diff --git a/go.sum b/go.sum
index 034ee22c..8348504a 100644
--- a/go.sum
+++ b/go.sum
@@ -89,6 +89,7 @@ github.com/multiformats/go-multihash v0.0.13 h1:06x+mk/zj1FoMsgNejLpy6QTvJqlSt/B
 github.com/multiformats/go-multihash v0.0.13/go.mod h1:VdAWLKTwram9oKAatUcLxBNUjdtcVwxObEQBtRfuyjc=
 github.com/multiformats/go-varint v0.0.1 h1:TR/0rdQtnNxuN2IhiB639xC3tWM4IUi7DkTBVTdGW/M=
 github.com/multiformats/go-varint v0.0.1/go.mod h1:3Ls8CIEsrijN6+B7PbrXRPxHRPuXSrVKRY101jdMZYE=
+github.com/multiformats/go-varint v0.0.2/go.mod h1:3Ls8CIEsrijN6+B7PbrXRPxHRPuXSrVKRY101jdMZYE=
 github.com/multiformats/go-varint v0.0.5 h1:XVZwSo04Cs3j/jS0uAEPpT3JY6DzMcVLLoWOSnCxOjg=
 github.com/multiformats/go-varint v0.0.5/go.mod h1:3Ls8CIEsrijN6+B7PbrXRPxHRPuXSrVKRY101jdMZYE=
 github.com/onsi/ginkgo v1.6.0/go.mod h1:lLunBs/Ym6LB5Z9jYTR76FiuTmxDTDusOGeTQH+WWjE=
diff --git a/network/conn.go b/network/conn.go
index e7844a0e..086d2e84 100644
--- a/network/conn.go
+++ b/network/conn.go
@@ -2,6 +2,7 @@ package network
 
 import (
 	"io"
+	"time"
 
 	ic "github.com/libp2p/go-libp2p-core/crypto"
 	"github.com/libp2p/go-libp2p-core/peer"
@@ -27,8 +28,17 @@ type Conn interface {
 
 	// Stat stores metadata pertaining to this conn.
 	Stat() Stat
+
+	// OnBetter is an callback when a better connection is found.
+	// OnBetter is threadsafe, it can be called even once the event raised and the
+	// callback we be yield.
+	OnBetter(OnBetterHandler)
 }
 
+// OnBetterHandler are args to pass to Conn.OnBetter The time is the deadline
+// before a hard close (fixed time not duration).
+type OnBetterHandler func(time.Time)
+
 // ConnSecurity is the interface that one can mix into a connection interface to
 // give it the security methods.
 type ConnSecurity interface {
diff --git a/transport/transport.go b/transport/transport.go
index 39a8fd38..a5dd1739 100644
--- a/transport/transport.go
+++ b/transport/transport.go
@@ -28,6 +28,9 @@ var AcceptTimeout = 60 * time.Second
 // capabilities required by libp2p: stream multiplexing, encryption and
 // peer authentication.
 //
+// DEPREACATED try to use QCapableConn instead, using this will result in
+// wrong transport choice when trying to pick a good one.
+//
 // These capabilities may be natively provided by the transport, or they
 // may be shimmed via the "connection upgrade" process, which converts a
 // "raw" network connection into one that supports such capabilities by
@@ -36,12 +39,65 @@ var AcceptTimeout = 60 * time.Second
 // CapableConn provides accessors for the local and remote multiaddrs used to
 // establish the connection and an accessor for the underlying Transport.
 type CapableConn interface {
+	BaseCapableConn
+
+	// Transport returns the transport to which this connection belongs.
+	Transport() Transport
+}
+
+// Quality is an estimation of how bad the connection will be.
+// It must be short and fast to run.
+// Lower is the returned score, better we expect the connection to be.
+// Don't implement a pinging/monitoring algorithm quality must be deterministic.
+//
+// To see where to place your transport on the scale take a look at this (note:
+// a proto with a Quality twice bigger is not twice slower or twice worst, it is
+// just worst, like the place on a leaderboard):
+// - TCP, 2^31, multiplexed stated continuous protocol (stream have fight for a
+//   place in the underlying protocol)
+// - QUIC, 2^30, async stated discontinuous protocol (stream doesn't have to
+//   fight but there is time taken to open the connection and stream)
+// - Circuit, router underlying connection quality + the number of hops * 8
+//   (that consider that all router are equal but there is really no better than
+//   pinging/monitoring to know that) + 2^16 (base circuit value).
+//
+// Its also not needed to follow that closely, thing can be added if a proto add
+// some overhead :
+// - WS tcp score + 50
+// - WSS ws score + 150
+//
+// If conn is on a private network Quality() must divide score by 2^8 (shift
+// right by 8).
+// If conn is on the loopback Quality() must divide score by 2^16 (shift right
+// by 16).
+//
+// QCapableConn embed CapableConn but with `Quality() uint32` support.
+type QCapableConn interface {
+	BaseCapableConn
+
+	// Quality returns the Quality we can expect from the connection to this peer.
+	// That must be deterministic and fast.
+	Quality() uint32
+
+	// Transport returns the transport to which this connection belongs.
+	Transport() QTransport
+}
+
+// CapableConnBase is used to build `CapableConn` and `QCapableConn`
+type BaseCapableConn interface {
 	mux.MuxedConn
 	network.ConnSecurity
 	network.ConnMultiaddrs
+}
 
-	// Transport returns the transport to which this connection belongs.
-	Transport() Transport
+// Score is used by transport to returns expectation about connection, might be
+// different than what the connection actualy return but that DEPREACATED.
+// (that will cause weird cancel issue)
+type Score struct {
+	// Score of the future connection.
+	Quality uint32
+	// Number of file descriptor expected to be open.
+	Fd uint8
 }
 
 // Transport represents any device by which you can connect to and accept
@@ -55,11 +111,36 @@ type CapableConn interface {
 // stream multiplexing and connection security (encryption and authentication).
 //
 // For a conceptual overview, see https://docs.libp2p.io/concepts/transport/
+//
+// DEPREACATED try to use QTransport instead, using this will result in
+// wrong transport choice when trying to pick a good one.
 type Transport interface {
+	BaseTransport
+
 	// Dial dials a remote peer. It should try to reuse local listener
 	// addresses if possible but it may choose not to.
 	Dial(ctx context.Context, raddr ma.Multiaddr, p peer.ID) (CapableConn, error)
 
+	// Listen listens on the passed multiaddr.
+	Listen(laddr ma.Multiaddr) (Listener, error)
+}
+
+type QTransport interface {
+	BaseTransport
+
+	// Dial dials a remote peer. It should try to reuse local listener
+	// addresses if possible but it may choose not to.
+	Dial(ctx context.Context, raddr ma.Multiaddr, p peer.ID) (QCapableConn, error)
+
+	// Listen listens on the passed multiaddr.
+	Listen(laddr ma.Multiaddr) (QListener, error)
+
+	// Score returns the Quality we can expect from the connection to this peer.
+	// That must be deterministic and fast.
+	Score(raddr ma.Multiaddr, p peer.ID) (Score, error)
+}
+
+type BaseTransport interface {
 	// CanDial returns true if this transport knows how to dial the given
 	// multiaddr.
 	//
@@ -68,9 +149,6 @@ type Transport interface {
 	// out addresses that we can't dial.
 	CanDial(addr ma.Multiaddr) bool
 
-	// Listen listens on the passed multiaddr.
-	Listen(laddr ma.Multiaddr) (Listener, error)
-
 	// Protocol returns the set of protocols handled by this transport.
 	//
 	// See the Network interface for an explanation of how this is used.
@@ -88,7 +166,20 @@ type Transport interface {
 // package, and also exposes a Multiaddr method as opposed to a regular Addr
 // method
 type Listener interface {
+	BaseListener
+
 	Accept() (CapableConn, error)
+}
+
+// QListener is like listener but produce QCapableConn instead of CapableConn.
+type QListener interface {
+	BaseListener
+
+	Accept() (QCapableConn, error)
+}
+
+// BaseListener is used to build `Lister` and `QListener`
+type BaseListener interface {
 	Close() error
 	Addr() net.Addr
 	Multiaddr() ma.Multiaddr
@@ -109,5 +200,8 @@ type TransportNetwork interface {
 	// local multiaddr and pick the *last* protocol registered with a proxy
 	// transport, if any. Otherwise, it'll pick the transport registered to
 	// handle the last protocol in the multiaddr.
-	AddTransport(t Transport) error
+	//
+	// Even if BaseTransport are accepted its needed to be able to cast to
+	// Transport or QTransport.
+	AddTransport(t BaseTransport) error
 }