8.2.56 Outer Header Creation
29.2443GPPInterface between the Control Plane and the User Plane nodesRelease 17TS
The Outer Header Creation IE type shall be encoded as shown in Figure 8.2.56-1. It contains the instructions to create an Outer Header.
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Bits |
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Octets |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
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1 to 2 |
Type = 84 (decimal) |
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3 to 4 |
Length = n |
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5 to 6 |
Outer Header Creation Description |
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m to (m+3) |
TEID |
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p to (p+3) |
IPv4 Address |
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q to (q+15) |
IPv6 Address |
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r to (r+1) |
Port Number |
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t to (t+2) |
C-TAG |
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u to (u+2) |
S-TAG |
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s to (n+4) |
These octet(s) is/are present only if explicitly specified |
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Figure 8.2.56-1: Outer Header Creation
The Outer Header Creation Description field, when present, shall be encoded as specified in Table 8.2.56-1. It takes the form of a bitmask where each bit indicates the outer header to be created in the outgoing packet. Spare bits shall be ignored by the receiver.
Table 8.2.56-1: Outer Header Creation Description
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Octet / Bit |
Outer Header to be created in the outgoing packet |
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5/1 |
GTP-U/UDP/IPv4 (NOTE 1), (NOTE 3) |
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5/2 |
GTP-U/UDP/IPv6 (NOTE 1), (NOTE 3) |
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5/3 |
UDP/IPv4 (NOTE 2, NOTE 5) |
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5/4 |
UDP/IPv6 (NOTE 2, NOTE 5) |
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5/5 |
IPv4 (NOTE 5) |
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5/6 |
IPv6 (NOTE 5) |
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5/7 |
C-TAG (see NOTE 4) |
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5/8 |
S-TAG (see NOTE 4) |
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6/1 |
N19 Indication (NOTE 6) |
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6/2 |
N6 Indication (NOTE 6) |
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6/3 |
Low Layer SSM and C-TEID (NOTE 7) |
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NOTE 1: The SGW-U/I-UPF shall also create GTP-U extension header(s) if any has been stored for this packet, during a previous outer header removal (see clause 8.2.64). NOTE 2: This value may apply to UL packets sent by a PGW-U for non-IP PDN connections with SGi tunnelling based on UDP/IP encapsulation (see clause 4.3.17.8.3.3.2 of 3GPP TS 23.401 [14]). NOTE 3: The SGW-U/I-UPF shall set the GTP-U message type to the value stored during the previous outer header removal. NOTE 4: This value may apply to UL packets sent by a UPF for Ethernet PDU sessions over N6 (see clause 5.8.2.11.6 of 3GPP TS 23.501 [28]). NOTE 5: This value may apply e.g. to UL packets sent by a UPF (PDU Session Anchor) over N6, when explicit N6 traffic routing information is provided to the SMF (see clause 5.6.7 of 3GPP TS 23.501 [28]). The IPv4 or IPv6 address shall correspond to the IP address of the tunnel endpoint in the data network. NOTE 6: When the "N19 Indication" or "N6 Indication" bit in the Outer Header Creation Description field is set to "1", the UPF shall associate an "N19 Indication" or "N6 Indication" internal flag with the packet to indicate that the packet has been received from a N19 or N6 interface respectively. This indication is further used to prevent the packet from being forwarded back over N19 or N6 respectively (see clause 8.2.130). NOTE 7: When the "Low Layer SSM and C-TEID" bit in the Outer Header Creation Description field is set to "1", the MB-UPF shall create a GTP-U header with the C-TEID and set the destination IP address and the source IP address as the IP Multicast Distribution Address and the IP Source Address in the Multicast Transport Information IE, which is the Low Layer SSM allocated to the MBS session. In this case, the TEID, IPv4/IPv6 address and Port Number fields shall not be present. |
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At least one bit of the Outer Header Creation Description field shall be set to "1". Bits 5/1 and 5/2 may both be set to "1" if an F-TEID with both an IPv4 and IPv6 addresses has been assigned by the GTP-U peer. In this case, the UP function shall send the outgoing packet towards the IPv4 or IPv6 address.
The TEID field shall be present if the Outer Header Creation Description requests the creation of a GTP-U header, i.e. if in Octet 5 any of the bits 5/1 and 5/2 are set. Otherwise it shall not be present. When present, it shall contain the destination GTP-U TEID to set in the GTP-U header of the outgoing packet.
The IPv4 Address field shall be present if the Outer Header Creation Description requests the creation of an IPv4 header, i.e. if in Octet 5 any of the bits 5/1, 5/3 and 5/5 are set. Otherwise it shall not be present. When present, it shall contain the destination IPv4 address to set in the IPv4 header of the outgoing packet.
The IPv6 Address field shall be present if the Outer Header Creation Description requests the creation of an IPv6 header, i.e. if in Octet 5 any of the bits 5/2, 5/4 and 5/6 are set. Otherwise it shall not be present. When present, it shall contain the destination IPv6 address to set in the IPv6 header of the outgoing packet.
The Port Number field shall be present if the Outer Header Creation Description requests the creation of a UDP/IP header, i.e. if in Octet 5 any of the bits 5/3 and 5/4 are set. Otherwise it shall not be present. When present, it shall contain the destination Port Number to set in the UDP header of the outgoing packet.
The C-TAG field shall be present if the Outer Header Creation Description requests the setting of the C-Tag in Ethernet packet. Otherwise it shall not be present. When present, it shall contain the destination Customer-VLAN tag to set in the Customer-VLAN tag header of the outgoing packet.
The S-TAG field shall be present if the Outer Header Creation Description requests the setting of the S-Tag in Ethernet packet. Otherwise it shall not be present. When present, it shall contain the destination Service-VLAN tag to set in the Service-VLAN tag header of the outgoing packet.