Identifies the numeric tag for packets traveling through trunk links.
USAGE: This field is conditional.
NOTE 1: Required when the RT field on the CN Form is “F”, the first position of the REQTYP field on the ASR Form is “X” or “V” and a VLAN TAG is assigned by the provider, otherwise prohibited.
DATA CHARACTERISTICS: 4 numeric characters
EXAMPLE: 0 2 0 1