Section: 5.3 GTP-C header for Echo and Version Not Supported Indication messages
Content: The GTPv2-C message header for the Echo Request, Echo Response and Version Not Supported Indication messages shall not contain the TEID field, but shall contain the Sequence Number fields, followed by one spare octet as depicted in figure 5.3-1. The spare bits shall be set to zero by the sender and ignored by the receiver. For the Version Not Supported Indication message header, the Sequence Number may be set to any number and shall be ignored by the receiver. Figure 5.3-1: The format of Echo and Version Not Supported Indication messages Header