GPRS Overview. GPRS = General Packet Radio Service. GPRS Network

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GPRS Overview

GPRS - Overview GPRS Network INTERNET/ INTRANET X.25 abcde

GPRS = General Packet Radio Service

Disclaimer: These overview slides are intended for informational purposes only. They have not been reviewed or officially presented, thus there may be some unintentional errors. For

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GPRS Overview

GPRS - Overview

GPRS is an emerging GSM phase 2+ packet radio standard, similar to NAC CDPD:

• Provides more efficient usage of the radio interface (mobiles can share the same radio channel).

• Direct interworking to Internet (TCP/IP), X.25 and ISO CLNS networks for point services (connection-less/connection oriented) and point-to-multipoint services (broadcast and groupcall).

• Concurrent operation with existing GSM services for Circuit-switched Speech, Circuit-switched data and SMS.

• Supports Data rates from 9.6kbps to 100+kbps • Best suited for burst forms of traffic.

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GPRS Overview

GPRS - Definitions

• GSN - GPRS Support Node

• GGSN - Gateway GSN

— Provides similar functionality as GMSC, for packet data.

— Uses Packet Data Protocol (PDP address) which contains IP routing information.

— Routing information is used to tunnel PDUs to the current point of attachment (i.e. SGSN).

— Required I/Fs: Gn (to SGSN), Gi (to packet network) — Optional I/Fs: Gc (to HLR) (can go via Gn and then Gr)

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GPRS Overview

GPRS - Definitions

• SGSN - Serving GSN

— performs mobility management, authentication procedures and routes packet data.

— Like the VLR, stores only a subset of subscriber data available at the HLR. Supports the same MAP I/F to HLR as VLR/HLR I/F. [Note: GPRS spec overall assumes co-located MSC/VLR (i.e. no B interface)].

— SMSC may transfer short messages to the MS using the GPRS (via Gd interface).

— Option to queue messages at the SGSN for a short time (versus going to the SM-SC).

— Required I/Fs: Gn (to GGSN), Gb (to BSS), Gr (to HLR)

— Optional I/Fs: Gd (to SMS-GMSC or SMS-IWMSC to enable GPRS

capable mobiles to send/receive SMs over GPRS radio chans), Gs (to MSC/VLR) (i.e. for class A mobile support for SMS)

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GPRS Overview

GPRS - Network Overview SMS-GMSC SMS-IWMSC SM-SC GGSN GGSN Other PLMN Packet Network TE MSC/ HLR VLR BSS MT TE EIR SGSN Gb Gn Gd MAP-F MAP-E _MAP-C Gc Gi Gp A Um MT = Mobile Terminal TE = Terminal Equipment Gr Gs Signalling I/F Existing GSM Network Elements

New GPRS Network Elements

Gf

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GPRS Overview

GPRS - Interfaces

• Gb - The equivalent of the A interface for GPRS (frame relay)

• Gc - Interface between the GGSN and HLR so that the GGSN can get the location details of an MS. To avoid implementing MAP/SS7 in the GGSN, this interface is optional. When not present, the GGSN routes inquires to the HLR via an SGSN. • Gd - Interfaces the SGSN to the SMS-GMSC. Allows for delivery of SMS traffic

over GPRS. This is a MAP interface.

• Gf - Interface between the SGSN and EIR, similar to the existing MSC/VLR EIR interface

• Gi - An external interface between GGSN and another type of packet network • Gn - SGSN to GGSN interface, based on IPv4 or IPv6.

• Gp - Inter PLMN GPRS interface. The Gp interface provides the functionality of the Gn interface along with the security functionality required for inter-PLMN communication. The security functionality is based on agreements between operators.

• Gr - Interface between SGSN and HLR, similar to the MSC-HLR interface. This is a MAP interface.

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GPRS Overview

GPRS - Addressing Elements/Identifiers

GPRS adds the following addressing elements to GSM:

• PDP Address - associated with each PDP Context. The PDP address itself is a Network layer ( X.121 or IP) address. The fields associated with a PDP context vary across the HLR, SGSN, GGSN and MS, but include items such as:

— PDP Type (X.25 or IP) — NSAPI

— Compression parameters negotiated

— Requested and negotiated QoS parameters — State

• SGSN IP address - HLR is enhanced to include GPRS subscription data and routing information including the SGSN IP address and SS7 addresses.

• NSAPI - Network Layer Service Access Point Identifier - user for Network Layer routing. In the MS, the NSAPI identifies the PDP-SAP. In the SGSN and GGSN, the NSAPI identifies the PDP context

associated with a PDP Address. Between the SGSN and the MS, the TLLI uniquely identifies the logical link. The NSAPI is part of the Tunnel ID (TID).

• TID - Tunnel ID - consists of an IMSI and NSAPI. This uniquely identifies a single PDP context.

• TLLI - Temporary Logical Link Identifier. Optional. The relationship between TLLI and IMSI is known only in the MS and SGSN. Unique within a RA. TLLI is derived from a P-TMSI allocated by the SGSN. • P-TMSI - Packet Temporary Mobile Subscriber Identity. Allocated to each GPRS attached MS ( 03.03) • RAI - Routing Area Identity - identifies one or several cells. RAI is broadcast as system information and

is used by the MS to determine (when changing cells), if a RA border was crossed. A Routing Area (RA) is a subset of a GSM Location Area (LA). A RA is served by only on SGSN. RAC (Routing Area Code) is only unique when presented with an LAI. A GSM Cell Identifier (CI) is unique when presented with an

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GPRS Overview

GPRS - Mobility Management

• HLR has been enhanced to include GPRS subscription data and routing information:

— IMSI

— SGSN IP & SS7 addresses

— up to fifty PDP (Protocol Data Protocol) specific data sets.

• Large impact to support Class A and Class B GPRS sets. There are 3 categories of GPRS Mobile Sets:

— Class A - supports full simultaneous connections . (Requires “Combined” procedures)

— Class B - supports simultaneous paging for either service, but NOT activation. GPRS services will be put on hold while a CS call is handled. (Requires “Combined” procedures)

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GPRS Overview

GPRS - Mobility Management - Location Registration

GPRS uses the concept of a routing area (RA), which is a subset of a GSM Location Area (LA). GPRS has three types of Routing Area Registration: • Routing Area Updating - when a mobile enters a new Routing Area (RA) • GPRS Attach/Detach

— Indicates mobile activation/deactivation within a Routing Area

— Prevents paging of a mobile that is not active (visited VLR rejects calls from the HLR or applies Call Forwarding)

— Note that the mobile station does not maintain an attach/detach state • Periodic Routing Area Update

— Periodicity is determined by the network

— Ensures that regular radio contact is maintained by the mobile

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GPRS Overview

GPRS - Inter-SGSN Routing Area Update - Message Flow

MS HLR

2. SGSN Context Request

7. Update Location 1. Routing Area Update Request

6. Update PDP Context Request

new SGSN old SGSN GGSN MSC/VLR

2. SGSN Context Response

5. Forward Packets 3 . Security Functions

6. Update PDP Context Response

8. Cancel Location 8. Cancel Location Ack

9. Insert Subscriber Data 9. Insert Subscriber Data Ack

11. Location Updating Accept 11. Location Updating Request

10. Update Location Ack

12. Routing Area Update Accept

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GPRS Overview

GPRS - Inter-SGSN Routing Area Update - Message Flow Details

1. The MS sends the Routing Area Update Request to the new SGSN.

2. The new SGSN then exchanges an SGSN Context Request/Response with the old SGSN.

3. Optionally, the GSM security procedures are performed.

4. Upon receipt of the SGSN Context Response and after optional security has been performed, the new SGSN sends an SGSN Context Acknowledge if the user has at least one PDP context active.

5. Upon receipt of the SGSN Context Acknowledge, the old SGSN forwards any packets from the old SGSN.

6. After sending the SGSN Context Acknowledge, the new SGSN initiates the Update PDP Context with the GGSN.

7. Upon completion of this, the Update Location is sent to the HLR. 8. This results in a Cancel Location to the old SGSN.

9. The subscriber data is then sent to the new SGSN.

10. Upon receipt of the Insert Subscriber Data Acknowledgement, the HLR acknowledges the Update Location.

11. (Note: this procedure can be combined with the GSM Location Update.

12. Upon completion of the Location Updating procedure, the new SGSN sends a Routing Area Update Accept to the MS.

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GPRS Overview

GPRS - Mobility Management - Security

GPRS uses some existing GSM security messaging and optional GPRS specific messaging:

• Authentication Request/Response/Reject - performed by SGSN as per MSC/ VLR

• Identity Request/Response - SGSN executed as per MSC/VLR

• TMSI Reallocation Command/Complete

•

Supported by 3 algorithms: • Authentication

• User Data Encryption (Note: the scope of ciphering for GPRS is between MS and SGSN).

• Generation of cipher key (TDMA frame number is unknown at the SGSN, therefore LLC frame number may replace TDMA frame number as an input to the algorithm). Uses standard key management procedures for Kc.

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GPRS Overview

GPRS - Authentication Procedure

MS SGSN HLR

2. Authentication Request

1. If the SGSN does not have previously stored authentication triplets, a Send Authentication Info (IMSI) is

sent to the HLR. The HLR responds with Send Authentication Info Ack (Authentication Triplets). Each

Authentication Triplet includes RAND, SRES and Kc.

2. The SGSN sends Authentication Request (RAND, CKSN, Ciphering Algorithm) to the MS. The MS

responds with Authentication Response (SRES).

1. Send Authentication Info

1. Send Authentication Info Ack

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GPRS Overview

GPRS - Protocol Stack Um Gb Gn Gi MS BSS SGSN GGSN GSM RF MAC RLC LLC SNDCP IP/X.25 Application IP/X.25 L1 L2 IP UDP/ TCP UDP/ TCP IP L2 L1 GTP GTP GSM RF MAC RLC Relay Relay BSSGP Network

Service NetworkService

L1bis L1bis

BSSGP LLC SNDCP

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GPRS Overview

GPRS - Transmission Protocol Definitions

• GTP - GPRS Tunneling Protocol - Tunnels user data and signalling between GPRS support nodes in the GRPS backbone network. All PTP PDP PDUs shall be encapsulated by GTP. GTP shall provide the mechanisms for flow control

between GSNs, if required (GSM 09.60)

• TCP - Transmission Control Protocol - carries GTP PDUs in the GPRS backbone network for ptotocols that need a reliable data link (e.g., X.25). Provides flow control and protection against lost and corrupted GTP PDUs.

• UDP - User Datagram Protocol - carries GTP PDUs for protocols that do not need a reliable data link (e.g., IP). Provides protection from corrupted PDUs.

• IP - Internet Protocol - GPRS backbone network protocol used for routing user data and control signalling. Initially based on IP version 4 protocol. Ultimately, IP version 6 protocol.

• SNDCP - Subnetwork Dependent Convergence Protocol (SNDCP) - maps

network-level characteristics onto the characteristics of the underlying network (GSM 4.65)

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GPRS Overview

GPRS - Transmission Protocol Definitions (continued)

• LLC - Logical Link Control - provides a highly reliable ciphered logical link. LLC shall be independent of the underlying radio interface protocols in order to allow introduction of alternative GPRS radio solutions with minimum changes to the NSS. (GSM 4.64)

• Relay - in the BSS, relays LLC PDUs between the Um and Gb interfaces. In the SGSN, relays PDP PDUs between the Gb and Gn interfaces.

• BSSGP - Base Station System GPRS Protocol - conveys routing and Qos related information between BSS and SGSN. Does not perform error correction. (GSM 8.18)

• NS - Network Service - transports BSSGP PDUs. Based on the Frame Relay

connection between BSS and SGSN and may be multi-hop and traverse a network of Frame Relay switching nodes. (GSM 8.16)

• RLC/MAC - Radio Link Control/Medium Access Control - layer controlling 2 functions: RLC provides a radio solution dependent reliable link. The MAC

function controls the access signalling (access and grant) for the radio channel, and the mapping of LLC frames onto the GSM physical channel. (GSM 4.60)

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GPRS Overview

GPRS - GPRS Tunnelling Protocol

The GPRS Tunneling Protocol (GTP) defines the protocol between GSN nodes in the GPRS backbone network.

• Applies to both the Gn and Gp interface.

• Signalling is used to create, modify and delete tunnels.

• User Datagram Protocol (UDP) used to transfer signalling messages. • Defines the following categories of signalling messages:

— Path Management Messages

— Tunnel Management Messages

— Location Management Messages

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GPRS Overview

GPRS - GPRS Tunnelling Protocol - Path Management

The following path management messages can be sent between any type of GSN pair:

• Echo Request - sent on a path to another GSN to determine if the other node is alive.

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GPRS Overview

GPRS - GPRS Tunnelling Protocol - Tunnel Management

The following tunnel management messages are used to create, update and delete tunnels used to route T-PDUs between a MS and an external PDN via SGSN and GGSN:

• Create PDP Context Request • Create PDP Context Response • Update PDP Context Request • Update PDP Context Response • Delete PDP Context Request • Delete PDP Context Response • Create AA PDP Context Request • Create AA PDP Context Response • Delete AA PDP Context Request • Delete AA PDP Context Response • Error Indication

• PDU Notification • PDU Reject

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GPRS Overview

Create PDP Context Request

• Sent from an SGSN to a GGSN node as part of a GPRS PDP Context Activation procedure or the Network-Requested PDP Context Activation procedure.

• A valid request initiates the creation of a tunnel.

• The destination GGSN for this message may be obtained by using DNS to get the IP address for the GGSN name in the current PDP context.

• Contains the following information elements:

Information element Description

Quality of Service QoS negotiated by the MS at PDP context activation SGSN Address for signalling Specific address for signalling.

SGSN Address for user traffic Specific address for user traffic.

Selection Mode Indicates the source of the Access Point Name (APN) Flow Label Data I Specifies a downlink (GGSN -> SGSN) flow label for G-PDUs

Flow Label Signalling Specifies a downlink (GGSN -> SGSN) flow label for signalling msgs. End User Address If PDP addr field is empty, then dynamic otw contains static addr. Access Point Name May be used by GGSN to differentiate accesses to different external

networks. APN is either MS provided, a subscribed APN or SGSN selected.

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GPRS Overview

Create PDP Context Response • Sent as a response to a Create PDP Context Request. • Contains the following information elements:

Cause Used to indicate error conditions (i.e. cannot allocate dynamic IP address, network prefix not supported, etc.)

Quality of Service QoS may be negotiated downwards GGSN Address for signalling Specific address for signalling. GGSN Address for user traffic Specific address for user traffic.

Reordering Required Indicates if reordering of messages is required. May be negotiated downwards (from Yes to No) by GGSN.

Flow Label Data I Specifies a downlink (GGSN -> SGSN) flow label for G-PDUs

Flow Label Signalling Specifies a downlink (GGSN -> SGSN) flow label for signalling msgs. End User Address If PDP addr field is empty, then dynamic otw contains static addr. Protocol configuration options Applies to IP protocol only.

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GPRS Overview

Update PDP Context Request

• Sent as part of the GPRS Inter-SGSN Routing Update procedure or PDP Context Modification procedure.

• Used to change QoS and the path.

Quality of Service QoS negotiated by the MS SGSN Address for signalling Specific address for signalling. SGSN Address for user traffic Specific address for user traffic.

Flow Label Signalling Specifies a downlink (GGSN -> SGSN) flow label for signalling msgs. Private Extension Contains vendor or operator specific information.

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GPRS Overview

Update PDP Context Response

• Sent as a response to the Update PDP Context Request.

•

Cause Used to indicate error conditions (i.e. cannot allocate dynamic IP address, network prefix not supported, etc.)

Quality of Service QoS may be negotiated downwards GGSN Address for signalling Specific address for signalling. GGSN Address for user traffic Specific address for user traffic.

Flow Label Signalling Specifies a downlink (GGSN -> SGSN) flow label for signalling msgs. Private Extension Contains vendor or operator specific information.

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GPRS Overview

Delete PDP Context Request

• Sent as part of the GPRS Detach Procedure or the GPRS PDP Context Deactivation procedure to deactivate an activated PDP Context.

• Contains Private Extension Information Element.

Delete PDP Context Response

• Sent as a response to the Delete PDP Context Request. • Contains Cause and Private Extension Information Elements.

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GPRS Overview

Create AA PDP Context Request

• Sent as part of the GPRS Anonymous Access PDP Context Activation.

• Used to create a tunnel between a context in the SGSN and a context in the GGSN. • Contains the following information elements:

Quality of Service QoS negotiated by the MS at Anonymous Access PDP context activa-tion

SGSN Address for signalling Specific address for signalling. SGSN Address for user traffic Specific address for user traffic.

Selection Mode Indicates the source of the Access Point Name (APN) Flow Label Data I Specifies a downlink (GGSN -> SGSN) flow label for G-PDUs

Flow Label Signalling Specifies a downlink (GGSN -> SGSN) flow label for signalling msgs. End User Address Contains the address of the Anonymous Server.

Access Point Name May be used by GGSN to differentiate accesses to different external networks. APN is either ‘MS provided, subscription not verified’ or ‘Network provided, subscription not verified’.

Protocol configuration options Applies to IP protocol only.

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GPRS Overview

Create AA PDP Context Response

Cause Non-zero value indicates error conditions Quality of Service QoS may be negotiated downwards GGSN Address for signalling Specific address for signalling. GGSN Address for user traffic Specific address for user traffic.

Reordering Required Indicates if reordering of messages is required. May be negotiated downwards (from Yes to No) by GGSN.

Flow Label Signalling Specifies a downlink (GGSN -> SGSN) flow label for signalling msgs. End User Address Contains the requested PDP type with the PDP addr field empty Protocol configuration options Applies to IP protocol only.

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GPRS Overview

Delete AA PDP Context Request

• Sent as part of the GPRS PDP Anonymous Access Context Deactivation procedure to deactivate an activated PDP Context.

• Contains Cause and Private Extension Information Elements:

Delete AA PDP Context Response

• Sent as a response to the Delete AA PDP Context Request. • Contains Cause and Private Extension Information Elements:

Error Indication

• Sent to the GGSN when a tunnel PDU is received for the following conditions: — No PDP context exists

— PDP context is inactive — No MM context exists

— GGSN deletes its PDP context when the message is received.

• Sent by the new SGSN to the old SGSN if no PDP context exists or is inactive for a received tunnel PDU. The old SGSN deletes its PDP context when message is received.

• Sent by the GGSN to the SGSN if no PDP context exists for a received tunnel PDU. The SGSN re-establishes the PDP context to the GGSN when the message is received.

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GPRS Overview

PDU Notification Request

• When receiving a Tunneled PDU (T-PDU), the GGSN checks if a PDP context is established for the given PDP address.

• If no PDP context has been established, the GGSN may initiate the Network-requested PDP Context Activation procedure by sending a PDU Notification Request to the SGSN.

• Message contains End User Address and Private Extension.

PDU Notification Response

• Sent by the SGSN to the GGSN in response to the PDU Notification Request.

• Message contains Cause and Private Extension.

PDU Notification Reject Request

• Sent when the PDP context requested by the GGSN cannot be established.

• Message contains a Cause indicating the reason why the Context could not be established, an End User Address and Private Extension.

• Upon receipt of this message, the GGSN may reject or discard the stored T-PDUs, depending on the PDP type.

PDU Notification Reject Response

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GPRS Overview

GPRS - PDP Context Activation Procedure

MS SGSN GGSN

1. Activate PDP Context Request

2. Security Functions

3. Create PDP Context Request

4. Create PDP Context Response

5. Activate PDP Context Accept

1. The MS sends an Activate PDP Context Request ( NSAPI, PDP type, PDP Address, Access Point Name, Qos Requested, PDP Configuration Options) message to the SGSN. Access Point Name is either a GGSN

IP address or a logical name referring to the GGSN to be used. PDP Configuration Options is send

transparently through the SGSN to the GGSN.

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GPRS Overview

GPRS - PDP Context Activation Procedure (continued)

3. The SGSN receives the Activate PDP Context Request:

— The SGSN checks that the MS is allowed to activate the PDP address against the subscription data that was stored in the SGSN during GPRS Attach. If allowed, the SGSN creates a Tunnel Identifier (TID) for the requested PDP context by combining the IMSI stored in the MM context with the NSAPI received from the MS. The GGSN used is the GGSN address stored in the PDP context (or if the PDP address in the context indicates that a dynamic address is allowed, the GGSN indicated by the

Access Point Name in the Activate PDP Context message is used).

— The SGSN sends a Create PDP Context Request ( PDP Type, PDP Address, Access Point Name, QoS Negotiated, TID, PDP Configuration Options) to the GGSN.

4. The GGSN receives the Create PDP Context Request:

— The GGSN creates a new entry in its PDP context table, which allows the GGSN to route PDP PDUs between the SGSN and external PDP Network.

— The GGSN sends a Create PDP Context Response(PDP Address, BB Protocol, Reordering

Required, PDP Configuration Options, Cause) message to the SGSN. The PDP address is included

if the GGSN allocated a PDP address. BB protocol indicates whether TCP or UDP shall be used to

transport user data on the backbone network between the SGSN and GGSN. Reordering Required

indicates whetehr the SGSN shall reorder N-PDUs before delivering to the MS. 5. The SGSN receives the Create PDP Context Response message:

— The SGSN inserts the NSAPI along with the GGSN address in its PDP context. If the MS requested a dynamic address, the PDP adddress received from the GGSN is inserted in the PDP context.

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GPRS Overview

GPRS - Network-Requested PDP Context Activation Procedure

MS HLR GGSN

2. Send Routing Info for GPRS

4. PDU Notification Request

6. Request PDP Context Activation

SGSN

1. PDP PDU

3. Send Routing Info for GPRS Ack

5. PDU Notification Response

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GPRS Overview

GPRS - Network-Requested PDP Context Activation Procedure (continued)

1. When a PDP PDU is received, the GGSN determines if the Network-Requested PDP Context Activation

Procedure needs to be initiated. (The GGSN may store subsequent PDUs received for the same PDP address). The GGSN may send a Send Routing Information for GPRS(IMSI) message to the HLR.

2. The HLR receives the Send Routing Information for GPRS message:

— If the HLR determines the request can be served, the HLR includes the IP address of the SGSN that currently serves the MS in the Send Routing Information for GPRS Response (IMSI, SGSN Address, Cause) message.

3. The GGSN receives the Send Routing Information for GPRS Response

— If the SGSN address is present and Cause is not present or equals “No Paging Response”, the

GGSN sends a PDU Notification Request (IMSI, PDP Type, PDP Address) message to the SGSN

indicated by the HLR.

— Otherwise, the GGSN sets the MNRG (Mobile Station Not Reachable) flag for that MS. 4. The SGSN receives the PDU Notification Request .

5. The SGSN sends a PDU Notification Response (Cause) message to the GGSN to acknowledge that it will

request the MS to activate the PDP context indicated by the PDP Address.

6. The SGSN sends a Request PDP Context Activation ( PDP type, PDP Address) message to the MS to

activate the indicated PDP context.

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GPRS Overview

GPRS - GPRS Tunnelling Protocol - Location Management

The following location management messages are used to obtain subscriber

location information from the HLR to support the Network-Requested PDP Context Activation. If the GGSN does not have an SS7 MAP interface the messages are sent via a GTP-MAP protocol converting GSN in the GPRS backbone network:

• Send Routing Information Request - sent by the GGSN to obtain location information for the MS. Message contains the IMSI of the MS and Private Extension.

• Send Routing Information Response - sent by the HLR to return the address of the SGSN currently serving the MS. Contains Cause, IMSI, IP address of the SGSN, Map Cause and Private Extension.

• Failure Report - sent by the GGSN to the HLR when a PDU reject message is received. GGSN sets the Mobile Detached Flag for GPRS (MDFG) and requests the HLR to set the flag and add the GGSN to the list of nodes to report to when activity from the subscriber that owns the PDP address is detected. Message contains the subscriber IMSI and Private Extension.

• Failure Report Response - sent by the HLR to the GGSN to acknowledge receipt of Failure Report. Contains Cause, MAP Cause and Private Extension.

• Note MS Present - When the HLR receives a message from a mobile with MDFG set, it clears the MDFG and sends the Note MS Present message to all GGSN’s in the subscriber’s list. Contains subscriber IMSI, GSN Address and Private

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GPRS Overview

GPRS - GPRS Tunnelling Protocol - Mobility Management

The following mobility management messages are used for GPRS Attach and Inter-SGSN Routing Update:

Identification Request

• Sent by the new SGSN to the old SGSN to request the IMSI for a MS when a GPRS Attach is done with a P-TMSI and the MS has changed SGSNs since the GPRS Detach was done.

• Contains the following parameters:

RAI Routeing Area Identity from old SGSN. P-TMSI Packet TMSI from old SGSN.

P-TMSI Signature Conditionally provided by the MS to the new SGSN for identification checking purposes per GSM 03.60 and 04.08.

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GPRS Overview

GPRS - GPRS Tunnelling Protocol - Mobility Management

Identification Response • Sent in response to the Identification request. • Contains the following parameters:

Cause Only value in the message if Cause is anything other than ‘Request Accepted’.

IMSI IMSI of MS, matching the P-TMSI and RAI in the Identification Request. Authentication Triplet Authentication triplets for MS.

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GPRS Overview

GPRS - GPRS Tunnelling Protocol - Mobility Management (continued)

SGSN Context Request

• Sent by the new SGSN to the old SGSN to request the MM and PDP Contexts for the MS.

RAI Routeing Area Identity

TLLI Temporary Logical Link Identifier

P-TMSI Signature Conditionally provided by the MS to the new SGSN for identification checking purposes per GSM 03.60 and 04.08.

Receive State Variable (V(r)) From the LLC in the old SGSN.

Flow Label Signalling Specifies a flow label chosen by the old SGSN. The new SGSN includes this flow label in the GTP header of all subsequent signalling msgs sent from new SGSN to the old SGSN related to the PDP context(s) requested.

MM Context Contains the Mobility Management, MS and security parms. PDP Context Contains the session mgmt parms.

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GPRS Overview

GPRS - GPRS Tunnelling Protocol - Mobility Management (continued)

SGSN Context Response • Sent by the old SGSN to the new SGSN.

• Contains the following:

Cause Non-zero value indicates error conditions

IMSI IMSI of MS, matching the TLLI and RAI in the SGSN Context Request. Receive State Variable (V(r)) From the LLC in the old SGSN.

Flow Label Signalling Specifies a flow label chosen by the old SGSN. The new SGSN includes this flow label in the GTP header of all subsequent signalling msgs sent from new SGSN to the old SGSN related t the PDP context(s) requested.

MM Context Contains the Mobility Management, MS and security parms. PDP Context Contains the session mgmt parms.

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GPRS Overview

GPRS - GPRS Network - Routing in Home PLMN to/from External PDN

BSS SGSN GGSN

MS External

SNDCP PDU (TLLI, NSAPI, PDP PDU)

PDN

o

Context: TLLI + NSAPI -> GGSN +TID GTP PDU (TID, PDP PDU)

o

Context: TID -> PDP Context (PDP Address) PDP PDU

PDP PDU

o

Context: PDP Address-> TID -> SGSN + TID GTP PDU (TID, PDP PDU)

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GPRS Overview

GGSN BG

SGSN SGSN

Intra-PLMN Backbone

Packet Data Network

Inter-PLMN Backbone GGSN BG SGSN SGSN Intra-PLMN Backbone Gp Gp Gi Gi

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GPRS Overview

BSS SGSN GGSN

MS External

SNDCP PDU (TLLI, NSAPI, PDP PDU)

PDN

o

Context: TLLI + NSAPI -> GGSN +TID GTP PDU (TID, PDP PDU)

o

Context: TID -> PDP Context (PDP Address) PDP PDU

PDP PDU

o

Context: PDP Address-> TID -> SGSN + TID GTP PDU (TID, PDP PDU)

GGSN PDN

Visited PLMN Home PLMN

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GPRS Overview

GPRS - References

[1] GPRS (General Packet Radio Service). Overview and Strategy Proposal, Nik Allen and John Candish, 20-97-0042, version 1.0.0, May 11, 1998.

[2] GSM 03.60 (version 6.1.1) - General Packet Radio Service (GPRS); Service Description; Stage 2. [3] GSM 09.60 (version 6.1.0) - General Packet Radio Service (GPRS); GPRS Tunnelling Protocol (GTP)

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GPRS Overview

GPRS - Channel Types

Packet Data Traffic Channels:

• Carry user information and signalling information (e.g. Session Management (SM) and Mobility Management (MM)) in packet mode.

• Allow a plurality of information streams, associated with different users to be multiplexed in a pre-emptive and dynamic fashion.

• Signalling functions between MS and BSS are carried out over control channels.