1. Goal Providing QoS guarantee without maintaining per- flow state on the data or control planes. Motivation Integrated Services – Per-flow state at all routers. Differentiated Services – Per-flow state at the edges and weak service semantics. DPS and CSFQ – Per flow state at the edge routers and stronger service than Differentiated services. Can we eliminate per flow state from the network completely? In other words, can per-flow state be maintained only at the endhosts?

2. Service Model Focus on bandwidth allocation Flows can reserve bandwidth (peak-rate) and then send data upto that rate. Weak service – no hard delay/bandwidth guarantees Overview of Solution Protect well-behaved flows by detecting and containing/barring misbehaving flows. Data plane - recursive monitoring of aggregate flows. Control plane – lightweight certificates and random sampling.

3. Recursive Aggregate Flow Monitoring Data Plane At a router, each flow is mapped (randomly) onto an aggregate flow (A-flow)aggregate flow. The A-Flow is monitored as a whole. Upon detection of misbehaving A-flow, recursive subdivision and monitoring of that A-flow occurs. In the limit, this involves policing individual flows of an aggregate flow. Resulting “A-Tree” size is constrained. Pros – Low state, trade-off between state and time of detection. Cons – Weaker service, time of detection, good only for small ratio of misbehaving flows

4. Time Misbehaving Aggregate Misbehaving Aggregate Misbehaving Flow Flow-ids Of packets Arriving at A router Aggregate flows Fine-grained aggregates Individual flows Resources and reservations of aggregate flows represent the sum of resources of component flows. Data Plane – Policing of aggregate flows…

5. Control plane Flows are admitted on a flow-by-flow basis when resources are available along all routers on the flow’s path. To enable dynamic re-mapping without per-flow state, is per-flow information required ? Aggregate flow reservations are stored as soft state at the routers and per-flow information is inferred from periodic refreshments by end-hosts. Lightweight certificates can be used to ensure that refreshes correspond to admitted flows. Control plane

6. Control Plane… Duplicate refreshes are still a problem… Can be checked by maintaining a small amount of information per flow. Alternative – random sampling of refreshes. Alternative – perform counting of refreshes received in aggregates, and compare with upper bounds on these counts, i.e. the counts from the previous time-period (These upper bounds need to be recalibrated periodically, by maintaining per-flow state within 1 or a small number of aggregates)