diff --git a/tools/taish/Makefile b/tools/taish/Makefile
index 77a500a..ac18c08 100644
--- a/tools/taish/Makefile
+++ b/tools/taish/Makefile
@@ -23,8 +23,12 @@ lib: proto $(LIB_OBJS)
 .cpp.o:
 	$(CC) $(CFLAGS) $(INCLUDE) -c -o $@ $<
 
-proto: proto/tai.proto
+proto: lib/tai.grpc.pb.cc lib/tai.grpc.pb.h lib/tai.pb.cc lib/tai.pb.h
+
+lib/tai.pb.cc lib/tai.pb.h: proto/tai.proto
 	protoc --cpp_out=./lib -I proto tai.proto
+
+lib/tai.grpc.pb.cc lib/tai.grpc.pb.h: proto/tai.proto
 	protoc --grpc_out=./lib --plugin=protoc-gen-grpc=`which grpc_cpp_plugin` -I proto tai.proto
 
 docker:
diff --git a/tools/taish/client/taish.py b/tools/taish/client/taish.py
index 9fa6255..36d9e4f 100755
--- a/tools/taish/client/taish.py
+++ b/tools/taish/client/taish.py
@@ -33,7 +33,8 @@ def show_help(hidden=False):
     d = [['list', 'list detected TAI objects'],
     ['list-attr', 'list attributes of the selected TAI object'],
     ['set <attr-name> <attr-value>', 'set an attribute'],
-    ['get <attr-name> [<attr-value>]', 'get an attribute']]
+    ['get <attr-name> [<attr-value>]', 'get an attribute'],
+    ['monitor', 'monitor state change']]
     print(tabulate(d, headers=['command', 'description']))
 
 def show_modules(modules):
@@ -66,6 +67,24 @@ def list_attr(stub, module, netif, hostif):
         d.append([m.short_name, 'ro' if m.is_readonly else 'r/w', m.usage, 'custom' if m.attr_id > TAI_ATTR_CUSTOM_RANGE_START else 'official'])
     print(tabulate(d, headers=['name', 'type', 'value', 'range']))
 
+def monitor(stub, module, netif, hostif):
+    req = tai_pb2.MonitorRequest()
+    req.oid = netif.oid
+
+    m = get_attribute_metadata(stub, module, netif, hostif)
+
+    try:
+        for res in stub.Monitor(req):
+            a = [ v.short_name for v in m if v.attr_id == res.attribute.attr_id ]
+            if len(a) == 1:
+                print('{} | {}'.format(a[0], res.attribute.value))
+            elif len(a) == 0:
+                print('0x{:x} | {}'.format(res.attribute.attr_id, res.attribute.value))
+            else:
+                print('error: more than one metadata matched for id 0x{:x}: {}'.format(res.attribute.attr_id, a))
+    except KeyboardInterrupt:
+        pass
+
 def get_attr(stub, module, netif, hostif, cmds):
     if not module:
         print ('no module selected.')
@@ -169,7 +188,7 @@ class TAIShellCompleter(Completer):
         if len(t) == 1:
             cmds = ['list', 'module', 'help', 'quit', 'exit']
             if self.module != None:
-                cmds += ['list-attr', 'netif', 'hostif', 'set', 'get']
+                cmds += ['list-attr', 'netif', 'hostif', 'set', 'get', 'monitor']
 
             for c in cmds:
                 if c.startswith(t[0]):
@@ -277,6 +296,8 @@ def loop(stub, modules):
                 print(get_attr(stub, module, netif, hostif, cmds))
             elif cmd == 'set':
                 set_attr(stub, module, netif, hostif, cmds)
+            elif cmd == 'monitor':
+                monitor(stub, module, netif, hostif)
             elif cmd in ['exit', 'quit', 'q']:
                 if netif:
                     netif = None
@@ -358,6 +379,8 @@ def main():
             set_attr(stub, module, netif, hostif, args)
         elif args[0] == 'help':
             show_help()
+        elif args[0] == 'monitor':
+            monitor(stub, module, netif, hostif)
         else:
             print('unknown cmd: {}'.format(args[0]))
             show_help()
diff --git a/tools/taish/include/taigrpc.hpp b/tools/taish/include/taigrpc.hpp
index a6668e2..fb2786d 100644
--- a/tools/taish/include/taigrpc.hpp
+++ b/tools/taish/include/taigrpc.hpp
@@ -26,6 +26,11 @@
 #include "tai.h"
 #include "tai.grpc.pb.h"
 #include <grpcpp/grpcpp.h>
+#include <mutex>
+#include <condition_variable>
+#include <queue>
+#include <map>
+#include <iostream>
 
 struct tai_api_module_t
 {
@@ -62,6 +67,46 @@ class TAIAPIModuleList {
         uint32_t m_netif_size;
 };
 
+struct tai_notification_t {
+    tai_object_id_t oid;
+    tai_attribute_t const * const attr;
+};
+
+struct tai_subscription_t {
+    std::mutex mtx;
+    std::queue<tai_notification_t> q;
+    std::condition_variable cv;
+};
+
+class TAINotifier {
+    public:
+        TAINotifier() {};
+        int notify(const tai_notification_t& n);
+        int subscribe(void* id, tai_subscription_t* s) {
+            std::unique_lock<std::mutex> lk(mtx);
+            if ( m.find(id) != m.end() ) {
+                return -1;
+            }
+            m[id] = s;
+            return 0;
+        }
+        int desubscribe(void* id) {
+            std::unique_lock<std::mutex> lk(mtx);
+            if ( m.find(id) == m.end() ) {
+                return -1;
+            }
+            m.erase(id);
+            return 0;
+        }
+        int size() {
+            std::unique_lock<std::mutex> lk(mtx);
+            return m.size();
+        }
+    private:
+        std::map<void*, tai_subscription_t*> m;
+        std::mutex mtx;
+};
+
 class TAIServiceImpl final : public tai::TAI::Service {
     public:
         TAIServiceImpl(const tai_api_method_table_t* const api) : m_api(api) {};
@@ -70,8 +115,19 @@ class TAIServiceImpl final : public tai::TAI::Service {
         ::grpc::Status GetAttributeMetadata(::grpc::ServerContext* context, const ::tai::GetAttributeMetadataRequest* request, ::tai::GetAttributeMetadataResponse* response);
         ::grpc::Status GetAttribute(::grpc::ServerContext* context, const ::tai::GetAttributeRequest* request, ::tai::GetAttributeResponse* response);
         ::grpc::Status SetAttribute(::grpc::ServerContext* context, const ::tai::SetAttributeRequest* request, ::tai::SetAttributeResponse* response);
+        ::grpc::Status Monitor(::grpc::ServerContext* context, const ::tai::MonitorRequest* request, ::grpc::ServerWriter< ::tai::MonitorResponse>* writer);
+        void notify(tai_object_id_t oid, tai_attribute_t const * const attribute);
     private:
+        TAINotifier* get_notifier(tai_object_id_t oid) {
+            std::unique_lock<std::mutex> lk(m_mtx);
+            if ( m_notifiers.find(oid) == m_notifiers.end() ) {
+                m_notifiers[oid] = new TAINotifier();
+            }
+            return m_notifiers[oid];
+        }
         const tai_api_method_table_t* const m_api;
+        std::map<tai_object_id_t, TAINotifier*> m_notifiers;
+        std::mutex m_mtx;
 };
 
 #endif // __TAIGRPC_HPP__
diff --git a/tools/taish/lib/server.cpp b/tools/taish/lib/server.cpp
index 5886f50..c7d83ad 100644
--- a/tools/taish/lib/server.cpp
+++ b/tools/taish/lib/server.cpp
@@ -23,10 +23,36 @@
 #include "taigrpc.hpp"
 #include "taimetadata.h"
 #include <sstream>
+#include <chrono>
 
 using grpc::Status;
 using grpc::StatusCode;
 
+static int _serialize_attribute(const tai_attr_metadata_t* meta, const tai_attribute_t* attr, std::string& out) {
+    tai_serialize_option_t option{true, true, true};
+    size_t buf_size = 64;
+    char bbuf[64] = {0}, *buf = bbuf;
+    auto count = tai_serialize_attribute(buf, buf_size, meta, attr, &option);
+    if ( count < 0 ) {
+        return count;
+    }
+    if ( count > buf_size ) {
+        buf_size = count + 1;
+        buf = new char[buf_size];
+        count = tai_serialize_attribute(buf, buf_size, meta, attr, &option);
+        if ( count < 0 || count > buf_size ) {
+            return count;
+        }
+        out = buf;
+    }
+    out = buf;
+    // check if buf is dynamically allocated
+    if ( buf != bbuf ) {
+        delete[] buf;
+    }
+    return 0;
+}
+
 TAIAPIModuleList::TAIAPIModuleList(uint32_t module_size, uint32_t hostif_size, uint32_t netif_size) : m_module_size(module_size), m_hostif_size(hostif_size), m_netif_size(netif_size) {
     m_list.count = module_size;
     m_list.list = new tai_api_module_t[module_size];
@@ -278,8 +304,8 @@ static void convert_metadata(const tai_attr_metadata_t* const src, ::tai::Attrib
     attr.id = id;
     tai_serialize_option_t option{true, true, true};
     tai_alloc_info_t alloc_info = { .list_size = 16 };
-    char bbuf[64] = {0}, *buf = bbuf;
-    size_t buf_size = 64, count = 0;
+    size_t count = 0;
+    std::string value;
 
 again:
     if( tai_metadata_alloc_attr_value(meta, &attr, &alloc_info) != TAI_STATUS_SUCCESS ) {
@@ -319,27 +345,15 @@ again:
         goto err;
     }
 
-    count = tai_serialize_attribute(buf, buf_size, meta, &attr, &option);
-    if ( count < 0 ) {
+    if ( _serialize_attribute(meta, &attr, value) != 0 ) {
+        ret = TAI_STATUS_FAILURE;
         goto err;
     }
-    if ( count > buf_size ) {
-        buf_size = count + 1;
-        buf = new char[buf_size];
-        count = tai_serialize_attribute(buf, buf_size, meta, &attr, &option);
-        if ( count < 0 || count > buf_size ) {
-            goto err;
-        }
-    }
 
     res = response->mutable_attribute();
     res->set_attr_id(id);
-    res->set_value(buf, count);
+    res->set_value(value);
 err:
-    // check if buf is dynamically allocated
-    if ( buf != bbuf ) {
-        delete[] buf;
-    }
     if ( tai_metadata_free_attr_value(meta, &attr, &alloc_info) != TAI_STATUS_SUCCESS ) {
         return Status(StatusCode::UNKNOWN, "failed to free value");
     }
@@ -398,3 +412,148 @@ err:
     }
     return Status::OK;
 }
+
+int TAINotifier::notify(const tai_notification_t& n) {
+    auto oid = n.oid;
+    auto type = tai_object_type_query(oid);
+    auto meta = tai_metadata_get_attr_metadata(type, n.attr->id);
+    tai_alloc_info_t alloc_info;
+    alloc_info.reference = n.attr;
+
+    std::unique_lock<std::mutex> lk(mtx);
+    for ( auto& s : m ) {
+        tai_attribute_t *attr = new tai_attribute_t();
+        attr->id = n.attr->id;
+
+        if ( tai_metadata_alloc_attr_value(meta, attr, &alloc_info) != TAI_STATUS_SUCCESS ) {
+            return -1;
+        }
+
+        if ( tai_metadata_deepcopy_attr_value(meta, n.attr, attr) != TAI_STATUS_SUCCESS ) {
+            return -1;
+        }
+
+        tai_notification_t nn{ oid, attr };
+
+        auto v = s.second;
+        std::unique_lock<std::mutex> lk(v->mtx);
+        v->q.push(nn);
+        v->cv.notify_one();
+    }
+    return 0;
+}
+
+void monitor_callback(void* context, tai_object_id_t oid, tai_attribute_t const * const attribute) {
+    if ( context == nullptr ) {
+        return;
+    }
+    auto impl = static_cast<TAIServiceImpl*>(context);
+    impl->notify(oid, attribute);
+}
+
+void TAIServiceImpl::notify(tai_object_id_t oid, tai_attribute_t const * const attribute) {
+    std::unique_lock<std::mutex> lk(m_mtx);
+    auto n = m_notifiers[oid];
+    if ( n != nullptr ) {
+        n->notify(tai_notification_t{oid, attribute});
+    }
+}
+
+::grpc::Status TAIServiceImpl::Monitor(::grpc::ServerContext* context, const ::tai::MonitorRequest* request, ::grpc::ServerWriter< ::tai::MonitorResponse>* writer) {
+    auto oid = request->oid();
+    auto type = tai_object_type_query(oid);
+    tai_attribute_t attr = {0};
+    tai_status_t ret;
+
+    switch (type) {
+    case TAI_OBJECT_TYPE_NETWORKIF:
+        attr.id = TAI_NETWORK_INTERFACE_ATTR_NOTIFY;
+        ret = m_api->netif_api->get_network_interface_attribute(oid, &attr);
+        break;
+    default:
+        return Status(StatusCode::UNKNOWN, "unsupported object type");
+    }
+
+    if ( ret != TAI_STATUS_SUCCESS ) {
+        std::stringstream ss;
+        ss << "failed to get notify attribute: ret:" << std::hex << -ret;
+        return Status(StatusCode::UNKNOWN, ss.str());
+    }
+
+    auto notifier = get_notifier(oid);
+
+    if ( attr.value.notification.notify == nullptr ) {
+        attr.value.notification.notify = monitor_callback;
+        attr.value.notification.context = this;
+        ret = m_api->netif_api->set_network_interface_attribute(oid, &attr);
+        if ( ret != TAI_STATUS_SUCCESS ) {
+            std::stringstream ss;
+            ss << "failed to set notify attribute: ret:" << std::hex << -ret;
+            return Status(StatusCode::UNKNOWN, ss.str());
+        }
+    } else if ( attr.value.notification.notify != nullptr && notifier->size() == 0 ) {
+        return Status(StatusCode::UNKNOWN, "notify attribute is set by others");
+    }
+
+    tai_subscription_t s;
+
+    if ( notifier->subscribe(writer, &s) < 0 ) {
+        return Status(StatusCode::UNKNOWN, "failed to subscribe");
+    }
+
+    std::unique_lock<std::mutex> lk(s.mtx);
+    while(true) {
+        std::chrono::seconds sec(1);
+        auto pred = s.cv.wait_for(lk, sec, [&]{ return !s.q.empty(); });
+        if ( !pred ) { // queue is empty
+            if ( context->IsCancelled() ) {
+                break;
+            }
+            // writer is still alive continue
+            continue;
+        }
+        auto n = s.q.front();
+        s.q.pop();
+
+
+        ::tai::MonitorResponse res;
+        auto a = res.mutable_attribute();
+        auto meta = tai_metadata_get_attr_metadata(type, n.attr->id);
+
+        a->set_attr_id(n.attr->id);
+        std::string value;
+        _serialize_attribute(meta, n.attr, value);
+        a->set_value(value);
+
+        tai_attribute_t *attr = const_cast<tai_attribute_t*>(n.attr);
+        if ( tai_metadata_free_attr_value(meta, attr, nullptr) < 0 ) {
+            return Status(StatusCode::UNKNOWN, "failed to free attribute");
+        }
+
+        delete attr;
+
+        if (!writer->Write(res)) {
+            break;
+        }
+    }
+
+    if ( notifier->desubscribe(writer) < 0 ) {
+        return Status(StatusCode::UNKNOWN, "failed to desubscribe");
+    }
+
+    if ( notifier->size() == 0 ) {
+        std::unique_lock<std::mutex> lk(m_mtx);
+        delete notifier;
+        m_notifiers.erase(oid);
+        attr.value.notification.notify = nullptr;
+        attr.value.notification.context = nullptr;
+        ret = m_api->netif_api->set_network_interface_attribute(oid, &attr);
+        if ( ret != TAI_STATUS_SUCCESS ) {
+            std::stringstream ss;
+            ss << "failed to clear notify attribute: ret:" << std::hex << -ret;
+            return Status(StatusCode::UNKNOWN, ss.str());
+        }
+    }
+
+    return Status::OK;
+}
diff --git a/tools/taish/proto/tai.proto b/tools/taish/proto/tai.proto
index 32df3a1..855c82b 100644
--- a/tools/taish/proto/tai.proto
+++ b/tools/taish/proto/tai.proto
@@ -8,6 +8,7 @@ service TAI {
     rpc GetAttributeMetadata(GetAttributeMetadataRequest) returns (GetAttributeMetadataResponse);
     rpc GetAttribute(GetAttributeRequest) returns (GetAttributeResponse);
     rpc SetAttribute(SetAttributeRequest) returns (SetAttributeResponse);
+    rpc Monitor(MonitorRequest) returns (stream MonitorResponse);
 }
 
 enum TAIObjectType {
@@ -61,6 +62,14 @@ message SetAttributeRequest {
 message SetAttributeResponse {
 }
 
+message MonitorRequest {
+    uint64 oid = 1;
+}
+
+message MonitorResponse {
+    Attribute attribute = 1;
+}
+
 message Attribute {
     uint64 attr_id = 1;
     string value = 2;