09.603GPPGeneral Packet Radio Service (GPRS)GPRS Tunnelling Protocol GPT) across the Gn and Gp InterfaceRelease 1998TS
For the purposes of the present document, the following terms and definitions apply.
Conditional When the presence requirement for the information element is conditional, the receiving protocol level can check the presence or absence of an IE based on the received information.
G-PDU: A T-PDU plus a GTP header. A G-PDU is sent in a path.
GTP-Flow: A GTP flow is defined by the unidirectional virtual aggregation of G-PDUs and/or signalling messages related to one or more GTP tunnels. A GTP flow is identified by a Flow Label included in the GTP header. The meaning of the Flow Label is transparent for the transmitter side, only the receiver may evaluate the Flow Label.
GTP tunnel: A GTP tunnel is defined by two associated PDP Contexts in different GSN nodes and is identified with a Tunnel ID. A GTP tunnel is necessary to forward packets between an external packet data network and a MS user.
MM Context: The information sets held in MS and GSNs for a GPRS subscriber related to mobility management (MM) (please refer to the MM Context Information Element).
MM Context ID: IMSI or equivalent for use in conjunction with Anonymous Access (please refer to section GTP Header).
NSAPI: Network Service Access Point Identifier. An integer value in the range [0; 15], identifying a certain PDP Context. It identifies a PDP context belonging to a specific MM Context ID.
Path: The UDP/IP path and TCP/IP path are examples of paths that may be used to multiplex GTP tunnels.
Path Protocol: The Path Protocol is the protocol(s) used as a bearer of GTP between GSNs.
PDP: A Packet Data Protocol (PDP) is a network protocol used by an external packet data network interfacing to GPRS.
PDP Context: The information sets held in MS and GSNs for a PDP address (please refer to the PDP Context Information Element).
Quality of Service: Quality of Service may be applicable for the GPRS backbone if the path media supports it. Separate paths with different priorities may be defined between a GSN pair. However, the possible use of QoS in the GGSN is outside the scope of the GTP specification.
Signalling message: GTP signalling messages are exchanged between GSN pairs in a path. The signalling messages are used to transfer GSN capability information between GSN pairs and to create, update and delete GTP tunnels.
TCP/IP path: A TCP/IP path is a reliable connection-oriented path defined by two end-points and an end-point is defined by an IP address and a TCP port number. TCP/IP paths should be used when the T-PDUs are based on connection-oriented protocols, such as the X.25 packet layer protocol.
T-PDU: An original packet, for example an IP datagram, from a MS or a network node in an external packet data network. A T-PDU is the payload that is tunnelled in the GTP tunnel.
TID: A Tunnel ID (TID) consists of a MM Context ID and a NSAPI.
UDP/IP path: A UDP/IP path is a connection-less path defined by two end-points and an end-point is defined by an IP address and a UDP port number. A UDP/IP path carries G-PDUs between GSN nodes related to one or more GTP tunnels. A UDP/IP path should be used when the T-PDUs are based on connection-less protocols, such as IP.
Abbreviations used in the present document are listed in GSM 01.04.
For the purposes of the present document, the following additional abbreviations apply:
BB Backbone Bearer
DF Don’t Fragment
FFS For Further Study
GTP GPRS Tunneling Protocol
IANA Internet Assigned Number Authority
ICMP Internet Control Message Protocol
IP Internet Protocol
IPv4 Internet Protocol version 4
IPv6 Internet Protocol version 6
MTU Maximum Transmission Unit
QoS Quality of Service
TID Tunnel IDentifier
TCP Transmission Control Protocol
UDP User Datagram Protocol
Gn interface Interface between GPRS Support Nodes (GSNs) within a PLMN
Gp interface Interface between GPRS Support Nodes (GSNs) in different PLMNs