diff --git a/configure.ac b/configure.ac
index 97ebbc1..e794d0a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -51,6 +51,8 @@ AC_CHECK_LIB([cunit], [CU_initialize_registry],
              [have_cunit=yes], [have_cunit=no])
 AM_CONDITIONAL([HAVE_CUNIT], [ test "x${have_cunit}" = "xyes" ])
 
+AC_SEARCH_LIBS([clock_gettime], [rt])
+
 # Checks for header files.
 AC_CHECK_HEADERS([ \
   arpa/inet.h \
@@ -58,6 +60,7 @@ AC_CHECK_HEADERS([ \
   stdint.h \
   stdlib.h \
   string.h \
+  time.h \
   unistd.h \
 ])
 
diff --git a/lib/includes/spdylay/spdylay.h b/lib/includes/spdylay/spdylay.h
index 73b628c..93fed61 100644
--- a/lib/includes/spdylay/spdylay.h
+++ b/lib/includes/spdylay/spdylay.h
@@ -179,11 +179,18 @@ typedef void (*spdylay_on_invalid_ctrl_recv_callback)
 (spdylay_session *session, spdylay_frame_type type, spdylay_frame *frame,
  void *user_data);
 
+/*
+ * Callback function invoked when PING reply is received from peer.
+ */
+typedef void (*spdylay_on_ping_recv_callback)
+(spdylay_session *session, const struct timespec *rtt, void *user_data);
+
 typedef struct {
   spdylay_send_callback send_callback;
   spdylay_recv_callback recv_callback;
   spdylay_on_ctrl_recv_callback on_ctrl_recv_callback;
   spdylay_on_invalid_ctrl_recv_callback on_invalid_ctrl_recv_callback;
+  spdylay_on_ping_recv_callback on_ping_recv_callback;
 } spdylay_session_callbacks;
 
 int spdylay_session_client_new(spdylay_session **session_ptr,
@@ -215,6 +222,8 @@ int spdylay_reply_submit(spdylay_session *session,
                          int32_t stream_id, const char **nv,
                          spdylay_data_provider *data_prd);
 
+int spdylay_submit_ping(spdylay_session *session);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/lib/spdylay_session.c b/lib/spdylay_session.c
index fbc605b..7fb6cfa 100644
--- a/lib/spdylay_session.c
+++ b/lib/spdylay_session.c
@@ -71,8 +71,14 @@ int spdylay_session_client_new(spdylay_session **session_ptr,
     return SPDYLAY_ERR_NOMEM;
   }
   memset(*session_ptr, 0, sizeof(spdylay_session));
+
+  /* IDs for use in client */
   (*session_ptr)->next_stream_id = 1;
   (*session_ptr)->last_recv_stream_id = 0;
+  (*session_ptr)->next_unique_id = 1;
+
+  (*session_ptr)->last_ping_unique_id = 0;
+  memset(&(*session_ptr)->last_ping_time, 0, sizeof(struct timespec));
 
   r = spdylay_zlib_deflate_hd_init(&(*session_ptr)->hd_deflater);
   if(r != 0) {
@@ -131,10 +137,12 @@ static void spdylay_outbound_item_free(spdylay_outbound_item *item)
   case SPDYLAY_RST_STREAM:
     spdylay_frame_rst_stream_free(&item->frame->rst_stream);
     break;
+  case SPDYLAY_PING:
+    spdylay_frame_ping_free(&item->frame->ping);
+    break;
   case SPDYLAY_HEADERS:
-    /* Currently we don't have any API to send HEADERS frame, so this
-       is unreachable. */
-    abort();
+    spdylay_frame_headers_free(&item->frame->headers);
+    break;
   case SPDYLAY_DATA:
     spdylay_frame_data_free(&item->frame->data);
     break;
@@ -195,6 +203,10 @@ int spdylay_session_add_frame(spdylay_session *session,
     }
     break;
   }
+  case SPDYLAY_PING:
+    /* Ping has "height" priority. Give it -1. */
+    item->pri = -1;
+    break;
   case SPDYLAY_HEADERS:
     /* Currently we don't have any API to send HEADERS frame, so this
        is unreachable. */
@@ -339,6 +351,12 @@ ssize_t spdylay_session_prep_frame(spdylay_session *session,
     }
     break;
   }
+  case SPDYLAY_PING:
+    framebuflen = spdylay_frame_pack_ping(&framebuf, &item->frame->ping);
+    if(framebuflen < 0) {
+      return framebuflen;
+    }
+    break;
   case SPDYLAY_HEADERS:
     /* Currently we don't have any API to send HEADERS frame, so this
        is unreachable. */
@@ -370,7 +388,7 @@ static void spdylay_active_outbound_item_reset
   memset(aob, 0, sizeof(spdylay_active_outbound_item));
 }
 
-static spdylay_outbound_item* spdylay_session_get_ob_pq_top
+spdylay_outbound_item* spdylay_session_get_ob_pq_top
 (spdylay_session *session)
 {
   return (spdylay_outbound_item*)spdylay_pq_top(&session->ob_pq);
@@ -401,6 +419,13 @@ static int spdylay_session_after_frame_sent(spdylay_session *session)
   case SPDYLAY_RST_STREAM:
     spdylay_session_close_stream(session, frame->rst_stream.stream_id);
     break;
+  case SPDYLAY_PING:
+    /* We record the time now and show application code RTT when
+       reply PING is received. */
+    session->last_ping_unique_id = frame->ping.unique_id;
+    /* TODO If clock_gettime() fails, what should we do? */
+    clock_gettime(CLOCK_MONOTONIC, &session->last_ping_time);
+    break;
   case SPDYLAY_HEADERS:
     /* Currently we don't have any API to send HEADERS frame, so this
        is unreachable. */
@@ -688,6 +713,39 @@ int spdylay_session_on_syn_reply_received(spdylay_session *session,
   return r;
 }
 
+int spdylay_session_on_ping_received(spdylay_session *session,
+                                     spdylay_frame *frame)
+{
+  int r = 0;
+  if(frame->ping.unique_id != 0) {
+    if(session->last_ping_unique_id == frame->ping.unique_id) {
+      /* This is ping reply from peer */
+      struct timespec rtt;
+      clock_gettime(CLOCK_MONOTONIC, &rtt);
+      rtt.tv_nsec -= session->last_ping_time.tv_nsec;
+      if(rtt.tv_nsec < 0) {
+        rtt.tv_nsec += 1000000000;
+        --rtt.tv_sec;
+      }
+      rtt.tv_sec -= session->last_ping_time.tv_sec;
+      /* Assign 0 to last_ping_unique_id so that we can ignore same
+         ID. */
+      session->last_ping_unique_id = 0;
+      if(session->callbacks.on_ping_recv_callback) {
+        session->callbacks.on_ping_recv_callback(session, &rtt,
+                                                 session->user_data);
+      }
+      spdylay_session_call_on_ctrl_frame_received(session, SPDYLAY_PING, frame);
+    } else if((session->server && frame->ping.unique_id % 2 == 1) ||
+              (!session->server && frame->ping.unique_id % 2 == 0)) {
+      /* Peer sent ping, so ping it back */
+      r = spdylay_session_add_ping(session, frame->ping.unique_id);
+      spdylay_session_call_on_ctrl_frame_received(session, SPDYLAY_PING, frame);
+    }
+  }
+  return r;
+}
+
 int spdylay_session_on_headers_received(spdylay_session *session,
                                         spdylay_frame *frame)
 {
@@ -770,6 +828,17 @@ int spdylay_session_process_ctrl_frame(spdylay_session *session)
       spdylay_frame_syn_reply_free(&frame.syn_reply);
     }
     break;
+  case SPDYLAY_PING:
+    r = spdylay_frame_unpack_ping(&frame.ping,
+                                  session->iframe.headbuf,
+                                  sizeof(session->iframe.headbuf),
+                                  session->iframe.buf,
+                                  session->iframe.len);
+    if(r == 0) {
+      r = spdylay_session_on_ping_received(session, &frame);
+      spdylay_frame_ping_free(&frame.ping);
+    }
+    break;
   case SPDYLAY_HEADERS:
     r = spdylay_frame_unpack_headers(&frame.headers,
                                      session->iframe.headbuf,
@@ -890,13 +959,35 @@ int spdylay_session_want_write(spdylay_session *session)
   return session->aob.item != NULL || !spdylay_pq_empty(&session->ob_pq);
 }
 
+int spdylay_session_add_ping(spdylay_session *session, uint32_t unique_id)
+{
+  int r;
+  spdylay_frame *frame;
+  frame = malloc(sizeof(spdylay_frame));
+  if(frame == NULL) {
+    return SPDYLAY_ERR_NOMEM;
+  }
+  spdylay_frame_ping_init(&frame->ping, unique_id);
+  r = spdylay_session_add_frame(session, SPDYLAY_PING, frame);
+  if(r != 0) {
+    spdylay_frame_ping_free(&frame->ping);
+    free(frame);
+  }
+  return r;
+}
+
+int spdylay_submit_ping(spdylay_session *session)
+{
+  return spdylay_session_add_ping(session,
+                                  spdylay_session_get_next_unique_id(session));
+}
+
 int spdylay_reply_submit(spdylay_session *session,
                          int32_t stream_id, const char **nv,
                          spdylay_data_provider *data_prd)
 {
   int r;
   spdylay_frame *frame;
-  spdylay_frame *data_frame = NULL;
   char **nv_copy;
   uint8_t flags = 0;
   frame = malloc(sizeof(spdylay_frame));
@@ -920,6 +1011,7 @@ int spdylay_reply_submit(spdylay_session *session,
     return r;
   }
   if(data_prd != NULL) {
+    spdylay_frame *data_frame;
     /* TODO If error is not FATAL, we should add RST_STREAM frame to
        cancel this stream. */
     data_frame = malloc(sizeof(spdylay_frame));
@@ -1001,3 +1093,15 @@ ssize_t spdylay_session_pack_data_overwrite(spdylay_session *session,
   frame->flags = flags;
   return r+8;
 }
+
+uint32_t spdylay_session_get_next_unique_id(spdylay_session *session)
+{
+  if(session->next_unique_id > SPDYLAY_MAX_UNIQUE_ID) {
+    if(session->server) {
+      session->next_unique_id = 2;
+    } else {
+      session->next_unique_id = 1;
+    }
+  }
+  return session->next_unique_id++;
+}
diff --git a/lib/spdylay_session.h b/lib/spdylay_session.h
index 90f72de..e606ab8 100644
--- a/lib/spdylay_session.h
+++ b/lib/spdylay_session.h
@@ -29,6 +29,8 @@
 #  include <config.h>
 #endif /* HAVE_CONFIG_H */
 
+#include <time.h>
+
 #include <spdylay/spdylay.h>
 #include "spdylay_pq.h"
 #include "spdylay_map.h"
@@ -62,6 +64,10 @@ typedef enum {
 
 #define SPDYLAY_HEAD_LEN 8
 
+/* Maximum unique ID in use for PING. If unique ID exeeds this number,
+   it wraps to 1 (client) or 2 (server) */
+#define SPDYLAY_MAX_UNIQUE_ID ((1u << 31)-1)
+
 typedef struct {
   spdylay_inbound_state state;
   uint8_t headbuf[SPDYLAY_HEAD_LEN];
@@ -77,7 +83,10 @@ typedef struct spdylay_session {
   uint8_t server;
   int32_t next_stream_id;
   int32_t last_recv_stream_id;
-  
+  /* Counter of unique ID of PING. Wraps when it exceeds
+     SPDYLAY_MAX_UNIQUE_ID */
+  uint32_t next_unique_id;
+
   spdylay_map /* <spdylay_stream*> */ streams;
   spdylay_pq /* <spdylay_outbound_item*> */ ob_pq;
 
@@ -89,6 +98,11 @@ typedef struct spdylay_session {
   spdylay_zlib hd_deflater;
   spdylay_zlib hd_inflater;
 
+  /* The last unique ID sent to the peer. */
+  uint32_t last_ping_unique_id;
+  /* Time stamp when last ping is sent. */
+  struct timespec last_ping_time;
+
   spdylay_session_callbacks callbacks;
   void *user_data;
 } spdylay_session;
@@ -102,6 +116,8 @@ int spdylay_session_add_frame(spdylay_session *session,
 int spdylay_session_add_rst_stream(spdylay_session *session,
                                    int32_t stream_id, uint32_t status_code);
 
+int spdylay_session_add_ping(spdylay_session *session, uint32_t unique_id);
+
 /*
  * Creates new stream in |session| with stream ID |stream_id|,
  * priority |pri| and flags |flags|. Currently, |flags| &
@@ -173,4 +189,15 @@ ssize_t spdylay_session_pack_data_overwrite(spdylay_session *session,
                                             uint8_t *buf, size_t len,
                                             spdylay_data *frame);
 
+/*
+ * Returns next unique ID which can be used with PING.
+ */
+uint32_t spdylay_session_get_next_unique_id(spdylay_session *session);
+
+/*
+ * Returns top of outbound frame queue. This function returns NULL if
+ * queue is empty.
+ */
+spdylay_outbound_item* spdylay_session_get_ob_pq_top(spdylay_session *session);
+
 #endif /* SPDYLAY_SESSION_H */
diff --git a/tests/main.c b/tests/main.c
index 531c737..fbd4d14 100644
--- a/tests/main.c
+++ b/tests/main.c
@@ -84,6 +84,8 @@ int main()
                    test_spdylay_session_reply_fail) ||
       !CU_add_test(pSuite, "session_on_headers_received",
                    test_spdylay_session_on_headers_received) ||
+      !CU_add_test(pSuite, "session_on_ping_received",
+                   test_spdylay_session_on_ping_received) ||
       !CU_add_test(pSuite, "frame_unpack_nv", test_spdylay_frame_unpack_nv) ||
       !CU_add_test(pSuite, "frame_count_nv_space",
                    test_spdylay_frame_count_nv_space) ||
diff --git a/tests/spdylay_session_test.c b/tests/spdylay_session_test.c
index cf63edc..8507d03 100644
--- a/tests/spdylay_session_test.c
+++ b/tests/spdylay_session_test.c
@@ -49,7 +49,7 @@ typedef struct {
 typedef struct {
   accumulator *acc;
   scripted_data_feed *df;
-  int valid, invalid;
+  int valid, invalid, ping_recv;
   size_t data_source_length;
 } my_user_data;
 
@@ -122,6 +122,14 @@ static void on_invalid_ctrl_recv_callback(spdylay_session *session,
   ++ud->invalid;
 }
 
+static void on_ping_recv_callback(spdylay_session *session,
+                                  const struct timespec *rtt,
+                                  void *user_data)
+{
+  my_user_data *ud = (my_user_data*)user_data;
+  ++ud->ping_recv;
+}
+
 static ssize_t fixed_length_data_source_read_callback
 (spdylay_session *session, uint8_t *buf, size_t len, int *eof,
  spdylay_data_source *source, void *user_data)
@@ -533,3 +541,44 @@ void test_spdylay_session_on_headers_received()
   spdylay_frame_headers_free(&frame.headers);
   spdylay_session_del(session);
 }
+
+void test_spdylay_session_on_ping_received()
+{
+  spdylay_session *session;
+  spdylay_session_callbacks callbacks = {
+    NULL,
+    NULL,
+    on_ctrl_recv_callback,
+    on_invalid_ctrl_recv_callback,
+    on_ping_recv_callback
+  };
+  my_user_data user_data;
+  const char *nv[] = { NULL };
+  spdylay_frame frame;
+  spdylay_outbound_item *top;
+  uint32_t unique_id;
+  user_data.valid = 0;
+  user_data.invalid = 0;
+  user_data.ping_recv = 0;
+
+  spdylay_session_client_new(&session, &callbacks, &user_data);
+  unique_id = 2;
+  spdylay_frame_ping_init(&frame.ping, unique_id);
+
+  CU_ASSERT(0 == spdylay_session_on_ping_received(session, &frame));
+  CU_ASSERT(1 == user_data.valid);
+  CU_ASSERT(0 == user_data.ping_recv);
+  top = spdylay_session_get_ob_pq_top(session);
+  CU_ASSERT(SPDYLAY_PING == top->frame_type);
+  CU_ASSERT(unique_id == top->frame->ping.unique_id);
+
+  session->last_ping_unique_id = 1;
+  frame.ping.unique_id = 1;
+
+  CU_ASSERT(0 == spdylay_session_on_ping_received(session, &frame));
+  CU_ASSERT(2 == user_data.valid);
+  CU_ASSERT(1 == user_data.ping_recv);
+
+  spdylay_frame_ping_free(&frame.ping);
+  spdylay_session_del(session);
+}
diff --git a/tests/spdylay_session_test.h b/tests/spdylay_session_test.h
index cf4da3b..153ef68 100644
--- a/tests/spdylay_session_test.h
+++ b/tests/spdylay_session_test.h
@@ -35,5 +35,6 @@ void test_spdylay_session_send_syn_reply();
 void test_spdylay_reply_submit();
 void test_spdylay_session_reply_fail();
 void test_spdylay_session_on_headers_received();
+void test_spdylay_session_on_ping_received();
 
 #endif // SPDYLAY_SESSION_TEST_H