TN_SP008_E1_1 Gn Interface and GTP overviewV1026

Course Objectives

Gn Interface GTP protocol GTP’ protocol

Gn/Gp Interface

Gn/Gp : Between the GSN nodes Gn : Between the GSN nodes within the same PL

MN Gp : Between the GSN nodes in two different PLM

Ns. The two interfaces adopt GTP for communication

Gn/Gp Interface

GGSNSGSN

Gn、 Gp

GTP-U

L2

L1

UDP

IP

GTP-U

L2

L1

UDP

IP

GTP-C

L2

L1

UDP

IP

GTP-C

L2

L1

UDP

IP

User Plane

Control Plane

Gn/Gp

Course Objectives

Gn Interface GTP protocol GTP’ protocol

GTP protocol

GTP － GPRS Tunneling Protocol Function: Encapsulate the network layer packet( IP pac

ket) in order to add current user information (such as IMSI and TEID etc.) add source GSN IP and destination GSN IP to tunnel the packet to destination GSN.

GTP PACKEGE FORMAT

UDPUDPIPIP GTPGTP Payload (IP or PPP)Payload (IP or PPP)

Route between the SGSN and GGSNRoute between the SGSN and GGSN

Identify the GTP’s well known portIdentify the GTP’s well known port

Identify the GTP sessionIdentify the GTP session

Data flows from end mobile OS stack to host/serverData flows from end mobile OS stack to host/server

GTP head format

Extension header

N-PDNSequence number

TEIDLength

Message type

Label

PNS FlagE FlagreservedPTversion

8 168 32 16

Optional partMust have part

Port 2123 for GTP-CPort 2152 for GTP-U

GTP protocol

GTP protocol is made up of ： Path management Tunnel management Location management Mobility management

Path management

Echo Request: find out if the peer GSN or RNC is alive Echo Response: a response to a received Echo

Request Version Not Support: indicates the latest GTP version

that the GTP entity on the identified UDP/IP address can support

Supported Extension Headers Notification: indicates a list of supported Extension Headers that the GTP entity on the identified IP address can support

Echo Request

Echo Request An Echo Request may be sent on a path to another

GSN or RNC to find out if the peer GSN or RNC is alive (see section Path Failure). Echo Request messages may be sent for each path in use.

A path is considered to be in use if at least one PDP context uses the path to the other GSN. When and how often an Echo Request message may be sent is implementation specific but an Echo Request shall not be sent more often than every 60 seconds on each path.

Echo Response

Echo Response The message shall be sent as a response to a received

Echo Request.

Echo Request / Echo Response

GGSN

Echo Response

Echo Request

SGSN

Version Not Support

Version Not Support This message contains only the GTP header and

indicates the latest GTP version that the GTP entity on the identified UDP/IP address can support.

Supported Extension Headers Notification

Supported Extension Headers Notification This message indicates a list of supported Extension

Headers that the GTP entity on the identified IP address can support. This message is sent only in case a GTP entity was required to interpret a mandatory Extension Header but the GSN or RNC was not yet upgraded to support that extension header. The GTP endpoint at the GSN or RNC sending this message is marked as not enabled to support some extension headers (as derived from the supported extension header list).

Tunnel management

Tunnel management Create PDP Context Request Create PDP Context Response Update PDP Context Request Update PDP Context Response Delete PDP Context Request Delete PDP Context Response

Tunnel management (cont.)

Tunnel Management PDU Notification Request PDU Notification Response PDU Notification Reject Request PDU Notification Reject Response

GGSN

Create PDP Context Response （reason etc.）

Create PDP Context Request （MSISDN, PDP address, APN, QoS, SGSN

address etc.）

SGSN

Create PDP Context Request /response

PDP Update

PDP Delete

PDU Notification Request /Response

PDU Notification Request /Response － MS Detached

SGSN GGSN

PDU Notification Request（PDPaddress）

HLR

Send Routeing Info for GPRS（IMSI etc ）

Send Routeing Info for GPRS Ack（ reason ， IMSIetc）

PDU Notification Response（ reason ）

Location Management

Location Management Send Routing Information for GPRS Request Send Routing Information for GPRS Response Failure Report Request Failure Report Response Note MS GPRS Present Request Note MS GPRS Present Response

Send Routing Information for GPRS Request/Response

Failure Report Request /Response

Note MS GPRS Present Request /Response—MS send attach request

Mobility Management

Mobility Management Identification Request Identification Response SGSN Context Request SGSN Context Response SGSN Context Acknowledge Forward Relocation Request Forward Relocation Response Forward Relocation Complete

Identification Response（ reason etc ）

Identification Request（ RAI ， P-TMSI etc ）

SGSN-B SGSN-A

Identification Request /Response

SGSN-B SGSN-A

SGSN Context Response（ reason etc ）

SGSN Context Request（ RAI,TLLI etc ）

SGSN Context Acknowledge（ reason etc ）

SGSN Context Request /Response/Acknowledge

Course Objectives

Gn Interface GTP protocol GTP’ protocol

GTP’ protocol

GTP’ protocol － used between GSN and CG to transfer billing data Path management: Provide two signals to detect if the p

ath between GSN and CG is available or not; provide a pair of redirection signal to establish redundant billing channel

CDR transfer: provide a pair of signal for normal CDR transfer (request and response).

GSN CG

Redirection Request

Redirection Response

Redirection Req/Resp

When CG notifies GSN to send CDR to another CG (within the same PLMN), when CG needs to conduct software or hardware maintenance or when CG discovers system error, Redirection Command is needed.

Redirection Request message carries IE cause code and suggested CG address

GSN CG

Data Record Transfer Request

Data Record Transfer Response

Data Record Transfer Req/Resp

When GSN sends CDRs to CG or supporting repeated CDR prevention mechanism, Data Record Transfer command will be activated.