Subject: [midcom] requirements - resource (p.k.a. pin-hole) operations

From: "Bob Penfield" <[email-masked]>
Date: Tue, 7 Aug 2001 08:59:00 -0400

Hi all,

Section 5.3 mentions 3 operations to be performed on a resource (pin-hole)
in a middlebox. I believe that we need at least 2 more. Namely "create" (or
"allocate") and "delete" (or "free").

The create operation would allocate the resource in the middlebox, but
packets would not be allowed through until an "open" operation is performed.
An open operation for an unallocated resource could imply a create & open
operation to minimize the number and size of messages between the agent and
the middlebox

The delete operation would be used to free the resource. Close would only
stop packets from flowing. The resource would not be freed for a close
operation. The resource could subsequently re-opened by the agent.
A delete operation on an open resource would imply close & delete.

A concrete example of an application that needs this capability is SIP. When
a session is initiated in SIP with an INVITE, the session description may
define multiple media streams that the client is willing to accept. The
response from the server may include only a subset of these media streams.
The resource in the middlebox needs to be allocated/reserved before the
INVITE is forwarded to the client. However, we do not want to enable packet
flow until the response is received from the client.

cheers,
(-:bob

Robert F. Penfield
Chief Software Architect
Acme Packet, Inc.
130 New Boston Street
Woburn, MA 01801
[email-masked]

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From: Scott Brim <[email-masked]>
Date: Thu, 9 Aug 2001 16:11:18 +0100

> flow until the response is received from the client.

The alternative is to receive the reply and then send your request to
the middlebox.  Are you saying you expect the interval between when the
response is received and when the media packets start arriving to be
very short?  If the pinholes have not been opened when the media packets
arrive, and they are dropped, what happens?

If such a thing as an "activate" message is needed I'm not against it,
but I want to understand the need.  I believe the requirement would be
phrased something like "the midcom protocol must make it possible for
the middlebox to have pinholes available when they are needed".  How
would you phrase it?  The real requirement, not the solution.

..Scott