HTTP authentication, request received in quick succession -

http request may received in quick succession, avoiding re-running while protocol each request, server nonce may re-used (timestamp nonce determine window in client request valid) client multiple requests.

what pros , cons using method?

the pros of re-using nonce take less resources maintaining , checking valid nonces , can avoid authentication failures pipelined requests:

[…] method chosen generating , checking nonce has performance , resource implications. example, server may choose allow each nonce value used once maintaining record of whether or not each issued nonce has been returned , sending next-nonce directive in authentication-info header field of every response. protects against immediate replay attack, has high cost checking nonce values, , perhaps more important cause authentication failures pipelined requests (presumably returning stale nonce indication).

however, cons replay attacks more probable one-time nonces:

for applications no possibility of replay attack can tolerated server can use one-time nonce values not honored second use. requires overhead of server remembering nonce values have been used until nonce time- stamp (and hence digest built it) has expired, protects against replay attacks.