C2MS11 — Consider forcing a limited subscription

In the case of Mnemonic Value Request Message and Archive Mnemonic Value Request Message, the requestor can specify a STOP-TIME or DURATION, but both are optional. If neither is specified, the subscription is open-ended with no knowable end, until the requestor sends a 'STOP' message. In order to avoid infinite fulfillment of a subscription to a potentially lost requestor, we could enforce a concept that a requestor must specify either a STOP-TIME or Duration.

In practice, this is an inadequate requirement, since a caller could specify a very long duration, like 1000 years, and circumvent the desire of this issue.

However, this is issue simply captures the idea to promote further discussion.

Add responder's fields for service DURATION and STOP-TIME support

The responder to the request shall determine the time it can support based on the original request. For example, unlimited or very large durations or stop times past the end of the archive and so on may not be supported, in which case the responder may clip the response to the duration or stop-time it can support and this will be placed in the response. It's up to the requester to monitor this field and do something useful with it. It's an implementation detail as how the responder implements this other than providing the value in the response.

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