management: clarify the inconsistency in UDP face timeouts in nfd.conf

refs #2473

Change-Id: Iceeda5f03bc426dfab1e67cf508996d3fe96ac42
diff --git a/daemon/mgmt/face-manager.cpp b/daemon/mgmt/face-manager.cpp
index 5256c92..3c590f5 100644
--- a/daemon/mgmt/face-manager.cpp
+++ b/daemon/mgmt/face-manager.cpp
@@ -380,8 +380,8 @@
   // udp
   // {
   //   port 6363 ; UDP unicast port number
-  //   idle_timeout 30 ; idle time (seconds) before closing a UDP unicast face
-  //   keep_alive_interval 25; interval (seconds) between keep-alive refreshes
+  //   idle_timeout 600 ; idle time (seconds) before closing a UDP unicast face
+  //   keep_alive_interval 25 ; interval (seconds) between keep-alive refreshes
 
   //   ; NFD creates one UDP multicast face per NIC
   //   mcast yes ; set to 'no' to disable UDP multicast, default 'yes'
@@ -392,7 +392,7 @@
   std::string port = "6363";
   bool enableV4 = true;
   bool enableV6 = true;
-  size_t timeout = 30;
+  size_t timeout = 600;
   size_t keepAliveInterval = 25;
   bool useMcast = true;
   std::string mcastGroup = "224.0.23.170";
diff --git a/nfd.conf.sample.in b/nfd.conf.sample.in
index 908ad7b..fa229b4 100644
--- a/nfd.conf.sample.in
+++ b/nfd.conf.sample.in
@@ -92,7 +92,11 @@
     port 6363 ; UDP unicast port number
     enable_v4 yes ; set to 'no' to disable IPv4 channels, default 'yes'
     enable_v6 yes ; set to 'no' to disable IPv6 channels, default 'yes'
-    idle_timeout 600 ; idle time (seconds) before closing a UDP unicast face
+
+    ; idle time (seconds) before closing a UDP unicast face, the actual timeout would be
+    ; anywhere within [idle_timeout, 2*idle_timeout), default is 600
+    idle_timeout 600
+
     keep_alive_interval 25; interval (seconds) between keep-alive refreshes
 
     ; UDP multicast settings