[pox-dev] When controller collecting statistics, can it know which switch the statistics come from?

[Weiyang Mo]

Hi,

I used following definition to send request and listen to reply:

def counter_request ():
  swnum = 0
  for connection in core.openflow._connections.values():
    swnum += 1
    connection.send(of.ofp_stats_request(body=of.ofp_flow_stats_request()))
    connection.send(of.ofp_stats_request(body=of.ofp_port_stats_request()))
    time.sleep(0.1)
  global switchnum
  switchnum = swnum
  print "total %i switches" % switchnum
  global requestcycle
  requestcycle +=1

def handle_PortStatsReceived(event):
     "main body"

def launch ():
  core.openflow.addListenerByName("PortStatsReceived",
handle_PortStatsReceived)
  Timer(5, counter_request, recurring=True)

However I met with difficulties distinguishing switches when receving port
status. The "PortStatsReceived" function will be triggered whenever a
switch replys back, however the controller doesn't know which switch.  I
also need switch information to distinguish the statistics, for example,
put switch1 stats into table 1, switch2 stats into table2..

Since I have no knowledge that the reply is from which switch, I play a
trick when I program "counter_request" to set a time interval for sending
each switch ( e.g switch1's request is sent on 0.1s,5.1s... switch is on
0.2s,5.2s), then assume I receive "ports status reply" in this switch
sequence. However this trick cannot help with too many switches, and it may
not work after a long timeline since each switch has a difference respoding
time.

Is there any approach to get the switch information (especially dpid) from
reply back when receving ports status?

Thanks very much.

Weiyang
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