diff --git a/model/ccnx-interest-header.cc b/model/ccnx-interest-header.cc
index 323c5fc..d44ac45 100644
--- a/model/ccnx-interest-header.cc
+++ b/model/ccnx-interest-header.cc
@@ -56,6 +56,8 @@
   , m_scope (-1)
   , m_interestLifetime (Seconds (0))
   , m_nonce (0)
+  , m_nack (false)
+  , m_congested (false)
 {
 }
 
@@ -174,7 +176,31 @@
 {
   return m_nonce;
 }
-  
+
+void
+CcnxInterestHeader::SetNack (bool isNack)
+{
+  m_nack = isNack;
+}
+    
+bool
+CcnxInterestHeader::IsNack () const
+{
+  return m_nack;
+}
+ 
+void
+CcnxInterestHeader::SetCongested (bool IsCongested)
+{
+  m_congested = IsCongested;
+}
+    
+bool
+CcnxInterestHeader::IsCongested () const
+{
+  return m_congested;
+}
+
 uint32_t
 CcnxInterestHeader::GetSerializedSize (void) const
 {
@@ -206,6 +232,8 @@
 CcnxInterestHeader::Print (std::ostream &os) const
 {
   os << "<Interest>\n  <Name>" << GetName () << "</Name>\n";
+  if (IsNack ())
+    os << "  <NACK />\n";
   if (GetMinSuffixComponents () >= 0)
     os << "  <MinSuffixComponents>" << GetMinSuffixComponents () << "</MinSuffixComponents>\n";
   if (GetMaxSuffixComponents () >= 0)