[ippm] RFC 8972, STAMP Optional Extensions Question, RFC 8762 stateless detection

["Ringel, Rick" <[e-mail]>]

I'm working to implement the DirectMeasurement TLV as described in RFC 8972.  There is a scenario where the reflector cannot give a correct response, but the available TLV flags don't allow the reflector to signal this to the sender.

A STAMP reflector can be started in stateless mode, in which case the reflector has no tx/rx counters to use in the DirectMeasurement TLV response.

I am currently setting the 'Unrecognized' flag so the sender doesn't try to interpret the results, but this seems inconsistent with the intent of the flag.

What should the reflector's response be in this situation?

I have played with algorithms on the sender side to determine if the reflector is stateful or stateless, as described in RFC 8762.  The best I have come up with is seeding the sender sequence number with a non-zero value on the first transmission.  If the reflector responds with a matching sequence number, it is stateless.  The sender can then inhibit transmission of the DirectMeasurement TLV.   Have I missed something in the RFC regarding the sender's method for determining stateful/stateless reflectors?  The RFC says the sender sequence number should start at zero, so this is a bit of a hack.

I look forward to your response.

Rick Ringel
Senior Software Engineer

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