8 Information Elements
29.2813GPPGeneral Packet Radio System (GPRS) Tunnelling Protocol User Plane (GTPv1-U)Release 17TS
8.1 Information Element Types
A GTP-U Signalling message may contain several information elements. The TLV (Type, Length, Value) or TV (Type, Value) encoding format shall be used for the GTP information elements. The information elements shall be sorted, with the Type fields in ascending order, in the signalling messages. The Length field contains the length of the information element excluding the Type and Length field.
For all the length fields, bit 8 of the lowest numbered octet is the most significant bit and bit 1 of the highest numbered octet is the least significant bit.
Within information elements, certain fields may be described as spare. These bits shall be transmitted with the value defined for them. To allow for future features, the receiver shall not evaluate these bits.
The most significant bit in the Type field is set to 0 when the TV format is used and set to 1 for the TLV format.
Figure 8.1-1: Type field for TV and TLV format
The complete range of information element types defined for GTPv1 is defined in 3GPP TS 29.060 [6]. The table below includes those applicable to GTP user plane.
Table 8.1-1: Information Elements
|
IE Type Value |
Format |
Information Element |
Reference |
|---|---|---|---|
|
0-13 |
TV |
Reserved in 3GPP TS 29.060 [6] |
|
|
14 |
TV |
Recovery |
8.2 |
|
15 |
TV |
Reserved in 3GPP TS 29.060 [6] |
|
|
16 |
TV |
Tunnel Endpoint Identifier Data I |
8.3 |
|
17-132 |
TV/TLV |
Reserved in 3GPP TS 29.060 [6] |
|
|
133 |
TLV |
GSN Address. See NOTE 1. |
8.4 |
|
134-140 |
TLV |
Reserved in 3GPP TS 29.060 [6] |
|
|
141 |
TLV |
Extension Header Type List |
8.5 |
|
142-229 |
TLV |
Reserved in 3GPP TS 29.060 [6] |
|
|
230 |
TLV |
GTP-U Tunnel Status Information |
8.7 |
|
231 |
TLV |
Recovery Time Stamp |
8.7 |
|
232-237 |
TLV |
Spare. For future use. |
|
|
238-254 |
TLV |
Reserved in 3GPP TS 29.060 [6] |
|
|
255 |
TLV |
Private Extension |
8.6 |
|
NOTE 1: This IE is named as " GTP-U Peer Address" in the rest of this specification. |
|||
8.2 Recovery
The value of the restart counter shall be set to 0 by the sending entity and ignored by the receiving entity. This information element is used in GTP user plane due to backwards compatibility reasons.
Figure 8.2-1: Restart Counter Information Element
8.3 Tunnel Endpoint Identifier Data I
The Tunnel Endpoint Identifier Data I information element contains the Tunnel Endpoint Identifier used by a GTP entity for the user plane.
|
Bits |
||||||||||
|
Octets |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
||
|
1 |
Type = 16 (Decimal) |
|||||||||
|
2 – 5 |
Tunnel Endpoint Identifier Data I |
|||||||||
Figure 8.3-1: Tunnel Endpoint Identifier Data I Information Element
8.4 GTP-U Peer Address
The GTP-U peer Address information element contains the address of a GTP. The Length field may have only two values (4 or 16) that determine if the Value field contains IPv4 or IPv6 address.
The IPv4 address structure is defined in RFC 791 [10].
The IPv6 address structure is defined in RFC 4291 [11].
The encoded address might belong not only to a GSN, but also to an RNC, eNodeB, SGW, ePDG, gNB, N3IWF, UPF, PGW or TWAN.
Figure 8.4-1: GTP-U Peer Address Information Element
8.5 Extension Header Type List
This information element contains a list of ‘n’ Extension Header Types. The length field is set to the number of extension header types included.
Figure 8.5-1: Extension Header Type List Information Element
8.6 Private Extension
The Private Extension information element contains vendor specific information. The Extension Identifier is a value defined in the Private Enterprise number list in the most recent "Assigned Numbers" RFC (RFC 1700 or later).
This is an optional information element that may be included in any GTP Signalling message. A signalling message may include more than one information element of the Private Extension type.
Figure 8.6-1: Private Extension Information Element
8.7 GTP-U Tunnel Status Information
The GTP-U Tunnel Status Information contains the status information related to the corresponding GTP-U tunnel in the sending GTP-U entity.
|
Bits |
||||||||||
|
Octets |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
||
|
1 to 2 |
Type = 230 (decimal) |
|||||||||
|
3 to 4 |
Length = n |
|||||||||
|
5 |
Spare |
SPOC |
||||||||
|
6 to (n+4) |
These octet(s) is/are present only if explicitly specified |
|||||||||
Figure 8.7-1: GTP-U Tunnel Status Information
The octet 5 shall be encoded as follows:
– Bit 1 – SPOC (Start Pause Of Charging): when set to "1", this indicates a request to the receiving GTP-U entity to stop usage measurement for the URR(s) with the Applicable for Start of Pause of Charging Flag set to "1" as specified in 3GPP TS 29.244 [39] for the PFCP session (identified by the IP address and TEID of the header of the Tunnel Status message). The GTP-U entity shall forward Tunnel Status message to the upstream GTP-U entity if it is not a PSA UPF or PGW-U connecting to N6/SGi interface.
– Bit 2 to 8 – Spare, for future use and set to "0".
8.7 Recovery Time Stamp
The Recovery Time Stamp IE is coded as shown in Figure 8.7-1. It indicates the UTC time when the GTP-U entity started. Octets 4 to 7 are encoded in the same format as the first four octets of the 64-bit timestamp format as defined in clause 6 of IETF RFC 5905 [41].
NOTE: The encoding is defined as the time in seconds relative to 00:00:00 on 1 January 1900.
|
Bits |
||||||||||
|
Octets |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
||
|
1 |
Type = aa (decimal) |
|||||||||
|
2 to 3 |
Length = n |
|||||||||
|
4 to 7 |
Recovery Time Stamp value |
|||||||||
|
8 to (n+3) |
These octet(s) is/are present only if explicitly specified |
|||||||||
Figure 8.7-1: Recovery Time Stamp