for information;
2 presented to TSG for approval;
3 or greater indicates TSG approved document under change control.
y the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections,
updates, etc.
z the third digit is incremented when editorial only changes have been incorporated in the document.
ETSI
3GPP TS 48.016 version 13.0.0 Release 13 7 ETSI TS 148 016 V13.0.0 (2016-01)
1 Scope
The present document specifies the Network Service used on the Base Station System (BSS) to Serving GPRS Support
Node (SGSN) interface (Gb interface).
The protocol stack on the Gb interface is defined in the stage 2 Technical Specification 3GPP TS 43.060.
The Network Service entity provides network services to the BSSGP entity specified in 3GPP TS 48.018.
The layer 1 of the Gb interface is specified in 3GPP TS 48.014.
In the present document, the communication between adjacent layers and the services provided by the layers are
distributed by use of abstract service primitives. But only externally observable behaviour resulting from the description
is normatively prescribed by the present document.
The service primitive model used in the present document is based on the concepts developed in ITU-T
Recommendation X.200.
2 References
The following documents contain provisions which, through reference in this text, constitute provisions of the present
document.
• References are either specific (identified by date of publication, edition number, version number, etc.) or
non-specific.
• For a specific reference, subsequent revisions do not apply.
• For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including
a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same
Release as the present document.
[1] 3GPP TR 21.905: "Vocabulary for 3GPP Specifications".
[2] 3GPP TS 22.060: "General Packet Radio Service (GPRS); Service description; Stage 1".
[3] 3GPP TS 23.060: "General Packet Radio Service (GPRS); Service description; Stage 2".
[4] 3GPP TS 48.014: "General Packet Radio Service (GPRS); Base Station System (BSS) - Serving
GPRS Support Node (SGSN) interface; Gb interface Layer 1".
[5] 3GPP TS 48.018: "General Packet Radio Service (GPRS); Base Station System (BSS) - Serving
GPRS Support Node (SGSN); BSS GPRS Protocol (BSSGP)".
[6] FRF 1.1 (1996): "User-to-Network Implementation Agreement (UNI)".
[7] (void).
[8] ITU-T Recommendation Q.921 (1997): "ISDN user-network interface - Data link layer
specification".
[9] ITU-T Recommendation Q.922 (1992): "ISDN data link layer specification for frame mode bearer
services".
[10] ITU-T Recommendation Q.931 (1998): "ISDN user-network interface layer 3 specification for
Basic Call Control".
[11] ITU-T Recommendation Q.933 (1995): "Digital Subscriber Signalling System No. 1 (DSS 1) -
Signalling specifications for frame mode switched and permanent virtual connection control and
status monitoring".
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[12] ITU-T Recommendation I.370 (1991): "Congestion management for the ISDN Frame Relaying
Bearer Service".
[13] ITU-T Recommendation X.200 (White Book): "Information technology - Open Systems
Interconnection - Basic Reference Model: The basic model".
[14] ANSI T1.602: "ISDN - Data Link Layer Signalling Specification for Application at the
User-Network Interface".
[15] ANSI T1.606 (1990): "Frame Relaying Bearer Service Architectural Framework and Service
description (R 1996)".
[16] ANSI T1.617 (1991): "Digital Subscriber System No. 1 (DSS1) Signaling Specification for Frame
Relay Bearer Service (R1997)".
[17] ANSI T1.618 (1991): "Digital Subscriber System No. 1 (DSS1) Core Aspects of Frame Relay
Protocol for Use with Frame Relay Bearer Service (R1997)".
[18] IETF RFC 768 (1980): "User Datagram Protocol" (STD 6).
[19] IETF RFC 791 (1981): "Internet Protocol" (STD 5).
[20] IETF RFC 2460 (1998): "Internet Protocol, Version 6 (IPv6) Specification".
[21] 3GPP TS 23.236: "Intra-domain connection of Radio Access Network (RAN) nodes to multiple
Core Network (CN) nodes".
3 Definitions, symbols and abbreviations
3.1 Definitions
For the purposes of the present document, the terms and definitions given in 3GPP TS 22.060 and the following in
apply:
BSSGP Virtual Connection (BVC): end-to-end virtual communication path between remote Network Service user
entities
BSSGP Virtual Connection Identifier (BVCI): identifier of a BVC, having end-to-end significance across the Gb
interface
IP endpoint: an endpoint defined by its IP address and UDP port. An IP endpoint can be a data endpoint and/or a
signalling endpoint
Data IP endpoint: an IP endpoint used for Data traffic
Signalling IP endpoint: an IP endpoint used for Signalling traffic
Data traffic: data traffic for an IP Sub-Network is defined as NS SDUs for PTP and PTM functional entities (BVCI≥1)
Signalling traffic: signalling traffic for an IP Sub-Network is defined as NS SDUs for Signalling functional entities
(BVCI=0) and all PDUs for IP Sub-Network Service Control
Full Mesh Connectivity: any IPv4 endpoint in an NSE is capable of communications with any IPv4 endpoint in its
peer NSE. Also any IPv6 endpoint in an NSE is capable of communications with any IPv6 endpoint in its peer NSE
Network Service Entity Identifier (NSEI): identifier of an NS Entity having end-to-end significance across the Gb
interface, i.e. the peer NSEs on the BSS side and the SGSN side are identified by the same NSEI value
Network Service Virtual Connection (NS-VC): end-to-end virtual communication path between Network Service
peer entities
Network Service Virtual Connection Identifier (NS-VCI): identifier of an NS-VC having end-to-end significance
across the Gb interface
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Network Service Virtual Link (NS-VL): virtual communication path between the BSS or the SGSN and the
intermediate network, or between the BSS and the SGSN in case of direct point-to-point configuration
Network Service Virtual Link Identifier (NS-VLI): identifier of an NS-VL, having local significance at the BSS or
SGSN
Network Service Virtual Connection Group: groups all NS-VCs together which provide communication between the
same peer NS entities. This grouping has local significance at the BSS or SGSN
Blocked / unblocked: when an NS-VC can not be used for NS user traffic, it is blocked. When an NS-VC can be used
for NS user traffic, it is unblocked
Dead / alive: when an NS-VC is able to provide communication between remote NS entities, it is alive. When it is not
able, it is dead. These states are supervised by means of a test procedure, as further described in the present document
Pool area: an area within which an MS may roam without need to change the serving SGSN. A pool area is served by
one or more SGSNs in parallel. All the cells controlled by a BSC belong to the same one (or more) pool area(s).
3.2 Symbols
For the purposes of the present document, the symbols given in 3GPP TS 23.060 apply.
3.3 Abbreviations
For the purposes of the present document, the abbreviations given in 3GPP TS 21.905 and the following apply:
BECN Backward Explicit Congestion Notification
BSSGP Base Station System GPRS Protocol
BVC BSSGP Virtual Connection
BVCI BSSGP Virtual Connection Identifier
CLLM Consolidated Link Layer Management
DE Discard Eligibility
FECN Forward Explicit Congestion Notification
FR Frame Relay
FRF Frame Relay Forum
IP Internet Protocol
IPv4 Internet Protocol version 4
IPv6 Internet Protocol version 6
LLC Logical Link Control
LSP Link Selector Parameter
MAC Medium Access Control
NS Network Service
NSEI Network Service Entity Identifier
NS-SAP Network Service Service Access Point
NS-VC Network Service Virtual Connection
NS-VCI Network Service Virtual Connection Identifier
NS-VL Network Service Virtual Link
NS-VLI Network Service Virtual Link Identifier
PDU Protocol Data Unit
PTM Point-To-Multipoint
PTP Point-To-Point
PVC Permanent Virtual Connection
RLC Radio Link Control
SGSN Serving GPRS Support Node
SNS Sub-Network Service
UDP User Datagram Protocol
UNI User-to-Network Interface
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4 Network Service general description
4.1 Overview
The position of the Network Service within the protocol stack of the Gb interface is shown in figure 4.1.1.

LLC
RELAY
BSSGP
RLC BSSGP
MAC
NS NS
L1 L1
Gb
BSS SGSN
NOTE: BSSGP, L1, LLC, MAC, RELAY, RLC are outside the scope of the present document, refer to
3GPP TS 43.060 for further details.

Figure 4.1.1: Position of the NS within the Gb interface protocol stack
The Network Service performs the transport of NS SDUs between the SGSN and BSS. The services provided to the NS
user shall be:
- Network Service SDU transfer. The Network Service entity shall provide network service primitives allowing
for transmission and reception of upper layer protocol data units between the BSS and SGSN. The NS SDUs are
transferred in order by the Network Service, but under exceptional circumstances order may not be maintained.
- Network congestion indication. Congestion recovery control actions may be performed by the Sub-Network
Service (e.g. Frame Relay). Congestion reporting mechanisms available in the Sub-Network Service
implementation shall be used by the Network Service to report congestion.
- Status indication. Status indication shall be used to inform the NS user of the NS affecting events e.g. change in
the available transmission capabilities.
The Network Service entity is composed of an entity dependent on the intermediate transmission network used on the
Gb interface, the Sub-Network Service, and of a control entity independent from that network, the Network Service
Control. There is a hierarchical relationship between both entities. This is reflected in figure 4.1.2. The detailed
communication mechanisms between both entities is an internal matter for the Network Service and is not further
standardized.
Network Service
Network Service Control /
Network Service Control protocol
Sub-Network Service /
Sub-Network Service protocol
Figure 4.1.2: Internal architecture of the Network Service
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The Sub-Network Service entity provides a communication service to Network Service Control peer entities. The
Network Service Control peer entities use the Sub-Network Service for communication with each other. The peer-to-
peer communication accross the Gb interface between remote Network Service Control entities is performed over
Network Service Virtual Connections (NS-VCs). An NS-VC is a virtual communication path between Network Service
Control peer entities.
The Network Service entity provides a communication service to NS user peer entities: the peer-to-peer communication
between remote NS user entities is performed over BSSGP Virtual Connections (BVCs). A BVC is a virtual
communication path between Network Service user peer entities. A Network Service Entity communicates with only
one peer Network Service Entity.
Addressing across the Gb interface is further detailed in the rest of the present document.
The Network Service Control entity is responsible for the following functions:
- NS SDU transmission: The NS SDUs shall be transmitted on the NS-VCs. The NS SDUs are encapsulated into
Network Service Control PDUs which in turn are encapsulated into Sub-Network Service PDUs.
- Load sharing: The load sharing function distributes the NS SDU traffic amongst the available (i.e. unblocked)
NS-VCs of a group.
- NS-VC management: A blocking procedure is used by an NS entity to inform an NS peer entity when an NS-VC
becomes unavailable for NS user traffic. An unblocking procedure is used for the reverse operation. A reset
procedure is used between peer NS entities in order to set an NS-VC to a determined state, after events resulting
in possibly inconsistent states of the NS-VC at both sides of the Gb interface. A test procedure is used to check
that an NS-VC is operating properly between peer NS entities.
4.2 Addressing
The purpose of this sub-clause is to describe the addressing principles on the Gb interface in a generic way, i.e.
irrespective of the exact configuration of the Gb interface and of the exact nature of the intermediate transmission
network, when present. Therefore, this sub-clause provides an abstract description of the addressing principles. These
principles are then applied to real networks in sub-clause "Sub-Network Service protocol".
In this sub-clause, addressing is considered in the general case where an SGSN is connected to several BSSs via an
intermediate transmission network and in the specific case where a BSS is connected to several SGSNs within one or
more pool areas, see 3GPP TS 23.236. Point-to-point physical connections may also be used, addressing in this special
case can be derived from the general case.
4.2.1 Network Service Virtual Link (NS-VL)
An SGSN and a BSS may use different physical links for connecting to each other (e.g. because of intermediate
equipment or transmission network). Each physical link is locally
...