diff --git a/net/swarm/conn.go b/net/swarm/conn.go
index f05c20dcb..bf32e0949 100644
--- a/net/swarm/conn.go
+++ b/net/swarm/conn.go
@@ -164,6 +164,7 @@ func (s *Swarm) connVersionExchange(remote *conn.Conn) error {
 	var remoteVersion, myVersion *version.SemVer
 	myVersion = version.Current()
 
+	// BUG(cryptix): do we need to use a NetMessage here?
 	myVersionMsg, err := msg.FromObject(s.local, myVersion)
 	if err != nil {
 		return fmt.Errorf("connVersionExchange: could not prepare local version: %q", err)
@@ -215,7 +216,12 @@ func (s *Swarm) connVersionExchange(remote *conn.Conn) error {
 		}
 	}
 
-	return errors.New("not yet")
+	if !version.Compatible(myVersion, remoteVersion) {
+		remote.Close()
+		return errors.New("protocol missmatch")
+	}
+
+	return nil
 }
 
 // Handles the unwrapping + sending of messages to the right connection.
diff --git a/net/version/version.go b/net/version/version.go
index bb1a67b13..be8e194f5 100644
--- a/net/version/version.go
+++ b/net/version/version.go
@@ -2,7 +2,7 @@ package version
 
 import semver "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/coreos/go-semver/semver"
 
-var currentVersion = semver.Version{
+var currentVersion = &semver.Version{
 	Major: 0,
 	Minor: 1,
 	Patch: 0,
@@ -13,8 +13,16 @@ func Current() *SemVer {
 	return toPBSemVer(currentVersion)
 }
 
+// Compatible checks wether two versions are compatible
+func Compatible(a, b *SemVer) bool {
+	aConv := fromPBSemVer(a)
+	bConv := fromPBSemVer(b)
+	return aConv.LessThan(*bConv)
+}
+
 // toPBSemVar converts a coreos/semver to our protobuf SemVer
-func toPBSemVer(in semver.Version) (out *SemVer) {
+func toPBSemVer(in *semver.Version) (out *SemVer) {
+
 	return &SemVer{
 		Major: &in.Major,
 		Minor: &in.Minor,
@@ -23,7 +31,7 @@ func toPBSemVer(in semver.Version) (out *SemVer) {
 }
 
 // toPBSemVar converts our protobuf SemVer to a coreos/semver
-func fromPBSemVer(in SemVer) *semver.Version {
+func fromPBSemVer(in *SemVer) *semver.Version {
 	return &semver.Version{
 		Major: *in.Major,
 		Minor: *in.Minor,