[pox-dev] buffer_id is None?

[Nan Zhu]

Hi, Murphy,

I think I have send packet_out for every packet_in....

I just added more statements to print out logs, it shows that a lot of IPV6
multicast packets going through my network ...will that overwhelm the
buffer?

For the second possibility, do you mean I set the limitation to a smaller
value so that every packet would be buffered? can you give some hint on
doing this?

Best,

Nan




On Tue, Nov 19, 2013 at 2:04 PM, Murphy McCauley
<murphy.mccauley at gmail.com>wrote:

> I'm aware of two possibilities.
>
> The first is that your switch is out of buffer space/IDs.  This can happen
> particularly if you are ignoring packet-ins in your controller.  You may be
> better off sending a packet-out that references the buffer_id but has no
> actions; this way the switch will deallocate the buffer (various examples
> in POX do this; e.g., l2_learning, I believe).
>
> The second is that there's always a size limit of how much of a packet the
> switch will send to the controller.  There's a single limit for packets
> which miss the table entirely, and every send-to-controller action has its
> own limit.  If a packet is larger than this limit, the controller buffers
> the packet locally and sends a truncated version to the controller.
>  However, if the packet is smaller than the limit, I believe OVS will
> simply send the entire packet to the controller *and not buffer it*.  In
> POX, the "maximum length" for output actions to send to the controller is
> the full size of the packet, but you can set it to be smaller.
>
> I'll also note that POX's packet_out and flow_mod have special cases to
> make it easier to deal with the fact that you may have either case (a
> buffer ID or a full packet).  The flow_mod one in particular isn't always
> ideal, but they work a lot of the time.
>
> -- Murphy
>
> On Nov 19, 2013, at 6:08 AM, Nan Zhu <zhunanmcgill at gmail.com> wrote:
>
> > Hi, all
> >
> > I'm developing some controller with POX,
> >
> > When I test it with mininet (--switch ovsk), I found that I will receive
> some packet_in which has a buffer_id with the value of None?
> >
> > Anyone had this problem before? obviously it is caused by my controller,
> I used other code to test, this type of packet never appear
> >
> > What can be the reason of that?
> >
> > Best,
> >
> > Nan
> >
> >
>
>
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