diff --git a/interface.go b/interface.go
index 512cb62..18de2a2 100644
--- a/interface.go
+++ b/interface.go
@@ -39,4 +39,7 @@ type Multiaddr interface {
 	//      /ip4/1.2.3.4/tcp/80 decapsulate /ip4/1.2.3.4 = /tcp/80
 	//
 	Decapsulate(Multiaddr) Multiaddr
+
+	// ValueForProtocol returns the value (if any) following the specified protocol
+	ValueForProtocol(code int) (string, error)
 }
diff --git a/multiaddr.go b/multiaddr.go
index 1cb7ad4..0dbcede 100644
--- a/multiaddr.go
+++ b/multiaddr.go
@@ -113,3 +113,19 @@ func (m *multiaddr) Decapsulate(o Multiaddr) Multiaddr {
 	}
 	return ma
 }
+
+var ErrProtocolNotFound = fmt.Errorf("protocol not found in multiaddr")
+
+func (m *multiaddr) ValueForProtocol(code int) (string, error) {
+	for _, sub := range Split(m) {
+		p := sub.Protocols()[0]
+		if p.Code == code {
+			if p.Size == 0 {
+				return "", nil
+			}
+			return strings.Split(sub.String(), "/")[2], nil
+		}
+	}
+
+	return "", ErrProtocolNotFound
+}
diff --git a/multiaddr_test.go b/multiaddr_test.go
index 3a60751..7c75274 100644
--- a/multiaddr_test.go
+++ b/multiaddr_test.go
@@ -300,3 +300,45 @@ func TestEncapsulate(t *testing.T) {
 		t.Error("decapsulate /ip4 failed.", "/", s)
 	}
 }
+
+func assertValueForProto(t *testing.T, a Multiaddr, p int, exp string) {
+	t.Logf("checking for %s in %s", ProtocolWithCode(p).Name, a)
+	fv, err := a.ValueForProtocol(p)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if fv != exp {
+		t.Fatalf("expected %q for %d in %d, but got %q instead", exp, p, a, fv)
+	}
+}
+
+func TestGetValue(t *testing.T) {
+	a := newMultiaddr(t, "/ip4/127.0.0.1/utp/tcp/5555/udp/1234/utp/ipfs/QmbHVEEepCi7rn7VL7Exxpd2Ci9NNB6ifvqwhsrbRMgQFP")
+	assertValueForProto(t, a, P_IP4, "127.0.0.1")
+	assertValueForProto(t, a, P_UTP, "")
+	assertValueForProto(t, a, P_TCP, "5555")
+	assertValueForProto(t, a, P_UDP, "1234")
+	assertValueForProto(t, a, P_IPFS, "QmbHVEEepCi7rn7VL7Exxpd2Ci9NNB6ifvqwhsrbRMgQFP")
+
+	_, err := a.ValueForProtocol(P_IP6)
+	switch err {
+	case ErrProtocolNotFound:
+		break
+	case nil:
+		t.Fatal("expected value lookup to fail")
+	default:
+		t.Fatalf("expected ErrProtocolNotFound but got: %s", err)
+	}
+
+	a = newMultiaddr(t, "/ip4/0.0.0.0") // only one addr
+	assertValueForProto(t, a, P_IP4, "0.0.0.0")
+
+	a = newMultiaddr(t, "/ip4/0.0.0.0/ip4/0.0.0.0/ip4/0.0.0.0") // same sub-addr
+	assertValueForProto(t, a, P_IP4, "0.0.0.0")
+
+	a = newMultiaddr(t, "/ip4/0.0.0.0/udp/12345/utp") // ending in a no-value one.
+	assertValueForProto(t, a, P_IP4, "0.0.0.0")
+	assertValueForProto(t, a, P_UDP, "12345")
+	assertValueForProto(t, a, P_UTP, "")
+}
diff --git a/protocols.go b/protocols.go
index c233cef..8364d4c 100644
--- a/protocols.go
+++ b/protocols.go
@@ -55,6 +55,20 @@ var Protocols = []Protocol{
 	Protocol{P_IPFS, LengthPrefixedVarSize, "ipfs", CodeToVarint(P_IPFS)},
 }
 
+func AddProtocol(p Protocol) error {
+	for _, pt := range Protocols {
+		if pt.Code == p.Code {
+			return fmt.Errorf("protocol code %d already taken by %q", p.Code, pt.Name)
+		}
+		if pt.Name == p.Name {
+			return fmt.Errorf("protocol by the name %q already exists", p.Name)
+		}
+	}
+
+	Protocols = append(Protocols, p)
+	return nil
+}
+
 // ProtocolWithName returns the Protocol description with given string name.
 func ProtocolWithName(s string) Protocol {
 	for _, p := range Protocols {