optimize transport performance in some extreme scenarios (#392)

* [+] demo_client/server supports specifying MTU size

* [~] slow down ack rate after startup

* [~] optimize BBR in scenarios with severe ACK compression and traffic policing

demo/demo_client.c

@@ -188,6 +188,8 @@ typedef struct xqc_demo_cli_quic_config_s {
 
     uint64_t least_available_cid_count;
 
+    size_t max_pkt_sz;
+
 } xqc_demo_cli_quic_config_t;
 
 
@@ -1643,6 +1645,8 @@ xqc_demo_cli_init_conneciton_settings(xqc_conn_settings_t* settings,
     settings->multipath_version = args->quic_cfg.mp_version;
     settings->mp_ping_on = 1;
     settings->is_interop_mode = args->quic_cfg.is_interop_mode;
+    settings->max_pkt_out_size = args->quic_cfg.max_pkt_sz;
+    settings->adaptive_ack_frequency = 1;
     if (args->req_cfg.throttled_req != -1) {
         settings->enable_stream_rate_limit = 1;
         settings->recv_rate_bytes_per_sec = 0;
@@ -1672,6 +1676,7 @@ xqc_demo_cli_init_args(xqc_demo_cli_client_args_t *args)
     args->quic_cfg.keyupdate_pkt_threshold = UINT64_MAX;
     /* default 04 */
     args->quic_cfg.mp_version = XQC_MULTIPATH_04;
+    args->quic_cfg.max_pkt_sz = 1200;
 
     args->req_cfg.throttled_req = -1;
 
@@ -1791,14 +1796,15 @@ xqc_demo_cli_usage(int argc, char *argv[])
         "   -n    Throttling the {1,2,...}xn-th requests\n"
         "   -e    NAT rebinding on path 0\n"
         "   -E    NAT rebinding on path 1\n"
+        "   -F    MTU size (default: 1200)\n"
         , prog);
 }
 
 void
 xqc_demo_cli_parse_args(int argc, char *argv[], xqc_demo_cli_client_args_t *args)
 {
     int ch = 0;
-    while ((ch = getopt(argc, argv, "a:p:c:Ct:S:0m:A:D:l:L:k:K:U:u:dMoi:w:Ps:bZ:NQT:R:V:B:I:n:eE")) != -1) {
+    while ((ch = getopt(argc, argv, "a:p:c:Ct:S:0m:A:D:l:L:k:K:U:u:dMoi:w:Ps:bZ:NQT:R:V:B:I:n:eEF:")) != -1) {
         switch (ch) {
         /* server ip */
         case 'a':
@@ -2033,6 +2039,11 @@ xqc_demo_cli_parse_args(int argc, char *argv[], xqc_demo_cli_client_args_t *args
             args->net_cfg.rebind_p1 = 1;
             break;     
 
+        case 'F':
+            printf("MTU size: %s\n", optarg);
+            args->quic_cfg.max_pkt_sz = atoi(optarg);
+            break;
+
         default:
             printf("other option :%c\n", ch);
             xqc_demo_cli_usage(argc, argv);

demo/demo_server.c

@@ -113,6 +113,8 @@ typedef struct xqc_demo_svr_quic_config_s {
 
     uint64_t keyupdate_pkt_threshold;
     uint64_t least_available_cid_count;
+
+    size_t max_pkt_sz;
 } xqc_demo_svr_quic_config_t;
 
 
@@ -1215,6 +1217,7 @@ xqc_demo_svr_usage(int argc, char *argv[])
             "   -s    multipath scheduler (interop, minrtt, backup), default: interop\n"
             "   -R    Reinjection (1,2,4) \n"
             "   -u    Keyupdate packet threshold\n"
+            "   -F    MTU size (default: 1200)\n"
             , prog);
 }
 
@@ -1253,13 +1256,14 @@ xqc_demo_svr_init_args(xqc_demo_svr_args_t *args)
 
     args->quic_cfg.keyupdate_pkt_threshold = UINT64_MAX;
     args->quic_cfg.least_available_cid_count = 1;
+    args->quic_cfg.max_pkt_sz = 1200;
 }
 
 void
 xqc_demo_svr_parse_args(int argc, char *argv[], xqc_demo_svr_args_t *args)
 {
     int ch = 0;
-    while ((ch = getopt(argc, argv, "p:c:CD:l:L:6k:rdMiPs:R:u:a:")) != -1) {
+    while ((ch = getopt(argc, argv, "p:c:CD:l:L:6k:rdMiPs:R:u:a:F:")) != -1) {
         switch (ch) {
         /* listen port */
         case 'p':
@@ -1377,6 +1381,11 @@ xqc_demo_svr_parse_args(int argc, char *argv[], xqc_demo_svr_args_t *args)
             args->quic_cfg.least_available_cid_count = atoi(optarg);
             break;
 
+        case 'F':
+            printf("MTU size: %s\n", optarg);
+            args->quic_cfg.max_pkt_sz = atoi(optarg);
+            break;
+
         default:
             printf("other option :%c\n", ch);
             xqc_demo_svr_usage(argc, argv);
@@ -1485,6 +1494,7 @@ xqc_demo_svr_init_conn_settings(xqc_demo_svr_args_t *args)
         .cc_params = {
             .customize_on = 1,
             .init_cwnd = 32,
+            .bbr_enable_lt_bw = 1,
         },
         .spurious_loss_detect_on = 1,
         .init_idle_time_out = 60000,
@@ -1498,6 +1508,8 @@ xqc_demo_svr_init_conn_settings(xqc_demo_svr_args_t *args)
         .keyupdate_pkt_threshold = args->quic_cfg.keyupdate_pkt_threshold,
         .least_available_cid_count = args->quic_cfg.least_available_cid_count,
         .is_interop_mode = args->quic_cfg.is_interop_mode,
+        .max_pkt_out_size = args->quic_cfg.max_pkt_sz,
+        .adaptive_ack_frequency = 1,
     };
 
     xqc_server_set_conn_settings(&conn_settings);

include/xquic/xquic.h

@@ -824,6 +824,7 @@ typedef struct xqc_cc_params_s {
     uint32_t    min_cwnd;
     uint32_t    expect_bw;
     uint32_t    max_expect_bw;
+    uint8_t     bbr_enable_lt_bw;
     uint32_t    cc_optimization_flags;
     /* 0 < delta <= delta_max, default 0.05, ->0 = more throughput-oriented */
     double      copa_delta_base; 
@@ -1217,6 +1218,7 @@ typedef struct xqc_conn_settings_s {
     uint32_t                    max_ack_delay;
     /* generate an ACK if received ack-eliciting pkts >= ack_frequency */
     uint32_t                    ack_frequency; 
+    uint8_t                     adaptive_ack_frequency;
     uint64_t                    loss_detection_pkt_thresh;
     double                      pto_backoff_factor;