diff --git a/common/network-common/src/main/java/org/apache/spark/network/server/TransportServer.java b/common/network-common/src/main/java/org/apache/spark/network/server/TransportServer.java
index 9b327d5404b47..8396e691e9db1 100644
--- a/common/network-common/src/main/java/org/apache/spark/network/server/TransportServer.java
+++ b/common/network-common/src/main/java/org/apache/spark/network/server/TransportServer.java
@@ -133,6 +133,8 @@ private void init(String hostToBind, int portToBind) {
     bootstrap.childHandler(new ChannelInitializer<SocketChannel>() {
       @Override
       protected void initChannel(SocketChannel ch) {
+        logger.debug("New connection accepted for remote address {}.", ch.remoteAddress());
+
         RpcHandler rpcHandler = appRpcHandler;
         for (TransportServerBootstrap bootstrap : bootstraps) {
           rpcHandler = bootstrap.doBootstrap(ch, rpcHandler);
diff --git a/common/network-common/src/main/java/org/apache/spark/network/util/TransportConf.java b/common/network-common/src/main/java/org/apache/spark/network/util/TransportConf.java
index 453bff23026d0..589dfcbefb6ea 100644
--- a/common/network-common/src/main/java/org/apache/spark/network/util/TransportConf.java
+++ b/common/network-common/src/main/java/org/apache/spark/network/util/TransportConf.java
@@ -108,8 +108,8 @@ public int numConnectionsPerPeer() {
     return conf.getInt(SPARK_NETWORK_IO_NUMCONNECTIONSPERPEER_KEY, 1);
   }
 
-  /** Requested maximum length of the queue of incoming connections. Default -1 for no backlog. */
-  public int backLog() { return conf.getInt(SPARK_NETWORK_IO_BACKLOG_KEY, -1); }
+  /** Requested maximum length of the queue of incoming connections. Default is 64. */
+  public int backLog() { return conf.getInt(SPARK_NETWORK_IO_BACKLOG_KEY, 64); }
 
   /** Number of threads used in the server thread pool. Default to 0, which is 2x#cores. */
   public int serverThreads() { return conf.getInt(SPARK_NETWORK_IO_SERVERTHREADS_KEY, 0); }
diff --git a/docs/configuration.md b/docs/configuration.md
index d20b41671c03b..216995162d034 100644
--- a/docs/configuration.md
+++ b/docs/configuration.md
@@ -734,6 +734,17 @@ Apart from these, the following properties are also available, and may be useful
     is 15 seconds by default, calculated as <code>maxRetries * retryWait</code>.
   </td>
 </tr>
+<tr>
+  <td><code>spark.shuffle.io.backLog</code></td>
+  <td>64</td>
+  <td>
+    Length of the accept queue for the shuffle service. For large applications, this value may
+    need to be increased, so that incoming connections are not dropped if the service cannot keep
+    up with a large number of connections arriving in a short period of time. This needs to
+    be configured wherever the shuffle service itself is running, which may be outside of the
+    application (see <code>spark.shuffle.service.enabled</code> option below).
+  </td>
+</tr>
 <tr>
   <td><code>spark.shuffle.service.enabled</code></td>
   <td>false</td>
@@ -1515,6 +1526,15 @@ Apart from these, the following properties are also available, and may be useful
     This is used for communicating with the executors and the standalone Master.
   </td>
 </tr>
+<tr>
+  <td><code>spark.rpc.io.backLog</code></td>
+  <td>64</td>
+  <td>
+    Length of the accept queue for the RPC server. For large applications, this value may
+    need to be increased, so that incoming connections are not dropped when a large number of
+    connections arrives in a short period of time.
+  </td>
+</tr>
 <tr>
   <td><code>spark.network.timeout</code></td>
   <td>120s</td>