When the Frontier decides which URIs should be treated as deferred and which has failed, it must check the fetch status and have knowledge about every possible status code. This complicates adding new status codes. It should be possible to constrain the number of status groups the Frontier has to know and then let the processors decide which group a new status code falls into. Possible status groups are:

successful

failure

disregard

retry immediately

retry after any prerequisite

retry at some later time