[NSIS] Adding Binding_Code to QoS NSLP BOUND_SESSION_ID object

Hi all,

As described in the NSIS Operation over IP tunnels draft
(http://www.ietf.org/internet-drafts/draft-shen-nsis-tunnel-01.txt), the
BOUND_SESSION_ID object may be used to carry the dependency of the tunnel
session and the corresponding e2e session. The BOUND_SESSION_ID object
defined in QoS NSLP draft however does not indicate the nature of session
dependency. It may also be used for bi-directional flows or flow aggregation
etc. The currently defined general rule to process a message with a
BOUND_SESSION_ID object (e.g. a QNE MUST copy the BOUND_SESSION_ID object
into all messages it sends for the same session.) might not fit in the
tunneling context. For NSIS-tunnel operation, the dependency is maintained
by  tunnel endpoints and should not be propagated further outside the
tunnel.  

Therefore we would like to know whether the WG thinks it is a good idea to
add a Binding_Code field to the current BOUND_SESSION_ID object (the format
is attached at the end of this email for reference).

Thanks!

Charles

P.s. BOUND_SESSION_ID object with Binding_Code: 

   Type: BOUND_SESSION_ID

   Length: Fixed - 5 32-bit words

   Value: contains an 8-bit Binding_Code that indicates the nature of
   binding.  The rest specifies the Session ID of the session that must
   be bound to the session associated with the message carrying this
   object.

      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  RESERVED                     |  Binding_Code |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      +                                                               +
      |                                                               |
      +                          Session ID                           +
      |                                                               |
      +                                                               +
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Figure 1: BOUND_SESSION_ID Object

   Currently defined Binding_Codes are:

   o  0x01 - Tunnel and end-to-end sessions
   o  0x02 - Bi-directional sessions
   o  0x03 - Aggregate sessions
   o  0x04 - Dependent sessions (one session is alive only if the other
      session is also alive)

   More binding codes maybe defined based on the above four atomic
   binding actions.  It is not clear whether we need to allow more than
   one SESSION ID in the binding object.

A BOUND_SESSION_ID object carrying the code 0x01 is called a tunnel
BOUND_SESSION_ID object in the tunneling draft.

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