AF test plan

AF Test Programme

Application 1: long-lived TCP connections
- Goals: packet loss minimization, i.e.
  - micro-flow throughput maximization
  - overall throughput maximization
- Traffic conditioning:
  - rate-base marker (single-rate, two-rate). The two color markers are compared
  - policing is per micro-flow at the edge of the network, it is performed on an aggregate flow in each aggregation point (policing is needed to verify that the aggregate does not exceed a given target rate). Policing can be applied at the input interface of the edge router, while in the core we have to verify the possibility to apply policing at the output interface - in this way policing is applied to the aggregate instead of each single input aggregate stream.
  - burst tolerance:
    at the edge the burst tolerance should be equal or greater than the maximum window size. The optimum window size should be least equal to product: RTT*target_rate. RTT could be specificed by the application when requesting a given service.
    at aggregation points: burst tolerance can be expressed as a function of the maximum output rate, by defining a fixed target RTT, e.g. 300 msec
- Scheduling
  Each TCP stream goes to the same AF class. Green, yellow and red packets are placed in the same queue. This is one of the WFQ queues, another queue is the best-effort queue.
  Additional AF queues can be configured, if needed for test purposes. Background traffic can be injected to feed that queues. Alternatively, a 5 queue-approach can be adopted: 1 BE queue and 1 queue for each AF class.
- WRED
  WRED is enabled for each AF queue.
  For a given AF queue, WRED configuration is such that priority packets have to be dropped only if all the remaining low priority packets have already been dropped from a given AF queue, for example:
  max_threshold(AF12) < min_threshold(AF11)
  min_threshold(AF12) < max_threshold(AF13)
  max_threshold(AF12) has to be at least as large as the burst tolerance admitted by the policer with a two rate color marker.
  In case of single rate marker given the Committed Burst Size (CBR) and the Excess Burst Size (EBS), we could configure the parameters so that:
  - min_th(AF13)=1/2 EBS, max_th(AF13)=2/3 EBS
  - min_th(AF12)= EBS, max_th(AF12)=3/2 EBS
  - min_th(AF11)= 2 EBS, max_th(AF11)=queue length
- Test methodology
  - test parameters: WRED parameters, TCP socket sizes, single or two rate color marker
  - traffic:
    - 1 TCP stream + UDP background traffic
    - n TCP stream + UDP background traffic
  - metric: throughput, packet loss
  - applications: netperf (TCP), mgen (UDP) and tcptrace (for pack loss estimation)
Application 2: video streaming - non delay and jitter sensitive
Application 3: IP telephony
Modified: Sep 07, 2000