DiffServ and ToS/VLAN-PCP

From OpenFlow Wiki

High Level

Use pre-existing functionality in switches for DiffServ and expose this as a preliminary, simple way to provide QoS means.

How

• Enable tos-field rewriting through openflow.
• Network Administrator define tos-based services (DiffServ).
• traffic can be classified using tos/pcp and routed accordingly.
• Configuration takes place through the CLI. OpenFlow is unaware of QoS primitives.

Pros & Cons

• + easy and fast to implement (could be done for 1.0 )
• + exploit functionality already residing in switches
• - not flexible, limited to predefined type of services.
• - no means do define a cross-network qos level (different admins-different services)

In the end, is a quick hack to provide basic QoS primitives. Could be useful for campus trials ( i.e. better separation through hypervisor )

Questions

• What is the number/type of services a switch support?
• Are these services attached to specific ports or to flows?
• Is there any limit to services/port?
• Are there any limitations for matching when we map flows to services?
• Is it possible to implement multicast using these services for all/subset of the recipients?
• Are there specific statistics related with these ports?