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Re: [MEXT] weird idea about flow bindings

George Tsirtsis escribió:
Hi Marcelo, I now understand what you propose better. and it makes more sense than I initially thought. 

Two issues, though:

1) this requires the CN to cooperate i.e., make proper use of flow labels.

according to RFC3697:

  To enable Flow Label based classification, source nodes SHOULD assign
  each unrelated transport connection and application data stream to a
new flow. 
...

  To enable applications and transport protocols to define what packets
  constitute a flow, the source node MUST provide means for the
  applications and transport protocols to specify the Flow Label values
  to be used with their flows.  The use of the means to specify Flow
  Label values is subject to appropriate privileges (see section 5.1).
  The source node SHOULD be able to select unused Flow Label values for
  flows not requesting a specific value to be used.

So, yes but node should do this if they expect things to work properly
It is not clear to me that even if all nodes populated the flow label (which I think is not even true) 
does anybody has information about the support of RFC3697 in current OSes?
, its use would be universally consistent in a way that would ensure that the setting of the flow label by the CN would be inline with what the MN would like to identify as a flow. 
that would determine the granularity of the method
I am not sure the spectrum of choices is so big that this can be a problem
could you think of some very different criteria to define what a flow is that this would be an issue? 
2) This does not work for IPv4 traffic.
i don't buy this argument. If we apply this argument, then we could never use the flow label for anything, since it doesn't work for IPv4. 

Reagrds, marcelo


Thoughts?
George On Sun, May 17, 2009 at 8:58 AM, marcelo bagnulo braun <marcelo at it.uc3m.es <mailto:marcelo at it.uc3m.es>> wrote: 

    ok, let me try again because it seems i am failing miserably to
    communicate what i want to say (or it simply so broken that people
    cannot believe what they are reading :-)

    Let's try with an example.

    We have the MN who has two CoAs, CoA1 and CoA2.

    The MN has a policy that says that it wants flows from app1 to be
    exchanged through CoA1 (well, the policy would say that they
    should be received by the interfece in which CoA1 is configured)
    and that flows from app2 to be exchanged through CoA2 (same
    comment about the interface applies here)

    In addition, MN has defined CoA1 to be the primary CoA i.e. the
    CoA with highest priority.

    So, we have two different situations. Either the MN starts the
    communication or the CN starts the communication. Actually, this
    is pretty irrelevant, cause the two directions of a connections
    are handled independently. the MN will send packets from app1
    through CoA1 and packets from app2 through CoA2 and it doesn't
    need any additional actions from the HA for outgoing packets.

    Now, the difficulty is with incoming packets. the MN needs to
    inform the HA about which CoA it wants to use to receive any flow.

    Suppose that the HA has no flow bindings for the MN so far.

    So, suppose that the app1 in CN starts a flow to the MN. The HA
    will receive the packet and will send it though the CoA1 cause it
    is the one with higher priority. the MN is happy and there is no
    need to do anything else.

    Suppose now that the app2 in the CN starts a flow to the MN.
    According to RFC3697, the CN SHOULD assign a different flow label
    to the packets belonging to this flow e.g. to this TCP connection.
    Let's assume it is actually a TCP connection to make the example
    more concrete.
    So, app2 opens a TCP connection to MN. CN then sends the TCP SYN
    to the MN.
    The HA receives the TCP SYN and since there is no flow binding
    state for this flow it forwards it through the CoA1 (the one with
    highest priority)
    The MN receives the TCP SYN through CoA1 and it realizes that this
    is not compliant with its flow policy. So, it extracts the flow
    label value, the src address and the dest address and it sends a
    BU to the HA stating that the flow identified by the flow label,
    src add and dest add needs to be bound to the CoA2.
    Simultaneously, it also sends the TCP SYN+ACK back to the CN.
    The CN receives the TCP SYN+ACK and sends the Ack back. the HA
    receives the ACk and will forward it based on the flow binding,
    i.e. through the CoA.

    the result is a method that never looks into higher layer
    information for setting the flows.

    makes sense?

    Regards, marcelo


    Hesham Soliman escribió:


        On 17/05/09 3:04 PM, "marcelo bagnulo braun"
        <marcelo at it.uc3m.es <mailto:marcelo at it.uc3m.es>> wrote:


            Hesham Soliman escribió:

                The flow label should be part of any filter descriptor
                anyway. So at anytime
                A MN can send a BU specifying that packets with flow
                label X should be
                directed to CoA1. I'm not sure how your proposal
                changes/adds to this.

            what i am saying is that you don't need anything else
            other than this


        => see below


                As a general issue, the flow label is unlikely to be
                used for this purpose
                until we resolve it's mutability issues

            what mutability issues are you referring to?
            AFAIU, the flow label is set randomly b the source and
            remains unchanged
            e2e and for the duration of the flow.


        => I thought RFC 3697 talked about it being changed en route
        then changed
        back before it hits the destination. But I just scanned it and
        I can't find
        this text. Maybe it was never included.


                 and until it is actually _used_ in
                the API. At least until recently no one was using it.

            why do we need to have it in the API? It is only imporntat
            the the
            source sets it to a random value and keep it unchenged e2e
            and for the
            duration of the flow. I understand that these conditions
            are met today,
            right?


        => But are you saying the src MIP6 module overwrites the
        potential flow
        label set in the API? Because it is possible that an app sets
        the flow
        label. RFC 3697 assumes the presence of an e2e mechanism to
        negotiate the
        flow label. If not then how do you make sure it's always
        unique? And how do
        you make sure that the CN echoes back the same value in the
        flow label?
        And what if the CN initiated the connection?

        Hesham






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