SP layering (a diagram)

[Martin Sustrik]

Hi all,

To make the discussion more clear, I though it would make sense to
represent the layering in a graphical way.

Here's how I imagine internal layering in SP could possibly look like:

1. Framing layer - message delimitation, message atomicity etc.
2. Labeling layer - generic formatting of fields used by patterns, can
possibly contain both "generic properties" and "per-peer" properties.
3. Pattern layer - packages of routing semantics (such as pub/sub or
req/rep). The routing decisions are based on the payload of the
underlying layer (labels), the layer defines semantics of the labels,
but not their formatting.
4. Application layer

Technically, the message would then look like this:

+----+----+-----+-----+-----+-----+----+--------------
| fh | gp | lb1 | lb2 | lb3 | ... | ad |
+----+----+-----+-----+-----+-----+----+
| | | | transport
| | | 4. | agnostic
| | +--- +
| | 2. |
| +---------------------------------+--------------
| | transport
| 1. | specific
+--------------------------------------+--------------

fh = frame header
gp = generic properies
lbx = individual labels together forming a stack
ad = application data

Note: Each messaging pattern could define the formatting of the data of
its own. The separation into labeling and pattern layer is just a
convenience thing: When defining a new pattern, it's easier to re-use a
generic formatting mechanism than to invent one of your own.

Martin