The GPRS system is used by GSM Mobile phones, the most common mobile phone system in the world (as of 2004), for transmitting IP packets. The GPRS Core Network is the centralised part of the GPRS system and also provides support for WCDMA based 3G networks. The GPRS core network is an integrated part of the GSM core network. Not to be confused with Get Some Mates The Global System for Mobile Communications (GSM) is the most popular standard for mobile phones in the world. ... 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... The Internet Protocol (IP) is a data-oriented protocol used for communicating data across a packet-switched internetwork. ... W-CDMA (Wideband Code Division Multiple Access), a wideband spread-spectrum 3G mobile telecommuncation air interface that utilizes code division multiple access (or CDMA the general multiplexing scheme, not to be confused with CDMA the standard), is a 3G mobile communications standard allied with the GSM standard. ... 3G is short for third-generation technology in the context of mobile phone standards. ... The GSM Core network is the heart of a GSM system, the most common mobile phone system in the world. ...

GPRS Core Network in General

http://en.wikipedia.org/wiki/Packet_Data_Protocol#GPRS_Tunnelling_Protocol_.28GTP.29

GPRS Core Network Structure

The GPRS Core Network (GPRS stands for General Packet Radio Services) provides mobility management, session management and transport for Internet Protocol packet services in GSM and WCDMA networks. The core network also provides support for other additional functions such as charging and lawful interception. It was also proposed, at one stage, to support packet radio services in the US TDMA system, however, in practice, most of these networks are being converted to GSM so this option is becoming largely irrelevant. Structure of a GPRS Core network. ... Structure of a GPRS Core network. ... Mobility Management is one of the major functions of a GSM or a UMTS network that allows mobile phones to work. ... In Human-Computer Interaction, session management is the process of keeping track of a users activity across sessions of interaction with the computer system. ... Charge is a word with many different meanings. ... Lawful interception (aka wiretapping) of telecommunications. ... Time division multiple access (TDMA) is a channel access method for shared medium (usually radio) networks. ...

Like GSM in general, GPRS is an open standards driven system and the standardisation body is the 3GPP. This article or section does not adequately cite its references or sources. ...

GPRS Tunnelling Protocol (GTP)

main article GPRS Tunnelling Protocol

GPRS Tunnelling Protocol is the defining IP protocol of the GPRS core network. Primarily it is the protocol which allows end users of a GSM or WCDMA network to move from place to place whilst continuing to connect to the internet as if from one location at the Gateway GPRS Support Node (GGSN). It does this by carrying the subscriber's data from the subscriber's current Serving GPRS Support Node (SGSN) to the GGSN which is handling the subscriber's session. Three forms of GTP are used by the GPRS core network. GPRS Tunneling Protocol (or GTP) is an IP based protocol used within GSM and UMTS networks. ... The Internet Protocol (IP) is a data-oriented protocol used for communicating data across a packet-switched internetwork. ... In the field of telecommunications, a communications protocol is the set of standard rules for data representation, signalling, authentication and error detection required to send information over a communications channel. ...

• GTP-U for transfer of user data in separated tunnels for each PDP context
• GTP-C for control reasons including:
  • setup and deletion of PDP contexts
  • verification of GSN reachability
  • updates, e.g. as subscribers move from one SGSN to another.
• GTP' for transfer of charging data from GSNs to the charging function.

GGSNs and SGSNs (collectively known as GSNs) listen for GTP-C messages on UDP port 2123 and for GTP-U messages on port 2152. This communication happens within a single network or may, in the case of international roaming, happen internationally, probably across a GPRS Roaming Exchange (GRX). The GPRS system is used by GSM Mobile phones, as of 2004 the most common mobile phone system in the world, for transmitting IP packets. ... The User Datagram Protocol (UDP) is one of the core protocols of the Internet protocol suite. ...

The "Charging Gateway Function" (CGF) listens to GTP' messages sent from the GSNs on UDP port 3386. The core network sends charging information to the CGF, typically including PDP context activation times and the quantity of data which the end user has transferred. However, this communication which occurs within one network is less standardised and may, depending on the vendor and configuration options, use proprietary encoding or even an entirely proprietary system.

GPRS Support Nodes (GSN)

A GSN is a network node which supports the use of GPRS in the GSM core network. All GSNs should have a Gn interface and support the GPRS tunnelling protocol. There are two key variants of the GSN; the GGSN and the SGSN defined below.

GGSN - Gateway GPRS Support Node

A gateway GPRS support node (GGSN) acts as an interface between the GPRS backbone network and the external packet data networks (radio network and the IP network). It converts the GPRS packets coming from the SGSN into the appropriate packet data protocol (PDP) format (e.g. IP or X.25) and sends them out on the corresponding packet data network. In the other direction, PDP addresses of incoming data packets are converted to the GSM address of the destination user. The readdressed packets are sent to the responsible SGSN. For this purpose, the GGSN stores the current SGSN address of the user and his or her profile in its location register. The GGSN is responsible for IP address assignment and is the default router for the connected UE (User Equipment).The GGSN also performs authentication and charging functions

SGSN - Serving GPRS Support Node

A Serving GPRS Support Node (SGSN) is responsible for the delivery of data packets from and to the mobile stations within its geographical service area. Its tasks include packet routing and transfer, mobility management (attach/detach and location management), logical link management, and authentication and charging functions. The location register of the SGSN stores location information (e.g., current cell, current VLR) and user profiles (e.g., IMSI, address(es) used in the packet data network) of all GPRS users registered with this SGSN.

Common SGSN Functions

• Detunnel GTP packets from the GGSN (downlink)
• Tunnel IP packets toward the GGSN (uplink)
• Carry out mobility management as Standby mode mobile moves from Routing Area to Routing Area.
• Billing user data

GSM/EDGE Specific SGSN functions

• Carry up to about 60 kbit/s (150 kbit/s for Edge) traffic per subscriber
• Connect via frame relay or IP to the PCU using the Gb protocol stack
• Accept uplink data to form IP packets
• Encrypt downlink data, decrypt uplink data
• Carry out mobility management to the level of a cell for connected mode mobiles;

// Look up Edge in Wiktionary, the free dictionary. ... In the context of computer networking, frame relay (also found written as frame-relay) consists of an efficient data transmission technique used to send digital information quickly and cheaply in a relay of frames to one or many destinations from one or many end-points. ... The Internet Protocol (IP) is a data-oriented protocol used for communicating data across a packet-switched internetwork. ... A cellular radio network is a radio network made up of a number of radio cells (or just cells) each served by a fixed transmitter, normally known as a base station. ...

WCDMA Specific SGSN functions

• Carry up to about 300 kbit/s traffic per subscriber
• Tunnel/detunnel downlink/uplink packets toward the RNC
• Carry out mobility management to the level of an RNC for connected mode mobiles.

These differences in functionality have led some manufacturers to create specialist SGSNs for each of WCDMA and GSM which do not support the other networks, whilst other manufacturers have succeeded in creating both together, but with a performance cost due to the compromises required. RNC can mean. ...

Access Point

Main article Access Point Name

An access point is: Access Point Name or APN is the name of an access point for GPRS. An access point is: An Internet network to which a mobile can be connected A set of settings which are used for that connection A particular option in a set of settings in a mobile phone...

• An IP network to which a mobile can be connected
• A set of settings which are used for that connection
• A particular option in a set of settings in a mobile phone

When a GPRS mobile phone sets up a PDP context, the access point is selected. At this point an Access Point Name (APN) is determined Access Point Name or APN is the name of an access point for GPRS. An access point is: An Internet network to which a mobile can be connected A set of settings which are used for that connection A particular option in a set of settings in a mobile phone...

Example: flextronics.mnc012.mcc345.gprs.

Example: internet

Example: mywap.

This access point is then used in a DNS query to a private DNS network. This process (called APN resolution) finally gives the IP address of the GGSN which should serve the access point. At this point a PDP context can be activated.. “DNS” redirects here. ...

PDP Context

The PDP context is a data structure present on both the SGSN and the GGSN which contains the subscriber's session information when the subscriber has an active session. When a mobile wants to use GPRS, it must first attach and then activate a PDP context. This allocates a PDP context data structure in the SGSN that the subscriber is currently visiting and the GGSN serving the subscribers access point. The data recorded includes. A binary tree, a simple type of branching linked data structure. ...

• Subscriber's IP address
• Subscriber's IMSI
• Subscriber's
  • Tunnel ID (TEID) at the GGSN
  • Tunnel ID (TEID) at the SGSN

The tunnel ID (TEID) is a number allocated by the GSN which identifies the tunnelled data related to a particular PDP context. IMSI IMSI is an acronym for International Mobile Subscriber Identity. ...

There are two kinds of PDP contexts.

• Primary PDP Context
  • Has a unique IP address associated with it
• Secondary PDP Context
  • Shares an IP address with another PDP context
  • Is created based on an existing PDP context (to share the IP address)
  • Secondary PDP contexts may have different Quality Of Service settings

A total of 11 PDP contexts (with any combination of Primary and Secondary) can co-exist.

Reference Points and Interfaces

Within the GPRS core network standards there are a number of interfaces and reference points (logical points of connection which probably share a common physical connection with other reference points). Some of these names can be seen in the network structure diagram on this page. In telecommunication and computer communication, the term network interface has the following meanings: The point of interconnection between a user terminal and a private or public network. ... A reference point is a location that is used in measurement of a huge variety of phenomena. ...

Interfaces in the GPRS network

• Gb - Interface between the Base Station Subsystem and the SGSN the transmission protocol could be Frame Relay or IP.
• Gn - IP Based interface between SGSN and other SGSNs and (internal) GGSNs. DNS also shares this interface. Uses the GTP Protocol.
• Gp - IP Based interface between internal SGSN and external GGSNs. Between the SGSN and the external GGSN, there is the Border Gateway (which is essentially a firewall). Also uses the GTP Protocol.
• Ga - The interface servers the CDRs (Accounting records) which are written in the GSN and sent to the CG (Charging Gateway). This interface uses an GTP Protocol, with extensions that supports CDRs (Called GTP' or GTP prime).
• Gr - Interface between the SGSN and the HLR. Messages going through this interface uses the MAP3 Protocol.
• Gd - Interface between the SGSN and the SMS Gateway. Can use MAP1, MAP2 or MAP3.
• Gs - Interface between the SGSN and the MSC (VLR). Uses the BSSAP+ Protocol. This interface allows paging and station availability when it performs data transfer. When the station is attached to the GPRS network, the SGSN keeps track of which RA (Routing Area) the station is attached to. An RA is a part of a larger LA (Location Area). When a station is paged this information is used to conserve network resources. When the station performs a PDP Context, the SGSN has the exact BTS the station is using.
• Gi - The interface between the GGSN and other external networks (Internet/WAP). Uses the IP protocol.
• Ge - The interface between the SGSN and the SCP (Service Control Point). Uses the CAP Protocol.
• Gx - The on-line policy interface between the GGSN and the CRF (Charging Rules Function). It is used for provisioning service data flow based charging rules. Uses the Diameter Protocol.
• Gy - The on-line charging interface between the GGSN and the OCS (Online Charging System). Uses the Diameter Protocol (DCCA application).
• Gz - The off-line charging interface between the GSN and the CG (Charging Gateway). Uses the CDRs (Accounting records).

The Base Station Subsystem (BSS) is the section of a GSM network which is responsible for handling traffic and signaling between a mobile phone and the Network Switching Subsystem. ... The GPRS system is used by GSM Mobile phones, as of 2004 the most common mobile phone system in the world, for transmitting IP packets. ... The GPRS system is used by GSM Mobile phones, as of 2004 the most common mobile phone system in the world, for transmitting IP packets. ... The GPRS system is used by GSM Mobile phones, as of 2004 the most common mobile phone system in the world, for transmitting IP packets. ... GPRS Gateway Support Node Interface between the GPRS wireless data network and other networks such as the Internet or private networks. ... “DNS” redirects here. ... The GPRS system is used by GSM Mobile phones, as of 2004 the most common mobile phone system in the world, for transmitting IP packets. ... GPRS Gateway Support Node Interface between the GPRS wireless data network and other networks such as the Internet or private networks. ... The GPRS system is used by GSM Mobile phones, as of 2004 the most common mobile phone system in the world, for transmitting IP packets. ... GPRS Gateway Support Node Interface between the GPRS wireless data network and other networks such as the Internet or private networks. ... It has been suggested that network layer firewall be merged into this article or section. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... SCP or Service Control Point is a standard component of IN (Intelligent Networks) that is used to control the IN Service. ... Diameter Credit-Control Application, DCCA in short, is a DIAMETER application used for credit control. ...

External links

• 3GPP web page including standards
• easy access to different specs
• GSM World's introduction to GPRS
• GPRS Attach and PDP Context Activation Sequence Diagrams
• Starent Networks, GGSN Vendor
• Internet Access over GPRS
• Computer Networking Resources