Comment at the top of ns-3.38/examples/tcp/tcp-validation.cc

// This program is designed to observe long-running TCP congestion control
// behavior over a configurable bottleneck link.  The program is also
// instrumented to check program data against validated results, when
// the validation option is enabled.
//
// ---> downstream (primary data transfer from servers to clients)
// <--- upstream (return acks and ICMP echo response)
//
//              ----   bottleneck link    ----
//  servers ---| WR |--------------------| LR |--- clients
//              ----                      ----
//  ns-3 node IDs:
//  nodes 0-2    3                         4        5-7
//
// - The box WR is notionally a WAN router, aggregating all server links
// - The box LR is notionally a LAN router, aggregating all client links
// - Three servers are connected to WR, three clients are connected to LR
//
// clients and servers are configured for ICMP measurements and TCP throughput
// and latency measurements in the downstream direction
//
// All link rates are enforced by a point-to-point (P2P) ns-3 model with full
// duplex operation.  Dynamic queue limits
// (BQL) are enabled to allow for queueing to occur at the priority queue layer;
// the notional P2P hardware device queue is limited to three packets.
//
// One-way link delays and link rates
// -----------------------------------
// (1) server to WR links, 1000 Mbps, 1us delay
// (2) bottleneck link:  configurable rate, configurable delay
// (3) client to LR links, 1000 Mbps, 1us delay
//
// By default, ns-3 FQ-CoDel model is installed on all interfaces, but
// the bottleneck queue uses CoDel by default and is configurable.
//
// The ns-3 FQ-CoDel model uses ns-3 defaults:
// - 100ms interval
// - 5ms target
// - drop batch size of 64 packets
// - minbytes of 1500
//
// Default simulation time is 70 sec.  For single flow experiments, the flow is
// started at simulation time 5 sec; if a second flow is used, it starts
// at 15 sec.
//
// ping frequency is set at 100ms.
//
// A command-line option to enable a step-threshold CE threshold
// from the CoDel queue model is provided.
//
// Measure:
//  - ping RTT
//  - TCP RTT estimate
//  - TCP throughput
//
// IPv4 addressing
// ----------------------------
// pingServer       10.1.1.2 (ping source)
// firstServer      10.1.2.2 (data sender)
// secondServer     10.1.3.2 (data sender)
// pingClient       192.168.1.2
// firstClient      192.168.2.2
// secondClient     192.168.3.2
//
// Program Options:
// ---------------
//    --firstTcpType:   first TCP type (cubic, dctcp, or reno) [cubic]
//    --secondTcpType:  second TCP type (cubic, dctcp, or reno) []
//    --queueType:      bottleneck queue type (fq, codel, pie, or red) [codel]
//    --baseRtt:        base RTT [+80ms]
//    --ceThreshold:    CoDel CE threshold (for DCTCP) [+1ms]
//    --linkRate:       data rate of bottleneck link [50000000bps]
//    --stopTime:       simulation stop time [+1.16667min]
//    --queueUseEcn:    use ECN on queue [false]
//    --enablePcap:     enable Pcap [false]
//    --validate:       validation case to run []
//
// validation cases (and syntax of how to run):
// ------------
// Case 'dctcp-10ms':  DCTCP single flow, 10ms base RTT, 50 Mbps link, ECN enabled, CoDel:
//     ./ns3 run 'tcp-validation --firstTcpType=dctcp --linkRate=50Mbps --baseRtt=10ms
//     --queueUseEcn=1 --stopTime=15s --validate=1 --validation=dctcp-10ms'
//    - Throughput between 48 Mbps and 49 Mbps for time greater than 5.6s
//    - DCTCP alpha below 0.1 for time greater than 5.4s
//    - DCTCP alpha between 0.06 and 0.085 for time greater than 7s
//
// Case 'dctcp-80ms': DCTCP single flow, 80ms base RTT, 50 Mbps link, ECN enabled, CoDel:
//     ./ns3 run 'tcp-validation --firstTcpType=dctcp --linkRate=50Mbps --baseRtt=80ms
//     --queueUseEcn=1 --stopTime=40s --validate=1 --validation=dctcp-80ms'
//    - Throughput less than 20 Mbps for time less than 14s
//    - Throughput less than 48 Mbps for time less than 30s
//    - Throughput between 47.5 Mbps and 48.5 for time greater than 32s
//    - DCTCP alpha above 0.1 for time less than 7.5
//    - DCTCP alpha below 0.01 for time greater than 11 and less than 30
//    - DCTCP alpha between 0.015 and 0.025 for time greater than 34
//
// Case 'cubic-50ms-no-ecn': CUBIC single flow, 50ms base RTT, 50 Mbps link, ECN disabled, CoDel:
//     ./ns3 run 'tcp-validation --firstTcpType=cubic --linkRate=50Mbps --baseRtt=50ms
//     --queueUseEcn=0 --stopTime=20s --validate=1 --validation=cubic-50ms-no-ecn'
//    - Maximum value of cwnd is 511 segments at 5.4593 seconds
//    - cwnd decreases to 173 segments at 5.80304 seconds
//    - cwnd reaches another local maxima around 14.2815 seconds of 236 segments
//    - cwnd reaches a second maximum around 18.048 seconds of 234 segments
//
// Case 'cubic-50ms-ecn': CUBIC single flow, 50ms base RTT, 50 Mbps link, ECN enabled, CoDel:
//     ./ns3 run 'tcp-validation --firstTcpType=cubic --linkRate=50Mbps --baseRtt=50ms
//     --queueUseEcn=0 --stopTime=20s --validate=1 --validation=cubic-50ms-no-ecn'
//    - Maximum value of cwnd is 511 segments at 5.4593 seconds
//    - cwnd decreases to 173 segments at 5.7939 seconds
//    - cwnd reaches another local maxima around 14.3477 seconds of 236 segments
//    - cwnd reaches a second maximum around 18.064 seconds of 234 segments