Index: channels/chan_iax2.c
===================================================================
--- channels/chan_iax2.c        (revision 48358)
+++ channels/chan_iax2.c        (working copy)
@@ -488,7 +488,7 @@
        /*! Next outgoing timestamp if everything is good */
        unsigned int nextpred;
        /*! True if the last voice we transmitted was not silence/CNG */
-       int notsilenttx;
+       unsigned int notsilenttx:1;
        /*! Ping time */
        unsigned int pingtime;
        /*! Max time for initial response */
@@ -770,9 +770,42 @@
        ast_verbose(buf);
 }
 
-/* XXX We probably should use a mutex when working with this XXX */
+/*!
+ * \brief an array of iax2 pvt structures
+ *
+ * The container for active chan_iax2_pvt strucutures is implemented as an
+ * array for extremely quick direct access to the correct pvt strucuture
+ * based on the local call number.  The local call number is used as the
+ * index into the array where the associated pvt structure is stored.
+ */
 static struct chan_iax2_pvt *iaxs[IAX_MAX_CALLS];
+/*!
+ * \brief chan_iax2_pvt strucuture locks
+ *
+ * These locks are used when accessing a pvt strucuture in the iaxs array.
+ * The index used here is the same as used in the iaxs array.  It is the
+ * local call number for the associated pvt struct.
+ */
 static ast_mutex_t iaxsl[IAX_MAX_CALLS];
+/*!
+ * \brief The last time a call number was used
+ *
+ * It is important to know the last time that a call number was used locally so
+ * that it is not used again too soon.  The reason for this is the same as the
+ * reason that the TCP protocol state machine requires a "TIME WAIT" state.
+ *
+ * For example, say that a call is up.  Then, the remote side sends a HANGUP,
+ * which we respond to with an ACK.  However, there is no way to know whether
+ * the ACK made it there successfully.  If it were to get lost, the remote
+ * side may retransmit the HANGUP.  If in the meantime, this call number has
+ * been reused locally, given the right set of circumstances, this retransmitted
+ * HANGUP could potentially improperly hang up the new session.  So, to avoid
+ * this potential issue, we must wait a specified timeout period before reusing
+ * a local call number.
+ *
+ * The specified time that we must wait before reusing a local call number is
+ * defined as MIN_REUSE_TIME, with a default of 60 seconds.
+ */
 static struct timeval lastused[IAX_MAX_CALLS];
 
 static enum ast_bridge_result iax2_bridge(struct ast_channel *c0, struct ast_channel *c1, int flags, struct ast_frame **fo, struct ast_channel **rc, int timeoutms);