Outer Header Creation

Per 3GPP TS 29.244 v16.4.0, the Outer Header Creation Description field, when present, is encoded as specified in following table. It takes the form of a bitmask where each bit indicates the outer header to be created in the outgoing packet. Spare bits are ignored by the receiver.

Octet / Bit Outer Header Created in the Outgoing Packet
5/1 GTP-U/UDP/IPv4
5/2 GTP-U/UDP/IPv6
5/3 UDP/IPv4
5/4 UDP/IPv6
5/5 IPv4
5/6 IPv6
5/7 C-TAG
5/8 S-TAG
6/1 N19 Indication
6/2 N6 Indication
6/3 TCP/IPv4
6/4 TCP/IPv6

NOTE:

  • Currently, the UP/UPF doesn't support the following values of Outer Header Creation Description:

    • IPv4

    • IPv6

    • C-TAG

    • S-TAG

    • N19 Indication

    • N6 Indication

  • Third and fourth bits of sixth Octet (that is, 6/3 and 6/4) are spare bits (that is, not part of 3GPP TS) used for LI over TCP.

Important

If SMF/CP uses older version for Outer Header Creation, then undefined behavior (including crashes) can be seen.