diff --git a/cmd/client.go b/cmd/client.go
index 67b23c2..533f1dd 100644
--- a/cmd/client.go
+++ b/cmd/client.go
@@ -39,6 +39,7 @@ var clientPacketConnFuncFactoryMap = map[string]pktconns.ClientPacketConnFuncFac
 
 func client(config *clientConfig) {
 	logrus.WithField("config", config.String()).Info("Client configuration loaded")
+	config.Fill() // Fill default values
 	// Resolver
 	if len(config.Resolver) > 0 {
 		err := setResolver(config.Resolver)
@@ -50,15 +51,11 @@ func client(config *clientConfig) {
 	}
 	// TLS
 	tlsConfig := &tls.Config{
+		NextProtos:         []string{config.ALPN},
 		ServerName:         config.ServerName,
 		InsecureSkipVerify: config.Insecure,
 		MinVersion:         tls.VersionTLS13,
 	}
-	if config.ALPN != "" {
-		tlsConfig.NextProtos = []string{config.ALPN}
-	} else {
-		tlsConfig.NextProtos = []string{DefaultALPN}
-	}
 	// Load CA
 	if len(config.CustomCA) > 0 {
 		bs, err := ioutil.ReadFile(config.CustomCA)
@@ -83,24 +80,11 @@ func client(config *clientConfig) {
 		InitialConnectionReceiveWindow: config.ReceiveWindow,
 		MaxConnectionReceiveWindow:     config.ReceiveWindow,
 		HandshakeIdleTimeout:           time.Duration(config.HandshakeTimeout) * time.Second,
+		MaxIdleTimeout:                 time.Duration(config.IdleTimeout) * time.Second,
+		KeepAlivePeriod:                time.Duration(config.IdleTimeout) * time.Second * 2 / 5,
 		DisablePathMTUDiscovery:        config.DisableMTUDiscovery,
 		EnableDatagrams:                true,
 	}
-	if config.IdleTimeout == 0 {
-		quicConfig.MaxIdleTimeout = DefaultClientMaxIdleTimeout
-		quicConfig.KeepAlivePeriod = DefaultClientKeepAlivePeriod
-	} else {
-		quicConfig.MaxIdleTimeout = time.Duration(config.IdleTimeout) * time.Second
-		quicConfig.KeepAlivePeriod = quicConfig.MaxIdleTimeout * 2 / 5
-	}
-	if config.ReceiveWindowConn == 0 {
-		quicConfig.InitialStreamReceiveWindow = DefaultStreamReceiveWindow
-		quicConfig.MaxStreamReceiveWindow = DefaultStreamReceiveWindow
-	}
-	if config.ReceiveWindow == 0 {
-		quicConfig.InitialConnectionReceiveWindow = DefaultConnectionReceiveWindow
-		quicConfig.MaxConnectionReceiveWindow = DefaultConnectionReceiveWindow
-	}
 	if !quicConfig.DisablePathMTUDiscovery && pmtud.DisablePathMTUDiscovery {
 		logrus.Info("Path MTU Discovery is not yet supported on this platform")
 	}
@@ -135,11 +119,7 @@ func client(config *clientConfig) {
 		var err error
 		aclEngine, err = acl.LoadFromFile(config.ACL, transport.DefaultClientTransport.ResolveIPAddr,
 			func() (*geoip2.Reader, error) {
-				if len(config.MMDB) > 0 {
-					return loadMMDBReader(config.MMDB)
-				} else {
-					return loadMMDBReader(DefaultMMDBFilename)
-				}
+				return loadMMDBReader(config.MMDB)
 			})
 		if err != nil {
 			logrus.WithFields(logrus.Fields{
diff --git a/cmd/config.go b/cmd/config.go
index 0b03f7a..11dec76 100644
--- a/cmd/config.go
+++ b/cmd/config.go
@@ -5,7 +5,6 @@ import (
 	"fmt"
 	"regexp"
 	"strconv"
-	"time"
 
 	"github.com/sirupsen/logrus"
 	"github.com/yosuke-furukawa/json5/encoding/json5"
@@ -15,17 +14,16 @@ const (
 	mbpsToBps   = 125000
 	minSpeedBPS = 16384
 
+	DefaultALPN = "hysteria"
+
 	DefaultStreamReceiveWindow     = 15728640 // 15 MB/s
 	DefaultConnectionReceiveWindow = 67108864 // 64 MB/s
 	DefaultMaxIncomingStreams      = 1024
 
-	DefaultALPN = "hysteria"
-
 	DefaultMMDBFilename = "GeoLite2-Country.mmdb"
 
-	ServerMaxIdleTimeout         = 60 * time.Second
-	DefaultClientMaxIdleTimeout  = 20 * time.Second
-	DefaultClientKeepAlivePeriod = 8 * time.Second
+	ServerMaxIdleTimeoutSec     = 60
+	DefaultClientIdleTimeoutSec = 20
 )
 
 var rateStringRegexp = regexp.MustCompile(`^(\d+)\s*([KMGT]?)([Bb])ps$`)
@@ -98,10 +96,10 @@ func (c *serverConfig) Speed() (uint64, uint64, error) {
 
 func (c *serverConfig) Check() error {
 	if len(c.Listen) == 0 {
-		return errors.New("no listen address")
+		return errors.New("missing listen address")
 	}
 	if len(c.ACME.Domains) == 0 && (len(c.CertFile) == 0 || len(c.KeyFile) == 0) {
-		return errors.New("ACME domain or TLS cert not provided")
+		return errors.New("need either ACME info or cert/key files")
 	}
 	if up, down, err := c.Speed(); err != nil || (up != 0 && up < minSpeedBPS) || (down != 0 && down < minSpeedBPS) {
 		return errors.New("invalid speed")
@@ -116,6 +114,24 @@ func (c *serverConfig) Check() error {
 	return nil
 }
 
+func (c *serverConfig) Fill() {
+	if len(c.ALPN) == 0 {
+		c.ALPN = DefaultALPN
+	}
+	if c.ReceiveWindowConn == 0 {
+		c.ReceiveWindowConn = DefaultStreamReceiveWindow
+	}
+	if c.ReceiveWindowClient == 0 {
+		c.ReceiveWindowClient = DefaultConnectionReceiveWindow
+	}
+	if c.MaxConnClient == 0 {
+		c.MaxConnClient = DefaultMaxIncomingStreams
+	}
+	if len(c.MMDB) == 0 {
+		c.MMDB = DefaultMMDBFilename
+	}
+}
+
 func (c *serverConfig) String() string {
 	return fmt.Sprintf("%+v", *c)
 }
@@ -128,10 +144,10 @@ type Relay struct {
 
 func (r *Relay) Check() error {
 	if len(r.Listen) == 0 {
-		return errors.New("no relay listen address")
+		return errors.New("missing relay listen address")
 	}
 	if len(r.Remote) == 0 {
-		return errors.New("no relay remote address")
+		return errors.New("missing relay remote address")
 	}
 	if r.Timeout != 0 && r.Timeout < 4 {
 		return errors.New("invalid relay timeout")
@@ -252,10 +268,10 @@ func (c *clientConfig) Check() error {
 		return errors.New("invalid TUN timeout")
 	}
 	if len(c.TCPRelay.Listen) > 0 && len(c.TCPRelay.Remote) == 0 {
-		return errors.New("no TCP relay remote address")
+		return errors.New("missing TCP relay remote address")
 	}
 	if len(c.UDPRelay.Listen) > 0 && len(c.UDPRelay.Remote) == 0 {
-		return errors.New("no UDP relay remote address")
+		return errors.New("missing UDP relay remote address")
 	}
 	if c.TCPRelay.Timeout != 0 && c.TCPRelay.Timeout < 4 {
 		return errors.New("invalid TCP relay timeout")
@@ -283,7 +299,7 @@ func (c *clientConfig) Check() error {
 		return errors.New("invalid TCP Redirect timeout")
 	}
 	if len(c.Server) == 0 {
-		return errors.New("no server address")
+		return errors.New("missing server address")
 	}
 	if up, down, err := c.Speed(); err != nil || up < minSpeedBPS || down < minSpeedBPS {
 		return errors.New("invalid speed")
@@ -301,6 +317,24 @@ func (c *clientConfig) Check() error {
 	return nil
 }
 
+func (c *clientConfig) Fill() {
+	if len(c.ALPN) == 0 {
+		c.ALPN = DefaultALPN
+	}
+	if c.ReceiveWindowConn == 0 {
+		c.ReceiveWindowConn = DefaultStreamReceiveWindow
+	}
+	if c.ReceiveWindow == 0 {
+		c.ReceiveWindow = DefaultConnectionReceiveWindow
+	}
+	if len(c.MMDB) == 0 {
+		c.MMDB = DefaultMMDBFilename
+	}
+	if c.IdleTimeout == 0 {
+		c.IdleTimeout = DefaultClientIdleTimeoutSec
+	}
+}
+
 func (c *clientConfig) String() string {
 	return fmt.Sprintf("%+v", *c)
 }
diff --git a/cmd/server.go b/cmd/server.go
index 9e3c51f..b9976aa 100644
--- a/cmd/server.go
+++ b/cmd/server.go
@@ -33,6 +33,7 @@ var serverPacketConnFuncFactoryMap = map[string]pktconns.ServerPacketConnFuncFac
 
 func server(config *serverConfig) {
 	logrus.WithField("config", config.String()).Info("Server configuration loaded")
+	config.Fill() // Fill default values
 	// Resolver
 	if len(config.Resolver) > 0 {
 		err := setResolver(config.Resolver)
@@ -54,6 +55,7 @@ func server(config *serverConfig) {
 				"error": err,
 			}).Fatal("Failed to get a certificate with ACME")
 		}
+		tc.NextProtos = []string{config.ALPN}
 		tc.MinVersion = tls.VersionTLS13
 		tlsConfig = tc
 	} else {
@@ -68,14 +70,10 @@ func server(config *serverConfig) {
 		}
 		tlsConfig = &tls.Config{
 			GetCertificate: kpl.GetCertificateFunc(),
+			NextProtos:     []string{config.ALPN},
 			MinVersion:     tls.VersionTLS13,
 		}
 	}
-	if config.ALPN != "" {
-		tlsConfig.NextProtos = []string{config.ALPN}
-	} else {
-		tlsConfig.NextProtos = []string{DefaultALPN}
-	}
 	// QUIC config
 	quicConfig := &quic.Config{
 		InitialStreamReceiveWindow:     config.ReceiveWindowConn,
@@ -83,22 +81,11 @@ func server(config *serverConfig) {
 		InitialConnectionReceiveWindow: config.ReceiveWindowClient,
 		MaxConnectionReceiveWindow:     config.ReceiveWindowClient,
 		MaxIncomingStreams:             int64(config.MaxConnClient),
-		MaxIdleTimeout:                 ServerMaxIdleTimeout,
+		MaxIdleTimeout:                 ServerMaxIdleTimeoutSec * time.Second,
 		KeepAlivePeriod:                0, // Keep alive should solely be client's responsibility
 		DisablePathMTUDiscovery:        config.DisableMTUDiscovery,
 		EnableDatagrams:                true,
 	}
-	if config.ReceiveWindowConn == 0 {
-		quicConfig.InitialStreamReceiveWindow = DefaultStreamReceiveWindow
-		quicConfig.MaxStreamReceiveWindow = DefaultStreamReceiveWindow
-	}
-	if config.ReceiveWindowClient == 0 {
-		quicConfig.InitialConnectionReceiveWindow = DefaultConnectionReceiveWindow
-		quicConfig.MaxConnectionReceiveWindow = DefaultConnectionReceiveWindow
-	}
-	if quicConfig.MaxIncomingStreams == 0 {
-		quicConfig.MaxIncomingStreams = DefaultMaxIncomingStreams
-	}
 	if !quicConfig.DisablePathMTUDiscovery && pmtud.DisablePathMTUDiscovery {
 		logrus.Info("Path MTU Discovery is not yet supported on this platform")
 	}
@@ -108,8 +95,8 @@ func server(config *serverConfig) {
 	switch authMode := config.Auth.Mode; authMode {
 	case "", "none":
 		if len(config.Obfs) == 0 {
-			logrus.Warn("No authentication or obfuscation enabled. " +
-				"Your server could be accessed by anyone! Are you sure this is what you intended?")
+			logrus.Warn("Neither authentication nor obfuscation is turned on. " +
+				"Your server could be used by anyone! Are you sure this is what you want?")
 		}
 		authFunc = func(addr net.Addr, auth []byte, sSend uint64, sRecv uint64) (bool, string) {
 			return true, "Welcome"
@@ -199,11 +186,7 @@ func server(config *serverConfig) {
 			return ipAddr, err
 		},
 			func() (*geoip2.Reader, error) {
-				if len(config.MMDB) > 0 {
-					return loadMMDBReader(config.MMDB)
-				} else {
-					return loadMMDBReader(DefaultMMDBFilename)
-				}
+				return loadMMDBReader(config.MMDB)
 			})
 		if err != nil {
 			logrus.WithFields(logrus.Fields{