1. Client / Server Correlation Values
Anthony Berglas

2. Revision History Logging spec note – Sue G
Renamed Client/Server to Request/Response for notify/put – Bruce R
Repeat Request Correlation in response – Bruce R
Addressed Unique Batch Item ID, Asynchronous Correlation Value, Batch Order Option – David F
Request Globally Unique identifier note – Mark J

3. Customer Requirement
Need to be able to include client context in server logs
E.g. Which storage device is being processed?
Need to be able to store server context in client logs
So can ask server administrator “What went wrong with request s739c983nf?”
Would like globally unique request identifier
Good logging is essential for security and usability
(Actual logging not part of the specification)

4. Proposed Solution
Add Request Correlation as a simple string in request header
Add Response Correlation as a simple string in response header
Plus MUST include Request Correlation if provided
Server should log Request Correlation value
Server should be able to identify log record using Response Correlation value
(Visa versa for server to client.)
Usage Guide warns not to include content useful to an attacker

5. Example Request
<RequestMessage> <RequestHeader> <ProtocolVersion> … <ProtocolVersion> <BatchCount type="Integer" value="1"/> <RequestCorrelation type=“TextString” value=“sid=s348sa3d”/> </RequestHeader> …

6. Example Response
<ResponseMessage> <ResponseHeader> <ProtocolVersion> … </ProtocolVersion> <TimeStamp type="DateTime" value=" T08:14:42+00:00"/> <BatchCount type="Integer" value="1"/> <RequestCorrelation type=“TextString” value=“sid=s348sa3d”/> <ResponseCorrelation type=“TextString” value=“s34:d8a8g7fd900a9d”/> </ResponseHeader> …

7. Alternatives Use Unique Batch Item Id
Current implementations only unique within a batch – 0, 1, 2
Changing the interpretation of an existing field bad
Use Asynchronous Correlation Value
Again, an changed meaning to an existing field

8. Conclusion Very simple additions
Enhance logging and analysis capabilities
Important information for forensic analysis
Very helpful information for diagnosing issues