diff -r c99c527f1186 Lib/http/client.py
--- a/Lib/http/client.py	Mon May 14 18:23:44 2012 +0200
+++ b/Lib/http/client.py	Tue May 15 01:30:35 2012 +0900
@@ -141,6 +141,9 @@
 LOCKED = 423
 FAILED_DEPENDENCY = 424
 UPGRADE_REQUIRED = 426
+PRECONDITION_REQUIRED = 428
+TOO_MANY_REQUESTS = 429
+REQUEST_HEADER_FIELDS_TOO_LARGE = 431
 
 # server error
 INTERNAL_SERVER_ERROR = 500
@@ -151,6 +154,7 @@
 HTTP_VERSION_NOT_SUPPORTED = 505
 INSUFFICIENT_STORAGE = 507
 NOT_EXTENDED = 510
+NETWORK_AUTHENTICATION_REQUIRED = 511
 
 # Mapping status codes to official W3C names
 responses = {
@@ -192,6 +196,9 @@
     415: 'Unsupported Media Type',
     416: 'Requested Range Not Satisfiable',
     417: 'Expectation Failed',
+    428: 'Precondition Required',
+    429: 'Too Many Requests',
+    431: 'Request Header Fields Too Large',
 
     500: 'Internal Server Error',
     501: 'Not Implemented',
@@ -199,6 +206,7 @@
     503: 'Service Unavailable',
     504: 'Gateway Timeout',
     505: 'HTTP Version Not Supported',
+    511: 'Network Authentication Required',
 }
 
 # maximal amount of data to read at one time in _safe_read
diff -r c99c527f1186 Lib/http/server.py
--- a/Lib/http/server.py	Mon May 14 18:23:44 2012 +0200
+++ b/Lib/http/server.py	Tue May 15 01:30:35 2012 +0900
@@ -628,6 +628,12 @@
               'Cannot satisfy request range.'),
         417: ('Expectation Failed',
               'Expect condition could not be satisfied.'),
+        428: ('Precondition Required',
+              'The origin server requires the request to be conditional.'),
+        429: ('Too Many Requests', 'The user has sent too many requests'
+              'in a given amount of time ("rate limiting").'),
+        431: ('Request Header Fields Too Large', 'The server is unwilling'
+              'to process the request because its header fields are too large.'),
 
         500: ('Internal Server Error', 'Server got itself in trouble'),
         501: ('Not Implemented',
@@ -638,6 +644,8 @@
         504: ('Gateway Timeout',
               'The gateway server did not receive a timely response'),
         505: ('HTTP Version Not Supported', 'Cannot fulfill request.'),
+        511: ('Network Authentication Required',
+              'The client needs to authenticate to gain network access.'),
         }