Use https for all external links

Change-Id: I4ee473737b911885cf32bc417310b04645610cde
diff --git a/tlv.rst b/tlv.rst
index 4d83ffc..969eb41 100644
--- a/tlv.rst
+++ b/tlv.rst
@@ -9,7 +9,7 @@
 There is also no packet fragmentation support at network level.
 Whenever needed, NDN packets may be fragmented and reassembled hop-by-hop. [#f1]_
 
-.. [#f1] `"Packet Fragmentation in NDN: Why NDN Uses Hop-By-Hop Fragmentation (NDN Memo)" by A. Afanasyev, J. Shi, L. Wang, B. Zhang, and L. Zhang., NDN Memo, Technical Report NDN-0032 <http://named-data.net/publications/techreports/ndn-0032-1-ndn-memo-fragmentation/>`__
+.. [#f1] `"Packet Fragmentation in NDN: Why NDN Uses Hop-By-Hop Fragmentation (NDN Memo)" by A. Afanasyev, J. Shi, L. Wang, B. Zhang, and L. Zhang., NDN Memo, Technical Report NDN-0032 <https://named-data.net/publications/techreports/ndn-0032-1-ndn-memo-fragmentation/>`__
 
 Variable Size Encoding for type (T) and length (L)
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