Subject: [Ibnemo] Discussion about connection and connectivity

From: "zhangyali (D)" <[email-masked]>
Date: Fri, 27 Nov 2015 09:31:15 +0000

Hi All,

These days we have discussed some important concepts, "connection", "connectivity" and "connect", with Pedro and Bert. Opinions are meaningful and worthy of consideration further. So I sum up the different views to make the topic clearer. Please point out it with no hesitations if I am biased.

In fact, the core of this topic is what is the real meaning of "connection" and "connectivity" (I think, "Connect" = "Connectivity"), and how to choose them when you want to express the communication.

Opinion 1,
connection is any connected resource for any communication. It may maps into physical links, tunnels, or just virtual connection between ports in ovs.
connectivity refers to the communication for all traffic or specific traffic, such as, allow http traffic.
So, connection is the basis of connectivity in this view. User has to apply connection (or resource) explicitly firstly. Then point out which service could be allowed with specific policy (some default rules can be applied here).
A typical scenario is the communication between distribute branches and headquarters in WAN network. Enterprise need to apply the resources between branches and headquarter, then assign the communication rules between them. For example, only the traffic between branches and headquarter are allowed.

Opinion 2,
Connection refers to the "real" connection between nodes. It could be mapped into a real link in the physical network.
Connectivity refers to the reachablity between nodes.
In this opinion, connectivity does not depends on the application of connection. A typical scenario is the communication in the DC. Resource could be taken as infinite and full-meshed, which means user just need to express the connectivity between nodes without caring about the resource between them.

Opinion 3,
Connection refers to the resource for communication.
Connectivity refers to the communication between nodes.
In this opinion, default connectivity does not need to express explicitly, that is, connectivity is achieved only there are resources could be found between them, and user just need to assign which connectivity is not allowed.

All we agree point is that resource is the base of community(though sometimes resource is infinite and applied or assured by other mechanism). The question now is that if we could unify these two concepts into one keyword and define the rules about how to use them, or if we need to add a new keyword to distinguish them explicitly?

The discussion will sharpen understanding of model. So, expect all your words!

Best Regards,
Yali