diff --git a/src/lte/model/lte-rlc-um.cc b/src/lte/model/lte-rlc-um.cc
index 794571591..19a276f0e 100644
--- a/src/lte/model/lte-rlc-um.cc
+++ b/src/lte/model/lte-rlc-um.cc
@@ -88,18 +88,13 @@ LteRlcUm::DoTransmitPdcpPdu (Ptr<Packet> p)
 
   if (m_txBufferSize + p->GetSize () <= m_maxTxBufferSize)
     {
-      /** Store arrival time */
-      RlcTag timeTag (Simulator::Now ());
-      p->AddPacketTag (timeTag);
-
       /** Store PDCP PDU */
-
       LteRlcSduStatusTag tag;
       tag.SetStatus (LteRlcSduStatusTag::FULL_SDU);
       p->AddPacketTag (tag);
 
       NS_LOG_LOGIC ("Tx Buffer: New packet added");
-      m_txBuffer.push_back (p);
+      m_txBuffer.push_back (TxPdu (p, Simulator::Now ()));
       m_txBufferSize += p->GetSize ();
       NS_LOG_LOGIC ("NumOfBuffers = " << m_txBuffer.size() );
       NS_LOG_LOGIC ("txBufferSize = " << m_txBufferSize);
@@ -153,13 +148,15 @@ LteRlcUm::DoNotifyTxOpportunity (LteMacSapUser::TxOpportunityParameters txOpPara
       return;
     }
 
+  Ptr<Packet> firstSegment = m_txBuffer.begin ()->m_pdu->Copy ();
+  Time firstSegmentTime = m_txBuffer.begin ()->m_waitingSince;
+
   NS_LOG_LOGIC ("SDUs in TxBuffer  = " << m_txBuffer.size ());
-  NS_LOG_LOGIC ("First SDU buffer  = " << *(m_txBuffer.begin()));
-  NS_LOG_LOGIC ("First SDU size    = " << (*(m_txBuffer.begin()))->GetSize ());
+  NS_LOG_LOGIC ("First SDU buffer  = " << firstSegment);
+  NS_LOG_LOGIC ("First SDU size    = " << firstSegment->GetSize ());
   NS_LOG_LOGIC ("Next segment size = " << nextSegmentSize);
   NS_LOG_LOGIC ("Remove SDU from TxBuffer");
-  Ptr<Packet> firstSegment = (*(m_txBuffer.begin ()))->Copy ();
-  m_txBufferSize -= (*(m_txBuffer.begin()))->GetSize ();
+  m_txBufferSize -= firstSegment->GetSize ();
   NS_LOG_LOGIC ("txBufferSize      = " << m_txBufferSize );
   m_txBuffer.erase (m_txBuffer.begin ());
 
@@ -209,12 +206,12 @@ LteRlcUm::DoNotifyTxOpportunity (LteMacSapUser::TxOpportunityParameters txOpPara
             {
               firstSegment->AddPacketTag (oldTag);
 
-              m_txBuffer.insert (m_txBuffer.begin (), firstSegment);
-              m_txBufferSize += (*(m_txBuffer.begin()))->GetSize ();
+              m_txBuffer.insert (m_txBuffer.begin (), TxPdu (firstSegment, firstSegmentTime));
+              m_txBufferSize += m_txBuffer.begin()->m_pdu->GetSize ();
 
               NS_LOG_LOGIC ("    TX buffer: Give back the remaining segment");
               NS_LOG_LOGIC ("    TX buffers = " << m_txBuffer.size ());
-              NS_LOG_LOGIC ("    Front buffer size = " << (*(m_txBuffer.begin()))->GetSize ());
+              NS_LOG_LOGIC ("    Front buffer size = " << m_txBuffer.begin()->m_pdu->GetSize ());
               NS_LOG_LOGIC ("    txBufferSize = " << m_txBufferSize );
             }
           else
@@ -275,8 +272,8 @@ LteRlcUm::DoNotifyTxOpportunity (LteMacSapUser::TxOpportunityParameters txOpPara
           NS_LOG_LOGIC ("        SDUs in TxBuffer  = " << m_txBuffer.size ());
           if (m_txBuffer.size () > 0)
             {
-              NS_LOG_LOGIC ("        First SDU buffer  = " << *(m_txBuffer.begin()));
-              NS_LOG_LOGIC ("        First SDU size    = " << (*(m_txBuffer.begin()))->GetSize ());
+              NS_LOG_LOGIC ("        First SDU buffer  = " << m_txBuffer.begin()->m_pdu);
+              NS_LOG_LOGIC ("        First SDU size    = " << m_txBuffer.begin()->m_pdu->GetSize ());
             }
           NS_LOG_LOGIC ("        Next segment size = " << nextSegmentSize);
 
@@ -305,15 +302,16 @@ LteRlcUm::DoNotifyTxOpportunity (LteMacSapUser::TxOpportunityParameters txOpPara
           NS_LOG_LOGIC ("        SDUs in TxBuffer  = " << m_txBuffer.size ());
           if (m_txBuffer.size () > 0)
             {
-              NS_LOG_LOGIC ("        First SDU buffer  = " << *(m_txBuffer.begin()));
-              NS_LOG_LOGIC ("        First SDU size    = " << (*(m_txBuffer.begin()))->GetSize ());
+              NS_LOG_LOGIC ("        First SDU buffer  = " << m_txBuffer.begin()->m_pdu);
+              NS_LOG_LOGIC ("        First SDU size    = " << m_txBuffer.begin()->m_pdu->GetSize ());
             }
           NS_LOG_LOGIC ("        Next segment size = " << nextSegmentSize);
           NS_LOG_LOGIC ("        Remove SDU from TxBuffer");
 
           // (more segments)
-          firstSegment = (*(m_txBuffer.begin ()))->Copy ();
-          m_txBufferSize -= (*(m_txBuffer.begin()))->GetSize ();
+          firstSegment = m_txBuffer.begin ()->m_pdu->Copy ();
+          firstSegmentTime = m_txBuffer.begin ()->m_waitingSince;
+          m_txBufferSize -= firstSegment->GetSize ();
           m_txBuffer.erase (m_txBuffer.begin ());
           NS_LOG_LOGIC ("        txBufferSize = " << m_txBufferSize );
         }
@@ -379,7 +377,7 @@ LteRlcUm::DoNotifyTxOpportunity (LteMacSapUser::TxOpportunityParameters txOpPara
 
   // Sender timestamp
   RlcTag rlcTag (Simulator::Now ());
-  packet->ReplacePacketTag (rlcTag);
+  packet->AddByteTag (rlcTag, 1, rlcHeader.GetSerializedSize ());
   m_txPdu (m_rnti, m_lcid, packet->GetSize ());
 
   // Send RLC PDU to MAC layer
@@ -414,8 +412,10 @@ LteRlcUm::DoReceivePdu (LteMacSapUser::ReceivePduParameters rxPduParams)
   // Receiver timestamp
   RlcTag rlcTag;
   Time delay;
-  NS_ASSERT_MSG (rxPduParams.p->PeekPacketTag (rlcTag), "RlcTag is missing");
-  rxPduParams.p->RemovePacketTag (rlcTag);
+
+  bool ret = rxPduParams.p->FindFirstMatchingByteTag (rlcTag);
+  NS_ASSERT_MSG (ret, "RlcTag is missing");
+
   delay = Simulator::Now() - rlcTag.GetSenderTimestamp ();
   m_rxPdu (m_rnti, m_lcid, rxPduParams.p->GetSize (), delay.GetNanoSeconds ());
 
@@ -1123,10 +1123,7 @@ LteRlcUm::DoReportBufferStatus (void)
 
   if (! m_txBuffer.empty ())
     {
-      RlcTag holTimeTag;
-      NS_ASSERT_MSG (m_txBuffer.front ()->PeekPacketTag (holTimeTag), "RlcTag is missing");
-      m_txBuffer.front ()->PeekPacketTag (holTimeTag);
-      holDelay = Simulator::Now () - holTimeTag.GetSenderTimestamp ();
+      holDelay = Simulator::Now () - m_txBuffer.front().m_waitingSince;
 
       queueSize = m_txBufferSize + 2 * m_txBuffer.size (); // Data in tx queue + estimated headers size
     }
diff --git a/src/lte/model/lte-rlc-um.h b/src/lte/model/lte-rlc-um.h
index 5cbcbca42..97ac7136d 100644
--- a/src/lte/model/lte-rlc-um.h
+++ b/src/lte/model/lte-rlc-um.h
@@ -97,7 +97,28 @@ private:
 private:
   uint32_t m_maxTxBufferSize; ///< maximum transmit buffer status
   uint32_t m_txBufferSize; ///< transmit buffer size
-  std::vector < Ptr<Packet> > m_txBuffer;       ///< Transmission buffer
+  /**
+   * \brief Store an incoming (from layer above us) PDU, waiting to transmit it
+   */
+  struct TxPdu
+  {
+    /**
+     * \brief TxPdu default constructor
+     * \param pdu the PDU
+     * \param time the arrival time
+     */
+    TxPdu (const Ptr<Packet> &pdu, const Time &time) :
+      m_pdu (pdu),
+      m_waitingSince (time)
+    { }
+
+    TxPdu () = delete;
+
+    Ptr<Packet> m_pdu;           ///< PDU
+    Time        m_waitingSince;  ///< Layer arrival time
+  };
+
+  std::vector < TxPdu > m_txBuffer; ///< Transmission buffer
   std::map <uint16_t, Ptr<Packet> > m_rxBuffer; ///< Reception buffer
   std::vector < Ptr<Packet> > m_reasBuffer;     ///< Reassembling buffer