Re: [IPFIX] RFC 5101bis: CP MUST Close and Simplified Template Management

Paul Aitken <[email protected]>
Newsgroups gmane.ietf.ipfix
Message-ID <[email protected]>
Brian, Gerhard,

>> 4. Template Withdrawals MAY be sent on UDP.
>
> Ok. Template Withdrawal does not hurt in case of UDP.

UDP doesn't guarantee in-order delivery. Therefore not waiting long 
enough after sending a TWM before sending a new template definition 
using the same template ID, could result in the new template definition 
arriving first, then being withdrawn.

ie, "Template N¹, TWM N, Template N²" becomes, "Template N¹, Template 
N², TWM N".

Of course, this can be avoided by checking the header timestamps, and 
ignoring the TWM if it originated prior to the current template.


Brian's reply later in this thread:

	The EP can ensure this by setting the Export Time in the header; all sequencing is done via this header (as opposed to actual time the packet leaves the EP or arrives at the CP).


I wonder how many collectors process data in time order versus order of 
receipt? Since 5101 has nothing to say on the matter, some interesting 
interop test cases could be devised around this question.

P.
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