FEAT: Packet idle time (#558)

Author: PaulRalnikov

configs/incast/network.yml

@@ -7,16 +7,13 @@ presets:
       type: single-cc
       packet-size: 1500B
       cc:
-        type: tahoe
+        type: swift
+        base_target: 5300ns
       path-chooser:
         type: round-robin
         flows:
           flow-1:
             type: tcp
-          flow-2:
-            type: tcp
-          flow-3:
-            type: tcp
 
 type: custom
 

configs/incast/scenario.yml

@@ -4,7 +4,7 @@ scenario:
 - action: send_data
   id: send-1
   when: 0ns
-  size: 50KB
+  size: 500KB
   repeat_count: 1
   connections: ^connection.*
   repeat_interval: 500000ns

configs/incast/topology.yml

@@ -1,16 +1,16 @@
 type: incast
 
 links:
-  latency: 0ns
-  throughput: 100Gbps
-  ingress_buffer_size: 1024000B
-  egress_buffer_size: 1024000B
+  latency: 1000ns
+  throughput: 10Gbps
+  ingress_buffer_size: 64KB
+  egress_buffer_size: 64KB
 
 bottleneck-link:
-  latency: 0ns
+  latency: 1000ns
   throughput: 100Gbps
-  ingress_buffer_size: 1024000B
-  egress_buffer_size: 1024000B
+  ingress_buffer_size: 64KB
+  egress_buffer_size: 64KB
 
 packet-spraying:
   type: ecmp
@@ -20,8 +20,8 @@ senders:
 
 switch:
   ecn:
-    min: 0.1
-    max: 0.3
+    min: 0.4
+    max: 0.8
     probability: 0.5
 
 receiver:

configs/simple/network.yml

@@ -10,7 +10,8 @@ connections:
       type: single-cc
       packet-size: 1500B
       cc:
-        type: tahoe
+        type: swift
+        base_target: 8800ns
       path-chooser:
         type: round-robin
         flows:

configs/simple/scenario.yml

@@ -4,5 +4,5 @@ scenario:
 - action: send_data
   id: send
   when: 0ns
-  size: 50KB
+  size: 500KB
   connections: connection

source/network/connection/flow/packet.hpp

@@ -37,6 +37,8 @@ struct Packet : FourTuple {
     TimeNs generated_time;  // Note: ACK's generated time is the data packet
                             // generated time
     TimeNs sent_time;  // Note: ACK's sent time is the data packet sent time
+    TimeNs idle_time = TimeNs(0);
+    TimeNs last_idle_start_time = TimeNs(0);
     SizeByte delivered_data_size_at_origin;  // For ACK this is inherited from
                                              // data packet
     TTL ttl = std::numeric_limits<TTL>::max();

source/network/connection/flow/tcp/tcp_flow.cpp

@@ -164,6 +164,7 @@ void TcpFlow::process_ack(const Packet& ack, SizeByte data_packet_size,
     // here ack.sent_time is the time when corresponding DATA packet was sent
     // (see process_data_packet)
     TimeNs rtt = now - ack.sent_time;
+
     m_context.rtt_statistics.add_record(rtt);
 
     m_metrics.rtt->add_record(now, rtt.value());

source/topology/device/host.cpp

@@ -21,7 +21,11 @@ bool Host::notify_about_arrival() {
 
 void Host::enqueue_packet(const Packet& packet) {
     LOG_INFO(fmt::format("Packet {} arrived to host", packet.to_string()));
+    TimeNs now = Scheduler::get_instance().get_current_time();
     m_nic_buffer.push(packet);
+
+    Packet& pckt = m_nic_buffer.back();
+    pckt.last_idle_start_time = now;
     if (m_nic_buffer.size() == 1) {
         // first packet in queue => start sending it
         send_packet();
@@ -95,8 +99,15 @@ void Host::send_packet() {
                               get_id()));
         return;
     }
+    Scheduler& sched = Scheduler::get_instance();
+    TimeNs now = sched.get_current_time();
     {
         Packet& data_packet = m_nic_buffer.front();
+
+        // increase idle time
+        TimeNs idle_time_gain = now - data_packet.last_idle_start_time;
+        data_packet.idle_time += idle_time_gain;
+
         utils::Defer defer{[this] { m_nic_buffer.pop(); }};
 
         LOG_INFO(fmt::format("Taken new data packet on host {}. Packet: {}",
@@ -124,7 +135,6 @@ void Host::send_packet() {
     }
 
     if (!m_nic_buffer.empty()) {
-        Scheduler& sched = Scheduler::get_instance();
         sched.add(sched.get_current_time() + PACKET_PROCESSING_TIME,
                   [host = shared_from_this()]() { host->send_packet(); });
     }

source/topology/link/link.cpp

@@ -23,13 +23,16 @@ std::shared_ptr<Link> Link::create_shared(
 
 void Link::schedule_arrival(Packet& packet) {
     bool empty_before_push = m_from_egress.empty();
+    TimeNs now = Scheduler::get_instance().get_current_time();
+    packet.last_idle_start_time = now;
 
     if (!m_from_egress.push(packet)) {
         LOG_ERROR(
             fmt::format("Link {}: from egress buffer overflow; packet {} lost",
                         m_id, packet.to_string()));
         return;
     }
+
     record_activity();
 
     if (empty_before_push) {
@@ -175,8 +178,15 @@ void Link::arrive(const Packet& packet) {
 
 void Link::start_head_packet_sending() {
     TimeNs current_time = Scheduler::get_instance().get_current_time();
+
+    // increase idle time
+    Packet& packet = m_from_egress.front();
+    TimeNs idle_time_gain = current_time - packet.last_idle_start_time;
+    packet.idle_time += idle_time_gain;
+    TimeNs transmition_time = get_transmission_delay(packet);
+
     Scheduler::get_instance().add(
-        current_time + get_transmission_delay(m_from_egress.front()),
+        current_time + transmition_time,
         [link = shared_from_this()]() { link->transmit(); });
 }