IPP>PRO another reason for needing byterange and documen

IPP>PRO another reason for needing byterange and documen

IPP>PRO another reason for needing byterange and documen

Roger K Debry rdebry at us.ibm.com
Mon May 12 09:58:14 EDT 1997


Bob, I'm glad that someone else finally realizes that we need
something in the IPP layer to help with recovery. If you would
go back to the protocol proposal that I presented in the San
Jose PWG meeting, you will see that what we are getting very
close to that proposal. However, that proposal used a
sequence number, rather than byte range.  I believe that
byte range is definate overkill, and a sequence number
would be simpler (especially for a re-director) to
generate.


Bob Berriot Wrote:


> A WebNFS client should follow the example of conventional
>NFS clients and handle server or network outages gracefully.
>If a reply is not  received  within a given timeout, the client
>should retransmit the request with its original XID (described
>in Section 8 of RFC 1831). The XID can be used  by the server
>to detect duplicate requests and avoid unnecessary work.
>While it would seem that retransmission over a TCP connection
>is unnecessary (since TCP is responsible for detecting and
>retransmitting lost data), at the RPC layer retransmission is
>still required for recovery from a lost TCP connection, perhaps
>due to a server crash or, because of resource limitations, the
>server has closed the connection.  When the TCP connection
>is lost, the client  must re-establish the connection and
>retransmit pending requests. It seems to me that this same issue
> exists with regard to IPP operations including those that send
>document data.  Thus a client may send a block of document
>data where the transmission succeeds at the TCP level, but
>the server crashes before sending a "data received and
>processed"  reponse.  In such a case, the server may or may
>not have processed the  data. Since the client will have to
>retransmit the data, the server  needs to know whether it is new
>data or another copy of the last data, thus the need for byte ranges
>and document numbers to identify the  piece of data.


>Comments?
>Bob Herriot



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