On Sun, Apr 16, 2017 at 11:30:33AM +0000, Ali Volkan Atli wrote:
> I am trying to understand auxiliary connection according to OpenFlow 1.5 
> specifications but I have some questions as follows
> 
> 1) Let's suppose I have one main and one auxiliary connection. How
> does the controller decide (or force) which connection to use for
> sending packet-in messages?

The OpenFlow specification says:

    The controller is free to use the various switch connections for
    sending OpenFlow messages at its entire discretion, however to
    maximise performance on most switches the following guidelines are
    suggested:

    • All OpenFlow controller requests which are not Packet-out
    (flow-mod, statistic request...) should be sent over the main
    connection.

    • Connection maintenance messages (hello, echo request, features
    request) should be sent on the main connection and on each auxiliary
    connection as needed.

    • All Packet-Out messages containing a packet from a Packet-In
    message should be sent on the connection where the Packet-In came
    from.

    • All other Packet-Out messages should be spread across the various
    auxiliary connections using a mechanism keeping the packets of a
    same flow mapped to the same connection.

    • If the desired auxiliary connection is not available, the
      controller should use the main connection.

> 2) If the switch will decide, how will it decide? In one case, if
> there is an auxiliary connection, then -by default- all packet-ins are
> sent over "only" the aux channel? Is this correct behavior?

The OpenFlow specification says:

    The switch is free to use the various controller connections for
    sending OpenFlow messages as it wishes, however the following
    guidelines are suggested :

    • All OpenFlow messages which are not Packet-in should be sent over
      the main connection.

    • All Packet-In messages spread across the various auxiliary
    connection using a mechanism keeping the packets of a same flow
    mapped to the same connection.

> 3) If there are multiple auxiliary connections, should the switch
> spread across the various auxiliary connection (for example for load
> balancing)

Same question applies.
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