diff --git a/src/common/protocol.h b/src/common/protocol.h
--- a/src/common/protocol.h
+++ b/src/common/protocol.h
@@ -61,12 +61,28 @@ enum distren_request_type
     */
     DISTREN_REQUEST_VERSION = 1,
     /**
+     * Test if the end has a live server.
+     *
+     * Only authenticated clients may use this request. Thus, if a
+     * client wants to confirm that a DISTREN_REQUEST_PASS request was
+     * successful, that client may send a DISTREN_REQUEST_PING
+     * immediately after the DISTREN_REQUEST_PASS and then wait for
+     * the PONG.
+     *
      * DATA: up to 32 bytes of a PING cookie
      *
      * REQUIRED: ALL
      */
     DISTREN_REQUEST_PING = 2,
     /**
+     * Response to DISTREN_REQUEST_PING.
+     *
+     * Unauthenticated clients may be penalized for responding to PING
+     * requests. This is because a newly connecting client should
+     * queue a DISTREN_REQUEST_VERSION and DISTREN_REQUEST_PASS
+     * back-to-back before checking for and processing data from the
+     * remote server.
+     *
      * DATA: up to 32 bytes copied from a received PING cookie
      *
      * REQUIRED: ALL
@@ -84,12 +100,31 @@ enum distren_request_type
      */
     DISTREN_REQUEST_DISCONNECT = 4,
 
+
+    /**
+     * Allow a client to identify itself using simple password
+     * authentication.
+     *
+     * As there is no distren request which affirms a
+     * DISTREN_REQUEST_PASS went through, clients may send a
+     * DISTREN_REQUEST_PING and wait for the DISTREN_REQUETS_PONG they
+     * want to block until they're authenticated.
+     *
+     * DATA: struct distren_request_pass
+     *
+     * REQUIRED: DISTREN_SERVERTYPE_SUBMIT (for now, since
+     * server2server links are only protected using password
+     * authentication, all server types have to support this except
+     * for the client.)
+     */
+    DISTREN_REQUEST_PASS = 5,
+
     /**
      * DATA: struct distren_request_submit
      *
      * REQUIRED: DISTREN_SERVERTYPE_SUBMIT
      */
-    DISTREN_REQUEST_SUBMIT = 5,
+    DISTREN_REQUEST_SUBMIT = 6,
 
     /**
      * Inform the other party about a job.
@@ -98,7 +133,7 @@ enum distren_request_type
      *
      * REQUIRED: ALL
      */
-    DISTREN_REQUEST_JOBINFO = 6,
+    DISTREN_REQUEST_JOBINFO = 7,
 
     /**
      * Request a DISTREN_REQUEST_JOBINFO
@@ -107,7 +142,7 @@ enum distren_request_type
      *
      * REQUIRED: DISTREN_SERVERTYPE_SUBMIT, DISTREN_SERVERTYPE_DISTRIBUTE
      */
-    DISTREN_REQUEST_JOBINFO_GET = 7,
+    DISTREN_REQUEST_JOBINFO_GET = 8,
 
     /**
      * Command the other party to render a frame
@@ -116,7 +151,7 @@ enum distren_request_type
      *
      * REQUIRED: DISTREN_SERVERTYPE_RENDER
      */
-    DISTREN_REQUEST_FRAME_RENDER = 8,
+    DISTREN_REQUEST_FRAME_RENDER = 9,
     /**
      * Inform the receiver of the sender's state, such as frames being
      * rendered or jobs that need to be completed.
@@ -125,7 +160,7 @@ enum distren_request_type
      *
      * REQUIRED: DISTREN_SERVERTYPE_RENDER, DISTREN_SERVERTYPE_DISTRIBUTE, DISTREN_SERVERTYPE_CLIENT
      */
-    DISTREN_REQUEST_STATUS = 9,
+    DISTREN_REQUEST_STATUS = 10,
 
     /**
      * Request that the receiver send a DISTREN_REQUEST_FRAME_STATUS
@@ -136,7 +171,7 @@ enum distren_request_type
      *
      * REQUIRED: DISTREN_SERVERTYPE_RENDER
      */
-    DISTREN_REQUEST_STATUS_GET = 10,
+    DISTREN_REQUEST_STATUS_GET = 11,
 
     /**
      * Declare that a client is preparing to post a file using a
@@ -157,7 +192,7 @@ enum distren_request_type
      *
      * REQUIRED: DISTREN_SERVERTYPE_SUBMIT, DISTREN_SERVERTYPE_DISTRIBUTE
      */
-    DISTREN_REQUEST_FILE_POST_START = 11,
+    DISTREN_REQUEST_FILE_POST_START = 12,
 
     /**
      * Allow a client to upload a job tarball over a remoteio line.  A
@@ -182,7 +217,7 @@ enum distren_request_type
      *
      * REQUIRED: DISTREN_SERVERTYPE_SUBMIT, DISTREN_SERVERTYPE_DISTRIBUTE
      */
-    DISTREN_REQUEST_FILE_POST = 12,
+    DISTREN_REQUEST_FILE_POST = 13,
 
     /**
      * Marks a post-id's file as having completely uploaded. Provides
@@ -193,7 +228,7 @@ enum distren_request_type
      *
      * REQUIRED: DISTREN_SERVERTYPE_SUBMIT, DISTREN_SERVERTYPE_DISTRIBUTE
      */
-    DISTREN_REQUEST_FILE_POST_FINISH = 13,
+    DISTREN_REQUEST_FILE_POST_FINISH = 14,
 
     /**
      * Request information about obtaining a file (such as a
@@ -203,7 +238,7 @@ enum distren_request_type
      *
      * REQUIRED: DISTREN_SERVERTYPE_DISTRIBUTE
      */
-    DISTREN_REQUEST_FILE_FIND = 14,
+    DISTREN_REQUEST_FILE_FIND = 15,
 
     /**
      * Provide information about obtaining a file (such as a URL).
@@ -212,7 +247,7 @@ enum distren_request_type
      *
      * REQUIRED: DISTREN_SERVERTYPE_DISTRIBUTE
      */
-    DISTREN_REQUEST_FILE = 15,
+    DISTREN_REQUEST_FILE = 16,
   };
 
 struct distren_request
@@ -236,6 +271,14 @@ struct distren_request_version
   char package_string[DISTREN_REQUEST_VERSION_PACKAGE_STRING_LEN + 1];
 };
 
+#define DISTREN_REQUEST_PASS_USERNAME_LEN (16)
+#define DISTREN_REQUEST_PASS_PASS_LEN (32)
+struct distren_request_pass
+{
+  char username[DISTREN_REQUEST_PASS_USERNAME_LEN];
+  char pass[DISTREN_REQUEST_PASS_PASS_LEN];
+};
+
 #define DISTREN_REQUEST_FILE_POST_NAME_LEN (64)
 struct distren_request_file_post_start
 {