Subject: RE: [manet] 802.11, MANETs and mesh networks?

From: "Giorgio Mulas" <[email-masked]>
Date: Wed, 29 Dec 2004 10:49:58 +0100

Hi Claudio, hi all, and happy xmas holidays,

I agree with you when you depict a meshnetworking/ubiquitous computing future, but I have some considerations about the second part of your intervention.

First of all, I think that ad hoc networking refers mainly to layer 3 (not considering cross-layering issues that are layer 1/2 technology specific). This implies that a MANET could be built for example on Bluetooth or Zigbee technology if you need only some kilo Bytes or on WiMax if you need more bandwidth, not just on WiFi. In all these cases layer 3 issues remains *roughly* the same.  

Second, in what I call a Lego-like approach you try to adapt existing mature (except WiMax of course) technologies, that are optimized for a certain type of architecture, to the ad hoc, and specifically MANET, architecture. The main advantage of this approach is that products are already available and "easy to use", but the disadvantage is that you undergo several trade-offs. In this sense there is no MANET technology.

Related to the second consideration, in the short term advantages exceed disadvantages and then some task or working groups arise in order to "patch" existing technologies, while R&D centers study on a true MANET technology.

About your last consideration about the use of 802.11 as underlying technology for MANETs, I suggest you to check the following PARs @ http://www.ieee802.org/11/PARs/

- 802.11p TGp - Amendment to the current 802.11 Standard to provide Wireless Access for Vehicular Environments  
- 802.11r TGr - Amendment to the current 802.11 Standard to provide Fast BSS - Transition 
- 802.11s TGs - Amendment to the current 802.11 Standard to provide Extended Service Set Mesh Networking  
- 802.11u TGu - Amendment to the current 802.11 Standard to provide Interworking with External Networks 

That are related to adding mesh networking capabilities to 802.11.

Hope this has been useful

Best regards

	Giorgio

------------------------------------------
Giorgio Mulas | Researcher

CEFRIEL  Politecnico di Milano
Via Fucini, 2 · 20133 Milano (Italy)

p. +39 02 23954 265
f. +39 02 23954 465
e. [email-masked]

> 
> 
> Hello to the MANET community and merry XMAS to you all. 
> 
> When the holidays will be over, I would like to open a 
> discussion on a subject that is not 100% related to MANETs 
> but could still interest some of you. 
> 
> I assume that 802.11 is the standard that has won the market 
> for wireless LAN applications. 
> Now, in my vision, one of the future developments of  
> wireless networks in the close future is the cooperation of 
> MANETs and wireless mesh networks. 
> Wireless mesh networks are networks that are essentially 
> composed by mobile and fixed wireless nodes: the fixed nodes 
> are used to cover a local area. The benefit of mesh 
> architecture is that if that we add fault and congestion 
> tolerance by using redudancy of nodes. In other words, a 
> dense mesh network that runs self-organizing routing 
> protocols and  self organizing congestion-avoidance 
> protocols, will re-route traffic to avoid broken links and 
> congested nodes. 
> Mesh networks will allow to extend MANETs, because two farway 
> mobile nodes will be able to connect to each other by using  
> the mesh network nodes. In this scenario, two close mobile 
> nodes will connect tdirectly without passing throuhg any mesh 
> network node.
> 
> Now the question is: is  this possible using 802.11 standard? 
> In my opinion the answer in NO because in 802.11 a device can 
> be EITHER in Ad-hoc OR in infrastructure mode. To my 
> knowledge, in 802.11 two access points cannot connect to each 
> other  using wireless connection or at least this is not 
> possible in a standard configuration. 
> 
> Am I right? Am I missing something? for comparison, you could 
> check the MEA technology by a company named MeshNetworks, 
> recently bought by Motorola (www.meshnetworks.com).
> 
> Thanks for your answers and merry XMAS again§
> 
> Claudio 
> 
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---

From: [email-masked]
Date: Thu, 30 Dec 2004 11:07:10 +0100

Ciao Giorgio e Buon anno...

OK, of course I agree 100% with you about the fact that the advances that derive
from mesh networking are usable regardless of the wireless technology on the top
of it.

And of course I agree on the fact that 802.11 was not born for that purpose and
that advantages exceed disadvantages at the moment.

So more or less I agree on anything and I will read the IEEE papers you suggest.

My question was a little bit more oriented to today real life. I could restate
it as follows:

If today I want to deploy a mesh network topology for veichular applications
using 802.11 as a wireless technology, could I do that in  a cost and
performances  effective way?
Is it true that such an architecture would need that all the access points have
two interfaces, one to be used for connections from mobile nodes and the second
one to route the traffic toward other access points of the mesh?
Is there any way, today and with 802.11, to make so that a mobile node cannot
connect directly to another mobile node (in ad-hoc mode) or to an access point
without changing any configuration?

Ciao

Claudio

Claudio

Quoting Giorgio Mulas <[email-masked]>:

> I agree with you when you depict a meshnetworking/ubiquitous computing
> future, but I have some considerations about the second part of your
> intervention.
> 
> First of all, I think that ad hoc networking refers mainly to layer 3 (not
> considering cross-layering issues that are layer 1/2 technology specific).
> This implies that a MANET could be built for example on Bluetooth or Zigbee
> technology if you need only some kilo Bytes or on WiMax if you need more
> bandwidth, not just on WiFi. In all these cases layer 3 issues remains
> *roughly* the same.  
> 
> Second, in what I call a Lego-like approach you try to adapt existing mature
> (except WiMax of course) technologies, that are optimized for a certain type
> of architecture, to the ad hoc, and specifically MANET, architecture. The
> main advantage of this approach is that products are already available and
> "easy to use", but the disadvantage is that you undergo several trade-offs.
> In this sense there is no MANET technology.
> 
> Related to the second consideration, in the short term advantages exceed
> disadvantages and then some task or working groups arise in order to "patch"
> existing technologies, while R&D centers study on a true MANET technology.
> 
> About your last consideration about the use of 802.11 as underlying
> technology for MANETs, I suggest you to check the following PARs @
> http://www.ieee802.org/11/PARs/
> 

-------------------------------------------------
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---

From: "Lusheng Ji" <[email-masked]>
Date: Thu, 30 Dec 2004 11:25:22 -0500

Greetings!

Sorry for jumping in.  On this day before the New Year holiday, sitting in
an empty office, I find your topic quite interesting ;)  So here is my 2
cents to stir up the discussion a little more.

A point of access does not have to be an "AP".  Set up a node bridging
between an Ethernet interface and an ad hoc mode 802.11 interface, you have
yourself a point of access (to Ethernet DS) too. 

In typical MANET/Mesh scenarios, there is really not much incentive of using
the additional functions of 802.11 AP.  The whole network has to be on the
same channel and using the same basic transmission rates anyway.  Regarding
functions such as authentication and security, well, my impression is that
MANET/Mesh is not there yet to talk about these, especially if you are
thinking about 11i.  Association is a double edged sword, which we may not
want in MANET/Mesh either.  Beacons?  Well they are good but MANET nodes
typically do their own hellos and gateway advertisements anyway.  After
stripping off these extraneous functions, what is left in an AP that we
really need for typical MANET/Mesh scenarios?  Actually not much different
from what any other ad hoc mode nodes have.  Then why not just putting up
another ad hoc node and stabbing a RJ45 plug into its back and using it as
the point of access?

Okay what if you want real APs, not faked ones?  There are a couple of
options too. 

Among the more recent AP products, many of them support something called the
"wireless distribution system", or WDS.  WDS enables APs to talk to each
other over wireless directly.  It also enables layer 2 forwarding in an
802.11 mesh because WDS frames use 4 MAC addresses not 3.  The additional
MAC address could be used to preserve the original source identity.  You
might want to look into that.  It's been in the standard but had not been
implemented until recently.  An AP can use the same physical interface to do
its AP things and WDS things.  The catch is: while this solves some
problems, it may open another can of worms.  In this type of deployments,
the APs need to be deployed very densely since they need to be in range with
each other.  Assuming they do not do super communication among themselves,
the AP density needs to be roughly 4 times (if you use square to model the
shape of each cell) of a WLAN type of deployment (without inter-AP wireless
communication) covering the same area.  The added costs, more frequent
mobile client handoffs....

Well, at last, if you really really want an all around all time
"WDS+adhoc+DCF/PCF" super power AP, seems that you would have to make you
own.  Fortunately as far as I can see, the differences between what you need
and what current APs offer pretty much are all above firmware level.  So you
could play with an open source kernel/user space AP implementation such as
the hostapd to tailor it towards your purpose.  Efficient or not is another
issue, but it is def. out of scope for this thread :)

Hope the above helps a little.  
Oh and, happy New Year!

Regards,

Lusheng Ji, Ph.D.
Senior Technical Specialist
AT&T Labs Research
180 Park Ave.,
Florham Park, NJ 07932, USA

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of
[email-masked]
Sent: Thursday, December 30, 2004 5:07 AM
To: Giorgio Mulas
Cc: [email-masked]; [email-masked]
Subject: RE: [manet] 802.11, MANETs and mesh networks?

OK, of course I agree 100% with you about the fact that the advances that
derive
from mesh networking are usable regardless of the wireless technology on the
top
of it.

And of course I agree on the fact that 802.11 was not born for that purpose
and
that advantages exceed disadvantages at the moment.

So more or less I agree on anything and I will read the IEEE papers you
suggest.

My question was a little bit more oriented to today real life. I could
restate
it as follows:

If today I want to deploy a mesh network topology for veichular applications
using 802.11 as a wireless technology, could I do that in  a cost and
performances  effective way?
Is it true that such an architecture would need that all the access points
have
two interfaces, one to be used for connections from mobile nodes and the
second
one to route the traffic toward other access points of the mesh?
Is there any way, today and with 802.11, to make so that a mobile node
cannot
connect directly to another mobile node (in ad-hoc mode) or to an access
point
without changing any configuration?

Ciao

Claudio

Claudio

Quoting Giorgio Mulas <[email-masked]>:

> - 802.11p TGp - Amendment to the current 802.11 Standard to provide
Wireless
> Access for Vehicular Environments  
> - 802.11r TGr - Amendment to the current 802.11 Standard to provide Fast
BSS
> - Transition 
> - 802.11s TGs - Amendment to the current 802.11 Standard to provide
Extended
> Service Set Mesh Networking