GPRS Tunneling Protocol (or GTP) is an IP based protocol used within GSM and UMTS networks. It can be used with UDP or TCP. GTP version one is used only on UDP. There are in fact three separate protocols, GTP-C, GTP-U and GTP'. In computing and telecommunications, the transport layer is the second highest layer in the four and five layer TCP/IP reference models, where it responds to service requests from the application layer and issues service requests to the Internet layer. ... The Transmission Control Protocol (TCP) is one of the core protocols of the Internet protocol suite. ... User Datagram Protocol (UDP) is one of the core protocols of the Internet protocol suite. ... The Datagram Congestion Control Protocol (DCCP) is a message-oriented transport layer protocol that is currently under development in the IETF. Applications that might make use of DCCP include those with timingconstraints on the delivery of data such that reliable in-order delivery, when combined with congestion control, is likely... In the field of computer networking, the IETF Signaling Transport (SIGTRAN) working group defined the Stream Control Transmission Protocol (SCTP) as a transport layer protocol in 2000. ... The Resource ReSerVation Protocol (RSVP), described in RFC 2205, is a Transport layer protocol designed to reserve resources across a network for an integrated services Internet. ... Network congestion avoidance is a process used in computer networks to avoid congestion. ... The network layer is third layer out of seven in OSI model and it is the third layer out of five in TCP/IP model. ... The Internet Protocol (IP) is a data-oriented protocol used for communicating data across a packet-switched internetwork. ... Internet Protocol version 4 (IPv4) is the fourth iteration of the Internet Protocol (IP) and it is the first version of the protocol to be widely deployed. ... Internet Protocol version 6 (IPv6) is a network layer for packet-switched internetworks. ... The Open Shortest Path First (OSPF) protocol is a hierarchical interior gateway protocol (IGP) for routing in Internet Protocol, using a link-state in the individual areas that make up the hierarchy. ... Is Is is Yeah Yeah Yeahs third EP, to be released on July 24, 2007. ... The Border Gateway Protocol (BGP) is the core routing protocol of the Internet. ... IPsec (IP security) is a suite of protocols for securing Internet Protocol (IP) communications by authenticating and/or encrypting each IP packet in a data stream. ... In computer networking, the Address Resolution Protocol (ARP) is the standard method for finding a hosts hardware address when only its network layer address is known. ... Reverse Address Resolution Protocol (RARP) is a network layer protocol used to obtain an IP address for a given hardware address (such as an Ethernet address). ... This article is chiefly about the Routing Information Protocol (RIP) for the Internet Protocol, but also discusses some other routing information protocols. ... The Internet Control Message Protocol (ICMP) is one of the core protocols of the Internet protocol suite. ... The ICMP for IPv6 (Internet Control Message Protocol Version 6) is an integral part of the IPv6 architecture and must be completely supported by all IPv6 implementations. ... The Internet Group Management Protocol (IGMP) is a communications protocol used to manage the membership of Internet Protocol multicast groups. ... This article does not cite any references or sources. ... IEEE 802. ... The IEEE 802. ... Wi-Fi (IPA: ) is the common name for a popular wireless technology used in home networks, mobile phones, video games and more. ... Official WiMax logo WiMAX, the Worldwide Interoperability for Microwave Access, is a telecommunications technology aimed at providing wireless data over long distances in a variety of ways, from point-to-point links to full mobile cellular type access. ... Asynchronous Transfer Mode (ATM) is a cell relay, packet switching network and data link layer protocol which encodes data traffic into small (53 bytes; 48 bytes of data and 5 bytes of header information) fixed-sized cells. ... Dynamic synchronous Transfer Mode , or DTM for short, is a network protocol. ... Token-Ring local area network (LAN) technology was developed and promoted by IBM in the early 1980s and standardised as IEEE 802. ... Ethernet is a large, diverse family of frame-based computer networking technologies that operate at many speeds for local area networks (LANs). ... In computer networking, fiber-distributed data interface (FDDI) is a standard for data transmission in a local area network that can extend in range up to 200 km (124 miles). ... In the context of computer networking, 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. ... General Packet Radio Service (GPRS) is a Mobile Data Service available to users of Global System for Mobile Communications (GSM) and IS-136 mobile phones. ... Evolution-Data Optimized or Evolution-Data only, abbreviated as EV-DO or EVDO and often EV, is one telecommunications standard for the wireless transmission of data through radio signals, typically for broadband Internet access. ... High-Speed Packet Access (HSPA) is a collection of mobile telephony protocols that extend and improve the performance of existing UMTS protocols. ... High-Level Data Link Control (HDLC) is a bit-oriented synchronous data link layer protocol developed by the International Organization for Standardization (ISO). ... In computing, the Point-to-Point Protocol, or PPP, is commonly used to establish a direct connection between two nodes. ... The Point-to-Point Tunneling Protocol (PPTP) is a method for implementing virtual private networks. ... In computer networking, the Layer 2 Tunneling Protocol (L2TP) is a tunneling protocol used to support virtual private networks (VPNs). ... ISDN redirects here. ... ARCNET (also CamelCased as ARCnet, an acronym from Attached Resource Computer NETwork) is a local area network (LAN) protocol, similar in purpose to Ethernet or Token Ring. ... Link Layer Topology Discovery (LLTD) is a licensed data link layer protocol for network topology discovery and quality of service diagnostics, developed by Microsoft as part of their Windows Rally set of technologies. ... This article does not cite any references or sources. ... The Ethernet physical layer is the physical layer component of the Ethernet standard. ... RS-232 (also referred to as EIA RS-232C or V.24) is a standard for serial binary data interchange between a DTE (Data terminal equipment) and a DCE (Data communication equipment). ... Synchronous optical networking, is a method for communicating digital information using lasers or light-emitting diodes (LEDs) over optical fiber. ... There are very few or no other articles that link to this one. ... Optical fibers An optical fiber (or fibre) is a glass or plastic fiber designed to guide light along its length. ... Coaxial Cable For the weapon, see coaxial weapon. ... 25 Pair Color Code Chart 10BASE-T UTP Cable Twisted pair cabling is a common form of wiring in which two conductors are wound around each other for the purposes of cancelling out electromagnetic interference known as crosstalk. ... The Internet Protocol (IP) is a data-oriented protocol used for communicating data across a packet-switched internetwork. ... For other uses, see GSM (disambiguation). ... Universal Mobile Telecommunications System (UMTS) is one of the third-generation (3G) mobile phone technologies. ... User Datagram Protocol (UDP) is one of the core protocols of the Internet protocol suite. ... The Transmission Control Protocol (TCP) is one of the core protocols of the Internet protocol suite. ...

GTP-C is used within the GPRS core network for signalling between GPRS Support Nodes (GGSNs and SGSNs). This allows the SGSN to activate a session on the users behalf (PDP context activation), to deactivate the same session, to adjust quality of service parameters or to update a session for a subscriber who has just arrived from another SGSN. 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. ... 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. ... 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. ... In the fields of packet-switched networks and computer networking, the traffic engineering term Quality of Service, abbreviated QoS, refers to resource reservation control mechanisms. ...

GTP-U is used for carrying user data within the GPRS core network and between the Radio Access Network and the core network. The user data transported can be packets in any of IPv4, IPv6 or PPP formats. Internet Protocol version 4 (IPv4) is the fourth iteration of the Internet Protocol (IP) and it is the first version of the protocol to be widely deployed. ... Internet Protocol version 6 (IPv6) is a network layer for packet-switched internetworks. ... In computing, the Point-to-Point Protocol, or PPP, is commonly used to establish a direct connection between two nodes. ...

GTP' (GTP prime) uses the same message structure as GTP-C and GTP-U, but it is largely a completely separate protocol. It can be used for carrying charging data from the "Charging Data Function" of the GSM or UMTS network to the "Charging Gateway Function". In most cases, this should mean from many individual network elements such as the GGSNs to a centralised computer which then delivers the charging data more conveniently to the network operator's billing center.

General Features of the GTP protocol

All variants of GTP have certain features in common. The structure of the messages is the same, with a GTP header following the UDP/TCP header.

Header

GTPv1 headers contain the following fields^[1]

Version 

The first header field in a GTP packet is the 3-bit version field. For GTPv1, this has a value of 1 (hence the name GTPv1).

Protocol Type (PT) 

a 1-bit value that differentiates GTP (value 1) from GTP' (value 0).

Reserved

a 1-bit reserved field (must be 0).

Extension Header (E)

a 1-bit value that states whether there is an Extension Header optional field.

Sequence Number (S)

a 1-bit value that states whether there is a Sequence Number optional field.

N-PDU number (PN)

a 1-bit value that states whether there is a N-PDU number optional field.

Type

A 8-bit field that states the packet type.

Length

A 16-bit field that states the length of the packet being encapsulated by GTP (not including the GTP header itself, but including the optional fields).

Tunnel Endpoint Identifier (TEID)

A 32-bit field used to multiplex different connections in the same GTP tunnel.

Sequence Number

An (optional) 16-bit field. This field exists if any of the E, S, or PN bits are on. The field must be interpreted only if the S bit is on.

N-PDU number

An (optional) 8-bit field. This field exists if any of the E, S, or PN bits are on. The field must be interpreted only if the PN bit is on.

Next Extension Header

An (optional) 8-bit field. This field exists if any of the E, S, or PN bits are on. The field must be interpreted only if the E bit is on.

Next Extension Headers are as follows: In information technology, a packet is a formatted block of data carried by a packet mode computer network. ...

Length

An 8-bit field. This field states the length of this extension header, including the length, the contents, and the Next Extension Header field, in 4-octet units. The length must be a multiple of 4.

Contents

Extension header contents.

Next Extension Header

An 8-bit field. It states the type of the next extension, or 0 if no next extension exists. This permits chaining several Next Extension headers.

Connectivity Mechanisms

Apart from the common message structure, there is also a common mechanism for verifying connectivity from GSN to GSN. This uses two messages.

• echo request
• echo response

As often as every 60 seconds, a GSN can send an echo request to each other GSN with which it has an active connection. If the other end does not respond it can be treated as down and active connections to it deleted.

Apart from the two messages previously mentioned, there are no other messages common across all GTP variants^[2] meaning that, for the most part, they effectively form three completely separate protocols.

GTP-C - GTP Control

The GTP-C protocol is the control section of the GTP standard. When a subscriber requests a PDP context, the SGSN will send a Create PDP Context Request GTP-C message to the GGSN giving details of the subscriber's request. The GGSN will then respond with a Create PDP Context Response GTP-C message which will either give details of the PDP context actually activated or will indicate a failure and give a reason for that failure. 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. ...

GTP-U - GTP User Data Tunnelling

GTP-U is, in effect a relatively simple IP based tunnelling protocol which permits many tunnels between each set of end points. When used in the UMTS, each subscriber will have one or more tunnel, one for each PDP context they have active plus, possibly separate tunnels for specific connections with different Quality of service requirements. Universal Mobile Telecommunications System (UMTS) is one of the third-generation (3G) mobile phone technologies. ... 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. ... In the fields of packet-switched networks and computer networking, the traffic engineering term Quality of Service, abbreviated QoS, refers to resource reservation control mechanisms. ...

The separate tunnels are identified by a TEID (Tunnel Endpoint Identifier) in the GTP-U messages, which should be a dynamically allocated random number. If this random number is of cryptographic quality, then it will provide a measure of security against certain attacks. Even so, the requirement of the 3GPP standard is that all GTP traffic, including user data should be sent within secure private networks, not directly connected to the Internet. The German Lorenz cipher machine, used in World War II for encryption of very high-level general staff messages Cryptography (or cryptology; derived from Greek κρυπτός kryptós hidden, and the verb γράφω gráfo write or λεγειν legein to speak) is the study of message secrecy. ...

GTP' - Charging Transfer

The GTP' (pronounced GTP prime) protocol is used to transfer charging data to the Charging Gateway Function. GTP' uses TCP/UDP port 3386.

Within the GPRS Core Network

see also GPRS Core Network

GTP is the primary protocol used in the GPRS core network. It is the protocol which allows end users of a GSM or UMTS network to move from place to place whilst continuing to connect to the Internet as if from one location at the GGSN. It does this by carrying the subscriber's data from the subscriber's current SGSN to the GGSN which is handling the subscriber's session. Three forms of GTP are used by the GPRS core network. 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. ...

• 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). GGSN和SGSN在UDP 2123端口监听GTP-C消息，在2152端口监听GTP-U消息。 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 Game Show Network (GSN) is an American cable television and direct broadcast satellite channel dedicated to game shows and interactive television games. ... The Game Show Network (GSN) is an American cable television and direct broadcast satellite channel dedicated to game shows and interactive television games. ...

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.

CGF负责计费，GSN通过UDP端口3386发送计费信息给CGF，主要包括PDP上下文，激活时间，数据质量等。

Use on the IuPS interface

GTP-U is used on the IuPS between the GPRS core network and the Radio Access Network, however the GTP-C protocol is not used. In this case, RANAP is used as a control protocol and establishes GTP-U tunnels between the SGSN and the RNC. Radio Access Network Application Part The RANAP-Protocol is used in UMTS signaling between the Core Network and the UTRAN ... 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 Radio Network Controller (or RNC) is the governing element in the UMTS radio access network (UTRAN) responsible for control of the Node-Bs, that is to say the base stations which are connected to the controller. ...

Protocol Stack

All variations of GTP are transported over UDP.

As of 2004 there are two versions defined, version 0 and version 1. Version 0 and version 1 differ considerably in structure. In version 0, the signalling protocol (the protocol which sets up the tunnels by activating the PDP context) is combined with the tunnelling protocol on one port. Version 1 is actually effectively two protocols, one for control (called GTP-C) and one for user data tunnelling (called GTP-U). 2004 is a leap year starting on Thursday of the Gregorian calendar. ... 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. ...

GTP-U is also used to transport user data from the RNC to the SGSN in UMTS networks. However, in this case signalling is done using RANAP instead of GTP-C. The Radio Network Controller (or RNC) is the governing element in the UMTS radio access network (UTRAN) responsible for control of the Node-Bs, that is to say the base stations which are connected to the controller. ... 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. ... Universal Mobile Telecommunications System (UMTS) is one of the third-generation (3G) mobile phone technologies. ... Radio Access Network Application Part The RANAP-Protocol is used in UMTS signaling between the Core Network and the UTRAN ...

Historical GTP Versions

The original version of GTP (version 0) had considerable differences from the current version (version 1).

• the tunnel identification was non random
• options were provided for transporting X.25
• the fixed port number 3386 was used for all functions (not just charging as in GTPv1).
• TCP was allowed as a transport option instead of UDP, but support for this was optional
• subscription related fields such as Quality of Service were more limited

The non random TEID in version 0 represented a security problem if an attacker had access to any roaming partner's network, or could find some other way to remotely send packets to the GPRS backbone. Version 0 is going out of use and being replaced by version 1 in almost all networks. Even so, the standard for the newer version states that the older version must be supported by the GSN. Fortunately, however the use of different port numbers allows easy blocking of version 0 through simple IP access lists.

GTP in standardisation

GTP was originally standardised within ETSI (GSM standard 09.60). With the creation of the UMTS standards this was moved over to the 3GPP which, as of 2005 maintains it as 3GPP standard 29.060. GTP' uses the same message format, but its special uses are covered in standard 32.295 along with the standardised formats for the charging data it transfers. The European Telecommunications Standards Institute (ETSI) is a standardization organization of the telecommunications industry (equipment makers and network operators) in Europe, with worldwide projection. ... Universal Mobile Telecommunications System (UMTS) is one of the third-generation (3G) mobile phone technologies. ... This article or section does not adequately cite its references or sources. ... 2005 is a common year starting on Saturday of the Gregorian calendar. ...

Notes

1. ^  3GPP TS 29.060 section 6 see bibliography for reference information
2. ^  3GPP TS 29.060 section 6 see bibliography for reference information

Bibliography

• GSM standard 09.60, ETSI, 1996-98, this standard covers the original version 0 of GTP.
• 3GPP TS 29.060 V6.9.0 (2005-06), 3rd Generation Partnership Project, 650 Route des Lucioles - Sophia Antipolis, Valbonne - FRANCE, 2005-06. This is the primary standard defining all of the GTP variants for GTP version 1.
• 3GPP TS 32.295 V6.1.0 (2005-06), 3rd Generation Partnership Project, 650 Route des Lucioles - Sophia Antipolis, Valbonne - FRANCE, 2005-06. This standard covers using GTP for charging.

External links

• the 3GPP web site, home of the GTP standard