[asterisk-users] Odd message: "correct auth, but ..."

[Richard Kenner]

I'm getting dozens of these at a very high rate:

[Jan 20 09:15:27] NOTICE[16958]: chan_sip.c:12687 check_auth: Correct auth, but based on stale nonce received from '"" <sip:121 at gnat.com>;tag=as5f1a9480'
[Jan 20 09:15:28] NOTICE[16958]: chan_sip.c:12687 check_auth: Correct auth, but based on stale nonce received from '"" <sip:130 at gnat.com>;tag=as15e2228a'
[Jan 20 09:15:28] NOTICE[16958]: chan_sip.c:12687 check_auth: Correct auth, but based on stale nonce received from '"" <sip:140 at gnat.com>;tag=as0984b061'
[Jan 20 09:15:30] NOTICE[16958]: chan_sip.c:12687 check_auth: Correct auth, but based on stale nonce received from '"" <sip:135 at gnat.com>;tag=as77d25989'
[Jan 20 09:15:36] NOTICE[16958]: chan_sip.c:12687 check_auth: Correct auth, but based on stale nonce received from '"" <sip:129 at gnat.com>;tag=as03aaa798'
[Jan 20 09:15:37] NOTICE[16958]: chan_sip.c:12687 check_auth: Correct auth, but based on stale nonce received from '"" <sip:201 at gnat.com>;tag=as6b67f553'
[Jan 20 09:15:38] NOTICE[16958]: chan_sip.c:12687 check_auth: Correct auth, but based on stale nonce received from '"" <sip:201 at gnat.com>;tag=as0797b09e'
[Jan 20 09:15:38] NOTICE[16958]: chan_sip.c:12687 check_auth: Correct auth, but based on stale nonce received from '"" <sip:116 at gnat.com>;tag=as3e2e8de7'
[Jan 20 09:15:38] NOTICE[16958]: chan_sip.c:12687 check_auth: Correct auth, but based on stale nonce received from '"" <sip:122 at gnat.com>;tag=as2ca773e0'

The "from" here are only used for hints, not real phones.  What do these
messages mean?  The NOTIFY's are coming from Aastra phones.