Nodes disappear from the HP VAN SDN controller 2.0 Topology view and Node Manager

[Dave-B]

New user of HP VAN SDN controller running version 2.0.0.4253 on Ubuntu 12.04.3 LTS with test SDN consisting of two HP 3800 switches with 2 Ubuntu 12.04.3 LTS servers connected as nodes.

When I send traffic between the 2 nodes (e.g.. ping or iperf), the nodes initially appear on the VAN web interface Openflow Topology page (https://SDN-Controller:8443/sdn/ui/app/index#oftopo) and are visible through the REST API using the curl command. e.g.

curl -sk -H "X-Auth-Token:XXXXXXXXXXXXXXXXXXXX" https://localhost:8443/sdn/v2.0/net/nodes
{"nodes":[{"ip":"10.0.0.100","mac":"00:24:e8:42:fd:fb","vid":2,"dpid":"00:02:c8:cb:b8:3e:fe:40","port":11},{"ip":"10.0.0.110","mac":"bc:30:5b:df:63:df","vid":2,"dpid":"00:02:6c:3b:e5:62:b2:80","port":11}]}

However, the nodes disappear from the Topology page after approx 20 minutes and cannot bel listed using the curl command, e.g..

curl -sk -H "X-Auth-Token:XXXXXXXXXXXXXXXXXXXX" https://localhost:8443/sdn/v2.0/net/nodes

{"nodes":[]}

The traffic is still running and the flows are still in place. This happens if I use th Path Daemon (com.hp.sdn.sdn-ctl-path) or stop com.hp.sdn.ctl.path and mannually add flows using the REST API with curl commands.

The nodes only repear, if I stop traffic for approx 20 mins and restart the traffic. During this time the flows are visible and still function.

I guess this is some sort of time out issue. | am intending to use my SDN for multiple live video feed conribution, where the traffic could last for hours at a time.

How do I stop the node manager from loosing the node information?

Dave.

[ShaunWackerly]

Hi Dave,

Have you tried changing the "arp.age" time under the "NodeManager" configuration? Increasing that value should cause the nodes/hosts to stick around longer in the controller's ARP cache.

[Dave-B]

Shaun,

Thanks for the reply. I increased the ARP age to 60 mins. But I think there is still a fundamnetal issue.

If i pre-configure a layer 1 or 2 path through  the network and then start traffic, the nodes are never discovered by the node controller.

The node controller only seems to discover nodes if packets from the node are forwarded to the controller. There can be a mismatch between what the switches are doing and what the controller knows.

If I am configuring a proactive SDN network, I can configure working flows between nodes without the controller being aware of the nodes. Is there another OpenFlow mechansim for the controller can learn nodes without seeing packets from the node?

Dave.

[ShaunWackerly]

Hi Dave,

Node discovery is accomplished by the controller seeing packets from the network to verify that the host is active (and to identify the source port and switch of the traffic). You said that you "pre-configure a layer 1 or 2 path through the network", which implies that the controller won't see any packets once the traffic starts because the path will already be paved.

As a workaround for your situation, you may just want to increase the arp.age setting to some very high value. The amount you set it to will determine how long NodeManager will keep hosts in the ARP cache without hearing from them (via data-plane packets stolen to the control-plane).

Your controller's arp.age setting should be set to the maximum value that either the end-hosts (which are sourcing the traffic) or your switches (3800's) are using, to ensure that the controller doesn't time out "node" entries before the end-hosts do.

NOTE:

If you are using OpenFlow 1.0, then what mode is the OpenFlow instance on your 3800's set to? If it's set to 'passive' then that would explain why the controllers are not seeing ARP reply packets from the switches. The 'passive' setting means that the switch will handle all packets by default, where the 'active' setting means that the controller will handle all packets by default.

Shaun

[sdnindia]

Hello Dave,

Doing a follow up to check if you need any further assistance with respect to the query posted.
Please do let us know  if your problem is solved.

If you have more questions on the same topic please do reply on the same thread or open a new post if new topic.

Thanks
HP SDN Team