Multicast Video to Unicast Conversion in an Aruba WLAN

By bala posted Dec 05, 2011 03:14 PM


Aruba APs are hybrid APs that can be deployed both at the campus and the remote sites.  As long as there is a WLAN controller that can adopt the APs and push the right operational settings to them, the APs are able to perform similar functions irrespective of their geographical location.


The only factor that determines their capabilities are the forwarding mode they are operating in. There are different forwarding modes that can be configured. This is a decision the network engineer has to take depending on what the company requirements are.  There are networks that might want to route all their user traffic back to their datacenter where the WLAN controller resides, inspect it and then distribute them based on their destination; and  there are networks that might not care about what the user traffic; and might terminate  it right at the access layer.


The datapath might further change for a remote deployment where you might not want to tunnel all the traffic back to the data center. Understanding the forwarding modes is  key to delivering multicast video as efficiently as possible.


There are three different forwarding modes for a Aruba AP deployed at a campus – tunnel, bridge and decrypt-tunnel modes. As the name indicates traffic is either tunneled back to the controller or dropped at the access layer. Aruba leaves the decision of where the encryption/decryption should occur in a network - either at the AP or the WLAN controller.


As you may note decrpt-tunnel is a forwarding mode where the decryption happens at the AP; where as for tunnel mode the WLAN controller takes care of the process. Similarly, a remote AP offers a few forwarding modes as follows - tunnel, decrypt-tunnel, split–tunnel and bridge forwarding modes. In the split-tunnel mode Aps route traffic based on the policy configured. Traffic destined to the corporate network is tunneled back the WLAN controller; and generic traffic destined to the internet is routed directly saving WAN bandwidth.


Depending on the forwarding mode the AP is operating in – dynamics to deliver multicast video may change. The conversion of multicast to unicast might either happen at the WLAN controller, or at the AP itself. What forwarding mode supports what kind of conversion. When do I enable what? The flowchart below is a step-by-step process that the Aruba reference design team has pt together to help make this decision.


The attached flowchart is put together by our reference design team that should help network engineers decide the right architecture for their network.




Multicast Video Decision Flow Chart.docx