diff --git a/src/usr.sbin/ntpd/client.c b/src/usr.sbin/ntpd/client.c
index f877e1f9..81d7eb86 100644
--- a/src/usr.sbin/ntpd/client.c
+++ b/src/usr.sbin/ntpd/client.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: client.c,v 1.11 2004/07/06 23:26:38 henning Exp $ */
+/*	$OpenBSD: client.c,v 1.12 2004/07/07 01:01:27 henning Exp $ */
 
 /*
  * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
@@ -58,7 +58,7 @@ client_peer_init(struct ntp_peer *p)
 	p->state = STATE_NONE;
 	p->next = time(NULL);
 	p->shift = 0;
-	p->valid = 0;
+	p->trustlevel = TRUSTLEVEL_PATHETIC;
 
 	return (0);
 }
@@ -144,18 +144,31 @@ client_dispatch(struct ntp_peer *p)
 	p->reply[p->shift].rcvd = time(NULL);
 	p->reply[p->shift].good = 1;
 
-	p->state = STATE_REPLY_RECEIVED;
-	p->next = time(NULL) + INTERVAL_QUERY;
+	if (p->trustlevel < TRUSTLEVEL_PATHETIC)
+		p->next = time(NULL) + INTERVAL_QUERY_PATHETIC;
+	else if (p->trustlevel < TRUSTLEVEL_AGRESSIVE)
+		p->next = time(NULL) + INTERVAL_QUERY_AGRESSIVE;
+	else
+		p->next = time(NULL) + INTERVAL_QUERY_NORMAL;
+
 	p->deadline = 0;
+	p->state = STATE_REPLY_RECEIVED;
 
 	log_debug("reply received from %s: offset %f delay %f",
 	    log_sockaddr((struct sockaddr *)&fsa), p->reply[p->shift].offset,
 	    p->reply[p->shift].delay);
 
-	if (++p->shift >= OFFSET_ARRAY_SIZE) {
-		p->shift = 0;
-		p->valid = 1;
+	/* every received reply which we do not discard increases trust */
+	if (p->trustlevel < 10) {
+		if (p->trustlevel < TRUSTLEVEL_BADPEER &&
+		    p->trustlevel + 1 >= TRUSTLEVEL_BADPEER)
+			log_info("peer %s now valid",
+			    log_sockaddr((struct sockaddr *)&fsa));
+		p->trustlevel++;
 	}
 
+	if (++p->shift >= OFFSET_ARRAY_SIZE)
+		p->shift = 0;
+
 	return (0);
 }
diff --git a/src/usr.sbin/ntpd/ntp.c b/src/usr.sbin/ntpd/ntp.c
index 05788e33..d9a66db0 100644
--- a/src/usr.sbin/ntpd/ntp.c
+++ b/src/usr.sbin/ntpd/ntp.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: ntp.c,v 1.12 2004/07/06 23:26:38 henning Exp $ */
+/*	$OpenBSD: ntp.c,v 1.13 2004/07/07 01:01:27 henning Exp $ */
 
 /*
  * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
@@ -165,9 +165,18 @@ ntp_main(int pipe_prnt[2], struct ntpd_conf *conf)
 		TAILQ_FOREACH(p, &conf->ntp_peers, entry) {
 			if (p->next > 0 && p->next < nextaction)
 				nextaction = p->next;
-			if ((p->next > 0 && p->next <= time(NULL)) ||
-			    (p->deadline > 0 && p->deadline <= time(NULL)))
+
+			if (p->next > 0 && p->next <= time(NULL))
+				client_query(p);
+
+			if  (p->deadline > 0 && p->deadline <= time(NULL)) {
+				if (p->trustlevel >= TRUSTLEVEL_BADPEER &&
+				    --p->trustlevel < TRUSTLEVEL_BADPEER)
+					log_info("peer %s now invalid",
+					    log_sockaddr(
+					    (struct sockaddr *)&p->ss));
 				client_query(p);
+			}
 
 			if (p->state == STATE_QUERY_SENT) {
 				pfd[i].fd = p->query->fd;
@@ -287,15 +296,11 @@ ntp_adjtime(struct ntpd_conf *conf)
 	double		 offset, offset_median = 0;
 	int		 offset_cnt = 0;
 
-	TAILQ_FOREACH(p, &conf->ntp_peers, entry) {
-		if (!p->valid)
-			continue;
-
+	TAILQ_FOREACH(p, &conf->ntp_peers, entry)
 		if (get_peer_update(p, &offset) == 0) {
 			offset_median += offset;
 			offset_cnt++;
 		}
-	}
 
 	offset_median /= offset_cnt;
 
@@ -322,16 +327,26 @@ get_peer_update(struct ntp_peer *p, double *offset)
 			best = i;
 		}
 
-	for (; i < OFFSET_ARRAY_SIZE; i++)
-		if (p->reply[i].good) {
+	for (; i < OFFSET_ARRAY_SIZE; i++) {
+		if (p->reply[i].good &&
+		    p->reply[i].rcvd + REPLY_MAXAGE < time(NULL))
+			p->reply[i].good = 0;
+
+		if (p->reply[i].good)
 			good++;
 			if (p->reply[i].delay < p->reply[best].delay)
 				best = i;
-		}
+	}
 
-	/* XXX lower trust in the peer when too few good replies received */
+	/* lower trust in the peer when too few good replies received */
+	if (good < 8 && p->trustlevel > 0) {
+		if (p->trustlevel >= TRUSTLEVEL_BADPEER)
+			log_info("peer %s now invalid",
+			    log_sockaddr((struct sockaddr *)&p->ss));
+		p->trustlevel /= 2;
+	}
 
-	if (good == 0)
+	if (good == 0 || p->trustlevel < TRUSTLEVEL_BADPEER)
 		return (-1);
 
 	for (i = 0; i < OFFSET_ARRAY_SIZE; i++)
diff --git a/src/usr.sbin/ntpd/ntpd.h b/src/usr.sbin/ntpd/ntpd.h
index 795fd55f..48b6be87 100644
--- a/src/usr.sbin/ntpd/ntpd.h
+++ b/src/usr.sbin/ntpd/ntpd.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: ntpd.h,v 1.13 2004/07/06 23:26:38 henning Exp $ */
+/*	$OpenBSD: ntpd.h,v 1.14 2004/07/07 01:01:27 henning Exp $ */
 
 /*
  * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
@@ -36,9 +36,17 @@
 #define	NTPD_OPT_VERBOSE	0x0001
 #define	NTPD_OPT_VERBOSE2	0x0002
 
-#define	INTERVAL_ADJTIME	240	/* call adjtime every n seconds */
-#define	INTERVAL_QUERY		30	/* sync with peers every n seconds */
+#define	INTERVAL_ADJTIME		240	/* call adjtime every n secs */
+#define	INTERVAL_QUERY_NORMAL		30	/* sync to peers every n secs */
+#define	INTERVAL_QUERY_PATHETIC		60
+#define	INTERVAL_QUERY_AGRESSIVE	5
+
+#define	TRUSTLEVEL_BADPEER		6
+#define	TRUSTLEVEL_PATHETIC		2
+#define	TRUSTLEVEL_AGRESSIVE		8
+
 #define	QUERYTIME_MAX		15	/* single query might take n secs max */
+#define	REPLY_MAXAGE		300
 #define	OFFSET_ARRAY_SIZE	8
 
 enum client_state {
@@ -70,7 +78,7 @@ struct ntp_peer {
 	time_t				 deadline;
 	struct ntp_offset		 reply[OFFSET_ARRAY_SIZE];
 	u_int8_t			 shift;
-	u_int8_t			 valid;
+	u_int8_t			 trustlevel;
 };
 
 struct ntpd_conf {