allow greater offset

Author: mertalev

draft-ietf-httpbis-resumable-upload.md

@@ -502,7 +502,7 @@ HTTP/1.1 405 Method Not Allowed
 
 If the client wants to resume the upload after an interruption, it has to know the amount of representation data received by the upload resource so far. It can fetch the offset by sending a `HEAD` request to the upload resource. Upon a successful response, the client can continue the upload by appending representation data ({{upload-appending}}) starting at the offset indicated by the `Upload-Offset` response header field.
 
-The offset can be less than or equal to the number of bytes of representation data that the client has already sent. The client MAY reject an offset which is greater than the number of bytes it has already sent during this upload by not continuing the upload and canceling the upload resource ({{upload-cancellation}}). The client is expected to handle backtracking of a reasonable length. If the offset is invalid for this upload, or if the client cannot backtrack to the offset and reproduce the same representation data it has already sent, the upload MUST be considered a failure. The client then MUST NOT continue the upload and SHOULD cancel the upload ({{upload-cancellation}}).
+The offset can be less than or equal to the total length of the representation data. If the offset is greater than the number of bytes the client has already sent during this upload, it can indicate that other upload sessions have successfully appended to the resource. The client is expected to handle backtracking of a reasonable length. If the offset is invalid for this upload, or if the client cannot reproduce the representation data for the received offset, the upload MUST be considered a failure. The client then MUST NOT continue the upload and SHOULD cancel the upload ({{upload-cancellation}}).
 
 The client MUST NOT perform offset retrieval while creation ({{upload-creation}}) or appending ({{upload-appending}}) is in progress as this can cause the previous request to be terminated by the server as described in {{concurrency}}.