I've been doing some work on
Mininet but still confused on some issues below:
1. As we know,a
controller, say POX, can set up a connection to a switch based on TCP,and
then
communicate with it using Openflow messages. Must the contrller connect
to one or more switches directly? Is it able to control a switch via another
switch?
2.When the switches
form a loop, how will the controller handle the connections and links?I create
a topo in
mininet:
mininet> net
c0
s1 lo:
s1-eth1:h1-eth0 s1-eth2:s2-eth2 s1-eth3:s3-eth3
s2 lo:
s2-eth1:h2-eth0 s2-eth2:s1-eth2 s2-eth3:s3-eth2
s3 lo: s3-eth1:h3-eth0
s3-eth2:s2-eth3 s3-eth3:s1-eth3
h1 h1-eth0:s1-eth1
h2 h2-eth0:s2-eth1
h3 h3-eth0:s3-eth1
And then startup the
POX controller,using the l2_multi component which will detect the links and
calculate the shortest path between the nodes,here are the link detect INFOS,
all correct:
INFO:openflow.discovery:link
detected: 00-00-00-00-00-02.3 -> 00-00-00-00-00-03.2
DEBUG:openflow.discovery:Dropping
LLDP packet 10915
INFO:openflow.discovery:link
detected: 00-00-00-00-00-02.2 -> 00-00-00-00-00-01.2
INFO:openflow.discovery:link
detected: 00-00-00-00-00-03.3 -> 00-00-00-00-00-01.3
INFO:openflow.discovery:link
detected: 00-00-00-00-00-03.2 -> 00-00-00-00-00-02.3
INFO:openflow.discovery:link
detected: 00-00-00-00-00-01.3 -> 00-00-00-00-00-03.3
INFO:openflow.discovery:link
detected: 00-00-00-00-00-01.2 -> 00-00-00-00-00-02.2
and there exist many
errors:
ERROR:openflow.of_01:[Con
2/1] OpenFlow Error:
[Con 2/1] Error:
header:
[Con 2/1] Error:
version: 1
[Con 2/1] Error:
type: 1 (OFPT_ERROR)
[Con 2/1] Error:
length: 28
[Con 2/1] Error:
xid: 61
[Con 2/1] Error: type:
OFPET_BAD_REQUEST (1)
[Con 2/1] Error: code:
OFPBRC_BUFFER_EMPTY (7)
I can't make it where
the error come from.
and then,another
problem is the path installed:
DEBUG:forwarding.l2_multi:Installing
path for 00:00:00:00:00:02 -> 00:00:00:00:00:01 0800 (2 hops)
if the l2_multi
component has calculated the shortest path ,shouldn't it just have 1 hop?
Any idea or comment
would be highly appreciated.
Thanks.
Jin mingshuang
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