1959155 - Failed to read response from Relay Server. Connection closed by server! - Afaria

Every afaria services are not available suddenly.
But It seems like there is no connection problem between Relay server and RSOE.
(checked by accessing to "http://relay-server-IP address/ias_relay_server/client/rs_client.dll")

You can find the below error message on RSOE log. There was no changes on rs.config.

   E. 2013-12-19 19:19:08. Error: Encountered authentication error with Relay Server, Farm ID or backend server ID could be invalid
   E. 2013-12-19 19:19:08. Failed to read response from Relay Server. Connection closed by server!
   I. 2013-12-19 19:19:15. Successfully connected to relay server: SUP-PRD:80
   I. 2013-12-19 19:19:15. Successfully connected to relay server: SUP-PRD:80

It is not related to specific version of afaria and relay server and RSOE.
Afaria7 <-> RSOE <-> Relay Server

Relay sever, RSOE, windows function add wizard, WCF, WebDAV, , KBA , MOB-AFA , Afaria , Problem