Subject: [manet] MANET Routing Below IP (spin off from Subnet Definition thread)

From: [email-masked]
Date: Thu, 7 Jun 2012 09:36:27 -0500

On Jun 6, 2012 at 154:45:20 (-0600), Fred Baker wrote:

> On Jun 6, 2012, at 3:16 PM, Charles E. Perkins wrote:
>> On 6/6/2012 12:00 PM, Fred Baker wrote:
>>> That said, to me, the data link layer tells me how to layer message 
exchange onto the physical layer and as a result get a message from one
>>> end to another of a single physical medium. When I start concatenating 
physical connectivity and have routing questions
>> 
>> Could they be bridging questions?
>
>here you hark back to a debate that actually kinda-sorta made sense 20 
years ago, but makes no sense in this context. IEEE 802.1, and 
specifically >802.1d, is a routing technology. It doesn't route in the 
sense that OSPF or BGP do, but it figures out how to get packets across a 
network from >point A to point B.

Actually, this debate makes a lot of sense today.  In fact, this is the 
way that a lot of companies have been developing & fielding multihop, 
mobile ad hoc networks for over 4 decades now - going all the way back to 
the original DARPA funded Packet Radio work in 1970s as part of the 
original Internet project.  Namely multihop routing below IP, so that the 
multihop wireless network below IP looks like a 1 hop IP link no matter 
how many wireless hops it takes.  In other words, the wireless network 
does routing analogous to ethernet switching (routing) below IP.

And we are still going strong this way today with over a dozen different 
MANET wireless technologies today that are working with multihop routing 
below IP - both from my company and other companies.  I believe that in 
total, there are over 100,000 fielded wireless nodes of one type or 
another of these MANET technologies. Some of these wireless technologies 
with MANET routing below IP that have been described in public domain 
documentation include Mil-Std-188-220, MARLIN (STANAG 4691), Link 22 
(although the final fielded standard dropped support for IP at layer 3), 
EPLRS, and FlexNet.  Some of these waveforms call this sub-layer below IP 
the Intranet, others the wireless Subnet, others the Data Link. 

As an aside, you may ask why are there so many different types of wireless 
technologies?  Well the answer is that there are lots of different 
requirements with different RF channel conditions with different fading 
conditions, frequency allocations (different freq bands and bandwidths), 
data rates (from burst rates with kbps to 100s of Mbps), threats (jamming 
or not jamming), user traffic with different QOS requirements (from ETE 
latencies of 10s of milliseconds to minutes, ETE message successful 
delivery rates (from 90% to 99.999% success), traffic mixes (unicast only, 
broadcast only, to mix of uni-, multi- & broadcast), etc. 

>>> , I'm in the network layer; the question is "where".
>> 
>> In my understanding, there isn't any ambiguity about this because, in
>> the network layer, network addresses are used.  In layer 2, layer 2 
addresses
>> are used (e.g., for bridging).
>
>again, harking back to a discussion that is kind of irrelevant. Are you 
going to tell me that an IP address used by two layers, one of which is 
>doing subnet routing using, say, OSPF, and the other is doing host 
routing through AODV, are not both in the network layer? If so, then why 
would a >network doing two layers of routing, one of which is using subnet 
routing using, say, OSPF, and the other is doing host routing through 
802.1d, is >not both in the network layer?

The reason all of the waveforms that I mentioned do routing below IP is 
that they are all omnidirectional wireless and multihop networks (without 
base stations or access points with out-of-band infrastructure to use for 
routing).  Thus, MANET operation for these networks is much more than just 
routing.  It includes determining what is a good neighbor and under what 
conditions (e.g. predicted transmission success probability for given FEC, 
transmit power, frequency, antenna setting, etc). It includes figuring out 
which neighbors to address for any given transmission as well as 
accounting for the self-interference caused by the transmissions. It also 
includes allocating more resources (e.g. time slots) to adapt to QOS and 
traffic loading at different nodes in an RF neighborhood. In general, then 
MANET in these networks means cross-layer optimization of the physical 
modulation, the channel access, and the Intranet routing. (For example, 
see my IETF MANET 12 Jul 2002 13:18:43 email, and follow on discussion 
threads, on "Interference in RF networks.")  In general, I claim that 
since this cross layer optimization cannot be performed by IP MANET 
routing alone, it makes architectural sense to do MANET Intranet routing 
below IP and just provide an abstracted IP link cost to the IP routing for 
that wireless MANET network technology.

As an aside, IMO most work in the IETF MANET has been concerned with 
802.11 networks and cross-layer optimization have focused on its CTS/RTS 
MAC layer.  This is why work was done to allow jitter to be inserted by 
the MANET protocols as a type of cross-layer optimization for 802.11 as an 
Internet Draft circa 2007 and included in RFC 6130 NHDP in 2011. Well 
Packet Radio already had that optimization included back in 1970s and in 
Mil-Std-188-220 in 1990s.

So, do I think that the IETF MANET work makes sense? Yes! For example, 
some of the wireless Intranet technologies I mentioned above are using 
optimized variants of IETF MANET protocols, namely OLSR. The most common 
optimization is to eliminate the use of Hellos for neighbor discovery 
(because it is part of the MAC function) as well as using the local MAC 
layer information to route to nodes that may be 1 or 2 hops away.

However, I think that some of the IETF MANET work is not applicable to 
these Intranet MANETs. For example, Hello messages should be optional if 
the MAC layer can provide that information directly. In fact, trying to 
determine neighbors from just hellos alone can lead to poor performance in 
many of these networks because it doesn't take into account interference 
as an example and doesn't help select which good nodes to use as good 
neighbors.

Twenty years ago, I used to say that wireless MANET routing **must** be 
below IP to enable such cross layer optimization. I no longer claim that 
because I now see some wireless technologies where IP layer MANET routing 
alone works just fine.  However, I am now concerned when people claim that 
wireless MANET routing must be at IP layer only - because they don't know 
or understand the issues involved with the cross layer optimization I 
discussed above.  And, it confuses non-networking people who say "if the 
IETF MANET says it, then it must be true."

>>> the Internet layer is an upper sub-layer of the Network Layer, and 
Ethernet/ATM/IP Tunnels/IP re-used within a manet|roll domain and etc
>>> are in a lower sub-layer I call the "Intranet" sub-layer. But yes, I 
think we agree that the LAN, however comprised, is in a sub-layer 
>>> lower than the Internet layer. 
>> 
>> Do you envision that an "Intranet" layer would use Internet addresses 
at all?
>
>RPL is a pretty good example of a routing protocol that makes that 
assumption. If AODV is used and the node ID is an IP address - very 
reasonable - >sure.

I have seen multiple different types of addressing used in the Intranet 
below the IP layer.  In most cases, the wireless Intranet has its own 
address separate from the IP address.  In many cases, this Intranet 
address maps to an IP subnet address (say the lower octect or two) for 
that wireless network.  Hence this is why some of the above mentioned 
wireless MANETs call this layer below IP the Subnet Layer rather than the 
Intranet layer.   In other cases, the wireless Intranet has its own 
address and a ARP or ARP-like function maps the Intranet address to the IP 
address. 

Jim Stevens

---

From: Henning Rogge <[email-masked]>
Date: Thu, 7 Jun 2012 20:09:09 +0200

On Thu, Jun 7, 2012 at 4:36 PM,  <[email-masked]> wrote:
>> years ago, but makes no sense in this context. IEEE 802.1, and specifically
>> >802.1d, is a routing technology. It doesn't route in the sense that OSPF or
>> BGP do, but it figures out how to get packets across a network from >point A
>> to point B.
>
> Actually, this debate makes a lot of sense today.  In fact, this is the way
> that a lot of companies have been developing & fielding multihop, mobile ad
> hoc networks for over 4 decades now - going all the way back to the original
> DARPA funded Packet Radio work in 1970s as part of the original Internet
> project.  Namely multihop routing below IP, so that the multihop wireless
> network below IP looks like a 1 hop IP link no matter how many wireless hops
> it takes.  In other words, the wireless network does routing analogous to
> ethernet switching (routing) below IP.

Yes, this grow of multihop capabilities directly in the radios can be
both a blessing and a pain, depending on the usecase.

> total, there are over 100,000 fielded wireless nodes of one type or another
> of these MANET technologies. Some of these wireless technologies with MANET
> routing below IP that have been described in public domain documentation
> include Mil-Std-188-220, MARLIN (STANAG 4691), Link 22 (although the final
> fielded standard dropped support for IP at layer 3), EPLRS, and FlexNet.
>  Some of these waveforms call this sub-layer below IP the Intranet, others
> the wireless Subnet, others the Data Link.

Some of them also do IP routing in their network, which can become a
problem when they cannot connect to a larger routing domain as a
transit network.

> data rates (from burst rates with kbps to 100s of Mbps), threats (jamming or
> not jamming), user traffic with different QOS requirements (from ETE
> latencies of 10s of milliseconds to minutes, ETE message successful delivery
> rates (from 90% to 99.999% success), traffic mixes (unicast only, broadcast
> only, to mix of uni-, multi- & broadcast), etc.

A lot of TDMA waveforms do (positive and negative) crazy things with
their explicit knowledge of their timings.

>> >doing subnet routing using, say, OSPF, and the other is doing host routing
>> through AODV, are not both in the network layer? If so, then why would a
>> >network doing two layers of routing, one of which is using subnet routing
>> using, say, OSPF, and the other is doing host routing through 802.1d, is
>> >not both in the network layer?
>
> The reason all of the waveforms that I mentioned do routing below IP is that
> they are all omnidirectional wireless and multihop networks (without base
> stations or access points with out-of-band infrastructure to use for
> which neighbors to address for any given transmission as well as accounting
> for the self-interference caused by the transmissions. It also includes
> allocating more resources (e.g. time slots) to adapt to QOS and traffic
> loading at different nodes in an RF neighborhood. In general, then MANET in
> these networks means cross-layer optimization of the physical modulation,
> the channel access, and the Intranet routing. (For example, see my IETF
> MANET 12 Jul 2002 13:18:43 email, and follow on discussion threads, on
> "Interference in RF networks.")  In general, I claim that since this cross
> layer optimization cannot be performed by IP MANET routing alone, it makes
> architectural sense to do MANET Intranet routing below IP and just provide
> an abstracted IP link cost to the IP routing for that wireless MANET network
> technology.

Thats why I think that the idea behind DLEP can become VERY important
for future digital radios.

> As an aside, IMO most work in the IETF MANET has been concerned with 802.11
> networks and cross-layer optimization have focused on its CTS/RTS MAC layer.
>  This is why work was done to allow jitter to be inserted by the MANET
> protocols as a type of cross-layer optimization for 802.11 as an Internet
> Draft circa 2007 and included in RFC 6130 NHDP in 2011. Well Packet Radio
> already had that optimization included back in 1970s and in Mil-Std-188-220
> in 1990s.

I think the existence of Jitter in IETF network protocols is older than NHDP.

> So, do I think that the IETF MANET work makes sense? Yes! For example, some
> of the wireless Intranet technologies I mentioned above are using optimized
> variants of IETF MANET protocols, namely OLSR. The most common optimization
> is to eliminate the use of Hellos for neighbor discovery (because it is part
> of the MAC function) as well as using the local MAC layer information to
> route to nodes that may be 1 or 2 hops away.

This would also be something DLEP could help with a small extension.
Lets the radio the link sensing and neighbor detection (which it
already has to do for TDMA handling anyways) and export them in a well
defined form into the Layer-3 routing to use it for something like
OLSRv2.

> However, I think that some of the IETF MANET work is not applicable to these
> Intranet MANETs. For example, Hello messages should be optional if the MAC
> layer can provide that information directly. In fact, trying to determine
> neighbors from just hellos alone can lead to poor performance in many of
> these networks because it doesn't take into account interference as an
> example and doesn't help select which good nodes to use as good neighbors.

OLSRv2 normally runs on top of NHDP... but I could imagine a "mixed
mode" to draw neighbor data from external sources.

> wireless MANET routing must be at IP layer only - because they don't know or
> understand the issues involved with the cross layer optimization I discussed
> above.  And, it confuses non-networking people who say "if the IETF MANET
> says it, then it must be true."

*G*

> address separate from the IP address.  In many cases, this Intranet address
> maps to an IP subnet address (say the lower octect or two) for that wireless
> network.  Hence this is why some of the above mentioned wireless MANETs call
> this layer below IP the Subnet Layer rather than the Intranet layer.   In
> other cases, the wireless Intranet has its own address and a ARP or ARP-like
> function maps the Intranet address to the IP address.

If they directly map onto IP addresses in a "one on one" way, they
could be called IP addresses. Just with some special "compression" and
handling scheme.

I think there are (at least) two usecases for upcoming digital radios
like the ones you mentioned. Some users just want to install them
somewhere, just with an ethernet plug to attach the local network
(like a laptop, an internal car network). Others want to integrate
them into a larger heterogeneous radio network based on IP routers.

In the first case, being able to do the whole "routing" in the device
is a great thing and simplifies a lot. But in the second case,
internal routing can become a problem for integration.

I think something like DLEP could maybe help us to solve this problem,
allowing a radio to run in two modes... one autonomous and another one
radio and attached router working hand in hand.

Henning Rogge
-- 
Steven Hawkings about cosmic inflation: "An increase of billions of
billions of percent in a tiny fraction of a second. Of course, that
was before the present government."

---

From: "Dearlove, Christopher (UK)" <[email-masked]>
Date: Fri, 8 Jun 2012 08:51:14 +0000

Jitter is described in RFC 5148, which is what NHDP and OLSRv2 reference (for use when appropriate, but not when not). The specific model 5148 uses comes from OLSR (RFC 3626) but 5148 has some informative references to other uses. Right now I don't recall if any of those informative references use the same [-T,0] offset as OLSR/5148 does (for at least two good reasons), some certainly use a [-T,T] offset.

-- 
Christopher Dearlove
Senior Principal Engineer, Communications Group
Communications, Networks and Image Analysis Capability
BAE Systems Advanced Technology Centre
West Hanningfield Road, Great Baddow, Chelmsford, CM2 8HN, UK
Tel: +44 1245 242194 |  Fax: +44 1245 242124
[email-masked] | http://www.baesystems.com

BAE Systems (Operations) Limited
Registered Office: Warwick House, PO Box 87, Farnborough Aerospace Centre, Farnborough, Hants, GU14 6YU, UK
Registered in England & Wales No: 1996687

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of Henning Rogge
Sent: 07 June 2012 19:09
To: [email-masked]
Cc: [email-masked]
Subject: Re: [manet] MANET Routing Below IP (spin off from Subnet Definition thread)

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Henning Rogge
-- 
Steven Hawkings about cosmic inflation: "An increase of billions of
billions of percent in a tiny fraction of a second. Of course, that
was before the present government."
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