// 802.1ad defines this, S-Tag
const bit<16> ETHERTYPE_VLAN_STAG = 0x88A8;
// Deprecated but used 
// const bit<16> ETHERTYPE_VLAN_STAG2 = 0x9100;
// Deprecated, Cisco official doc mentions, maybe even 0x9300.
// const bit<16> ETHERTYPE_VLAN_STAG3 = 0x9200;
// C-Tag, 802.1q
const bit<16> ETHERTYPE_VLAN_CTAG = 0x8100;

const bit<16> ETHERTYPE_IPV4 = 0x0800;
const bit<16> ETHERTYPE_IPV6 = 0x86DD;

const bit<8>  IPPROTO_TCP = 0x06;
const bit<8>  IPPROTO_UDP = 0x11;

//Tester does not generate GRE. GRE headers will be all 0s but we can define a custom IP_PROTO for GRE.
const bit<8>  IPPROTO_GRE    = 0x2F;
//Tester cannot generate nGRE header so proto has to be 0x0. In reality it should be 0x6558.
const bit<16> GRE_PROTO_NVGRE = 0x0;// should be 0x6558 

//Similar case for VXLAN, we can define port but VXLAN header will be all 0s. 
const bit<16> UDP_PORT_VXLAN = 0x12B5; // or 4789