Subject: RE: [manet] IP-802.11 interface

From: "Yang, Lily L" <[email-masked]>
Date: Tue, 25 Mar 2003 10:25:21 -0800

In the recent IEEE Plenary meeting, Mesh Network presented a proposal to
extend 802.11 to better support mesh networking. One of the recommendations
is to extend the existing 802.11 standard MAC to allow information pertinent
to ad hoc networking to be passed across the network efficiently.  I quote a
few paragraphs relevant to the discussion here --
"Feedback from MAC/LLC to Routing implementation:
Immediate feedback of the TX and Rx status of packets received is critical
in
developing a reliable ad-hoc routing network. This status data is typically
available in some form from the MAC layer implementations of 802.11
hardware,
but is seldom available outside of the scope of the link layer. In Layer 2
routing
implementations based in or immediately above the link layer this
information
can be passed directly. In layer 3 implementations the cost of reporting
per-packet
information up to the network layer of a protocol stack may be
computationally or
architecturally prohibitive. In that case a cumulative derivative value can
be
computed in a small module collocated near the MAC. This value can then be
reported to the routing layer on a less frequent per-destination basis. Most
current
driver/stack combinations do not pass this information up in the stack.
Mac layer acknowledgements for transmitted directed packets must be reported
to
some agent of the routing implementations. This is necessary to determine
the
status of links in the multi-hop network.
Some normalized measure of signal quality or S/N ratio of received packets
must
be reported on a per packet basis to some agent of the routing
implementation.
Management packets should be made available to some agent of the routing
implementation so they can be used to inform the routing of status of
individual
neighboring stations."
"Feedback from the PHY:
A normalized measure of the number of corrected bit errors on a received
perpacket
should be made available to some agent of the routing implementation.
This can be used to predict degrading links in the network and proactively
switch
routes."

The full presentation can be found at:
http://www.ieee802.org/meeting/meeting_files/Ad%20Hoc%20And%208022.pdf

So maybe IEEE instead of IETF is the right place to do this ...
In any event, if 802.11 is going to work well for mesh networking, perhaps
it also calls for better coordination/interaction between the two groups.

-----Original Message-----
From: Joe Macker [mailto:[email-masked]]
Sent: Tuesday, March 25, 2003 7:31 AM
To: Paul Tan Hock Lai; [email-masked]; Sukanta Kumar Hazra;
[email-masked]
Cc: [email-masked]
Subject: RE: [manet] IP-802.11 interface

At 05:49 PM 3/25/2003 +0800, Paul Tan Hock Lai wrote:
>Hi,
>
>I am also interest in this issue too. I have actually tried to query the
mailing list on the similar matter, but failed to get a response. Maybe it's
out of the scope of MANET. 8-)

Its not that its out of scope, but that there has not been a standard
interface mechanisms to work with.  We have discussed this quite a bit when
the WG began. However, that doesn't one can't do something. The MAC ACK
monitoring approach has some drawbacks (unicast only and congestion
problems) and shouldn't be seen as the best approach, even though that is
typically what is simulated.

More precise link quality (filtered S/N-based) or simple link up/down would
be useful if available..

In most specs the protocols are designed to work in the absence of such
mechanisms, but most have wording to say take advantage of such an interface
if available.

>> Some of the manet routing protocols (e.g., AODV abd DSR) have the
>> option of using MAC layer messages to realize link failures. 
>
>MANET protocol (layer) requires triggers (link-up, link-down, etc) from the
mobile node (itself),
>I am not sure it TrigTrans can apply here (triggers sent by other
entities).
>
>The timing and the reliability of the triggers are important too.

Yes, these are important issues.

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---

From: "Alhussein Abouzeid" <[email-masked]>
Date: Tue, 25 Mar 2003 17:40:44 -0500

For some time now, many have advocated that the layering approach doesn't
work well for ad-hoc (transport, routing etc.) and have proposed solutions
when the layers were allowed to "talk" to each other. It is actually quite
refreshing to see some serious talk here about standardization activities
for interlayer interactions. My question pertains to a statement you make
below that interlayer interactions may incur prohibitively high additional
cost. It would be quite helpful if you would provide some details on this
assessment from your experiments. You also raise a point about scalability
in the introductory part of your report. Gupta and Kumar's work comes to
mind, among others. Again, I was wondering if you had some experimental
results regarding this.

Many thanks.

AA

----- Original Message -----
From: "Yang, Lily L" <[email-masked]>
To: "'Joe Macker'" <[email-masked]>; "Paul Tan Hock Lai"
<[email-masked]>; <[email-masked]>; "Sukanta Kumar
Hazra" <[email-masked]>; <[email-masked]>
Cc: <[email-masked]>
Sent: Tuesday, March 25, 2003 1:25 PM
Subject: RE: [manet] IP-802.11 interface

---

From: "Herbert Rubens" <[email-masked]>
Date: Tue, 25 Mar 2003 18:51:34 -0500

I absolutely agree that the availability of MAC and physical layer
signal quality information is essential in order to make efficient
routing decisions. Aside from link failure detection, this information
can be used to increase route stability and throughput. This is briefly
mentioned in the presentation you referred to. We have been actively
researching how this information can be used to enhance routing. A
technical report is available which examines this in detail. 

http://www.cnds.jhu.edu/research/networks/archipelago/publications/MTM-T
echnicalReport2.pdf

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of
Yang, Lily L
Sent: Tuesday, March 25, 2003 1:25 PM
To: 'Joe Macker'; Paul Tan Hock Lai; [email-masked]; Sukanta
Kumar Hazra; [email-masked]
Cc: [email-masked]
Subject: RE: [manet] IP-802.11 interface

In the recent IEEE Plenary meeting, Mesh Network presented a proposal to
extend 802.11 to better support mesh networking. One of the
recommendations
is to extend the existing 802.11 standard MAC to allow information
pertinent
to ad hoc networking to be passed across the network efficiently.  I
quote a
few paragraphs relevant to the discussion here --
"Feedback from MAC/LLC to Routing implementation:
Immediate feedback of the TX and Rx status of packets received is
critical
in
developing a reliable ad-hoc routing network. This status data is
typically
available in some form from the MAC layer implementations of 802.11
hardware,
but is seldom available outside of the scope of the link layer. In Layer
2
routing
implementations based in or immediately above the link layer this
information
can be passed directly. In layer 3 implementations the cost of reporting
per-packet
information up to the network layer of a protocol stack may be
computationally or
architecturally prohibitive. In that case a cumulative derivative value
can
be
computed in a small module collocated near the MAC. This value can then
be
reported to the routing layer on a less frequent per-destination basis.
Most
current
driver/stack combinations do not pass this information up in the stack.
Mac layer acknowledgements for transmitted directed packets must be
reported
to
some agent of the routing implementations. This is necessary to
determine
the
status of links in the multi-hop network.
Some normalized measure of signal quality or S/N ratio of received
packets
must
be reported on a per packet basis to some agent of the routing
implementation.
Management packets should be made available to some agent of the routing
implementation so they can be used to inform the routing of status of
individual
neighboring stations."
"Feedback from the PHY:
A normalized measure of the number of corrected bit errors on a received
perpacket
should be made available to some agent of the routing implementation.
This can be used to predict degrading links in the network and
proactively
switch
routes."

So maybe IEEE instead of IETF is the right place to do this ...
In any event, if 802.11 is going to work well for mesh networking,
perhaps
it also calls for better coordination/interaction between the two
groups.

-----Original Message-----
From: Joe Macker [mailto:[email-masked]]
Sent: Tuesday, March 25, 2003 7:31 AM
To: Paul Tan Hock Lai; [email-masked]; Sukanta Kumar Hazra;
[email-masked]
Cc: [email-masked]

>I am also interest in this issue too. I have actually tried to query
the
mailing list on the similar matter, but failed to get a response. Maybe
it's
out of the scope of MANET. 8-)

Its not that its out of scope, but that there has not been a standard
interface mechanisms to work with.  We have discussed this quite a bit
when
the WG began. However, that doesn't one can't do something. The MAC ACK
monitoring approach has some drawbacks (unicast only and congestion
problems) and shouldn't be seen as the best approach, even though that
is
typically what is simulated.

More precise link quality (filtered S/N-based) or simple link up/down
would
be useful if available..

In most specs the protocols are designed to work in the absence of such
mechanisms, but most have wording to say take advantage of such an
interface
if available.

mobile node (itself),
entities).

---

From: "Petar Popovski" <[email-masked]>
Date: Wed, 26 Mar 2003 13:25:19 +0100

I would also like to share some thoughts regarding the interlayer
interactions.

To my understanding, the traditional layering in the communication protocols
reflects the way in which the communication system is usually decomposed.
For example, there is a procedure for reliable transmission over a link,
while the routing concatenates several such link procedures in order to
produce a full route, but without intervention into the mechanisms employed
by the link procedure itself. This works fine as long as the link procedures
within a route are mutually independent. But, when they are not, as it is a
case in the wireless ad hoc networks, some "other" system decomposition is
needed and this decomposition depends on the goal we want to achieve.

The layering decomposition is suitable for the case when the communication
is across heterogenous link layers. However, in ad hoc networks the usual
target is to optimize the power consumption, while the network is (usually)
homogeneous. That is, in ad hoc nets where all devices are connected through
a single radio interface, the system can be observed as homogenous up to and
including the routing layer. Hence, a node uses a communication block that
spans routing, link and physical layer in order to establish multihop
connection.

Now my question is: Is there any work at present that makes a general
discussion how this communication block should be designed (decomposed into
subblocks), depending on goal to be achieved (e.g. power-efficient
communication)?

Best regards,
Petar Popovski