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OpenFlow
To understand the overview of OpenFlow, replicate the tutorial. To use mininet, create a virtual network and test its features. The URL of the original tutorial is shown below.
http://www.openflow.org/wk/index.php/OpenFlow_Tutorial
Creating a virtual network environment †
To use mininet, create a virtual network environment. The topology is shown below.
To start the virtual network, apply the command shown below.
$ sudo mn --topo single,3 --mac --switch ovsk --controller remote
*** Creating network
*** Adding controller
Unable to contact the remote controller at 127.0.0.1:6633
*** Adding hosts:
h1 h2 h3
*** Adding switches:
s1
*** Adding links:
(h1, s1) (h2, s1) (h3, s1)
*** Configuring hosts
h1 h2 h3
*** Starting controller
*** Starting 1 switches
s1
*** Starting CLI:
mininet>
Using these commands, three virtual hosts (h1, h2, and h3) and a software switch are created in the kernel. Each of these three virtual hosts receives a unique, individual, and different IP address, and the software is based upon Open wSwitch and has three ports. Each virtual host is connected to the software switch via a virtual ethernet cable. The OpenFlow Switch is configured to be connected to the remote controller (c0) via link local.
To apply a mininet-specific command, nodes, check the list of nodes.
mininet> nodes
available nodes are:
h2 h3 h1 s1 c0
To check the IP of a virtual host and switch, the detail of each setting is shown.
mininet> h1 ifconfig
h1-eth0 Link encap:Ethernet HWaddr 00:00:00:00:00:01
inet addr:10.0.0.1 Bcast:10.255.255.255 Mask:255.0.0.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
mininet> h2 ifconfig
h2-eth0 Link encap:Ethernet HWaddr 00:00:00:00:00:02
inet addr:10.0.0.2 Bcast:10.255.255.255 Mask:255.0.0.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:0 errors:0 dropped:0 Overruns:0 frame:0
TX packets:0 errors:0 dropped:0 Overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
mininet> h3 ifconfig
h3-eth0 Link encap:Ethernet HWaddr 00:00:00:00:00:03
inet addr:10.0.0.3 Bcast:10.255.255.255 Mask:255.0.0.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
mininet> s1 ifconfig
eth0 Link encap:Ethernet HWaddr 00:23:8b:56:f9:ed
inet addr:192.168.0.146 Bcast:192.168.0.255 Mask:255.255.255.0
inet6 addr: 2001:268:321:8000:223:8bff:fe56:f9ed/64 Scope:Global
inet6 addr: fe80::223:8bff:fe56:f9ed/64 Scope:Link
inet6 addr: 2001:268:321:8000:4c96:18c9:b0b1:bb7a/64 Scope:Global
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:4906 errors:0 dropped:0 overruns:0 frame:0
TX packets:670 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:589463 (589.4 KB) TX bytes:78711 (78.7 KB)
Interrupt:16
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:876 errors:0 dropped:0 Overruns:0 frame:0
TX packets:876 errors:0 dropped:0 Overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:58056 (58.0 KB) TX bytes:58056 (58.0 KB)
s1-eth1 Link encap:Ethernet HWaddr d6:7e:38:49:0f:3d
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
s1-eth2 Link encap:Ethernet HWaddr 9e:62:1c:ea:62:0e
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 Overruns:0 frame:0
TX packets:0 errors:0 dropped:0 Overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
s1-eth3 Link encap:Ethernet HWaddr da:ab:31:04:07:d6
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
Example of how to use dpctl †
Once mininet boots, execute dpctl by a different Shell. dpctl is a utility, which is included in OpenFlow Reference, and it is a command line program that monitors and manages OpenFlow datapath.
To execute show, connect OpenFlow switch and show the present status.
$ dpctl show tcp:127.0.0.1:6634
features_reply (xid=0x77393f77): ver:0x1, dpid:1
n_tables:255, n_buffers:256
features: capabilities:0xc7, actions:0xfff
1(s1-eth1): addr:d6:7e:38:49:0f:3d, config: 0, state:0
current: 10GB-FD COPPER
2(s1-eth2): addr:9e:62:1c:ea:62:0e, config: 0, state:0
current: 10GB-FD COPPER
3(s1-eth3): addr:da:ab:31:04:07:d6, config: 0, state:0
current: 10GB-FD COPPER
LOCAL(s1): addr:de:5f:fc:4b:49:4a, config: 0x1, state:0x1
get_config_reply (xid=0x85b71d0d): miss_send_len=0
To execute dump-flows, display the present status of a table flow.
$ dpctl dump-flows tcp:127.0.0.1:6634
stats_reply (xid=0x265ded5c): flags=none type=1(flow)
Since OpenFlow Controller has not worked, its flow table remains empty.
At the mininet console, try to send a ping from h1 to h2.
mininet> h1 ping -c3 h2
PING 10.0.0.2 (10.0.0.2) 56(84) bytes of data.
From 10.0.0.1 icmp_seq=1 Destination Host Unreachable
From 10.0.0.1 icmp_seq=2 Destination Host Unreachable
From 10.0.0.1 icmp_seq=3 Destination Host Unreachable
--- 10.0.0.2 ping statistics ---
3 packets transmitted, 0 received, +3 errors, 100% packet loss, time 1999ms
pipe 3
Since The table flow of the switch is still empty and the controller does not connect to the switch, the switch does not know how to handle the traffic. Therefore, ping does not go through.
Then, to use dpctl command, add flows.
$ dpctl add-flow tcp:127.0.0.1:6634 in_port=1,actions=output:2
$ dpctl add-flow tcp:127.0.0.1:6634 in_port=2,actions=output:1
To use the console, check the flow table.
$ dpctl dump-flows tcp:127.0.0.1:6634
stats_reply (xid=0x2fbc71b7): flags=none type=1(flow)
cookie=0, duration_sec=14s, duration_nsec=964000000s, table_id=0, priority=32768, n_packets=0, n_bytes=0, idle_timeout=60,hard_timeout=0,in_port=1,actions=output:2
cookie=0, duration_sec=8s, duration_nsec=934000000s, table_id=0, priority=32768, n_packets=0, n_bytes=0, idle_timeout=60,hard_timeout=0,in_port=2,actions=output:1
Then, try to send a ping again.
mininet> h1 ping -c3 h2
PING 10.0.0.2 (10.0.0.2) 56(84) bytes of data.
64 bytes from 10.0.0.2: icmp_req=1 ttl=64 time=1.39 ms
64 bytes from 10.0.0.2: icmp_req=2 ttl=64 time=0.132 ms
64 bytes from 10.0.0.2: icmp_req=3 ttl=64 time=0.140 ms
--- 10.0.0.2 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2001ms
rtt min/avg/max/mdev = 0.132/0.557/1.399/0.595 ms
To use add-flow, configure to send a packet from port1 to port2 and vice versa, so now ping goes through. Try to send a ping the other way around.
mininet> h2 ping -c3 h1
PING 10.0.0.1 (10.0.0.1) 56(84) bytes of data.
64 bytes from 10.0.0.1: icmp_req=1 ttl=64 time=0.711 ms
64 bytes from 10.0.0.1: icmp_req=2 ttl=64 time=0.128 ms
64 bytes from 10.0.0.1: icmp_req=3 ttl=64 time=0.135 ms
--- 10.0.0.1 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 1998ms
rtt min/avg/max/mdev = 0.128/0.324/0.711/0.273 ms
After sending a ping, check the condition of the flow table.
$ dpctl dump-flows tcp:127.0.0.1:6634
stats_reply (xid=0x35d81496): flags=none type=1(flow)
cookie=0, duration_sec=21s, duration_nsec=123000000s, table_id=0, priority=32768, n_packets=8, n_bytes=672, idle_timeout=60,hard_timeout=0,in_port=1,actions=output:2
cookie=0, duration_sec=19s, duration_nsec=312000000s, table_id=0, priority=32768, n_packets=8, n_bytes=672, idle_timeout=60,hard_timeout=0,in_port=2,actions=output:1
The connection time, packets, and bytes are increased.
Revision History †
- 2013/08/28 This article is initially uploaded.
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