communication: sync protocol adapater to add psync

refs: #4082

Change-Id: Ibe4649e709dfbc3cdc1f2afbfc4ff03f75a3f136
diff --git a/docs/beginners-guide.rst b/docs/beginners-guide.rst
index ddbf4e6..9807191 100644
--- a/docs/beginners-guide.rst
+++ b/docs/beginners-guide.rst
@@ -18,7 +18,7 @@
 The following instructions are based on the information provided at the
 Named Data Networking project web page [NDNmain]_.
 Before installing NLSR it is necessary to install different libraries
-and programs: ndn-cxx, NFD and ChronoSync. This document describes the
+and programs: ndn-cxx, NFD, ChronoSync, and PSync. This document describes the
 necessary steps to correctly install these programs (§ `2 <#ndncxx>`__,
 `3 <#nfd>`__ and `4 <#nlsr>`__) and a brief guide on how to configure
 and test NLSR using a simple two-node network (§ `5 <#test>`__).
@@ -365,9 +365,9 @@
 -------------------------
 
 Before installing NLSR, it is necessary to first download and install
-ChronoSync, which is a library that allows NLSR routers to verify that
-their routing information coincides. More information about ChronoSync
-may be found at [Chronosync]_. This library may be
+ChronoSync, which is a synchronization library which allows NLSR routers
+to synchronize Link State Advertisements (LSAs). More information about
+ChronoSync may be found at [Chronosync]_. This library may be
 installed by running the following commands as a regular user and at the
 directory defined at § `1 <#intro>`__:
 
@@ -383,7 +383,7 @@
 
 ::
 
-      $ sudo ldconfig -v | grep ndn
+      $ sudo ldconfig -v | grep -i chronosync
 
 This command should display a line similar to the following:
 
@@ -391,7 +391,36 @@
 
          libChronoSync.so.0.5.0 -> libChronoSync.so.0.5.0
 
-4.2 Downloading and installing NLSR
+4.2 Installing PSync
+-------------------------
+
+Before installing NLSR, it is also necessary to download and install
+PSync. PSync is a synchronization library which allows NLSR to synchronize LSAs
+similar to ChronoSync. More information about PSync may be found at [PSync]_.
+This library may be installed by running the following commands as a regular
+user and at the directory defined at § `1 <#intro>`__:
+
+::
+
+      $ git clone --depth 1 https://github.com/named-data/PSync.git
+      $ cd PSync
+      $ ./waf configure
+      $ ./waf
+      $ sudo ./waf install
+
+The following command needs to be used again to configure the libraries:
+
+::
+
+      $ sudo ldconfig -v | grep -i psync
+
+This command should display a line similar to the following:
+
+::
+
+         libPSync.so.0.1.0 -> libPSync.so.0.1.0
+
+4.3 Downloading and installing NLSR
 -----------------------------------
 
 NLSR is downloaded and installed in a folder called *NLSR* which should
@@ -406,7 +435,7 @@
       $ ./waf
       $ sudo ./waf install
 
-4.3 Configuring NLSR
+4.4 Configuring NLSR
 --------------------
 
 Create and configure the following directory by running the following
@@ -844,6 +873,8 @@
 
 .. [Chronosync] Z. Zhu and A. Afanasyev. *Let’s ChronoSync: Decentralized dataset state synchronization in Named Data Networking*, in IEEE ICNP, October 2013.
 
+.. [PSync] M. Zhang, V. Lehman, and L. Wang. *Scalable Name-based Data Synchronization for Named Data Networking*, in IEEE INFOCOM, May 2017.
+
 .. [NLSRsecconf] *NLSR Security Configuration*, http://named-data.net/doc/NLSR/current/SECURITY-CONFIG.html June 2018.
 
 .. [NLSRdevguide] V. Lehman, M. Chowdhury, N. Gordon, A. Gawande. *NLSR Developer’s Guide*, University of Memphis, November 2017.