In this part of the blog we will try to explain overlay networking and the evolution of data center networks.
Overlay networking is popular with VXLAN and it is basically decoupling the logical network with underlying physical hardware. Overlay networks are a standard in any data center these days and enhance the agility of data centers. However, currently we are in the process of transition and the data center architecture is going through another wave of change. The differentiator today is that we are talking about hundreds or thousands of overlay networks per data center, with up to multiple thousand endpoints. Also, overlay networks are more dynamic than in the past.
This illustration below shows the evolution of Cloud Data Center Networking.
Underlay network design & L2 overlay
These overlay networks share the same underlay network but for the user it is a fully transparent network. This is good for the user of the L2 network because they can do whatever they want. For example, use any IP address or any VLAN. However, the drawback is the monitoring of the underlay network because you would see also the overlay network. Additionally, it is complex to determine the different overlay networks.
This diagram shows the general issue. Each of these services can use the same IP ranges. This is obviously because the network engineers who run these services want to make it simple for them. The underlay network infrastructure handles the separation of these different services. This is done by tunnels. Today this is typically VXLAN; in the old days, it was MPLS or VLAN. The difference is today it is dynamic.
In this scenario we have several visibility options:
- Visibility of the underlay network
- Visibility of a specific overlay network
- Visibility of all overlay networks
- Visibility of the underlay and overlay at the same time "full end to end view"
In the next blog we will highlight the difference between network and endpoint visibility and describe the issues with the current overlay networking approaches. Finally, we will cover a holistic approach to monitor overlay networks.