[pox-dev] Install actions to indirectly connected

[David Li]

Hi Lucas,

I launched a simple tree-like topology in mininet with 3 switches and
4 hosts. Then I started a POX controller, it seems that the controller
automatically connects to all three switches. Are these all direct
links from the controller to each switch? Is there anyway to specify
which switch the controller can connect to?


The command lines are like:

sudo mn --topo tree,depth=2,fanout=2 --mac --switch ovsk --controller remote

and

./pox.py log.level --DEBUG l2_learning


output:

POX 0.2.0 (carp) / Copyright 2011-2013 James McCauley, et al.
DEBUG:core:POX 0.2.0 (carp) going up...
DEBUG:core:Running on CPython (2.7.6/Mar 22 2014 22:59:56)
DEBUG:core:Platform is Linux-3.13.0-24-generic-x86_64-with-Ubuntu-14.04-trusty
INFO:core:POX 0.2.0 (carp) is up.
DEBUG:openflow.of_01:Listening on 0.0.0.0:6633
INFO:openflow.of_01:[00-00-00-00-00-03 3] connected
DEBUG:.home.mininet.pox-controller.l2_learning_dc:Connection
[00-00-00-00-00-03 3]
INFO:openflow.of_01:[00-00-00-00-00-02 1] connected
DEBUG:.home.mininet.pox-controller.l2_learning_dc:Connection
[00-00-00-00-00-02 1]
INFO:openflow.of_01:[00-00-00-00-00-01 2] connected
DEBUG:.home.mininet.pox-controller.l2_learning_dc:Connection
[00-00-00-00-00-01 2]


> ------------------------------
>
> Message: 2
> Date: Tue, 5 May 2015 09:43:23 -0300
> From: Lucas Brasilino <lrbbs at cin.ufpe.br>
> To: Ayush Dusia <adusia at udel.edu>
> Cc: pox-dev <pox-dev at lists.noxrepo.org>
> Subject: Re: [pox-dev] Install actions to indirectly connected
>         switches
> Message-ID:
>         <CAGE5s_CWYe8-ETSFn7AkR_RoQnb67c_3YOZYqNYpXZLL9wuFxQ at mail.gmail.com>
> Content-Type: text/plain; charset=UTF-8
>
> HI Ayush
>
>> I am under an impression that in real scenarios with complex typologies, not
>> all switches have direct connection to a controller. And, they are connect
>> to a controller through other switches (which become OpenFlow 'proxy', like
>> S1 in our example). So, I am trying to connect to S2 through S1.
>
> You are right. But, those 'other switches' traditionally aren't OF
> switches. They are
> 'ordinary switches' (I mean, learning switches) creating a 'management network'.
> This is the topology frequently seen (at least by myself).
> So, if you are using 'learning switches' on top layer  they wouldn't be a
> 'proxy' because your layer 3 connection is direct from controller to
> bottom layer
> switches through the ' top switches'. Top switches are simply
> switching layer 2 frames
> from controller to bottom switches, they do not know that these frames
> are OF messages.
> You can make top switches 'learning switches' by controlling them with the
> 'forwarding.l2_learning' Pox's component.
> In order words, top switches' control plane would be the same (or similar) to
> 'commercial available' learning switches.
>
>> My main goal is to have hierarchy in data plane, where the top layer of
>> switches is just used for communication between controller and bottom layer;
>> whereas, the bottom layer of switches is used to connect to the hosts and
>> other network components.
>>
>> Is this feasible with POX and mininet?
>
> Sure it is! Just make top switches be controlled by
> 'forwarding.l2_learning' component and bottom
> switches be controlled by your component.
>
> --
> Att
> Lucas Brasilino
> MSc Student @ Federal University of Pernambuco (UFPE) / Brazil
> twitter: @lucas_brasilino
>
>>
>> On Thu, Apr 23, 2015 at 9:21 PM, Lucas Brasilino <lrbbs at cin.ufpe.br> wrote:
>>>
>>> Hi Ayush:
>>>
>>> > I have installed a permanent rule in S1 to forward the packets to S2
>>> > that have destination address of S2.
>>>
>>> Forwarding at L2, right ? Or are you doing some kind of NAT ?
>>>
>>> > Topology: C0 - S1 - S2
>>> > Now, when I want to install rules in S2, how should I go about it?
>>> >
>>> > 1) Should I create a ofp_packet_out with destination of S2, attached
>>> > ofp_flow_mod packet (rules for S2) as data to it and send it to S1?
>>> >
>>> > 2) Should I create a ofp_flow_mod packet which has destination address
>>> > of S2 and send it to S1?
>>>
>>> Assuming S1 are forwarding at L2, S1 will not be an OpenFlow 'proxy'
>>> for S2. You just need to make S2 connect to C0's IP address. For
>>> instance. if S2 is an Open vSwitch, you just do:
>>>
>>> $ sudo ovs-vsctl set-controller s2 tcp:192.168.56.1:6633
>>>
>>> Where 192.168.56.1 is the controller's IP address.
>>>
>>> --
>>> Att
>>> Lucas Brasilino
>>> MSc Student @ Federal University of Pernambuco (UFPE) / Brazil
>>> twitter: @lucas_brasilino
>>>
>>> > On Wed, Apr 22, 2015 at 8:19 AM, Lucas Brasilino <lrbbs at cin.ufpe.br>
>>> > wrote:
>>> >>
>>> >> Hi Ayush,
>>> >>
>>> >> Since controller connects to switch using a TCP session, if S1 acts
>>> >> like a learning switch or already has rules on its flow table
>>> >> allowing TCP connections from C0 to S2, C0 will control S2.
>>> >>
>>> >> Just be aware that if S1 is an OF switch and those rules mentioned
>>> >> above expires, you will lost control over S2, even for a while.
>>> >> What I mean is that until you restore S1 rules, some
>>> >> switch-to-controller messages like 'Packet In', 'Port Status', 'FlowRemoved'
>>> >> and
>>> >> so forth can be lost, leading for a network's state mismatch.
>>> >>
>>> >> --
>>> >> Att
>>> >> Lucas Brasilino
>>> >> MSc Student @ Federal University of Pernambuco (UFPE) / Brazil
>>> >> twitter: @lucas_brasilino
>>> >>
>>> >>
>>> >>
>>> >> 2015-04-22 0:10 GMT-03:00 Ayush Dusia <adusia at udel.edu>:
>>> >>
>>> >>> Hello Everyone,
>>> >>>
>>> >>> I have a question regarding installation of actions in switches.
>>> >>>
>>> >>> If I assume that a controller does not have direct connections to all
>>> >>> the switches in a network. In that case how can a controller install actions
>>> >>> in a switch to which it is not directly connected?
>>> >>>
>>> >>> e.g. for a topology like: C0 - S1 - S2
>>> >>>
>>> >>> How can C0 install actions in S2 through S1?
>>> >>>
>>> >>> Thanks,
>>> >>> Ayush
>>> >>
>>> >>
>>> >>
>>> >>
>>> >>
>>> >
>>
>>
>
>