diff --git a/src/engine_robust.cc b/src/engine_robust.cc
index cd393f445..44497bfbe 100644
--- a/src/engine_robust.cc
+++ b/src/engine_robust.cc
@@ -9,6 +9,7 @@
 #define NOMINMAX
 #include <limits>
 #include <utility>
+#include "./io.h"
 #include "./utils.h"
 #include "./engine_robust.h"
 
@@ -16,6 +17,7 @@ namespace rabit {
 namespace engine {
 AllReduceRobust::AllReduceRobust(void) {
   result_buffer_round = 1;
+  seq_counter = 0;
 }
 /*!
  * \brief perform in-place allreduce, on sendrecvbuf 
@@ -58,9 +60,26 @@ void AllReduceRobust::AllReduce(void *sendrecvbuf_,
  * \param root the root worker id to broadcast the data
  */
 void AllReduceRobust::Broadcast(void *sendrecvbuf_, size_t total_size, int root) {
-  utils::Assert(TryBroadcast(sendrecvbuf_, total_size, root) == kSuccess,
-                "AllReduce failed");
-  // TODO
+  bool recovered = RecoverExec(sendrecvbuf_, total_size, 0, seq_counter);
+  // now we are free to remove the last result, if any
+  if (resbuf.LastSeqNo() != -1 &&
+      (resbuf.LastSeqNo() % result_buffer_round != rank % result_buffer_round)) {
+    resbuf.DropLast();
+  }
+  void *temp = resbuf.AllocTemp(1, total_size);
+  while (true) {
+    if (recovered) {
+      std::memcpy(temp, sendrecvbuf_, total_size); break;
+    } else {
+      if (CheckAndRecover(TryBroadcast(sendrecvbuf_, total_size, root))) {
+        std::memcpy(temp, sendrecvbuf_, total_size); break;
+      } else {
+        recovered = RecoverExec(sendrecvbuf_, total_size, 0, seq_counter);
+      }
+    } 
+  }
+  resbuf.PushTemp(seq_counter, 1, total_size);
+  seq_counter += 1;
 }
 /*!
  * \brief load latest check point
@@ -69,15 +88,43 @@ void AllReduceRobust::Broadcast(void *sendrecvbuf_, size_t total_size, int root)
  *   false if there was no stored checkpoint, means we are start over gain
  */
 bool AllReduceRobust::LoadCheckPoint(utils::ISerializable *p_model) {
-  // TODO
-  return false;
+  // check if we succesfll
+  if (RecoverExec(NULL, 0, ActionSummary::kLoadCheck, ActionSummary::kMaxSeq)) {
+    // if loaded model is empty, this simply means we did not call checkpoint yet
+    // ask caller to reinit model
+    if (checked_model.length() == 0) return false;
+    // load from buffer
+    utils::MemoryBufferStream fs(&checked_model);
+    p_model->Load(fs);
+    // reset result buffer
+    resbuf.Clear(); seq_counter = 0;
+    // run another phase of check ack, if recovered from data
+    utils::Assert(RecoverExec(NULL, 0, ActionSummary::kCheckAck, ActionSummary::kMaxSeq),
+                  "check ack must return true");
+    return true;
+  } else {
+    // nothing loaded, a fresh start, everyone init model
+    return false;
+  }
 }
 /*!
  * \brief checkpoint the model, meaning we finished a stage of execution
  * \param p_model pointer to the model
  */
 void AllReduceRobust::CheckPoint(const utils::ISerializable &model) {
-  // TODO
+  // save model
+  checked_model.resize(0);
+  utils::MemoryBufferStream fs(&checked_model);
+  model.Save(fs);
+  utils::Check(checked_model.length() != 0, "CheckPoint: empty model, model.Save must save something");
+  // execute checkpoint, note: when checkpoint existing, load will not happen
+  utils::Assert(RecoverExec(NULL, 0, ActionSummary::kCheckPoint, ActionSummary::kMaxSeq),
+                "check point must return true");
+  // reset result buffer
+  resbuf.Clear(); seq_counter = 0;  
+  // execute check ack step, load happens here
+  utils::Assert(RecoverExec(NULL, 0, ActionSummary::kCheckAck, ActionSummary::kMaxSeq),
+                "check ack must return true");  
 }
 /*!
  * \brief reset the all the existing links by sending Out-of-Band message marker
diff --git a/src/engine_robust.h b/src/engine_robust.h
index 0dbf31852..703a54469 100644
--- a/src/engine_robust.h
+++ b/src/engine_robust.h
@@ -154,7 +154,7 @@ class AllReduceRobust : public AllReduceBase {
       rptr_.clear(); rptr_.push_back(0);
       data_.clear();
     }
-    // allocate temporal space for 
+    // allocate temporal space
     inline void *AllocTemp(size_t type_nbytes, size_t count) {
       size_t size = type_nbytes * count;
       size_t nhop = (size + sizeof(uint64_t) - 1) / sizeof(uint64_t);
diff --git a/src/io.h b/src/io.h
index 913acaa9a..ed01545f2 100644
--- a/src/io.h
+++ b/src/io.h
@@ -91,6 +91,7 @@ class IStream {
 
 /*! \brief interface of se*/
 class ISerializable {
+ public:
   /*! \brief load the model from file */
   virtual void Load(IStream &fi) = 0;
   /*! \brief save the model to the stream*/