LTE

Contents

Doc. Code

eRAN2.2S1AP

Issue01

Date2011-09-30

DOCPROPERTY Confidential

HUAWEI TECHNOLOGIES CO., LTD.

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.

Trademarks and Permissions

and other Huawei trademarks are trademarks of Huawei Technologies Co., Ltd.

All other trademarks and trade names mentioned in this document are the property of their respective holders.

Notice

The purchased products, services and features are stipulated by the contract made between Huawei and the customer. All or part of the products, services and features described in this document may not be within the purchase scope or the usage scope. Unless otherwise specified in 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.

Huawei Technologies Co., Ltd.

Address:Huawei Industrial Base

Bantian, Longgang

Shenzhen 518129

People's Republic of China

Website:http://www.huawei.com

Email:support@huawei.com

About This Document

Change HistoryThe change history describes the changes in each release, and the latest document contains all change histories in earlier documents.

Issue 01 (2011-09-30)

First official release. Contents

iiiAbout This Document

11 Overview

11.1 S1 User Plane

21.2 S1 Control Plane

62 E-RAB Management

62.1 E-RAB Setup

62.2 E-RAB Modify

72.3 E-RAB Release

83 Context Management

83.1 Initial Context Setup

93.2 UE Context Release

103.3 UE Context Modification

114 Handover Signaling

114.1 Handover Preparation

124.2 Handover Resource Allocation

134.3 Handover Notification

134.4 Path Switch Request

144.5 Handover Cancelation

144.6 eNodeB Status Transfer

154.7 MME Status Transfer

165 Paging

176 NAS Transport

176.1 Initial UE Message

186.2 Downlink NAS Transport

186.3 Uplink NAS Transport

196.4 NAS Non Delivery Indication

207 Management Procedures

207.1 Reset

217.2 Error Indication

227.3 S1 Setup

227.4 eNodeB Configuration Update

237.5 MME Configuration Update

247.6 Overload Start

247.7 Overload Stop

258 UE Capability Information Indication

269 eNodeB Direct Information Transfer

2710 MME Direct Information Transfer

2811 eNodeB Configuration Transfer

2912 MME Configuration Transfer

1 Overview

The S1 interface connects the eNodeB and the mobility management entity (MME) or serving gateway (S-GW) and has two planes: user plane and control plane.

1.1 S1 User Plane

The S1 interface transmits data between the eNodeB and the S-GW. The S1 user plane transmits data at the transport network layer based on the Internet Protocol (IP).

Figure 1-1 S1 user plane

1.2 S1 Control Plane

Figure 1-2 S1 control plane

The S1 control plane transmits data based on the IP and Stream Control Transmission Protocol (SCTP) to provide reliable data transmission for radio networks.

The S1 Application Protocol (S1AP) transmits signaling between the evolved packet core (EPC) and the evolved universal terrestrial radio access network (E-UTRAN) to provide S1AP services. The S1AP has the following functions:

E-UTRAN radio access bearer (E-RAB) management. This function is used to establish, modify, and release an E-RAB.

Initial context transfer. This function is used to establish S1 user equipment (UE) contexts on an eNodeB, to establish one or more E-RABs if requested by an MME, and to transfer information about non-access stratum (NAS) signaling to the eNodeB.

UE capability information indication.

UE mobility management in LTE_ACTIVE mode, including intra-LTE handovers and inter-RAT handovers.

Paging. This function enables the EPC to page UEs.

S1 interface management. For example, error indication and S1 setup.

NAS signaling transfer between the UE and the MME.

S1 UE context release.

UE context modification.

Status transfer.

Tracing

Location reporting.

LPPa signaling transfer.

S1AP has two classes of basic procedures, as shown in Table 1-1 and Table 1-2.

Table 1-1 Class 1 procedures

Elementary ProcedureInitiating MessageSuccessful OutcomeUnsuccessful Outcome

Response MessageResponse Message

Handover PreparationHANDOVER REQUIREDHANDOVER COMMANDHANDOVER PREPARATION FAILURE

Handover Resource AllocationHANDOVER REQUESTHANDOVER REQUEST ACKNOWLEDGEHANDOVER FAILURE

Path Switch RequestPATH SWITCH REQUESTPATH SWITCH REQUEST ACKNOWLEDGEPATH SWITCH REQUEST FAILURE

Handover CancelationHANDOVER CANCELHANDOVER CANCEL ACKNOWLEDGE

E-RAB SetupE-RAB SETUP REQUESTE-RAB SETUP RESPONSE

E-RAB ModifyE-RAB MODIFY REQUESTE-RAB MODIFY RESPONSE

E-RAB ReleaseE-RAB RELEASE COMMANDE-RAB RELEASE RESPONSE

Initial Context SetupINITIAL CONTEXT SETUP REQUESTINITIAL CONTEXT SETUP RESPONSEINITIAL CONTEXT SETUP FAILURE

ResetRESETRESET ACKNOWLEDGE

S1 SetupS1 SETUP REQUESTS1 SETUP RESPONSES1 SETUP FAILURE

UE Context ReleaseUE CONTEXT RELEASE COMMANDUE CONTEXT RELEASE COMPLETE

UE Context ModificationUE CONTEXT MODIFICATION REQUESTUE CONTEXT MODIFICATION RESPONSEUE CONTEXT MODIFICATION FAILURE

eNB Configuration UpdateENB CONFIGURATION UPDATEENB CONFIGURATION UPDATE ACKNOWLEDGEENB CONFIGURATION UPDATE FAILURE

MME Configuration UpdateMME CONFIGURATION UPDATEMME CONFIGURAION UPDATE ACKNOWLEDGEMME CONFIGURATION UPDATE FAILURE

Write-Replace Warning WRITE-REPLACE WARNING REQUESTWRITE-REPLACE WARNING RESPONSE

KillKILL REQUESTKILL RESPONSE

Table 1-2 Class 2 procedures

Elementary ProcedureMessage

Handover NotificationHANDOVER NOTIFY

E-RAB Release IndicationE-RAB RELEASE INDICATION

PagingPAGING

Initial UE MessageINITIAL UE MESSAGE

Downlink NAS TransportDOWNLINK NAS TRANSPORT

Uplink NAS TransportUPLINK NAS TRANSPORT

NAS non delivery indicationNAS NON DELIVERY INDICATION

Error IndicationERROR INDICATION

UE Context Release RequestUE CONTEXT RELEASE REQUEST

DownlinkS1 CDMA2000 TunnelingDOWNLINK S1 CDMA2000 TUNNELING

Uplink S1 CDMA2000 TunnelingUPLINK S1 CDMA2000 TUNNELING

UE Capability Info IndicationUE CAPABILITY INFO INDICATION

eNB Status TransfereNB STATUS TRANSFER

MME Status TransferMME STATUS TRANSFER

Deactivate TraceDEACTIVATE TRACE

Trace StartTRACE START

Trace Failure IndicationTRACE FAILURE INDICATION

Location Reporting ControlLOCATION REPORTING CONTROL

Location Reporting Failure IndicationLOCATION REPORTING FAILURE INDICATION

Location ReportLOCATION REPORT

Overload StartOVERLOAD START

Overload StopOVERLOAD STOP

eNodeB Direct Information TransfereNB DIRECT INFORMATION TRANSFER

MME Direct Information TransferMME DIRECT INFORMATION TRANSFER

eNodeB Configuration TransfereNB CONFIGURATION TRANSFER

MME Configuration TransferMME CONFIGURATION TRANSFER

Cell Traffic TraceCELL TRAFFIC TRACE

Downlink UE Associated LPPa TransportDOWNLINK UE ASSOCIATED LPPA TRANSPORT

Uplink UE Associated LPPa TransportUPLINK UE ASSOCIATED LPPA TRANSPORT

Downlink Non UE Associated LPPa TransportDOWNLINK NON UE ASSOCIATED LPPA TRANSPORT

Uplink Non UE Associated LPPa TransportUPLINK NON UE ASSOCIATED LPPA TRANSPORT

2 E-RAB Management

2.1 E-RAB Setup

The purpose of this procedure is to allocate resources to the Uu and the S1 interfaces for one or more E-RABs and to set up data radio bearers (DRBs) for a specific UE.

Figure 2-3 E-RAB Setup procedure (successful operation)

The MME sends an E-RAB SETUP REQUEST message to initiate the procedure. After receiving the message, the eNodeB sends the MME an E-RAB SETUP REQUEST message if the required resources are available.

If the E-RAB SETUP REQUEST message contains the UE Aggregate Maximum Bit Rate information element (IE), the eNodeB replaces the UE Aggregate Maximum Bit Rate IE with the UE Aggregate Maximum Bit Rate IE. If the E-RAB SETUP REQUEST message does not contain the UE Aggregate Maximum Bit Rate IE, the eNodeB uses the UE Aggregate Maximum Bit Rate IE in the UE context. Resources are set up or modified on an eNodeB based on the Allocation and Retention Priority IE.

2.2 E-RAB Modify

The purpose of this procedure is to modify an E-RAB configured for UEs.

Figure 2-4 E-RAB Modify procedure (successful operation)

The MME sends an E-RAB SETUP REQUEST message to initiate the procedure. An E-RAB MODIFY REQUEST message contains information about one or more configured E-RABs.

2.3 E-RAB Release

The purpose of this procedure is to release a configured E-RAB in either of the following modes:

MME-initiated E-RAB release

Figure 2-5 MME-initiated E-RAB Release procedure (successful operation)

eNodeB-initiated E-RAB release

Figure 2-6 eNodeB-initiated E-RAB Release procedure (successful operation)

3 Context Management

3.1 Initial Context Setup

The purpose of this procedure is to set up mandatory UE contexts, including the E-RAB context, security key, and handover restriction list.

Figure 3-7 Initial Context Setup procedure (successful operation)

The EPC must get ready for receiving user-plane data on an E-RAB before the MME receives a CONTEXT SETUP RESPONSE message from an eNodeB.

The eNodeB must perform the following operations after receiving an INITIAL CONTEXT SETUP REQUEST message:

2. Attempts to execute the requested E-RAB configuration.

3. Saves the UE Aggregate Maximum Bit Rate IE in the UE context and uses the received UE Aggregate Maximum Bit Rate IE.

4. Saves the handover restriction list in the UE context.

5. Saves the UE capability in the UE context.

If the eNodeB cannot set up the UE context, it sends an INITIAL CONTEXT SETUP FAILURE message to the MME.

Figure 3-8 Initial Context Setup procedure (unsuccessful operation)

3.2 UE Context Release

The UE context can be released in either of the following modes:

eNodeB-initiated UE context release

A UE CONTEXT RELEASE REQUEST message contains the reasons why UEs are not in the active state and why UEs exit the wireless network.

MME-initiated UE Context Release procedure

The MME sends the eNodeB a UE CONTEXT RELEASE COMMAND message to initiate the procedure. The UE CONTEXT RELEASE COMMAND message contains the UE S1AP ID pair IE. If the message does not contain the IE, it must contain the MME UE S1AP ID IE. After receiving the UE CONTEXT RELEASE COMMAND message, the eNodeB releases all related resources for the IEs and user-plane data transmission and responds to the MME with a UE CONTEXT RELEASE COMPLETE message.

3.3 UE Context Modification

This purpose of this procedure is to modify the configured UE context.

Figure 3-9 UE Context Modification procedure (successful operation)

A UE CONTEXT MODIFICATION REQUEST message contains the following IEs:

Security Key

Subscriber Profile ID for RAT/Frequency Priority

UE Aggregate Maximum Bit Rate

CS Fallback Indicator

UE Security Capabilities

CSG Membership Status

Registered LAI

Figure 3-10 UE Context Modification procedure (unsuccessful operation)

If UE context modification fails, the eNodeB responds to the MME with a UE CONTEXT MODIFICATION FAILURE message that contains the Cause IE.

4 Handover Signaling

4.1 Handover Preparation

The purpose of this procedure is to enable the EPC to instruct a target eNodeB to prepare all resources before a handover is performed. Each UE has only one handover preparation process at the same time.

Figure 4-11 Handover Preparation procedure (successful operation)

The source eNodeB sends the MME a HANDOVER REQUIRED message to initiate the procedure. When the source eNodeB sends the message, it starts the TS1RELOCprep timer. After the handover preparation, including resource subscription on the target eNodeB, the MME responds to the source eNodeB a HANDOVER COMMAND message. After receiving the HANDOVER COMMAND message, the source eNodeB stops the TS1RELOCprep timer and starts the TS1RELOCOverall timer.

If the EPC or the target eNodeB cannot accept any bearers or the handover fails, the MME sends the source eNodeB a HANDOVER PREPARATION FAILURE message that contains the reason why the failure occurs.

Figure 4-12 Handover Preparation procedure (unsuccessful operation)

4.2 Handover Resource Allocation

The purpose of this procedure is to reserve resources at the target eNodeB for a UE to be handed over.

Figure 4-13 Hanover Resource Allocation procedure (successful operation)

The MME sends the target eNodeB a HANDOVER REQUEST message to initiate the procedure. After receiving the HANDOVER REQUEST message, the target eNodeB saves the UE Security Capabilities IE and uses the configuration of the IE and related UE access stratum (AS) to encrypt data.

Figure 4-14 Hanover Resource Allocation procedure (unsuccessful operation)

4.3 Handover Notification

The purpose of this procedure is to inform the MME, UE, and target cell of a successful S1 handover.

Figure 4-15 Handover Notification procedure

4.4 Path Switch Request

The purpose of this procedure is to request the switch of a downlink GPRS tunneling protocol (GTP) tunnel towards a new GTP tunnel. GPRS is short for general packet radio service. Figure 4-16 Path Switch Request procedure (successful operation)

An eNodeB sends to the MME a PATH SWITCH REQUEST message to initiate the procedure.

Figure 4-17 Path Switch Request procedure (unsuccessful operation)

If the handover fails on the EPC, the MME responds to the eNodeB with a PATH SWITCH REQUEST FAILURE message that contains the reason why the failure occurs.

4.5 Handover Cancelation

The purpose of this procedure is to enable a source eNodeB to cancel ongoing handover preparations or a prepared handover.

Figure 4-18 Handover Cancelation procedure (successful operation)

The source eNodeB sends the MME a HANDOVER CANCEL message to initiate the procedure. A HANDOVER CANCEL message contains the Cause IE. After receiving the HANDOVER CANCEL message, the EPC stops the ongoing process, releases resources for a handover, and sends the source eNodeB a HANDOVER CANCEL ACKNOWLEDGE message.

4.6 eNodeB Status Transfer

In this procedure, two types of status are transmitted: the receiving status of uplink Packet Data Convergence Protocol-sequence number (PDCP-SN) and hyper frame number (HFN) and the transmitting status of downlink PDCP-SN and HFN.

Figure 4-19 eNodeB Status Transfer procedure

4.7 MME Status Transfer

Figure 4-20 MME Status Transfer procedure

5 Paging

The purpose of this procedure is to enable the MME to page UEs.

Figure 5-21 Paging procedure

6 NAS Transport

The purpose of this procedure is to carry UEMME signaling over the S1 interface. The NAS messages are transported in an IE of the INITIAL UE MESSAGE, DOWNLINK NAS TRANSPORT, or UPLINK NAS TRANSPORT message.

6.1 Initial UE Message

Figure 6-22 Initial UE Message procedure

After receiving the first UL NAS message transmitted on a radio resource control (RRC) connection to be forwarded to an MME, the eNodeB must activate the NAS transport procedure and send the MME an INITIAL UE MESSAGE message.

6.2 Downlink NAS Transport

Figure 6-23 Downlink NAS Transport procedure

The MME sends a UE an NAS message through the eNodeB.

6.3 Uplink NAS Transport

Figure 6-24 Uplink NAS Transport procedure

6.4 NAS Non Delivery Indication

Figure 6-25 NAs Non Delivery Indication procedure

If an eNodeB decides not to start the delivery of a NAS message or the eNodeB cannot ensure that a UE receives the message, the eNodeB reports the non-delivery of this NAS message by sending the MME an NAS NON DELIVERY INDICATION message.

7 Management Procedures

7.1 Reset

The reset procedure can be initiated by either the MME or the E-UTRAN.

MME-initiated reset procedure:

Figure 7-26 MME-initiated Reset procedure (successful operation)

If the MME loses some or all transaction reference information, it sends the eNodeB a RESET message. After receiving the RESET message, the eNodeB releases all allocated resources over the S1 interface and Uu interface related to UEs. Then, the eNodeB responds to the MME with a RESET ACKNOWLEDGE message.

E-UTRAN-initiated reset procedure:

Figure 7-27 E-UTRAN-initiated Reset procedure (successful operation)

If the eNodeB loses some or all transaction reference information, it sends the MME a RESET message. After receiving the RESET message, the MME releases all allocated resources over the S1 interface related to UEs. Then, the MME responds to the eNodeB with a RESET ACKNOWLEDGE message.

7.2 Error Indication

The purpose of this procedure is to report detected errors in one incoming message at one node. This procedure can be initiated either by the MME or by an eNodeB.

Figure 7-28 MME-initiated Error Indication procedure (successful operation)

Figure 7-29 eNodeB-initiated Error Indication procedure (successful operation)

An ERROR INDICATION message must contain a minimum of one Cause IE or Criticality Diagnostics IE.

7.3 S1 Setup

Figure 7-30 S1 Setup procedure (successful operation)

The eNodeB sends the MME an S1 SETUP REQUEST message to initiate the procedure. Then, the MME responds to the eNodeB with an S1 SETUP RESPONSE message. When this procedure is finished, the S1 interface is operational and other S1 messages can be exchanged.

Figure 7-31 S1 Setup procedure (unsuccessful operation)

If the MME cannot accept the setup, it responds to the eNodeB with an S1 SETUP FAILURE message.

7.4 eNodeB Configuration Update

The purpose of this procedure is to update configuration data at the application layer over the S1 interface.

Figure 7-32 eNodeB Configuration Update procedure (successful operation)

An eNodeB sends the MME an ENB CONFIGURATION UPDATE message including a set of updated configuration data. If the MME successfully updates the configuration data, it sends the eNodeB an ENB CONFIGURATION UPDATE ACKNOWLEDGE message. If the MME cannot update the configuration data, it responds to the eNodeB with an ENB CONFIGURATION UPDATE FAILURE message.

Figure 7-33 eNodeB Configuration Update procedure (unsuccessful operation)

7.5 MME Configuration Update

The purpose of this procedure is to update configuration data at the application layer over the S1 interface.Figure 7-34 MME Configuration Update procedure (successful operation)

The MME sends an eNodeB an MME CONFIGURATION UPDATE message including a set of updated configuration data. If the eNodeB successfully updates the configuration data, it sends the MME an MME CONFIGURATION UPDATE ACKNOWLEDGE message. If the eNodeB cannot update the configuration data, it responds to the MME with an MME CONFIGURATION UPDATE FAILURE message.

7.6 Overload Start

The purpose of this procedure is to inform an eNodeB to reduce the signaling load towards the connected MME.

Figure 7-35 Overload Start procedure

7.7 Overload Stop

The purpose of this procedure is to inform an eNodeB that the overload status at the MME has ended and normal operation resumes.

Figure 7-36 Overload Stop procedure

8 UE Capability Information Indication

The purpose of this procedure is to enable an eNodeB to provide UE capability information for the MME.

Figure 8-37 UE Capability Information Indication procedure (successful operation)

An eNodeB sends the MME a UE CAPABILITY INFO INDICATION message to provide UE capability information for the MME. After obtaining UE capability information in the received message, the MME replaces any previously stored UE capability information for UEs.

9 eNodeB Direct Information Transfer

The purpose of this procedure is to transfer RAN information from an eNodeB to the MME in unacknowledged mode.

Figure 9-38 eNodeB Direct Information Transfer procedure (successful operation)

10 MME Direct Information Transfer

The MME sends an eNodeB a DIRECT INFORMATION TRANSFER message to initiate the procedure.

Figure 10-39 MME Direct Information Transfer procedure (successful operation)

11 eNodeB Configuration Transfer

The purpose of this procedure is to transfer RAN configuration information from an eNodeB to the MME in unacknowledged mode.

Figure 11-40 eNodeB Configuration Transfer procedure (successful operation)

12 MME Configuration Transfer

The purpose of this procedure is to transfer RAN configuration information from the MME to an eNodeB in unacknowledged mode.

Figure 12-41 MME Configuration Transfer procedure (successful operation)

ivHuawei Proprietary and Confidential Copyright Huawei Technologies Co., LtdIssue 01 (2009-04-10)

_1382791348.doc

HANDOVER FAILURE

target eNB

MME

HANDOVER REQUEST

_1382791357.doc

MME

eNB

INITIAL UE MESSAGE

_1382791367.doc

S1 SETUP RESPONSE

eNB

MME

S1 SETUP REQUEST

_1382791371.doc

MME CONFIGURATION UPDATE ACKNOWLEDGE

eNB

MME

MME CONFIGURATION UPDATE

_1382791374.doc

OVERLOAD STOP

eNB

MME

_1382791376.doc

eNB

MME

ENB DIRECT INFORMATION TRANSFER

_1382791379.doc

eNB

MME

ENB CONFIGURATION TRANSFER

_1382791380.doc

eNB

MME

MME CONFIGURATION TRANSFER

_1382791377.doc

eNB

MME

MME DIRECT INFORMATION TRANSFER

_1382791375.doc

UE CAPABILITY INFO INDICATION

MME

eNB

_1382791373.doc

OVERLOAD START

eNB

MME

_1382791369.doc

ENB CONFIGURATION UPDATE ACKNOWLEDGE

eNB

MME

ENB CONFIGURATION UPDATE

_1382791370.doc

ENB CONFIGURATION UPDATE FAILURE

eNB

MME

ENB CONFIGURATION UPDATE

_1382791368.doc

S1 SETUP FAILURE

eNB

MME

S1 SETUP REQUEST

_1382791362.doc

MME

RESET

RESET ACKNOWLEDGE

eNB

_1382791364.doc

ERROR INDICATION

MME

eNB

_1382791365.doc

ERROR INDICATION

MME

eNB

_1382791363.doc

MME

RESET ACKNOWLEDGE

RESET

eNB

_1382791359.doc

MME

eNB

UPLINK NAS TRANSPORT

_1382791361.doc

MME

eNB

NAS NON DELIVERY INDICATION

_1382791358.doc

eNB

MME

DOWNLINK NAS TRANSPORT

_1382791352.doc

HANDOVER CANCELACKNOWLEDGE

HANDOVER CANCEL

MME

Source eNB

_1382791355.doc

eNB

MME

MME STATUS TRANSFER

_1382791356.doc

eNB

MME

PAGING

_1382791354.doc

eNB

MME

eNB STATUS TRANSFER

_1382791350.doc

PATH SWITCH REQUEST ACKNOWLEDGE

eNB

MME

PATH SWITCH REQUEST

_1382791351.doc

PATH SWITCH REQUEST FAILURE

eNB

MME

PATH SWITCH REQUEST

_1382791349.doc

target eNB

MME

HANDOVER NOTIFY

_1382791338.doc

MME

eNB

INITIAL CONTEXT SETUP FAILURE

INITIAL CONTEXT SETUP REQUEST

_1382791343.doc

MME

UE CONTEXT MODIFICATION FAILURE

UE CONTEXT MODIFICATION REQUEST

eNB

_1382791345.doc

HANDOVER PREPARATION FAILURE

source eNB

MME

HANDOVER REQUIRED

_1382791346.doc

HANDOVER REQUEST ACKNOWLEDGE

target eNB

MME

HANDOVER REQUEST

_1382791344.doc

HANDOVER COMMAND

source eNB

MME

HANDOVER REQUIRED

_1382791340.doc

MME

UE CONTEXT RELEASE COMPLETE

UE CONTEXT RELEASE COMMAND

eNB

_1382791342.doc

MME

UE CONTEXT MODIFICATION RESPONSE

UE CONTEXT MODIFICATION REQUEST

eNB

_1382791339.doc

UE CONTEXT RELEASE REQUEST

MME

eNB

_1382791333.doc

E-RAB MODIFY REQUEST

E-RAB MODIFY RESPONSE

eNB

MME

_1382791336.doc

MME

eNB

E-RAB RELEASE INDICATION

_1382791337.doc

MME

eNB

INITIAL CONTEXT SETUP RESPONSE

INITIAL CONTEXT SETUP REQUEST

_1382791334.doc

eNB

MME

E-RAB RELEASE COMMAND

E-RAB RELEASE RESPONSE

_1382791331.doc

SCTP

Physical layer

S1-AP

Data link layer

IP

_1382791332.doc

E-RAB SETUP REQUEST

MME

eNB

E-RAB SETUP RESPONSE

_1382791330.doc

UDP

Physical layer

GTP-U

User plane PDUs

Data link layer

IP