// 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;

const bit<6>  DSCP_INT = 0x0; //DSCP could be 0x17, or use any other recommendaiton from standard

const bit<8> TWO_SIZE_METADATA_STACK = 0x0; // In a real case it should be 8w7 - 0x07    
const bit<8> ONE_SIZE_METADATA_STACK = 0x05; //