[Standards] Proposed XMPP Extension: Quality of Service

Florian Schmaus flo at geekplace.eu
Wed Dec 9 14:52:27 UTC 2015

On 08.12.2015 18:40, XMPP Extensions Editor wrote:
> The XMPP Extensions Editor has received a proposal for a new XEP.
> Title: Quality of Service
> Abstract: This specification describes a generic method whereby messages can be sent between clients using a predefined Quality of Service level.
> URL: http://xmpp.org/extensions/inbox/qos.html
> The XMPP Council will decide in the next two weeks whether to accept this proposal as an official XEP.

§ 2.1 does not explain how "At most once" is enforced. I assume it
requires support by the involved routing entities. But this means that
you can't use it without ensuring that every involved routing entity
supports it. I highly doubt that this will every be practicable. Or,
using Matthew words: it opens a can of worms.

$ 2.2 duplicates Message Delivery Receipts (XEP-184).

§ 2.3 is AFAIK something no other XEP specifies and does *not* require
support by the routing entities. I would split the part off into a new
XEP "Exactly Once Delivery" describing the double IQ process used. Dave
already mentioned that you run into issues because you theoretically
need to keep the state forever - the used ID and entity tuples to be
precise - but I think something like that could be implemented in a
sound and pragmatic way. The usefulness of "Exactly once" is, however, a
different topic. Most distributed protocols rely on idempotent actions
and therefore are happy with "At least once".

- Florian

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