Clarifying uniqueness of stream_id

[traib-google]

In the description of stream_id we say that it's:

A string that uniquely identifies the stream. A Transmitter MUST generate a unique ID for each of its non-deleted streams ...

It would be good to clarify that:

1. The stream_id must be globally unique - up to a reasonable standard (like the various UUID versions), since guaranteeing global uniqueness is impossible.
   As opposed to the implication that being unique within that particular Transmitter's domain is enough.

2. Uniqueness should persist across deletions - basically the stream_id should not be reused.
   The phrase "unique ID for each of its non-deleted streams" seems to imply that uniqueness only holds for the set of non-deleted streams, so a deleted stream's id could be reused.

If this is the general understanding of the Working Group, I'm happy to send a pull request.

[jogu]

1. I don't see a need for the stream_id to be globally unique - the stream id is scoped to a specific transmitter, if the receiver needs a globally unique id it can use a combination of the transmitter's id and the stream id.

2. I would tend to agree that stream_id's should not be reused.

[iamseanodentity]

We have reached a consensus in the WG call today to add a 9.4 section to Security Consideration.