Subject: [manet] Question about LAR (location aided routing protocol)

From: "" <[email-masked]>
Date: Sun, 24 Jul 2005 00:50:27 -0400 (EDT)

Hi:

I am simulating an ad hoc network with LAR (location aided routing protocol) as the routing protocl. I use Glomosim. The configuration of my simulation is 600 nodes in (5000 X 2000) region, random way point model, four 512B packets per second, CBR, 40 source/destinatin pairs. 

The strange thing is that, the average end-to-end delay of some nodes is very large, about 100-200 seconds. The average end-to-end delay of most of the nodes are normal, about 0.5-3 seconds. 

What is the problem? Is the result correct? I use the original code of LAR in Glomosim. I do not modify anything.

Thanks.  

_______________________________________________
Join Excite! - http://www.excite.com
The most personalized portal on the Web!

_______________________________________________
manet mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/manet

---

From: "Mullen, John" <[email-masked]>
Date: Mon, 25 Jul 2005 14:10:45 -0600

Hi,

You might want to look at the routes on those high-delay paths.  You
might have a bottleneck. For example, if your net is nearly partitioned
into two regions; A and B, then any messages from A to B or vice versa
would go through a constrained path while exchanges within A or within B
would be unaffected.  This might also happen if there are a few links
that are very heavily utilized.

You also don't mention the distribution of message initiations.  It is
possible that some senders consistently start their messages after
another user of common elements of the path and, as a result, have to
wait for the channel.

Also, is this the result of a single run?  If so, you may want to run
some more replicates to get a better picture of the situation.  This
might indicate that what you are looking at is an outlier or give you
further insight into the cause.

Maybe one of these suggestions is the cause, but if not, hopefully, they
will help you find the problem.

John P. Mullen, Ph.D.
(505) 646-2958
[email-masked]
 
-----Original Message-----
From: [email-masked] [mailto:[email-masked]] 
Sent: Saturday, July 23, 2005 10:50 PM
To: [email-masked]
Subject: [manet] Question about LAR (location aided routing protocol)

Hi:

I am simulating an ad hoc network with LAR (location aided routing
protocol) as the routing protocl. I use Glomosim. The configuration of
my simulation is 600 nodes in (5000 X 2000) region, random way point
model, four 512B packets per second, CBR, 40 source/destinatin pairs. 

The strange thing is that, the average end-to-end delay of some nodes is
very large, about 100-200 seconds. The average end-to-end delay of most
of the nodes are normal, about 0.5-3 seconds. 

What is the problem? Is the result correct? I use the original code of
LAR in Glomosim. I do not modify anything.

Thanks.

---

From: "" <[email-masked]>
Date: Tue, 26 Jul 2005 12:45:05 -0400 (EDT)

Hi Dr. Mullen:

Thank you for your reply.

I simulated the same configuration with different seeds. For each seed there are always some nodes whose end-to-end delay is very high.  

The average of end-to-end delay of all forty source/destination pairs is about 5-30 seconds depending on the seed. The packet delivery ratio is about 70-80 percent.

I also tried the same configuration with AODV. AODV has much better performance with about 90 percent packet delivery ratio and 0.05 end-to-end delay.

In AODV, if a node can not find a path, it puts the data packet into a queue and stores for a short time. For LAR, if the end-to-end delay is several hundred seconds, the data packets must be stored in a queue for several hundred seconds, which is too long.

I do not know if it is LAR's problem or glomosim's problem.

Regards,

Jack

 --- On Mon 07/25, Mullen, John < [email-masked] > wrote:

From: Mullen, John [mailto: [email-masked]]

To: [email-masked], [email-masked]

Date: Mon, 25 Jul 2005 14:10:45 -0600

Subject: RE: [manet] Question about LAR (location aided routing protocol)

Hi,<br><br>You might want to look at the routes on those high-delay paths.  You<br>might have a bottleneck. For example, if your net is nearly partitioned<br>into two regions; A and B, then any messages from A to B or vice versa<br>would go through a constrained path while exchanges within A or within B<br>would be unaffected.  This might also happen if there are a few links<br>that are very heavily utilized.<br><br>You also don't mention the distribution of message initiations.  It is<br>possible that some senders consistently start their messages after<br>another user of common elements of the path and, as a result, have to<br>wait for the channel.<br><br>Also, is this the result of a single run?  If so, you may want to run<br>some more replicates to get a better picture of the situation.  This<br>might indicate that what you are looking at is an outlier or give you<br>further insight into the cause.<br><br>Maybe one of these suggestions is the cause, but if not, hopefully!
 , 
they<br>will help you find the problem.<br><br><br>John P. Mullen, Ph.D.<br>(505) 646-2958<br>[email-masked]<br> <br>-----Original Message-----<br>From: [email-masked] [mailto:[email-masked]] <br>Sent: Saturday, July 23, 2005 10:50 PM<br>To: [email-masked]<br>Subject: [manet] Question about LAR (location aided routing protocol)<br><br><br>Hi:<br><br><br><br>I am simulating an ad hoc network with LAR (location aided routing<br>protocol) as the routing protocl. I use Glomosim. The configuration of<br>my simulation is 600 nodes in (5000 X 2000) region, random way point<br>model, four 512B packets per second, CBR, 40 source/destinatin pairs. <br><br>The strange thing is that, the average end-to-end delay of some nodes is<br>very large, about 100-200 seconds. The average end-to-end delay of most<br>of the nodes are normal, about 0.5-3 seconds. <br><br>What is the problem? Is the result correct? I use the original code of<br>LAR in Glomosim. I do not modify 
anything.<br><br><br><br>Thanks.  <br><br><br><br><br><br><br><br>_______________________________________________<br>Join Excite! - http://www.excite.com<br>The most personalized portal on the Web!<br><br><br><br>_______________________________________________<br>manet mailing list<br>[email-masked]<br>https://www1.ietf.org/mailman/listinfo/manet<br>

---

From: "Mullen, John" <[email-masked]>
Date: Fri, 29 Jul 2005 07:31:42 -0600

Hi Jack,

It sounds to me like you have a bottleneck.  Does the simulation place
the nodes or are you starting with the same initial node positions and
and have movement along the same routes each time?  If the distribution
of nodes is not changing, the topology could be the cause.  If that is
the case, I suggest you check the mean queue length and/or utilization
of each node to see if some are very high.  The channel could also be
heavily used somewhere, but I'm not sure if you can isolate that.
However, if the channel is heavily utilized, local queues should get
long.

I'm assuming, of course, this is not a Glomosim bug.   

Also, I'm not sure of your physical layer model.  If your model includes
fine grain variation effects, such as multipath fading, the problem
could be that the system is getting clogged up with retransmissions.  If
that is the case, you might want to check the limit on the number of
re-transmissions attempted at the MAC level.  Here, we've found that if
the cap is more than three, the MANET tends to retain poor paths too
long, leading to a significant increase in the average number of
retransmissions.  With fewer, the MANET tends to drop poor paths and
look for better ones sooner.  However, this behavior is only apparent in
simulations if you simulate these fine grain variations in signal
strength.  If this feature is not being used, this would not be a
problem.

Best of luck!

John P. Mullen, Ph.D.
(505) 646-2958
[email-masked]
 
-----Original Message-----
From: [mailto:[email-masked]] 
Sent: Tuesday, July 26, 2005 10:45 AM
To: Mullen, John; [email-masked]
Subject: RE: [manet] Question about LAR (location aided routing
protocol)

Hi Dr. Mullen:

Thank you for your reply.
I simulated the same configuration with different seeds. For each seed
there are always some nodes whose end-to-end delay is very high.  
The average of end-to-end delay of all forty source/destination pairs is
about 5-30 seconds depending on the seed. The packet delivery ratio is
about 70-80 percent.

I also tried the same configuration with AODV. AODV has much better
performance with about 90 percent packet delivery ratio and 0.05
end-to-end delay.

In AODV, if a node can not find a path, it puts the data packet into a
queue and stores for a short time. For LAR, if the end-to-end delay is
several hundred seconds, the data packets must be stored in a queue for
several hundred seconds, which is too long.

Regards,

Jack

Subject: RE: [manet] Question about LAR (location aided routing
protocol)

Hi,<br><br>You might want to look at the routes on those high-delay
paths.  You<br>might have a bottleneck. For example, if your net is
nearly partitioned<br>into two regions; A and B, then any messages from
A to B or vice versa<br>would go through a constrained path while
exchanges within A or within B<br>would be unaffected.  This might also
happen if there are a few links<br>that are very heavily
utilized.<br><br>You also don't mention the distribution of message
initiations.  It is<br>possible that some senders consistently start
their messages after<br>another user of common elements of the path and,
as a result, have to<br>wait for the channel.<br><br>Also, is this the
result of a single run?  If so, you may want to run<br>some more
replicates to get a better picture of the situation.  This<br>might
indicate that what you are looking at is an outlier or give
you<br>further insight into the cause.<br><br>Maybe one of these
suggestions is the cause, but if not, hopefully,
  
they<br>will help you find the problem.<br><br><br>John P. Mullen,
Ph.D.<br>(505) 646-2958<br>[email-masked]<br> <br>-----Original
Message-----<br>From: [email-masked]
[mailto:[email-masked]] <br>Sent: Saturday, July 23, 2005 10:50
PM<br>To: [email-masked]<br>Subject: [manet] Question about LAR
(location aided routing protocol)<br><br><br>Hi:<br><br><br><br>I am
simulating an ad hoc network with LAR (location aided
routing<br>protocol) as the routing protocl. I use Glomosim. The
configuration of<br>my simulation is 600 nodes in (5000 X 2000) region,
random way point<br>model, four 512B packets per second, CBR, 40
source/destinatin pairs. <br><br>The strange thing is that, the average
end-to-end delay of some nodes is<br>very large, about 100-200 seconds.
The average end-to-end delay of most<br>of the nodes are normal, about
0.5-3 seconds. <br><br>What is the problem? Is the result correct? I use
the original code of<br>LAR in Glomosim. I do not modify
anything.<br><br><br><br>Thanks.
<br><br><br><br><br><br><br><br>________________________________________
_______<br>Join Excite! - http://www.excite.com<br>The most personalized
portal on the
Web!<br><br><br><br>_______________________________________________<br>m
anet mailing
list<br>[email-masked]<br>https://www1.ietf.org/mailman/listinfo/manet<b
r>