adc.README
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- The attached nam file (adc.nam) shows a simple comparison between a
- comparison between measurement-based admission control and
- parameter-based admission control. The measurement-based algorithm
- is the Measured Sum algorithm given in "Comparison of
- Measurement-Based Admission Control Algorithms for Controlled-Load
- Service", by Jamin, Shenker and Danzig in Infocomm '97. The
- parameter-based algorithm makes admission control decisions based on
- reserved rates.
- In the animation, there are two bottleneck links with capacity 1Mbps.
- Link 6-7 uses the parameter-based algorithm, and Link 0-1 uses the
- measurement based algorithm. The remaining links in the topology have
- 5Mbps capacity and are never congested.
- The key point to notice is that when presented with equal average
- offered load (in terms of the number of flows requesting reservations)
- the measurement-based algorithm, which makes admission decisions based
- on the token bucket parameters of the flow requesting service and on
- the measurements of traffic sent by flows with existing reservations,
- admits more flows and achieves a higher measured utilization on the
- bottleneck link than the parameter-based algorithm, which makes
- admission decisions using the token bucket parameters of the new flow
- and the reserved rate of existing flows.
- The 3 magenta nodes on the left are the sources of traffic and the 3
- orange nodes on the right are destinations. Flows are started
- randomly between pairs of source and destination nodes. When a flow
- is started, a reservation request (white packets in the animation) is
- sent from the source (Node 8, 2 or 3) to the destination (Node 9, 5 or
- 4). The token bucket parameters in the reservation packet are r =
- 64kbps are b = 1. Admission control decisions are made at either node
- 0 or node 6. Based on the admission control decision, the destination
- returns either an Accept packet (green) or Reject packet (red) to the
- source. A source that receives an Accept then transmits data (the
- data packets are not shown in the animation). After sending its data,
- the source transmits a Teardown packet (black) to signal the network
- it no longer needs its reservation.
- The bottleneck links change color to reflect the last admission
- control decision made on the link. When reservation requests are
- accepted, the link turns (or remains) green. When a reservation
- request is rejected, the link turns (or remains) red.
- Monitors associated with the admission control agents at Nodes 0 and 6
- display relevant information about the state of the admission control
- process and link utilization. Each monitor shows the number of flows
- with reservations in place on the adjacent link, and the measured
- utilization on the adjacent link (utilization measures are averaged
- over 2 second intervals). For the parameter-based admission control
- algorithm, the total amount of reserved bandwidth is shown. For the
- measurement-based algorithm, the estimated link utilization, which is
- an input parameter to the decision process, is shown. (See the
- above-reference paper for an explanation of how this estimate is
- computed and used.)
- Other relevant parameters to the simulation that created this
- animation:
- Flow inter-arrival times are exponentially distributed with average of
- 400 ms on each link. Average flow lifetime is 30 seconds (again
- exponentially distributed). Flows transmit data according to the
- Exponential On/Off source model in the ns-2 simulator. Relevant
- parameters are: packet size = 125 bytes, on time = 312.5 msec, off
- time = 325 msec, and rate = 64 kbps.