Created LinkService and added unit tests.

Change-Id: I1f2104c873e5a9e2df34074d36cddc823e3b3ec5
diff --git a/incubator/protobuf/models/src/main/proto/net/ConnectPointProto.proto b/incubator/protobuf/models/src/main/proto/net/ConnectPointProto.proto
index 3749b6f..e0444b4 100644
--- a/incubator/protobuf/models/src/main/proto/net/ConnectPointProto.proto
+++ b/incubator/protobuf/models/src/main/proto/net/ConnectPointProto.proto
@@ -7,8 +7,8 @@
     oneof element_id {
         // DeviceID as String DeviceId#toString
         string device_id = 1;
-
-        // TODO add support to other element_id if required
+        string host_id = 3;
+        string ip_element_id = 4;
     }
     // PortNumber as String PortNumber#toString
     string port_number = 2;
diff --git a/incubator/protobuf/models/src/main/proto/net/LinkProto.proto b/incubator/protobuf/models/src/main/proto/net/LinkProto.proto
index 77bb32b..9b41dc4 100644
--- a/incubator/protobuf/models/src/main/proto/net/LinkProto.proto
+++ b/incubator/protobuf/models/src/main/proto/net/LinkProto.proto
@@ -5,6 +5,7 @@
 
 import "net/link/LinkEnumsProto.proto";
 import "net/ConnectPointProto.proto";
+import "net/ProviderIdProto.proto";
 
 // Corresponds to org.onosproject.net.Link.
 message LinkProto {
@@ -13,6 +14,6 @@
     net.ConnectPointProto dst = 3;
     net.link.LinkTypeProto type = 4;
     map<string, string> annotations = 5;
-}
-
-
+    net.ProviderIdProto provider_id = 6;
+    bool isExpected = 7;
+}
\ No newline at end of file
diff --git a/incubator/protobuf/models/src/main/proto/net/ProviderIdProto.proto b/incubator/protobuf/models/src/main/proto/net/ProviderIdProto.proto
new file mode 100644
index 0000000..3e470c7
--- /dev/null
+++ b/incubator/protobuf/models/src/main/proto/net/ProviderIdProto.proto
@@ -0,0 +1,11 @@
+syntax = "proto3";
+option java_package = "org.onosproject.grpc.net.models";
+
+package net;
+
+// Corresponds to org.onosproject.net.provider.ProviderId
+message ProviderIdProto {
+    string scheme = 1;
+    string id = 2;
+    bool ancillary = 3;
+}
\ No newline at end of file