The Print System Remote Protocol uses RPC over named pipes (see [MS-RPCE] section 126.96.36.199) for RPC sequences. The well-known endpoint \pipe\spoolss is used for RPC calls made from the print client to the print server. The client MUST use no authentication, and the server MUST accept connections without authentication.
An endpoint with the same name MUST also be used for RPC calls made from the server to send printer change notifications back to the client; those calls are RpcReplyOpenPrinter (section 188.8.131.52.1), RpcRouterReplyPrinter (section 184.108.40.206.2), RpcReplyClosePrinter (section 220.127.116.11.3), and RpcRouterReplyPrinterEx (section 18.104.22.168.4). The client MUST accept connections without authentication from the server for these methods. If the client provides authentication information (as specified in [MS-RPCE] 22.214.171.124.8), the server MAY impersonate the client (as specified in [MS-RPCE] 126.96.36.199.9), while processing a method.<3>