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| 1 .. include:: replace.txt |
| 2 .. highlight:: cpp |
| 3 |
| 4 RED queue disc |
| 5 --------------------- |
| 6 |
| 7 Model Description |
| 8 ***************** |
| 9 |
| 10 Random Early Detection (RED) is a queue discipline that aims to provide |
| 11 early signals to transport protocol congestion control (e.g. TCP) that |
| 12 congestion is imminent, so that they back off their rate gracefully |
| 13 rather than with a bunch of tail-drop losses (possibly incurring |
| 14 TCP timeout). The model in ns-3 is a port of Sally Floyd's ns-2 |
| 15 RED model. |
| 16 |
| 17 Note that, starting from ns-3.25, RED is no longer a queue variant and |
| 18 cannot be installed as a NetDevice queue. Instead, RED is a queue disc |
| 19 and must be installed in the context of the traffic control (see the |
| 20 examples mentioned below). |
| 21 |
| 22 The RED queue disc does not require packet filters, does not admit |
| 23 child queue discs and uses a single internal queue. If not provided by |
| 24 the user, a DropTail queue operating in the same mode (packet or byte) |
| 25 as the queue disc and having a size equal to the RED queue limit attribute |
| 26 is created. If the user provides an internal queue, such a queue must |
| 27 operate in the same mode as the queue disc and have a size not less than |
| 28 the RED queue limit attribute. |
| 29 |
| 30 The RED model just supports default RED. Adaptive RED is not supported. |
| 31 |
| 32 References |
| 33 ========== |
| 34 |
| 35 The RED queue aims to be close to the results cited in: |
| 36 S.Floyd, K.Fall http://icir.org/floyd/papers/redsims.ps |
| 37 |
| 38 Attributes |
| 39 ========== |
| 40 |
| 41 The RED queue contains a number of attributes that control the RED |
| 42 policies: |
| 43 |
| 44 * Mode (bytes or packets) |
| 45 * MeanPktSize |
| 46 * IdlePktSize |
| 47 * Wait (time) |
| 48 * Gentle mode |
| 49 * MinTh, MaxTh |
| 50 * QueueLimit |
| 51 * Queue weight |
| 52 * LInterm |
| 53 * LinkBandwidth |
| 54 * LinkDelay |
| 55 |
| 56 Consult the ns-3 documentation for explanation of these attributes. |
| 57 |
| 58 Examples |
| 59 ======== |
| 60 |
| 61 The RED queue example is found at ``src/traffic-control/examples/red-tests.cc``. |
| 62 |
| 63 Validation |
| 64 ********** |
| 65 |
| 66 The RED model has been validated and the report is currently stored |
| 67 at: https://github.com/downloads/talau/ns-3-tcp-red/report-red-ns3.pdf· |
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