openflow.discovery
This component sends specially-crafted LLDP messages out of OpenFlow switches so that it can discover the network topology. It raises events (which you can listen to) when links go up or down.
More specifically, you can listen to LinkEvent events on core.openflow_discovery. When a link is detected, such an event is raised with the .added attribute set to True. When a link is detected as having been removed or failed, the .removed attribute is set to True. LinkEvent also has a .link attribute, which is a Link object, and a port_for_dpid(<dpid>) method (pass it the DPID of one end of the link and it will tell you the port used on that datapath).
Link objects have the following attributes:
| name | value |
| dpid1 | The DPID of one of the switches involved in the link |
| dpid2 | The DPID of the other switch involved in the link |
| end[0 or 1] | The ends of the link as a tuple, i.e., end[0] = (dpid1,port1) |
| port1 | The port on dpid1 involved in the link |
| port2 | The port on dpid2 |
| uni | A "unidirectional" version of the link. This normalizes the order of the DPIDs and ports, allowing you to compare two links (which may be different directions of the same physical links). |
A number of the other example components use discovery and can serve as demonstrations for using discovery. Obvious possibilities are misc.gephitopo and forwarding.l2multi.
This example shows how to discovery topology created in previous post.
Component Discovery mentioned above is used to find discovery topology.
This component can return the dpid and ports of switches involved in the link.
Create a python file in ~/pox/ext/topoDiscovery.py
vi ~/pox/ext/topoDiscovery.py
from pox.core import core
import pox.openflow.libopenflow_01 as of
from pox.lib.revent import *
from pox.lib.recoco import Timer
from collections import defaultdict
from pox.openflow.discovery import Discovery
from pox.lib.util import dpid_to_str
import time
class topoDiscovery(EventMixin):
def __init__(self):
def startup():
core.openflow.addListeners(self, priority = 0)
core.openflow_discovery.addListeners(self)
core.call_when_ready(startup, ('openflow','openflow_discovery'))
print "init over"
def _handle_LinkEvent(self, event):
l = event.link
sw1 = l.dpid1
sw2 = l.dpid2
pt1 = l.port1
pt2 = l.port2
print 'link added is %s'%event.added
print 'link removed is %s' %event.removed
print 'switch1 %d' %l.dpid1
print 'port1 %d' %l.port1
print 'switch2 %d' %l.dpid2
print 'port2 %d' %l.port2
def launch():
core.registerNew(topoDiscovery)
First open a terminal and run topology file in mininet as previous post.
mininet@mininet-vm:~$ sudo ./type1.py
and open a new terminal and run pox with above code and openflow.discovery
mininet@mininet-vm:~$ sudo ./pox/pox.py topoDiscovery openflow.discovery
mininet@mininet-vm:~$ sudo ./pox/pox.py topoDiscovery openflow.discovery
POX 0.2.0 (carp) / Copyright 2011-2013 James McCauley, et al.
init over
INFO:core:POX 0.2.0 (carp) is up.
INFO:openflow.of_01:[00-00-00-00-00-02 4] connected
INFO:openflow.of_01:[00-00-00-00-00-04 2] connected
INFO:openflow.of_01:[00-00-00-00-00-06 5] connected
INFO:openflow.of_01:[00-00-00-00-00-03 3] connected
INFO:openflow.of_01:[00-00-00-00-00-01 6] connected
INFO:openflow.of_01:[00-00-00-00-00-05 1] connected
INFO:openflow.discovery:link detected: 00-00-00-00-00-02.1 -> 00-00-00-00-00-01.2
link added is True
link removed is False
switch1 2
port1 1
switch2 1
port2 2
INFO:openflow.discovery:link detected: 00-00-00-00-00-02.2 -> 00-00-00-00-00-03.2
link added is True
link removed is False
switch1 2
port1 2
switch2 3
port2 2
INFO:openflow.discovery:link detected: 00-00-00-00-00-04.1 -> 00-00-00-00-00-01.3
link added is True
link removed is False
switch1 4
port1 1
switch2 1
port2 3
INFO:openflow.discovery:link detected: 00-00-00-00-00-04.2 -> 00-00-00-00-00-05.1
link added is True
link removed is False
switch1 4
port1 2
switch2 5
port2 1
INFO:openflow.discovery:link detected: 00-00-00-00-00-06.1 -> 00-00-00-00-00-03.3
link added is True
link removed is False
switch1 6
port1 1
switch2 3
port2 3
INFO:openflow.discovery:link detected: 00-00-00-00-00-03.3 -> 00-00-00-00-00-06.1
link added is True
link removed is False
switch1 3
port1 3
switch2 6
port2 1
INFO:openflow.discovery:link detected: 00-00-00-00-00-03.1 -> 00-00-00-00-00-05.2
link added is True
link removed is False
switch1 3
port1 1
switch2 5
port2 2
INFO:openflow.discovery:link detected: 00-00-00-00-00-03.2 -> 00-00-00-00-00-02.2
link added is True
link removed is False
switch1 3
port1 2
switch2 2
port2 2
INFO:openflow.discovery:link detected: 00-00-00-00-00-01.3 -> 00-00-00-00-00-04.1
link added is True
link removed is False
switch1 1
port1 3
switch2 4
port2 1
INFO:openflow.discovery:link detected: 00-00-00-00-00-01.2 -> 00-00-00-00-00-02.1
link added is True
link removed is False
switch1 1
port1 2
switch2 2
port2 1
INFO:openflow.discovery:link detected: 00-00-00-00-00-05.1 -> 00-00-00-00-00-04.2
link added is True
link removed is False
switch1 5
port1 1
switch2 4
port2 2
INFO:openflow.discovery:link detected: 00-00-00-00-00-05.2 -> 00-00-00-00-00-03.1
link added is True
link removed is False
switch1 5
port1 2
switch2 3
port2 1
And in Mininet, let link between s1 and s4 down
mininet> link s1 s4 down
wait a few seconds, pox outputs following information:
INFO:openflow.discovery:link timeout: 00-00-00-00-00-04.1 -> 00-00-00-00-00-01.3
link added is False
link removed is True
switch1 4
port1 1
switch2 1
port2 3
INFO:openflow.discovery:link timeout: 00-00-00-00-00-01.3 -> 00-00-00-00-00-04.1
link added is False
link removed is True
switch1 1
port1 3
switch2 4
port2 1
Next, let link between s1 and s4 up
mininet> link s1 s4 up
wait a few seconds, pox outputs following information:
INFO:openflow.discovery:link detected: 00-00-00-00-00-04.1 -> 00-00-00-00-00-01.3
link added is True
link removed is False
switch1 4
port1 1
switch2 1
port2 3
INFO:openflow.discovery:link detected: 00-00-00-00-00-01.3 -> 00-00-00-00-00-04.1
link added is True
link removed is False
switch1 1
port1 3
switch2 4
port2 1
References:
POX Wiki
Create a custom topology in Mininet (2)