1. Using OpenDaylight in Hybrid Cloud: issues or challenges
Yi Inspur.com

2. New Trends in Cloud VMs, Containers and Baremetals coexist
Using containers for elastic scale-in and scale-out, self-healing, automated replication
Meet 3-layer application scenarios: frontend:web services, middleware:Java application, backend: database system
Kubernetes is very popular, but not all the applications can be split into microservices.
Some applications prefer to run in baremetal for performance.
Openstack over kubernetes: Openstack infrastructure runs in containers
What CNI plugin is selected will impact on Opendaylight and Openstack integration less or more

3. Issue/Challenge #1: How to unify networking
Containers, VMs and baremetals had better use unified networking solution
Opendaylight seems one not-bad choice for this: networking-odl for Openstack, kuryr-kubernetes for Kubernetes, Opendaylight also can leverage networking-l2gw and ovsdb to manage ToR switch for VMs and Baremetals interconnection.
But Opendaylight is not ready for this: other issues and challenges…

4. Issue/Challenge #2: How to manage ToR switches
Many ToR switches can’t support ovsdb
Opendaylight only can support ovsdb to manage ToR switch, just in test phase, not ready for production environment
ToR switch has limit, maximal number of VXLAN VTEPs is small, it is 64 in our switch case, far from enough.

5. Issue/Challenge #3: How to Run Opendaylight in pod/containers
Split Opendaylight into many small microservices: lighty.io, opendaylight-simple, strongly call Opendaylight community to take actions towards this direction, it is a very big big challenge.
Standalone Opendaylight is a monster, very slow startup, occupy huge amount of memory, it is much much slower than VM launching, let alone container
Deploy, online upgrade, etc…

6. Issue/Challenge #4: How to integrate with kata container
In public cloud scenario, native container can’t meet multi-tenancy isolation, VM-level isolation is must-have.
i.e. run container in lightweight VM, but container and its host VM are scheduled as a container by kubernetes.
It is a challenge to use vhost/vhostuser for kata container (it is veth pair by default), it is very important for OVS DPDK case because veth performance is very very poor in OVS DPDK.

7. Present
Future

8. Issue/Challenge #5: How to Use Opendaylight to control all the switches in leaf spine architecture
SDN controller is a necessary requirement in private cloud tenders
It will be better if Opendaylight can configure switches in leaf and spine, it is one factor why customers want to deploy SDN controller
I propose Opendaylight can launch a new project which can create a switch configuration abstract layer (like SoNiC: I believe switch vendors would like to add support for their switches by themselves.

10. Issue/Challenge #6: Is Centralized SDN controller model best in super scale data center
Packet-in, Packet-out
OVN model seems counter-example
Cascaded SDN Controllers are typical use case to break such limitation

11. Issue/Challenge #7: How to support hierarchical port binding and EVPN
VXLAN VTEP is handled in ToR switch in layer 3 leaf spine architecture
EVPN is must-have in this case.
Neutron ML2 plugin is needed to support hierarchical port binding
HPB Networks:
 Provide VXLAN scale with VLAN type host complexity
 Encapsulation done on network edge in wire speed
But Opendaylight can’t handle this case

12. Neutron Hierarchical Port Binding
Each Port can be bound against mutilple segments, dependant on the binding host.
It needs special ML2 mechanism driver.

13. Issue/Challenge #8: How to visualize network topology, traffic and troubleshooting
Similar to Cumulus NetQ: show network toplogy including physical networks (ToR, spine) and virtual networks (virtual bridges, virtual ports) and hosts (compute nodes and network nodes)
lighty.io UI Network Topology Visibility Component
Flow stats and monitoring, sFlow, NetFlow

15. Issue/Challenge #9: Controller Cluster Scalability
How can it work with 127 cluster nodes?
Replication to other 126?
More granular shard: e.g. per openvswitch group for topology and inventory
Cluster leader, shard leader and openvswitch master, it will be better if shard leader is same as openflowplugin master for openvswitch.
Is read possible in any follower shard?
Is asymmetric clustering possible? Nodes for neutron server and nodes for southbound device/openvswitch.
Does Database backend help on these issues?

16. Issue/Challenge #10: Southbound Plugin Scalability
Inventory and network topology data store are big
Openflowplugin clustering just uses 3 controller nodes (one master, two slaves), master can do read, write, flow statistics and async messages handling, slave only can read.
A small lightweight southbound 3 node cluster is preferred for a group of compute node/network node.
The same solution is applied to ovsdb

17. ZTE vDC ZENIC SDN Controller V2.00.10 Distributed Controller Cluster
Agile Controller - DCN
ZENIC vDC Controller
ZTE vDC ZENIC SDN Controller V
Distributed Controller Cluster
2+N nodes：2 master controllers （Active/Passive），N（1-128）southbound controllers
Database
Distributed Message Queue
Distributed Lock
Distributed Cache
O&M Proxy

18. Summary of Issues/Challenges
#1: how to unify networking for VMs, containers and baremetals?
#2: how to manage ToR switches?
#3: how to run Opendaylight in k8s pod?
#4: How to integrate with kata container?
#5: how to use Opendaylight to control all the switches in leaf spine architecture?
#6: Is Centralized SDN controller model best in super scale data center?
#7: How to support hierarchical port binding and EVPN?
#8: How to visualize network topology and troubleshooting?
#9: ODL controller cluster scalability issue
#10: ODL southbound plugin scalability issue
These may be the directions ODL community can take efforts in the future.