You are correct.
virtual network is just a very specific
I really like this definition of an
Affinity Group. You can see as you read it that it is exactly what a local network (or virtual in our case) is supposed to do.
Narahari Dogiparthi's blog states:
Affinity groups are the way to group the services in your Windows Azure subscription that need to work together in order to achieve optimal performance.
When you create an affinity group, it lets Windows Azure know to keep all of the services that belong to your affinity group running at the same data center cluster. For example, if you want to keep the services running your data and your code together, you would specify the same affinity group for those services. That way, when you deploy those services, Windows Azure will locate them in a data center as close to each other as possible. This reduces latency and increases performance, while potentially lowering costs.
Microsoft's Azure documentation suggests that using both together can give you a
WAN style network. Multiple
VLAN's connected through one
Affinity Group. So you can see that its the same thing, but just another abstraction layer.
Mark Russinovich is also a great guy to follow in this area as well.
Check out this session where he talks about how Microsoft structures its
virtual networks in
Azure. (at ~30:00)