Direct Tunnel

Huawei Proprietary and Confidential

Copyright © Huawei Technologies Co., Ltd

WCDMA RAN

One Tunnel Feature Parameter Description

Copyright © Huawei Technologies Co., Ltd. 2011. All rights reserved.

No part of this document may be reproduced or transmitted in any form or by any means without prior written consent of Huawei Technologies Co., Ltd.

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Notice

The purchased products, services and features are stipulated by the commercial contract made between Huawei and the customer. All or partial products, services and features described in this document may not be within the purchased scope or the usage scope. Unless otherwise agreed by the contract, all statements, information, and recommendations in this document are provided “AS IS” without warranties, guarantees or representations of any kind, either express or implied.

The information in this document is subject to change without notice. Every effort has been made in the preparation of this document to ensure accuracy of the contents, but all statements, information, and recommendations in this document do not constitute a warranty of any kind, express or implied.

WCDMA RAN

One Tunnel Contents

Issue 01 (2011-04-30) Huawei Proprietary and Confidential


i

Contents

1 Introduction ................................................................................................................................ 1-1

1.1 Scope ............................................................................................................................................ 1-1

1.2 Intended Audience ........................................................................................................................ 1-1

1.3 Change History .............................................................................................................................. 1-1

2 Overview ..................................................................................................................................... 2-1

3 Technical Description .............................................................................................................. 3-1

3.1 Overview ....................................................................................................................................... 3-1

3.1 Parameters Description ................................................................................................................. 3-2

3.2 Feature Impact and Requirements ................................................................................................ 3-2

4 Parameters ................................................................................................................................. 4-1

5 Counters ...................................................................................................................................... 5-1

6 Glossary ...................................................................................................................................... 6-1

7 Reference Documents ............................................................................................................. 7-1

WCDMA RAN

One Tunnel 1 Introduction



1-1

1 Introduction

1.1 Scope

This document describes the principles of Huawei One Tunnel feature on the RNC side.

1.2 Intended Audience

This document is intended for:

Personnel who are familiar with WCDMA basics

Personnel who need to understand One Tunnel

Personnel who work with Huawei products

1.3 Change History

This section provides information on the changes in different document versions.

There are two types of changes, which are defined as follows:

Feature change: refers to the change in the One Tunnel feature.

Editorial change: refers to the change in wording or the addition of the information that was not described in the earlier version.

Document Issues

The document issues are as follows:

01 (2011-04-30)

Draft B (2011-03-30)

Draft A (2010-12-30)

01 (2011-04-30)

This is the document for the first commercial release of RAN13.0.

Compared with issue Draft B (2011-03-30) of RAN13.0, this issue optimizes the description.

Draft B (2011-03-30)

This is the draft of the document for RAN13.0.

Compared with issue Draft A (2010-12-30) of RAN13.0, this issue optimizes the description.

Draft A (2010-12-30)

This is the draft of the document for RAN13.0.

Compared with issue 01 (2010-03-30) of RAN12.0, this issue optimizes the description.

WCDMA RAN

One Tunnel 2 Overview



2-1

2 Overview

The specification of One Tunnel (direct connection between RNC and GGSN) is a part of 3GPP Release 7.

In 3G packet core architecture, the Serving GPRS Support Node (SGSN), which is the gateway between the radio network and the core network, processes both signaling traffic for example, to keep track of a user's location and the actual data packets exchanged between the user and the Internet. Since the user's location may change at any time, data packets are tunneled (encapsulated) from the Gateway GPRS Support Node (GGSN) to the Internet through the SGSN over the radio network to the mobile device. The current architecture uses one tunnel between the GGSN and the SGSN and the other one between the SGSN and the Radio Network Controller (RNC). All data packets thus have to pass the SGSN, which has to terminate one tunnel, extract the packet, and then put it into the other tunnel. This requires both time and processing power.

With one tunnel approach, the SGSN can set up a direct tunnel between the RNC and the GGSN and thus remove itself from the chain. Mobility management remains on the SGSN. For example, the SGSN is still responsible for modifying the tunnel when the mobile device moves to an area served by another RNC.

The one tunnel feature has the following advantages:

Reducing a majority of SGSN user plane resource investment and thus reducing CAPEX and OPEX for operators

Shortening the delay and thus improving customer experience

Supporting expansion of the user plane with upgrade of only the GGSN and the RNC and thus improving the network expansibility

WCDMA RAN

One Tunnel 3 Technical Description



3-1

3 Technical Description

3.1 Overview

The one tunnel feature (WRFD-020111 One Tunnel) improves efficiency for PS traffic. It avoids the SGSN to be the bottleneck of the network when high PS traffic occurs.

The preexistent architecture of 3G packet core uses two tunnels. One tunnel is located between the GGSN and the SGSN, and the other between the SGSN and the RNC. All data packets thus have to pass the SGSN, which extracts packets of one tunnel and puts it into the other tunnel. This requires both time and processing power.

Figure 3-1 shows the user plane protocol stack in the two-tunnel scenario.

Figure 3-1 User plane protocol stack

Since both the RNC and the GGSN are IP routers, this process (the SGSN extracts packets of one tunnel and puts it into the other tunnel) is not required in most circumstances. With one tunnel approach, the SGSN can create a direct tunnel between the RNC and the GGSN and thus remove itself from the chain.

Figure 3-2 shows the user plane protocol stack in the one tunnel scenario, in which the control plane protocol stack remains the same.

Figure 3-2 User plane protocol stack

Figure 3-3 shows the data transmission of one tunnel and two tunnels.

WCDMA RAN




3-2

Figure 3-3 Data transmission of one tunnel and two tunnels

Mobility management remains on the SGSN. For example, the SGSN is still responsible for modifying the tunnel when the mobile device moves to an area served by another RNC.

3.1 Parameters Description

To support the one tunnel configuration, the RNC only needs to meet the following requirements:

The RNC follows the GTP-U error handling procedure regardless of the GTP-U Error indication from the SGSN or GGSN.

TS23.060 13.8.3 defines the GGSN fault and the procedure when the RNC receives a GTP error indication. The RNC initiates the RAB release procedure with the error cause value GTP Resources Unavailable. The RNC also triggers the Local Connection Release immediately without waiting for the response from the SGSN.

TS25.413 9.2.1.4 adds the error cause value GTP Resources Unavailable (263) to the IE, that is, Radio Network Layer Cause Extension.

For the configuration and reconfiguration, a new parameter SGSNFLG is added in the ADD ADJNODE command.

3.2 Feature Impact and Requirements

The one tunnel feature requires the support from the GGSN, the SGSN, and the RNC. In the case of one tunnel, the following NEs or interfaces may have new functions or new information elements (IEs):

SGSN

− The DTI field in the PDP context is used to indicate whether one tunnel is supported.

− Determine whether to establish one tunnel.

GGSN

The DTI field in the PDP context is used to indicate whether one tunnel is supported.

RNC

− Support Error Indication messages.

− Manage the paths between the GGSN and the RNC.

Gn

− Add DTI information to the Update PDP Context Request.

../RNCParaHtml/mbsc/m-para/adjnode_sgsnflg.html

WCDMA RAN




3-3

− Replace the SGSN user plane address of the Update PDP Context Request with the RNC user plane address. The number of signaling points, however, remains the same.

− Add GCSI information to the Forward Relocation Request for CAMEL service indication.

− The GGSN sends the Update PDP Context Request to the SGSN during the Error Indication procedure. The Update PDP Context Request contains the error information.

Iu

− Replace the SGSN user plane address of the RAB Assignment Request with the GGSN user plane address. The number of signaling points, however, remains the same.

− Add Error Cause (GTP Resources Unavailable) to the RAB Release Request.

WCDMA RAN

One Tunnel 4 Parameters



4-1

4 Parameters

Table 4-1 Parameter description

Parameter ID NE MML Command Description

SGSNFLG BSC6900 ADD ADJNODE(Mandatory)

Meaning:This parameter specifies whether the BSC6900 is connected to a SGSN or a GGSN. This parameter is valid when the node type is set to IUPS. A parameter value YES indicates that the BSC6900 is connected to a SGSN. A parameter value NO indicates that the BSC6900 is connected to a GGSN

GUI Value Range:NO(GGSN), YES(SGSN)

Actual Value Range:NO, YES

Default Value:None

../RNCParaHtml/mbsc/m-para/adjnode_sgsnflg.html

../RNCParaHtml/mbsc/m-mml/add-adjnode.html

../RNCParaHtml/mbsc/m-mml/add-adjnode.html

WCDMA RAN

One Tunnel 5 Counters



5-1

5 Counters

There are no specific counters associated with this feature.

WCDMA RAN

One Tunnel 6 Glossary



6-1

6 Glossary

For the acronyms, abbreviations, terms, and definitions, see the Glossary.

Glossary.htm

WCDMA RAN

One Tunnel 7 Reference Documents



7-1

7 Reference Documents

[1] 3GPP TS23.060 Service description

[2] 3GPP TS25.413 UTRAN Iu interface RANAP signalling

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