The LS type field dictates the format and function of the link state advertisement. Advertisements of different types have different names (e.g., router links or network links). All advertisement types, except the AS external link advertisements (LS type = 5), are flooded throughout a single area only. AS external link advertisements are flooded throughout the entire Autonomous System, excepting stub areas (see Section 3.6). Each separate advertisement type is briefly described below in Table 15.