The OPES Engine redirecting the client to a call-out server is more than an
artifact, it is a requirement.
For real-time or high-density, low-latency, real-time transcoding services
(e.g., transcoding a http chunked fetch of an mp3 to RTP delivery of GSM),
it is incredibly inefficient and unrealistic to route all packets through
the OPES Engine.
One model for this sort of interaction is the IMAP CHANNEL mechanism. See
draft-nerenberg-imap-channel-01.txt .
The "connection" is already in Figure 1, the UPIF flow. However, UPIF is
for something entirely different. I would propose a dotted connection
between the User Agent and the other Call-out server, with text along the
following lines:
"The OPES Engine may redirect the User Agent to retrieve content directly
from a call-out server. It can do this to satisfy requests which are more
efficiently delivered via a direct connection. [we can insert the example I
gave above]"
P.S., should "User Agent" be "OPES Client"?