diff --git a/src/ipc.cpp b/src/ipc.cpp
index f4c5fa8..a9916ce 100755
--- a/src/ipc.cpp
+++ b/src/ipc.cpp
@@ -20,6 +20,7 @@
 
 #include "libipc/utility/log.h"
 #include "libipc/utility/id_pool.h"
+#include "libipc/utility/scope_guard.h"
 #include "libipc/utility/utility.h"
 
 #include "libipc/memory/resource.h"
@@ -39,7 +40,7 @@ struct msg_t;
 
 template <std::size_t AlignSize>
 struct msg_t<0, AlignSize> {
-    msg_id_t     conn_;
+    msg_id_t     cc_id_;
     msg_id_t     id_;
     std::int32_t remain_;
     bool         storage_;
@@ -50,8 +51,8 @@ struct msg_t : msg_t<0, AlignSize> {
     std::aligned_storage_t<DataSize, AlignSize> data_ {};
 
     msg_t() = default;
-    msg_t(msg_id_t conn, msg_id_t id, std::int32_t remain, void const * data, std::size_t size)
-        : msg_t<0, AlignSize> {conn, id, remain, (data == nullptr) || (size == 0)} {
+    msg_t(msg_id_t cc_id, msg_id_t id, std::int32_t remain, void const * data, std::size_t size)
+        : msg_t<0, AlignSize> {cc_id, id, remain, (data == nullptr) || (size == 0)} {
         if (this->storage_) {
             if (data != nullptr) {
                 // copy storage-id
@@ -96,9 +97,21 @@ IPC_CONSTEXPR_ std::size_t align_chunk_size(std::size_t size) noexcept {
 }
 
 IPC_CONSTEXPR_ std::size_t calc_chunk_size(std::size_t size) noexcept {
-    return ipc::make_align(alignof(std::max_align_t), align_chunk_size(size));
+    return ipc::make_align(alignof(std::max_align_t), align_chunk_size(
+           ipc::make_align(alignof(std::max_align_t), sizeof(std::atomic<ipc::circ::cc_t>)) + size));
 }
 
+struct chunk_t {
+    std::atomic<ipc::circ::cc_t> &conns() noexcept {
+        return *reinterpret_cast<std::atomic<ipc::circ::cc_t> *>(this);
+    }
+
+    void *data() noexcept {
+        return reinterpret_cast<ipc::byte_t *>(this)
+             + ipc::make_align(alignof(std::max_align_t), sizeof(std::atomic<ipc::circ::cc_t>));
+    }
+};
+
 struct chunk_info_t {
     ipc::id_pool<> pool_;
     ipc::spin_lock lock_;
@@ -107,13 +120,13 @@ struct chunk_info_t {
         return ipc::id_pool<>::max_count * chunk_size;
     }
 
-    ipc::byte_t* chunks_mem() noexcept {
-        return reinterpret_cast<ipc::byte_t*>(this + 1);
+    ipc::byte_t *chunks_mem() noexcept {
+        return reinterpret_cast<ipc::byte_t *>(this + 1);
     }
 
-    ipc::byte_t* at(std::size_t chunk_size, ipc::storage_id_t id) noexcept {
+    chunk_t *at(std::size_t chunk_size, ipc::storage_id_t id) noexcept {
         if (id < 0) return nullptr;
-        return chunks_mem() + (chunk_size * id);
+        return reinterpret_cast<chunk_t *>(chunks_mem() + (chunk_size * id));
     }
 };
 
@@ -145,7 +158,7 @@ chunk_info_t *chunk_storage_info(std::size_t chunk_size) {
     return chunk_storages()[chunk_size].get_info(chunk_size);
 }
 
-std::pair<ipc::storage_id_t, void*> acquire_storage(std::size_t size) {
+std::pair<ipc::storage_id_t, void*> acquire_storage(std::size_t size, ipc::circ::cc_t conns) {
     std::size_t chunk_size = calc_chunk_size(size);
     auto info = chunk_storage_info(chunk_size);
     if (info == nullptr) return {};
@@ -156,7 +169,10 @@ std::pair<ipc::storage_id_t, void*> acquire_storage(std::size_t size) {
     auto id = info->pool_.acquire();
     info->lock_.unlock();
 
-    return { id, info->at(chunk_size, id) };
+    auto chunk = info->at(chunk_size, id);
+    if (chunk == nullptr) return {};
+    chunk->conns().store(conns, std::memory_order_relaxed);
+    return { id, chunk->data() };
 }
 
 void *find_storage(ipc::storage_id_t id, std::size_t size) {
@@ -167,7 +183,7 @@ void *find_storage(ipc::storage_id_t id, std::size_t size) {
     std::size_t chunk_size = calc_chunk_size(size);
     auto info = chunk_storage_info(chunk_size);
     if (info == nullptr) return nullptr;
-    return info->at(chunk_size, id);
+    return info->at(chunk_size, id)->data();
 }
 
 void release_storage(ipc::storage_id_t id, std::size_t size) {
@@ -183,13 +199,53 @@ void release_storage(ipc::storage_id_t id, std::size_t size) {
     info->lock_.unlock();
 }
 
+template <ipc::relat Rp, ipc::relat Rc>
+bool sub_rc(ipc::wr<Rp, Rc, ipc::trans::unicast>, 
+            std::atomic<ipc::circ::cc_t> &/*conns*/, ipc::circ::cc_t /*curr_conns*/, ipc::circ::cc_t /*conn_id*/) noexcept {
+    return true;
+}
+
+template <ipc::relat Rp, ipc::relat Rc>
+bool sub_rc(ipc::wr<Rp, Rc, ipc::trans::broadcast>, 
+            std::atomic<ipc::circ::cc_t> &conns, ipc::circ::cc_t curr_conns, ipc::circ::cc_t conn_id) noexcept {
+    auto last_conns = curr_conns & ~conn_id;
+    for (unsigned k = 0;;) {
+        auto chunk_conns  = conns.load(std::memory_order_acquire);
+        if (conns.compare_exchange_weak(chunk_conns, chunk_conns & last_conns, std::memory_order_release)) {
+            return (chunk_conns & last_conns) == 0;
+        }
+        ipc::yield(k);
+    }
+}
+
+template <typename Flag>
+void recycle_storage(ipc::storage_id_t id, std::size_t size, ipc::circ::cc_t curr_conns, ipc::circ::cc_t conn_id) {
+    if (id < 0) {
+        ipc::error("[recycle_storage] id is invalid: id = %ld, size = %zd\n", (long)id, size);
+        return;
+    }
+    std::size_t chunk_size = calc_chunk_size(size);
+    auto info = chunk_storage_info(chunk_size);
+    if (info == nullptr) return;
+
+    auto chunk = info->at(chunk_size, id);
+    if (chunk == nullptr) return;
+
+    if (!sub_rc(Flag{}, chunk->conns(), curr_conns, conn_id)) {
+        return;
+    }
+    info->lock_.lock();
+    info->pool_.release(id);
+    info->lock_.unlock();
+}
+
 template <typename MsgT>
-bool recycle_message(void* p) {
+bool clear_message(void* p) {
     auto msg = static_cast<MsgT*>(p);
     if (msg->storage_) {
         std::int32_t r_size = static_cast<std::int32_t>(ipc::data_length) + msg->remain_;
         if (r_size <= 0) {
-            ipc::error("[recycle_message] invalid msg size: %d\n", (int)r_size);
+            ipc::error("[clear_message] invalid msg size: %d\n", (int)r_size);
             return true;
         }
         release_storage(
@@ -278,8 +334,10 @@ struct queue_generator {
 template <typename Policy>
 struct detail_impl {
 
-using queue_t     = typename queue_generator<Policy>::queue_t;
-using conn_info_t = typename queue_generator<Policy>::conn_info_t;
+using policy_t    = Policy;
+using flag_t      = typename policy_t::flag_t;
+using queue_t     = typename queue_generator<policy_t>::queue_t;
+using conn_info_t = typename queue_generator<policy_t>::conn_info_t;
 
 constexpr static conn_info_t* info_of(ipc::handle_t h) noexcept {
     return static_cast<conn_info_t*>(h);
@@ -373,7 +431,8 @@ static bool send(F&& gen_push, ipc::handle_t h, void const * data, std::size_t s
         ipc::error("fail: send, que->ready_sending() == false\n");
         return false;
     }
-    if (que->elems()->connections(std::memory_order_relaxed) == 0) {
+    ipc::circ::cc_t conns = que->elems()->connections(std::memory_order_relaxed);
+    if (conns == 0) {
         ipc::error("fail: send, there is no receiver on this connection.\n");
         return false;
     }
@@ -386,7 +445,7 @@ static bool send(F&& gen_push, ipc::handle_t h, void const * data, std::size_t s
     auto msg_id   = acc->fetch_add(1, std::memory_order_relaxed);
     auto try_push = std::forward<F>(gen_push)(info_of(h), que, msg_id);
     if (size > ipc::large_msg_limit) {
-        auto   dat = acquire_storage(size);
+        auto   dat = acquire_storage(size, conns);
         void * buf = dat.second;
         if (buf != nullptr) {
             std::memcpy(buf, data, size);
@@ -426,7 +485,7 @@ static bool send(ipc::handle_t h, void const * data, std::size_t size, std::size
                 }, tm)) {
                 ipc::log("force_push: msg_id = %zd, remain = %d, size = %zd\n", msg_id, remain, size);
                 if (!que->force_push(
-                        recycle_message<typename queue_t::value_t>, 
+                        clear_message<typename queue_t::value_t>,
                         info->cc_id_, msg_id, remain, data, size)) {
                     return false;
                 }
@@ -467,15 +526,14 @@ static ipc::buff_t recv(ipc::handle_t h, std::size_t tm) {
     for (;;) {
         // pop a new message
         typename queue_t::value_t msg;
-        bool recycled = false;
-        if (!wait_for(info_of(h)->rd_waiter_, [que, &msg, &recycled] {
-                return !que->pop(msg, [&recycled](bool r) { recycled = r; });
+        if (!wait_for(info_of(h)->rd_waiter_, [que, &msg] {
+                return !que->pop(msg);
             }, tm)) {
             // pop failed, just return.
             return {};
         }
         info_of(h)->wt_waiter_.broadcast();
-        if ((info_of(h)->acc() != nullptr) && (msg.conn_ == info_of(h)->cc_id_)) {
+        if ((info_of(h)->acc() != nullptr) && (msg.cc_id_ == info_of(h)->cc_id_)) {
             continue; // ignore message to self
         }
         // msg.remain_ may minus & abs(msg.remain_) < data_length
@@ -490,12 +548,24 @@ static ipc::buff_t recv(ipc::handle_t h, std::size_t tm) {
             ipc::storage_id_t buf_id = *reinterpret_cast<ipc::storage_id_t*>(&msg.data_);
             void* buf = find_storage(buf_id, msg_size);
             if (buf != nullptr) {
-                if (recycled) {
-                    return ipc::buff_t{buf, msg_size, [](void* pmid, std::size_t size) {
-                        release_storage(ipc::detail::horrible_cast<ipc::storage_id_t>(pmid) - 1, size);
-                    }, ipc::detail::horrible_cast<void*>(buf_id + 1)};
-                } else {
+                struct recycle_t {
+                    ipc::storage_id_t storage_id;
+                    ipc::circ::cc_t   curr_conns;
+                    ipc::circ::cc_t   conn_id;
+                } *r_info = ipc::mem::alloc<recycle_t>(recycle_t{
+                    buf_id, que->elems()->connections(std::memory_order_relaxed), que->connected_id()
+                });
+                if (r_info == nullptr) {
+                    ipc::log("fail: ipc::mem::alloc<recycle_t>.\n");
                     return ipc::buff_t{buf, msg_size}; // no recycle
+                } else {
+                    return ipc::buff_t{buf, msg_size, [](void* p_info, std::size_t size) {
+                        auto r_info = static_cast<recycle_t *>(p_info);
+                        IPC_UNUSED_ auto finally = ipc::guard([r_info] {
+                            ipc::mem::free(r_info);
+                        });
+                        recycle_storage<flag_t>(r_info->storage_id, size, r_info->curr_conns, r_info->conn_id);
+                    }, r_info};
                 }
             } else {
                 ipc::log("fail: shm::handle for large message. msg_id: %zd, buf_id: %zd, size: %zd\n", msg.id_, buf_id, msg_size);
diff --git a/src/libipc/circ/elem_def.h b/src/libipc/circ/elem_def.h
index f2379e2..4003948 100755
--- a/src/libipc/circ/elem_def.h
+++ b/src/libipc/circ/elem_def.h
@@ -16,7 +16,7 @@ namespace circ {
 using u1_t = ipc::uint_t<8>;
 using u2_t = ipc::uint_t<32>;
 
-/** only supports max 32 connections */
+/** only supports max 32 connections in broadcast mode */
 using cc_t = u2_t;
 
 constexpr u1_t index_of(u2_t c) noexcept {
diff --git a/src/libipc/policy.h b/src/libipc/policy.h
index d2ad313..8959607 100755
--- a/src/libipc/policy.h
+++ b/src/libipc/policy.h
@@ -15,8 +15,10 @@ struct choose;
 
 template <typename Flag>
 struct choose<circ::elem_array, Flag> {
+    using flag_t = Flag;
+
     template <std::size_t DataSize, std::size_t AlignSize>
-    using elems_t = circ::elem_array<ipc::prod_cons_impl<Flag>, DataSize, AlignSize>;
+    using elems_t = circ::elem_array<ipc::prod_cons_impl<flag_t>, DataSize, AlignSize>;
 };
 
 } // namespace policy
diff --git a/test/test_ipc.cpp b/test/test_ipc.cpp
index 45590e3..16c076c 100755
--- a/test/test_ipc.cpp
+++ b/test/test_ipc.cpp
@@ -170,7 +170,7 @@ TEST(IPC, 1vN) {
     //test_sr<relat::single, relat::multi , trans::unicast  >("smu", 1, MultiMax);
     //test_sr<relat::multi , relat::multi , trans::unicast  >("mmu", 1, MultiMax);
     test_sr<relat::single, relat::multi , trans::broadcast>("smb", 1, MultiMax);
-    //test_sr<relat::multi , relat::multi , trans::broadcast>("mmb", 1, MultiMax);
+    test_sr<relat::multi , relat::multi , trans::broadcast>("mmb", 1, MultiMax);
 }
 
 TEST(IPC, Nv1) {