Subject: [manet] Testing DSR over ethernet

From: Pradeepkumar Mani <[email-masked]>
Date: Thu, 31 Oct 2002 00:59:32 -0600 (CST)

hi

My apologies if you get multiple copies of this email. My friend, who is
not a member of the group, tried to send the same email. Since he was not
successful, I am sending it now. Sorry about that!!

we are trying to run DSR (Alex Song's implementation) over an ethernet
LAN. we are trying to set up a network (with eight nodes) as follows:
node 1 is within the transmission range of nodes 2 and 3 but not other
nodes. if node 1 has to reach node 4, node 1 will broadcast a RREQ
(route request)  and only nodes 2 and 3 have to send RREPs (route
replies) and not the other  nodes (including node 4 though they are all
in the same broadcast medium - the  wired ethernet). this is just to
setup a multihop network.

at node 4, we tried to block broadcast packets from node 1 using
iptables so  that node 4 would not reply to RREQs from node 1.
when nodes 1 and 4 were the only ones up, this seemed to work (ie. we
were not  able to ping node 4 from node 1). then we up- ed node 3 (which
is in the  "transmission range" of both node 1 and node 4. we were able
to ping node 3  from both node 1 and node 4). but we still we were
unable to ping node 4 from  node 1 (we were expecting node 3, being
within the "transmission range" of  node 4 to aid node 1 in reaching
node 4. but this didnt happen).

could anyone help us in figuring out what the problem is ? Any suggestions
are most welcome (we have setting up VLANs in mind instead of using
iptables, but would like to explore other options before disturbing the
current network setup)

we have tried to be as clear as possible in stating our problem.

thanks in advance!
regards
girish & pradeep.

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From: David Young <[email-masked]>
Date: Thu, 31 Oct 2002 01:43:05 -0600

Have you monitored the network using tcpdump or ethereal? Also, have
you compared the routing table with your expectations? That will help
you to see what is going on, "on the wire."

I think I might know what is happening.

If nodes 1, 3, and 4 are configured as hosts on the same IP subnet, then
node 3 will send ICMP Redirects to 1 and 4 whenever one tries to contact
the other through 3. The reason is that as far as node 3 is concerned,
1 and 4 can reach each other directly, and so it tells them so.

In a lot of IP implementations, such as NetBSD's and Linux's, it is
default behavior for a router to honor ICMP Redirects.  In Linux and in
NetBSD, there are sysctl's which will turn off ICMP Redirects. (In Linux,
a zillion sysctl's affect ICMP Redirects, and you may have to turn off
more than one.)

Dave

-- 
David Young             OJC Technologies
[email-masked]      Engineering from the Right Brain
                        Urbana, IL * (217) 278-3933
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---

From: David Young <[email-masked]>
Date: Thu, 31 Oct 2002 01:43:05 -0600

Dave

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From: Sourabh Sharma <[email-masked]>
Date: Fri, 1 Nov 2002 00:21:43 +0800 (GMT-8)

> a zillion sysctl's affect ICMP Redirects, and you may have to turn off

   Instead of all this trouble why doesn't Pradeep configue
 the nodes to be in different subnets.I've said this before
 and emphasize again:
  Apart from the automatic update of routing tables- and this finding
  routes to new nodes, the
test of an ad-hoc  routing protocol is to find routes when
 the nodes have totally different/unrelated Ipaddreses.
  
  Pradeep, I strongly , suggest you try this, if what Dave says
 is the actual problem, viz ICMP redirects.

 -Sourabh

> > we have tried to be as clear as possible in stating our problem.

--------------------------------------------------
There is an answer to everything in this world.
   The only question which remains to be answered
     IS whether we know the answers or not.

---

From: Sourabh Sharma <[email-masked]>
Date: Fri, 1 Nov 2002 00:21:43 +0800 (GMT-8)

-Sourabh

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From: "Tao Lin" <[email-masked]>
Date: Thu, 31 Oct 2002 11:56:26 -0500

Turning off ICMP Redirects is not difficult.  For example, AODV Linux
distribution at http://www.docs.uu.se/~henrikl/aodv/.
Bascially, just echo 0 to /proc/sys/net/ipv4/conf/wlan0/send_redirects,
/proc/sys/net/ipv4/conf/wlan0/accept_redirects (here wlan0 is the NIC used
for ad hoc routing), and similar files in /proc/sys/net/ipv4/conf/all/
directory.

Hope this helps.

---

From: "Tao Lin" <[email-masked]>
Date: Thu, 31 Oct 2002 11:56:26 -0500

Hope this helps.

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From: [email-masked]
Date: Thu, 31 Oct 2002 10:30:09 -0700

Hi Sourabh,

The issue of IP addresses is not so simple.

I believe Pradeep is trying to emulate a MANET situation on a Eithernet.  If 
so, he wants Node 3 to be reachable by Node 1 and Node 4.  To try to do this 
with subnet addresses, he would have to have Node 3 in two diferent subnets; 
one for Node 1 and one for Node 4.  In addition, to simulate movement, he would 
have to reassign subnets to different nodes as the simulation progresses.  That 
would mean changing IP addresses as he goes.  If Node 3 is reachable by Nodes 1 
and 4, then it must be in a supernet.  If this changes, not only will Node 3 
get a new IP, but it may have to change levels within the hierarchy.

Sounds pretty complicated to me.

Also, there are schemes by which a MANET assigns internal IPs to or augments 
existing IP addresses of its nodes, thereby permitting aggregation of routes by 
IP subnets.  In effect, part of the routing update problem is replaced by the 
dynamic IP update and forwarding address problems.  For smallish MANETS, it 
offers no clear advantage, but for very large ones, it might be beneficial.  
There doesn't seem to be a consensus on if and when this is a good strategy at 
this time.  

Point is, the dealing with unrelated IP addresses can be done in a number of 
ways within a MANET and, in some schemes, the routing algorithm might 
actually "see" related IP addresses.

John Mullen

Quoting Sourabh Sharma <[email-masked]>:

> <snip>

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From: [email-masked]
Date: Thu, 31 Oct 2002 10:30:09 -0700

Hi Sourabh,

John Mullen

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From: "Tao Lin" <[email-masked]>
Date: Thu, 31 Oct 2002 12:43:34 -0500

For the topology emulation of wireless ad hoc networks in a wired testbed,
we developed such a tool in our lab. The link for this free software at
http://io.irean.vt.edu/~tlin/ (196 downloads till now) and a paper for it
can also be found at this web page.

Use this tool, users only need to setup a wired testbed.  No need to modify
mobile nodes.  Mobile nodes can be configured using IP addresses in one
subnet or different subnets if they may talk to each other directly.

Thanks,

 Tao

----- Original Message -----
From: <[email-masked]>
To: "Sourabh Sharma" <[email-masked]>
Cc: <[email-masked]>
Sent: Thursday, October 31, 2002 12:30 PM
Subject: Re: [manet] Testing DSR over ethernet

> > > > My apologies if you get multiple copies of this email. My friend,
who
> > is
> > > > not a member of the group, tried to send the same email. Since he
was
> > not

---

From: "Tao Lin" <[email-masked]>
Date: Thu, 31 Oct 2002 12:43:34 -0500

Thanks,

 Tao

----- Original Message -----
From: <[email-masked]>
To: "Sourabh Sharma" <[email-masked]>
Cc: <[email-masked]>
Sent: Thursday, October 31, 2002 12:30 PM
Subject: Re: [manet] Testing DSR over ethernet

who
was

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From: Lawrence MacIntyre <[email-masked]>
Date: 31 Oct 2002 13:16:03 -0500

A simple way is to configure the machines with different subnet
addresses, but hook them to the same layer 2 network (e.g. ethernet
switch).  By adding interface routes to the machines, you can simulate
reachability.

e.g.

Laptop 1: 10.100.0.1/24
Laptop 2: 10.100.1.1/24
Laptop 3: 10.100.2.1/24

On Laptop 1:
route add -host 10.100.1.1 eth0

On Laptop 2:
route add -host 10.100.0.1 eth0
route add -host 10.100.2.1 eth0

On Laptop 3:
route add -host 10.100.1.1 eth0

Now Laptop 1 can only see Laptop 2, Laptop 3 can only see Laptop 2, and
Laptop 2 can see both other machines.  If your Ad-Hoc routing is working
correctly, you should be able to communicate from Laptop 3 to Laptop 1
via Laptop 2.

-- 
     Lawrence MacIntyre     865.574.8696     [email-masked]
                Oak Ridge National Laboratory
Center for High Performance Information Infrastructure Technology

---

From: Lawrence MacIntyre <[email-masked]>
Date: 31 Oct 2002 13:16:03 -0500

e.g.

Laptop 1: 10.100.0.1/24
Laptop 2: 10.100.1.1/24
Laptop 3: 10.100.2.1/24

On Laptop 1:

On Laptop 2:

On Laptop 3:

---

From: Sourabh Sharma <[email-masked]>
Date: Fri, 1 Nov 2002 01:50:57 +0800 (GMT-8)

Hi all,
         I think there has been too much discussion on 
 Ipadresses and subnetting. I would like to put a
 clearer picture for everyone.
  Please continue reading.

On Thu, 31 Oct 2002 [email-masked] wrote:
> one for Node 1 and one for Node 4.  
 <snip>

 John,
      Thanks for the insight. I agree of this. This holds well for
 Ethernet and normal routing protocols.
 Now for mobile nodes(802.11):
   Iamgine this situation with me.
 Node A : Ip: 97.98.99.100  (class A /8 )  
 Node B:  Ip: 147.148.149.150 (Class B /16)
 
 Under normal IP "circumstances": these nodes will not ping each other.
  As soon as we run AODV (on both the nodes) they both discover each other
 as neighbours and consequently can communicate.( As a proof we see
 A and B's routing table being updated. I've experimented and have 
 actually seen this happen.)
   Now when we bring in a new node C. ( which is within the transmission
 range of B but not A) 

  Node C: ip: 201.202.203.204 (class C /24)

  Now, I see no reason why B and C should not be able to communicate
 with each other. Since AODV helps them detect each other as neighbour.
   Following up with AODv's capabilty to allow discovery of new paths,
 I see no reason why A should not be able to reach C using B as a hop.
   
  So in the ideal scenario:
  A -- B  -- C
  All 3 nodes can have IPaddresses of diff classes but should still
 be able to route packets to each other though A and C are not in
 each other's direct transmission range!
  I see no reason, why this should not work.
  I hope everyone agrees with me on this.

  -Sourabh .

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From: Sourabh Sharma <[email-masked]>
Date: Fri, 1 Nov 2002 01:50:57 +0800 (GMT-8)

Hi all,

 <snip>

 John,

   

  -Sourabh .

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From: Joe Macker <[email-masked]>
Date: Thu, 31 Oct 2002 15:25:41 -0500

>have to reassign subnets to different nodes as the simulation progresses.  That 

dynamic filtering works fine as an emulator.. and isn't complex.

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From: Joe Macker <[email-masked]>
Date: Thu, 31 Oct 2002 15:25:41 -0500