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.