I solved session replication by configuring jboss-web.xml under WEB-INF folder as follows...
<?xml version="1.0" encoding="UTF-8"?>
<jboss-web version="6.0"
xmlns="http://www.jboss.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.jboss.com/xml/ns/javaee http://www.jboss.org/j2ee/schema/jboss-web_6_0.xsd">
<replication-config>
<!-- The default value is SET_AND_NON_PRIMITIVE_GET, therefore the byte array which is carrying the data is considered
non-primitive and would cause replication even in read only scenario. -->
<replication-trigger>SET</replication-trigger>
<!-- Replicating entire session is the default. -->
<replication-granularity>SESSION</replication-granularity>
<replication-mode>SYNCHRONOUS</replication-mode>
</replication-config>
In this case no need to use cookies to store values...