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RA41234EN06GLA1 EPC Protocol Overview 1

04 RA41234EN06GLA1 LTE EPC Network Interface Protocols

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04 RA41234EN06GLA1 LTE EPC Network Interface Protocols

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Each interface supports a different set of control and status messages.

• Uu Interface – The air interface between the UE and the eNodeB.

• S1-MME Interface – The logical signaling interface between an eNodeB and MME. Each eNodeB must be logically connected to every MME in the serving MME pool. This interface carries S1 Application Protocol (S1AP) control plane traffic.

• S1-U Interface – The logical “data” interface between an eNodeB and S-GW. This interface carries GPRS Tunneling Protocol – User Plane (GTP-U) traffic between an eNodeB and S-GW on behalf of a UE. Each eNodeB must be logically connected to every S-GW in the serving S-GW pool.

• S5 Interface – The logical interface between an S-GW and P-GW. This interface carries GTP-C control plane traffic and GTP-U user plane traffic.

• S6a Interface – The logical signaling interface between an MME and HSS. This interface carries Diameter control plane traffic to authenticate the UE, and update the UE context.

• S10 Interface – The logical interface between two MMEs. This interface carries GTP-C control plane traffic which manages UE handovers between two MMEs.

• S11 Interface – The logical signaling interface between an MME and S-GW. This interface carries GTP-C control plane traffic which sets up and manages S5 user plane tunnels, and signals paging is required for incoming data sessions.

• X2 Interface – The logical interface between two adjacent eNodeBs. The X2 interface carries both control plane and GTP-U user plane traffic. The control plane traffic uses the X2 Application Protocol (X2AP).

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• S3: It enables user and bearer information exchange for inter 3GPP access network mobility in idle and/or active state. This reference point can be used intra-PLMN or inter-PLMN (e.g. in the case of Inter-PLMN HO).

• S4: It provides related control and mobility support between GPRS Core and the 3GPP Anchor function of Serving GW. In addition, if Direct Tunnel is not established, it provides the user plane tunneling

• Gx: It provides transfer of (QoS) policy and charging rules from PCRF to Policy and Charging Enforcement Function (PCEF) in the PDN GW..

• S12: Reference point between UTRAN and Serving GW for user plane tunneling when Direct Tunnel is established. It is based on the Iu-u/Gn-u reference point using the GTP-U protocol as defined between SGSN and UTRAN or respectively between SGSN and GGSN. Usage of S12 is an operator configuration option.

• S13: It enables UE identity check procedure between MME and EIR.

• SGi: It is the reference point between the PDN GW and the packet data network. Packet data network may be an operator external public or private packet data network or an intra operator packet data network, e.g. for provision of IMS services. This reference point corresponds to Gi for 3GPP accesses.

• Rx: The Rx reference point resides between the AF and the PCRF in the TS 23.203

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The 3GPP standards describe an all-IP network. Both control plane (signaling) traffic and user plane (bearer) traffic use the TCP/IP protocol suite. Except for the LTE air (Uu) interface, (almost) any Data Link and Physical Layer protocols are allowed.

3GPP mandates support for either IPv4 or IPv6, or both. Depending on the interface and traffic type, Transmission Control Protocol(TCP), User Datagram Protocol (UDP), or Stream Control Transmission Protocol (SCTP) may be used at the Transport Layer.

The LTE air (Uu) interface subdivides the Data Link Layer into sublayers for user bearer and control traffic.

All bearer traffic, including voice, video and data, uses IP for transport. Either IPv4 or IPv6, or both, may be supported.

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S1-MME Functions

The S1-MME interface functions are:

• UE context management

• E-RAB management

• S1-MME and S1-U link management

• GTP-U tunnels management

• Mobility for active Ues

• Paging

• Network sharing and NAS node selection coordination

• Security, including data confidentiality, air interface encryption and key management, and data integrity

• Service and network access, including signaling data transfer, UE tracing, and location reporting

3GPP TS 36.411 S1 Layer 1

3GPP TS 36.412 S1 Signaling Transport

3GPP TS 36.413 S1 Application Program (S1AP)

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The graphic illustrates the S1-MME Interface signaling protocol stack. Any Physical Layer and Data Link Layer are allowed. The IP version may be IPv6 and/or IPv4. In either case, the S1 endpoints must support IP Differentiated Services (DiffServ) Code Points for QoS. Instead of using TCP or UDP, 3GPP selected Stream Control Transmission Protocol (SCTP) at Layer 4. Essentially SCTP offers TCP-like reliability and error recovery with UDP-like throughput. The S1 signaling state machine and messages are controlled by the S1 Application Protocol (S1AP).

The S1 Interface signaling protocol stack provides:

• Reliable transfer of S1AP messages over the S1 Interface

• Networking and routing

• Redundancy in the signaling network

• Flow control and overload protection

• In the future, this Interface may support load-sharing and dynamic S1-MME configuration

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S1AP Functions

The S1 Application Protocol (S1AP) provides the following functions:

• UE context transfer and context release

• E-RAB management, including setting up, modifying and releasing E-RAB channels

• Provides capability information to the UE

• Mobility Functions, including changing eNodeBs within LTE or RAN nodes between different RATs

• Paging

• S1 interface management functions, including S1 configuration and reset capability, error indication, overload handling, and load balancing

• Transfer NAS signaling before or after the UE context is established in the eNodeB S1 UE context release

• PDCP sequence number status transfer

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3GPP TS 36.413 S1 Application Program (S1AP)

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In the following tables, all EPs are divided into Class 1 and Class 2 Eps

An EP consists of an initiating message and possibly a response message. Two kinds of EPs are used:

- Class 1: Elementary Procedures with response (success and/or failure).

- Class 2: Elementary Procedures without response.

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The following applies concerning interference between Elementary Procedures:

- The Reset procedure takes precedence over all other EPs.

- The UE Context Release procedure takes precedence over all other EPs that are using the UE-associated signaling.

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The E-RAB Setup procedure is initiated by the MME to support:

- Assignment of resources to a dedicated E-RAB.

- Assignment of resources for a default E-RAB.

- Setup of S1 Bearer (on S1) and Data Radio Bearer (on Uu).

The E-RAB Setup procedure comprises the following steps:

− The E-RAB SETUP REQUEST message is sent by the MME to the eNB to setup

resources on S1 and Uu for one or several E-RAB(s). The E-RAB SETUP

REQUEST message contains the Serving GW TEID, QoS indicator(s) and the

corresponding NAS message per E-RAB within the E-RAB To Be Setup List. When

there are multiple NAS messages in the E-RAB SETUP REQUEST message, the

MME shall ensure that the NAS messages in the E-RAB to be Setup List are aligned

in the order of reception from the NAS layer to ensure the in-sequence delivery of

the NAS messages.

− Upon receipt of the E-RAB SETUP REQUEST message the eNB establishes the

Data Radio Bearer(s) (RRC: Radio Bearer Setup) and resources for S1 Bearers.

When there are multiple NAS messages to be sent in the RRC message, the order

of the NAS messages in the RRC message shall be kept the same as that in the E-

RAB SETUP REQUEST message.

− The eNB responds with a E-RAB SETUP RESPONSE messages to inform whether

the setup of resources and establishment of each E-RAB was successful or

unsuccessful, with the E-RAB Setup list (E-RAB ID , eNB TEID) and the E-RAB

Failed to Setup list (E-RAB ID, Cause) The eNB also creates the binding between

the S1 bearer(s) (DL/UL TEID) and the Data Radio Bearer(s).

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The E-RAB Modification procedure is initiated by the MME to support the modification of already established E-RAB configurations:

Modify of S1 Bearer (on S1) and Radio Bearer (on Uu)

The EPS Bearer Modification procedure comprises the following steps:

− The E-RAB MODIFY REQUEST message is sent by the MME to the eNB to modify one or several E-RAB(s). The E-RAB MODIFY REQUEST message contains the QoS indicator(s), and the corresponding NAS message per E-RAB in the E-RAB To Be Modified List. When there are multiple NAS messages in the E-RAB MODIFY REQUEST message, the MME shall ensure that the NAS messages in the E-RAB to be Modified List are aligned in the order of reception from the NAS layer to ensure the in-sequence delivery of the NAS messages.

− Upon receipt of the E-RAB MODIFY REQUEST message the eNB modifies the Data Radio Bearer configuration (RRC procedure to modify the Data Radio bearer). When there are multiple NAS messages to be sent in the RRC message, the order of the NAS messages in the RRC message shall be kept the same as that in the E-RAB MODIFY REQUEST message.

− The eNB responds with an E-RAB MODIFY RESPONSE message to inform whether the E-RAB modification has succeeded or not indicating with the E-RAB Modify list and E-RAB Failed to Modify list. With E-RAB ID(s) in the E-RAB Modify List or E-RAB Failed to Modify List the eNB identifies the E-RAB(s) successfully modified or failed to modify.

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The E-RAB Release procedure is initiated by the MME to release resources

for the indicated E-RABs.

The E-RAB Release procedure comprises the following steps:

- The E-RAB RELEASE COMMAND message is sent by the MME to

the eNB to release resources on S1 and Uu for one or several E-

RAB(s). With the E-RAB ID(s) in the E-RAB To Be Released List

contained in E-RAB RELEASE COMMAND message the MME

identifies, the E-RAB(s) to be released.

- Upon receipt of the E-RAB RELEASE COMMAND message the eNB

releases the Data Radio Bearers (RRC: Radio bearer release) and S1

Bearers.

- The eNB responds with an E-RAB RELEASE COMPLETE message

containing E-RAB Release list and E-RAB Failed to Release list. With

the E-RAB IDs in the E-RAB Release List/E-RAB Failed to Release

List the eNB identifies the E-RAB(s) successfully released or failed to

release.

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• The Initial Context Setup procedure establishes the necessary overall initial UE

context in the eNB in case of an Idle-to Active transition. The Initial Context Setup

procedure is initiated by the MME.

• The Initial Context Setup procedure comprises the following steps:

− The MME initiates the Initial Context Setup procedure by sending INITIAL

CONTEXT SETUP REQUEST to the eNB. This message may include

general UE Context (e.g. security context, roaming restrictions, UE

capability information, UE S1 signaling connection ID, etc.), E-RAB context

(Serving GW TEID, QoS information), and may be piggy-backed with the

corresponding NAS messages. When there are multiple NAS messages in

the INITIAL CONTEXT SETUP REQUEST message, the MME shall

ensure that the NAS messages in the E-RAB to be Setup List are aligned

in the order of reception from the NAS layer to ensure the in-sequence

delivery of the NAS messages.

− Upon receipt of INITIAL CONTEXT SETUP REQUEST, the eNB setup the

context of the associated UE, and perform the necessary RRC signaling

towards the UE, e.g. Radio Bearer Setup procedure. When there are

multiple NAS messages to be sent in the RRC message, the order of the

NAS messages in the RRC message shall be kept the same as that in the

INITIAL CONTEXT SETUP REQUEST message.

− The eNB responds with INITIAL CONTEXT SETUP COMPLETE to inform

a successful operation, and with INITIAL CONTEXT SETUP FAILURE to

inform an unsuccessful operation.

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• The S1 UE Context Release procedure causes the eNB to remove all UE

individual signaling resources and the related user data transport

resources.

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The UE Context Modification procedure comprises the following steps:

− The MME initiates the UE Context Modification procedure by sending

UE CONTEXT MODIFICATION REQUEST to the eNB to modify the

UE context in the eNB for UEs in active state.

− The eNB responds with UE CONTEXT MODIFICATION RESPONSE

in case of a successful operation

− If the UE is served by a CSG cell, and is no longer a member of the

CSG cell, the eNB may initiate a handover to another cell. If the UE is

not handed over, the eNB should request the release of UE context;

− If the UE is served by a hybrid cell, and is no longer a CSG member

of the hybrid cell, the eNB may provide the QoS for the UE as a non

CSG member.

− The eNB responds with UE CONTEXT MODIFICATION FAILURE in

case of an unsuccessful operation.

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The INITIAL UE MESSAGE procedure is initiated by the eNB by sending the

INITIAL UE MESSAGE to the MME. The INITIAL UE MESSAGE contains a

NAS message (e.g. Service Request), the UE signaling reference ID and other

S1 addressing information. In case of UE access to a CSG cell the INITIAL UE

MESSAGE contains the CSG id of the cell. In case of UE access to a hybrid

cell the INITIAL UE MESSAGE contains the CSG id and Access Mode of the

cell.

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The Uplink NAS Transport procedure is initiated by the eNB by sending the

UPLINK NAS TRANSPORT message to the MME. The UPLINK NAS

TRANSPORT message contains a NAS message, UE identification and other

S1 related addressing information.

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The Downlink NAS Transport procedure is initiated by the MME by sending the

DOWNLINK NAS TRANSPORT message to the eNB. The DOWNLINK NAS

TRANSPORT contains a NAS message, UE identification and other S1 related

addressing information.

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− The eNB initiates the S1 Setup procedure by sending the S1 SETUP

REQUEST message including supported TAs and broadcasted PLMNs

to the MME.

− In the successful case the MME responds with the S1 SETUP

RESPONSE message which includes served PLMNs as well as a

relative MME capacity indicator to achieve load balanced MMEs in the

pool area.

− If the MME cannot accept the S1 Setup Request the MME responds

with the S1 SETUP FAILURE message indicating the reason of the

denial. The MME optionally indicates in the S1 SETUP FAILURE

message when the eNB is allowed to re-initiate the S1 Setup Request

procedure towards the same MME again.

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− The eNB initiates the eNB Configuration Update procedure by sending the

ENB CONFIGURATION UPDATE message including updated configured

data like supported TAs and broadcasted PLMNs to the MME. In case one

or more supported TA(s) needs to be updated, the eNB shall provide the

whole list of TA(s), including those which has not been changed, in the

ENB CONFIGURATION UPDATE message.

− The MME responds with the ENB CONFIGURATION UPDATE

ACKNOWLEDGE message to acknowledge that the provided

configuration data are successfully updated.

− The MME shall overwrite and store the received configuration data which

are included in the ENB CONFIGURATION UPDATE message.

Configuration data which has not been included in the ENB

CONFIGURATION UPDATE message are interpreted by the MME as still

valid. For the provided TA(s) the MME shall overwrite the whole list of

supported TA(s).

− In case the MME cannot accept the received configuration updates the

MME shall respond with the ENB CONFIGURATION UPDATE FAILURE

message including an appropriate cause value to indicate the reason of

the denial. The MME optionally indicates in the ENB CONFIGURATION

UPDATE FAILURE message when the eNB is allowed to re-initiate the

eNB Configuration Update procedure towards the same MME again. For

the unsuccessful update case the eNB and the MME shall continue with

the existing configuration data.

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− The MME initiates the MME Configuration Update procedure by sending

the MME CONFIGURATION UPDATE message including updated

configured data like served PLMNs and changes of the relative MME

capacity values to the eNB.

− The eNB responds with the MME CONFIGURATION UPDATE

ACKNOWLEDGE message to acknowledge that the provided

configuration data and the relative MME capacity values are successfully

updated.

− The eNB shall overwrite and store the received configuration data and

relative MME capacity values which are included in the MME

CONFIGURATION UPDATE message. Configuration data which has not

been included in the MME CONFIGURATION UPDATE message are

interpreted by the eNB as still valid.

− In case the eNB cannot accept the received configuration updates the

eNB shall respond with the MME CONFIGURATION UPDATE FAILURE

message including an appropriate cause value to indicate the reason of

the denial. The eNB optionally indicates in the MME CONFIGURATION

UPDATE FAILURE message when the MME is allowed to re-initiate the

MME Configuration Update procedure towards the same eNB again. For

the unsuccessful update case the eNB and the MME shall continue with

the existing configuration data and relative MME capacity values.

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The graphic illustrates the control plane between the UE and the MME, including the air (Uu) and S1-MME interfaces.

For Access Stratum (AS) messages, the eNodeB interworks RRC and S1AP signaling. Non-Access Stratum (NAS) signaling is passed transparently from the UE to the MME.

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The graphic lists the RRC and S1AP messages used to transport NAS signaling. The eNodeB interworks RRC Connection Setup Complete and the S1AP Initial UE Message, RRC DL Information Transport and S1AP DL NAS Transport, and RRC UL Information Transport and S1AP UL NAS Transport. Although the eNodeB transfers the NAS message without interpretation, it will add any additional Information Elements required, such as the cell identity.

In one case the eNodeB does interpret and act upon the NAS signaling. If the S1AP DL NAS Transport message (from the MME) contains a Handover Restriction List IE, the eNodeB will store that information in the UE context. The Handover Restriction List contains roaming area or access restrictions. The eNodeB uses that information during a handover.

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3GPP TS 24.301 NAS Protocol for EPS

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When present, a piggybacked message shall have its "P" flag set to "0" in its

own header. If Create Session Response message (as part of EUTRAN initial

attach or UE-requested PDN connectivity procedure) has the "P" flag set to

"1", then a Create Bearer Request message shall be present as the

piggybacked message. As a response to the Create Bearer Request message,

if the Create Bearer Response has the "P" flag set to "1", then a Modify Bearer

Request (as part of EUTRAN initial attach or UE-requested PDN connectivity

procedure) shall be present as the piggybacked message. A Create Bearer

Response with "P" flag set to "1" shall not be sent unless a Create Session

Response with "P" flag set to "1" has been received for the same procedure.

Apart from Create Session Response and Create Bearer Response

messages, all the EPC specific messages shall have the "P" flag set to "0".

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Version field, shall be set to '1'.

Protocol Type (PT). ‘1’ means GTP and ‘0’ means GTP’.

Extension Header flag (E): This flag indicates the presence of a meaningful

value of the Next Extension Header field.

Sequence number flag (S): This flag indicates the presence of a meaningful

value of the Sequence Number field.

N-PDU Number flag (PN): This flag indicates the presence of a meaningful

value of the N-PDU Number field. This field is used to co-ordinate the data

transmission for acknowledged mode of communication between the MS and

the SGSN.

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GRE = Generic Routing Encapsulation

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The graphic illustrates the protocol stack required to forward user data traffic over the S1-U interface. A user data packet (Layers 3-5) is encapsulated by the GPRS Tunneling Protocol (GTP). The GTP packet is carried by UDP/IP over any Data Link and Physical Layer. IPv4 and/or IPv6 may be supported. GTP is the IP mobility protocol initially defined for GPRS mobile devices.

Each data stream is carried on a dedicated transport bearer; each transport bearer is uniquely identified by the IP address and Tunnel Endpoint ID of the GTP tunnel.

3GPP TS 29.281 GPRS Tunneling Protocol User Plane (GTPv1-U)

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The S1-U interface forwards user data traffic between the eNodeB and S-GW, and the S5 interface forwards user data traffic between the S-GW and P-GW. Both interfaces support GPRS Tunneling Protocol (GTP) for IP mobility. The EPS uses GTPv1 for user plane traffic and GTPv2 for GTP control packets.

The S5 interface connects an S-GW and P-GW in the same PLMN.

The S8 interface is the inter-PLMN reference point providing user and control plane between an S-GW in the Visited PLMN (VPLMN) and a P-GW in the Home PLMN (HPLMN).

3GPP TS 29.274 Evolved GPRS Tunneling Protocol for EPS (GTPv2)

3GPP TS 29.281 GPRS Tunneling Protocol User Plane (GTPv1-U)

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GTP-C message types 64-70 do not have an explicit response.

3GPP TS 29.274 Evolved GPRS Tunneling Protocol for EPS (GTPv2)

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The graphic illustrates the user plane between the UE and the P-GW, including the Uu, S1-U, and S5-U interfaces.

Note that the P-GW extracts the original user traffic (Layer 3-5) from the GTP mobility tunnel. The resulting packet may be forwarded based on the user-supplied destination IP address, or placed in another GTP or Mobile IP tunnel and forwarded to another network. In the latter case, the P-GW will interwork the two mobility tunnels.

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The S10 interface carries signaling between two MMEs. This interface is used when a UE moves to a cell served by a different MME. The old MME passes UE context information to the new MME over the S10 interface. S10 uses GTPv2 for GTP-C (control) packets.

3GPP TS 29.274 Evolved GPRS Tunneling Protocol for EPS (GTPv2)

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The graphic illustrates the S11 control plane protocol stack. S11 signaling uses GTP-C control messages.

Interface between MME and a SGW.

Control plane only interface.

A single MME can handle multiple SGW each one with its own S11 interface.

Used to coordinate the establishment of SAE bearers within the EPC.

SAE bearer setup can be started by the MME (default SAE bearer) or by the PGW (dedicated SAE bearer).

3GPP TS 29.274 Evolved GPRS Tunneling Protocol for EPS (GTPv2)

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The graphic illustrates the Diameter protocol stack.

Interface between the MME and the HSS

The MME uses it to retrieve subscription information from HSS (handover/tracking area restrictions, external PDN allowed, QoS, etc.) during attaches and updates

The HSS can during these procedures also store the user’s current MME address in its database.

The S6a interface carries signaling that manages the UE authentication and context between the MME and HSS. S6a uses Diameter packets. Based upon RADIUS, Diameter is an IETF remote access, authentication, policy, and user context protocol. Basic Diameter architecture and operation is described in RFC 3588, and extended in many other RFCs and 3GPP technical specifications. E-UTRAN specific extensions are described in TS 29.272.

IETF RFC 3588 Diameter Base Protocol

IETF RFC 4740 Diameter SIP Application

IETF RFC 5224 Diameter Policy Processing Application

3GPP TS 29.272 MME and SGSN Related Interfaces Based on Diameter

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3GPP TS 29.272 Diameter Protocol

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IANA = Internet Assigned Numbers Authority

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The 'V' bit, known as the Vendor-Specific bit, indicates whether the optional

Vendor-ID field is present in the AVP header. When set the AVP Code belongs

to the specific vendor code address space.

The 'M' Bit, known as the Mandatory bit, indicates whether support of the AVP

is required. If an AVP with the 'M' bit set is received by a Diameter client,

server, proxy, or translation agent and either the AVP or its value is

unrecognized, the message MUST be rejected. Diameter Relay and redirect

agents MUST NOT reject messages with unrecognized AVPs.

The 'P' bit indicates the need for encryption for end-to-end security.

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3GPP TS 29.274 Evolved GPRS Tunneling Protocol for EPS (GTPv2)

3GPP TS 29.281 GPRS Tunneling Protocol User Plane (GTPv1-U)

3GPP TS 36.420 X2 General Aspects and Principles

3GPP TS 36.421 X2 Layer 1

3GPP TS 36.422 X2 Signaling Transport

3GPP TS 36.423 X2 Application Program (X2AP)

3GPP TS 36.424 X2 Data Transport

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The graphic illustrates the X2 Interface signaling protocol stack. Any Physical Layer and Data Link Layer are allowed. The IP version may be IPv6 and/or IPv4. In either case, the X2 (eNodeB) endpoints must support Differentiated Services (DiffServ) Code Points for QoS.

Instead of using TCP or UDP, 3GPP selected Stream Control Transmission Protocol (SCTP) at Layer 4. Essentially SCTP offers TCP-like reliability and error recovery with UDP-like throughput. In addition, SCTP supports multi-homing for redundancy and continued operation even during a transport network failure.

The X2 signaling messages and state machine are controlled by the X2 Application Protocol (X2AP).

The X2 Interface signaling protocol stack provides:

• Reliable transfer of X2AP messages over the X2 Interface

• Networking and routing

• Redundancy in the signaling network

• Flow control and overload protection

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The X2 Application Protocol (X2AP) provides the following functions:

• Mobility management – Allows the eNodeB to move the responsibility for a UE to another eNodeB. Mobility management includes forwarding of user plane data, Status Transfer and UE Context Release.

• Load management – Indicates resource status, overload, and traffic load to an adjacent eNodeB.

• Reporting general error situations – Reports general error situations, for which function- specific error messages have not been defined.

• Resetting the X2 – Completely resets the X2 interface.

• Setting up the X2 – Exchanges necessary data for the eNodeB to setup the X2 interface.

• eNodeB configuration update – Updates application level data needed for two eNodeBs to interoperate correctly over the X2 interface.

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X2AP signaling messages are generated based on state changes, S1 or Uu signaling, measured conditions, or eNodeB configuration changes.

3GPP TS 36.423 X2 Application Program (X2AP)

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Same as other GTP-U tunnels, Handover transfer of data.

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The S1-U data plane is defined between the HeNB, HeNB GW and the S-GW.

3GPP TS 36.300 Overall description

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3GPP TS 36.300 Overall description

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The diagram shows the S1-MME protocol stacks without the HeNB GW.

When the HeNB GW is not present, all the S1 procedures are terminated at the HeNB and the MME.

3GPP TS 36.300 Overall description

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The diagram shows the S1-MME protocol stacks with the HeNB GW.

When present the HeNB GW shall terminate the non-UE-dedicated procedures – both with the HeNB, and with the MME. The HeNB GW shall provide a relay function for relaying Control Plane data between the HeNB and the MME. The scope of any protocol function associated to a non-UE-dedicated procedure shall be between HeNB and HeNB GW and/or between HeNB GW and MME.

Any protocol function associated to an UE-dedicated-procedure shall reside within the HeNB and the MME only.

3GPP TS 36.300 Overall description

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The S1 user plane protocol stacks for supporting RNs are shown. There is a GTP tunnel associated with each UE EPS bearer, spanning from the S-GW associated with the UE to the DeNB, which is switched to another GTP tunnel in the DeNB, going from the DeNB to the RN (one-to-one mapping).

3GPP TS 36.300 Overall description

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The X2 user plane protocol stacks for supporting RNs during inter-eNB handover are shown. There is a GTP forwarding tunnel associated with each UE EPS bearer subject to forwarding, spanning from the other eNB to the DeNB, which is switched to another GTP tunnel in the DeNB, going from the DeNB to the RN (one-to-one mapping).

The S1 and X2 user plane packets are mapped to radio bearers over the Un interface. The mapping can be based on the QCI associated with the UE EPS bearers. UE EPS bearer with similar QoS can be mapped to the same Un radio bearer.

3GPP TS 36.300 Overall description

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The S1 control plane protocol stacks for supporting RNs are shown. There is only one S1 interface relation between the RN and the DeNB, and there is one S1 interface relation between the DeNB and each MME in the MME pool. The DeNB processes and forwards all S1 messages between the RN and the MMEs for all UE-dedicated procedures. The processing of S1-AP messages includes modifying S1-AP UE IDs, Transport Layer address and GTP TEIDs but leaves other parts of the message unchanged.

All non-UE-dedicated S1-AP procedures are terminated at the DeNB, and handled locally between the RN and the DeNB, and between the DeNB and the MME(s). Upon reception of an S1 non-UE-dedicated message from an MME, the DeNB may trigger corresponding S1 non-UE-dedicated procedure(s) to the RN(s). If more than one RN is involved, the DeNB may wait and aggregate the response messages from all involved RNs before responding to the MME. Upon reception of an S1 non-UE-dedicated message from an RN, the DeNB may trigger associated S1 non-UE-dedicated procedure(s) to the MME(s). In case of the RESET procedure, the DeNB does not need to wait the response message(s) from the MME(s) or RN(s) before the DeNB responds with the RESET ACKNOWLEDGE message to the originating node. Upon reception of a PAGING message, the DeNB sends the PAGING message toward the RN(s) which support any tracking area(s) indicated in the List of TAIs. Upon reception of an S1 MME overload message, the DeNB sends the MME overload message towards the RN(s), including in the message the identities of the affected CN node.

3GPP TS 36.300 Overall description

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There is only one X2 interface relation between the RN and the DeNB, and there is one X2 interface relation between the DeNB and every other eNB that the DeNB has an X2 relationship with. The DeNB processes and forwards all X2 messages between the RN and other eNBs for all UE-dedicated procedures. The processing of X2-AP messages includes modifying X2-AP UE IDs, Transport Layer address and GTP TEIDs but leaves other parts of the message unchanged.

All non-UE-dedicated X2-AP procedures are terminated at the DeNB, and handled locally between the RN and the DeNB, and between the DeNB and other eNBs. Upon reception of an X2 non cell related non-UE-associated message from RN or neighbor eNB, the DeNB may trigger associated non-UE-dedicated X2-AP procedure(s) to the neighbor eNB or RN(s). Upon reception of an X2 cell related non-UE-dedicated message from RN or neighbor eNB, the DeNB may pass associated information to the neighbor eNB or RN(s) based on the included cell information. If one or more RN(s) are involved, the DeNB may wait and aggregate the response messages from all involved nodes to respond to the originating node. Further, parallel Cell Activation procedures are not allowed on each X2 interface instance. The processing of Resource Status Reporting Initiation/ Resource Status Reporting messages includes modification of measurement ID.

The S1 and X2 interface signaling packets are mapped to radio bearers over the Un interface.

3GPP TS 36.300 Overall description

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The Public Land Mobile Network (PLMN) is the mobile service provider. The PLMN ID consists of the 3-digit Mobile Country Code (MCC) and the 2- or 3-digit Mobile Network Code (MNC).

The MCC uniquely identifies the country a mobile carrier operates in, while the MNC uniquely identifies a mobile carrier within a country. MCC and MNC use 4-bit binary coded decimal digits. MCCs and PLMN IDs are defined in the ITU E.212 standard.

ITU E.212 Land Mobile Numbering Plan

3GPP TS 23.003 Numbering, Addressing and Identification

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In EPS, an MME is assigned the following IDs.

• MME Group ID (MMEGI) – 16-bit value assigned by the carrier to uniquely identify the MME group.

• MME Code (MMEC) – 8-bit value assigned to a specific MME within a group.

• Globally Unique MME ID (GUMMEI) – Uniquely identifies a specific MME within the PLMN. The GUMMI consists of the MCC, MNC, MME Group ID (MMEGI), and MME Code (MMEC).

In EPS, a subscriber is assigned the following IDs.

• International Mobile Subscriber ID (IMSI) – 14 or 15 decimal digits assigned by the home mobile network to uniquely identify the subscriber. The IMSI consists of the MCC, MNC, and the subscriber ID.

• International Mobile Equipment ID (IMEI) – 14 decimal digits assigned by the manufacturer to uniquely identify the type of mobile device. The 16 digit IMEI/SVN includes the Software Version Number (SVN).

• Cell Radio Network Temporary ID (C-RNTI) – 16-bit value assigned by the eNodeB for scheduling air interface resources.

• Mobile Temporary Mobile Subscriber ID (M-TMSI) – 32-bit value assigned by the MME for paging the UE.

• Globally Unique Temporary ID (GUTI) – Uniquely identifies an M-TMSI within the PLMN. The GUTI consists of the GUMMEI and the M-TMSI (80 bits).

• Subscriber Temporary Mobile Subscriber ID (S-TMSI) – A smaller version of the GUTI used for paging the UE. The S-TMSI consists of the MMEC plus the M-TMSI (40 bits).

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ITU E.212 Land Mobile Numbering Plan

3GPP TS 23.003 Numbering, Addressing and Identification

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