Hi,

On 2016年10月04日 11:04, illlusioner77367 . wrote:
> Hi
>
> Recently I find out some problems during the development of a Ryu's
> application.
>
> The first problem I found out is I don't know how to enable the buffering
> in the SDN switch.
>
> Basically most of the time when adding a rule we use OFP_NO_BUFFER to tell
> the switch not to buffer the packet .

"buffer_id=OFP_NO_BUFFER" in OFPFlowMod is not used for telling the switch
not to buffer the packets.
According to "7.3.4.1 Modify Flow Entry Message" in the OpenFlow Spec 1.3.5,
The buffer_id is used to refer to the buffered packet when OFPFlowMod is
received.

>
> I try to change the OFP_NO_BUFFER to the number of byte the switch can
> transmit.
>
> However I found out when the number is small like 60~70 bytes, the switch
> will send an incomplete packet to the controller. But the effect I want is
> the switch will add the packet into its own buffer and will only send the
> buffer id and the packet header  to the controller without any payload. Is
> there something I miss or need to add in the .EventOFPSwitchFeature handler
> ?

If you want to specify the packet data length that should be sent, please
specify the "max_len" in OFPActionOutput for Packet-In.
http://ryu.readthedocs.io/en/latest/ofproto_v1_3_ref.html#ryu.ofproto.ofproto_v1_3_parser.OFPActionOutput

>
>
> The second problem I need to know is the cookie in the SDN flow table. I
> can only guess that, every SDN flow rule in the SDN switch will have a
> cookie, and when we want to modify or delete the flow rule, we basically
> can use the cookie mask to filter out some flow rules. But how does this
> work, what is the maximum number of the cookie mask ? An example will be
> appreciated.

The cookie field is chosen by the controller (not the switch side).
You can set the arbitrary value/mask by sending OFPFlowMod.
http://ryu.readthedocs.io/en/latest/ofproto_v1_3_ref.html#ryu.ofproto.ofproto_v1_3_parser.OFPFlowMod

And the max value of the cookie is 0xffffffffffffffe.
(0xfffffffffffffff is reserved and must not be used.)


Thanks,
Iwase

>
> BR
>
>
>
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