diff --git a/app/cmd/client.go b/app/cmd/client.go
index e1ce48f..dbe554f 100644
--- a/app/cmd/client.go
+++ b/app/cmd/client.go
@@ -184,18 +184,19 @@ func (c *clientConfig) fillQUICConfig(hyConfig *client.Config) error {
 }
 
 func (c *clientConfig) fillBandwidthConfig(hyConfig *client.Config) error {
-	if c.Bandwidth.Up == "" || c.Bandwidth.Down == "" {
-		// New core now allows users to omit bandwidth values and use built-in congestion control
-		return nil
-	}
+	// New core now allows users to omit bandwidth values and use built-in congestion control
 	var err error
-	hyConfig.BandwidthConfig.MaxTx, err = convBandwidth(c.Bandwidth.Up)
-	if err != nil {
-		return configError{Field: "bandwidth.up", Err: err}
+	if c.Bandwidth.Up != "" {
+		hyConfig.BandwidthConfig.MaxTx, err = convBandwidth(c.Bandwidth.Up)
+		if err != nil {
+			return configError{Field: "bandwidth.up", Err: err}
+		}
 	}
-	hyConfig.BandwidthConfig.MaxRx, err = convBandwidth(c.Bandwidth.Down)
-	if err != nil {
-		return configError{Field: "bandwidth.down", Err: err}
+	if c.Bandwidth.Down != "" {
+		hyConfig.BandwidthConfig.MaxRx, err = convBandwidth(c.Bandwidth.Down)
+		if err != nil {
+			return configError{Field: "bandwidth.down", Err: err}
+		}
 	}
 	return nil
 }
diff --git a/core/client/client.go b/core/client/client.go
index 24c3be8..c3750c4 100644
--- a/core/client/client.go
+++ b/core/client/client.go
@@ -132,7 +132,7 @@ func (c *clientImpl) connect() error {
 		conn.SetCongestionControl(bbr.NewBBRSender(
 			bbr.DefaultClock{},
 			bbr.GetInitialPacketSize(conn.RemoteAddr()),
-			32*common.InitMaxDatagramSize,
+			bbr.InitialCongestionWindow*common.InitMaxDatagramSize,
 			bbr.DefaultBBRMaxCongestionWindow*common.InitMaxDatagramSize,
 		))
 	}
diff --git a/core/server/server.go b/core/server/server.go
index 82e2168..5781851 100644
--- a/core/server/server.go
+++ b/core/server/server.go
@@ -135,7 +135,7 @@ func (h *h3sHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 				h.conn.SetCongestionControl(bbr.NewBBRSender(
 					bbr.DefaultClock{},
 					bbr.GetInitialPacketSize(h.conn.RemoteAddr()),
-					32*common.InitMaxDatagramSize,
+					bbr.InitialCongestionWindow*common.InitMaxDatagramSize,
 					bbr.DefaultBBRMaxCongestionWindow*common.InitMaxDatagramSize,
 				))
 			}