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[mininet-discuss] Significance of DPID

Rushit Parekh rparekh081052 at gmail.com
Tue Apr 22 13:50:10 PDT 2014


controller manages datapath indexes for each connection,

controller recvs from s/w-1 using dpid=xyz
controller recvs from s/w-2 using dpid=pqr(anything but unique)

so when ever controller recvs/send packet checks dpid from that controller
decides from where packet came  or where to send..





On Wed, Apr 23, 2014 at 2:16 AM, Rushit Parekh <rparekh081052 at gmail.com>wrote:

> dpid=datapath index
> controller manages datapath indexes
>
>
> On Tue, Apr 22, 2014 at 11:20 AM, Murphy McCauley <
> murphy.mccauley at gmail.com> wrote:
>
>> This is really an OpenFlow question, and it's answered in the OpenFlow
>> spec.  Sort of.
>>
>> The short of it is that it's a unique identifier for a switch so that
>> someone/something (e.g., an OpenFlow controller) can uniquely identify the
>> switch.  It's 64 bits, so it's not an ethernet address, though the spec
>> claims the lower 48 bits are *intended* to be the switch's ethernet
>> address.  In my opinion, this statement has always been a bit confusing --
>> traditionally, a switch isn't an endpoint, so what addresses does a switch
>> even really have?  The only answer that makes sense to me is that it's the
>> ethernet address associated with the IP address used for the OpenFlow
>> control channel.  But in implementations, this is not always the case
>> because the OpenFlow control channel often may originate from one of
>> several interfaces and it'll use whatever ethernet address goes with it.
>>
>> In practice, its pretty arbitrary, and often user-configurable
>> independent of any ethernet address.  My advice is to always just treat it
>> as an opaque value which should be unique.  If a vendor happens to base it
>> on some particular ethernet address, I'd treat that as an implementation
>> detail for how they achieve uniqueness and not as there being any sort of
>> real relationship between the two.
>>
>> To give a different type of answer:  With Open vSwitch, it defaults to
>> the ethernet address of the switch's "local" port with the top 16 bits
>> zeroed (this ethernet address being generated at random when last I
>> checked).  With Mininet, this generally gets overridden to match the number
>> of the Mininet switch.
>>
>> Hope that helps?
>>
>> -- Murphy
>>
>> On Apr 21, 2014, at 10:11 PM, Karthik Sharma <karthik.sharma at gmail.com>
>> wrote:
>>
>> Hi,
>>
>> When you are creating switches for mininet topology you pass the dpid as
>> given below.
>>
>>
>>
>>
>>     info( '*** Add switches\n')
>>
>>     s1 = net.addSwitch('s1', cls=OVSKernelSwitch, dpid='0000000000000201')
>>
>>
>>     s2 = net.addSwitch('s2', cls=OVSKernelSwitch, dpid='0000000000000202')
>>
>>
>>     s3 = net.addSwitch('s3', cls=OVSKernelSwitch, dpid='0000000000000203')
>>
>>
>>     s4 = net.addSwitch('s4', cls=OVSKernelSwitch, dpid='0000000000000204')
>>
>>
>>     s5 = net.addSwitch('s5', cls=OVSKernelSwitch, dpid='0000000000000205')
>>
>>
>>     s6 = net.addSwitch('s6', cls=OVSKernelSwitch, dpid='0000000000000206')
>>
>>
>>
>>
>> My question is
>>
>>
>>
>>
>> What is dpid? How is it related to MAC addresses for each port of the Ethernet
>>
>> switch.Suppose the switch has 12 ports (for e.g) each of the ports will have a
>>
>> MAC address.(48 -bits long).How come a switch has a single data path identifier?
>>
>> How is related to MAC address?
>>
>>
>> Regards,
>> Karthik.
>>
>>
>>
>>
>>
>>
>> _______________________________________________
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>> mininet-discuss at lists.stanford.edu
>> https://mailman.stanford.edu/mailman/listinfo/mininet-discuss
>>
>>
>>
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>>
>>
>
>
> --
>
> With Regards,
>
> Rushit Parekh
>
>


-- 

With Regards,

Rushit Parekh
9426317847
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