Subject: FW: U-SCTP

From: "Fairlie-Cuninghame, Robert" <[email-masked]>
Date: Mon, 12 Mar 2001 07:07:04 -0800

As per Lyndon's request to copy Sigtran.

-----Original Message-----
From: Fairlie-Cuninghame, Robert 
Sent: Monday, March 12, 2001 2:17 PM
To: [email-masked]'; [email-masked]'; [email-masked]';
[email-masked]'
Cc: [email-masked]'
Subject: U-SCTP

Hi,

I would like to suggest a change to the U-SCTP draft. 

I would like to suggest that the U-SCTP draft allow the option of media
being sent before the COOKIE exchange has completed. The receiving side is
not forced to process these early DATA chunks (and the transport is after
all unreliable).

Motivations: Many media streams are time-sensitive and the 4 way handshake
may result in clipped voice (or whatever). In these streaming applications
it is often not critical if a small number of packets are processed even if
the COOKIE authentication fails.

In particular I am suggesting that 
-When a TCB is waiting for a COOKIE ECHO chunk, DATA chunks maybe sent on
U-SCTP streams if the ULP has indicated this desire. 
-Any U-SCTP data received before the COOKIE ECHO/COOKIE ACK is received MAY
be passed to the ULP if the ULP has indicated its willingness to receive
such data. 

These changes would also be combined with the RECOMMENDATION that
- Before accepting early DATA chunks, an SCTP stack should also check if
there has been high failure rate in recent associations attempts on this
SCTP port or across all SCTP ports. [Eg, undergoing recent masquerade or DOS
attacks]
- The ULP must be able to control whether it receives or sends data before
the COOKIE exchange completes.
- If the cookie exchange subsequently fails, the ULP is obviously informed
and the connection aborted (unchanged). 

The default action would be to enforce the COOKIE exchange but providing the
socket option to streaming applications is in my mind very important.

As I see it, it will be these applications using USCTP to send streaming
media that are more likely to need to setup an association dynamically
(rather than at start time). For instance, SDP bodies in MGCP messages could
be used to instruct the media gateway to establish an SCTP media connection
(for which no association may be currently established).

I'll be interested to hear your comments.

Regards,

Robert.