Can an OpenFlow Switch Replace a Tap Aggregator?

I had an interesting conversation during lunch about the future of network taps and aggregators now that OpenFlow switches can do many of the same types of operations.  In my testing I have used Pica8 switches to replicate traffic, lots of traffic, using static OpenFlow commands.  For example, here is a design where I take 10G of  traffic and mirror it across 5 ports.

Here is the configuration I use for a Pica8 3922 to do the replication a 10G stream to 5 ports.

This configuration assumes that you have already configured the switch to run in OpenFlow mode.

First we setup a new bridge, br0 and add the interfaces (1-6) to it.

# Add Bridge br0 - for PCAP Replication - 1st Port
##############################
# te-1/1/1 is input te-1/1/2, te-1/1/3, te-1/1/4, te-1/1/5, te-1/1/6 are output
#-------------------------------------------------------------------------------------
$VSCTL add-br br0 -- set bridge br0 datapath_type=pica8 other-config=datapath-id=100
$VSCTL add-port br0 te-1/1/1 -- set interface te-1/1/1 type=pica8
$VSCTL add-port br0 te-1/1/2 -- set interface te-1/1/2 type=pica8
$VSCTL add-port br0 te-1/1/3 -- set interface te-1/1/3 type=pica8
$VSCTL add-port br0 te-1/1/4 -- set interface te-1/1/4 type=pica8
$VSCTL add-port br0 te-1/1/5 -- set interface te-1/1/5 type=pica8
$VSCTL add-port br0 te-1/1/6 -- set interface te-1/1/6 type=pica8


Next we remove the default flow so that we can program the ports specifically.

# Remove Default Flow (not treating this as HUB!)
ovs-ofctl del-flows br0
# Add replication flow 1 -> 2,3,4,5,6
ovs-ofctl add-flow br0 in_port=1,dl_dst="*",dl_src="*",dl_type="*",dl_vlan_pcp="*",dl_vlan="*",actions=output:2,3,4,5,6


Finally we drop all of the ingress traffic from the ports that the mirror traffic is going out of.

# Drop ingress traffic from mirror ports
ovs-ofctl add-flow br0 in_port=2,dl_dst="*",dl_src="*",dl_type="*",dl_vlan_pcp="*",dl_vlan="*",actions=drop
ovs-ofctl add-flow br0 in_port=3,dl_dst="*",dl_src="*",dl_type="*",dl_vlan_pcp="*",dl_vlan="*",actions=drop
ovs-ofctl add-flow br0 in_port=4,dl_dst="*",dl_src="*",dl_type="*",dl_vlan_pcp="*",dl_vlan="*",actions=drop
ovs-ofctl add-flow br0 in_port=5,dl_dst="*",dl_src="*",dl_type="*",dl_vlan_pcp="*",dl_vlan="*",actions=drop
ovs-ofctl add-flow br0 in_port=6,dl_dst="*",dl_src="*",dl_type="*",dl_vlan_pcp="*",dl_vlan="*",actions=drop


This same configuration can be extended to include more ports, repeated to mirror different traffic to other ports, etc.

In the next post, I will cover filtering traffic to better control egress data.