Subject: [Pce] P & I flags

From: dimitri papadimitriou <[email-masked]>
Date: Fri, 14 Jul 2006 15:43:34 +0200

the comments around the P and I flags are

o) we have two levels of optionality in listing the protocol object and 
usage level of the protocol object - however it is much more appropriate 
to be sure that mandatory constraints have been taken rather than having 
the optional having been taken into account

    P flag (Processing-Rule - 1-bit): the P flag allows a PCC to specify
    in a PCReq message sent to a PCE whether the object must be taken
    into account by the PCE during path computation or is just optional.
    When the P flag is set, the object MUST be taken into account by the
    PCE.  Conversely, when the P flag is cleared, the object is optional
    and the PCE is free to ignore it if not supported.

o) on the I flag issue is identical why include an object which has not 
considered during computation ? there are so many things that the PCE 
has not taken into account during computation so why bother ? it is imho 
  more important to include the mandatory object not taken into account

    I flag (Ignore - 1 bit): the I flag is used by a PCE in a PCRep
    message to indicate to a PCC whether or not an optional object was
    processed.  The PCE MAY include the ignored optional object in its
    reply and set the I flag to indicate that the optional object was
    ignored during path computation.  When the I flag is cleared, the PCE
    indicates that the optional object was processed during the path
    computation.  The setting of the I flag for optional objects is
    purely indicative and optional.  The I flag MUST be cleared if the P
    flag is set.

o) the result of all these flags is that a PCC can be wrapping around 
unknown constraints create processing churn on the PCE;

    If the PCE does not understand an object with the P Flag set or
    understands the object but decides to ignore the object, the entire
    PCEP message MUST be rejected and the PCE MUST send a PCErr message
    with Error-Type="Unknown Object" or "Not supported Object".

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