[manet] Re: MANET WG Charter and MANET Internetworking

Date: Fri, 18 Jul 2025 08:11:33 +0200

From: Henning Rogge <[email protected]<mailto:[email protected]>>

Subject: [manet] Re: MANET WG Charter and MANET Internetworking

To: "Stevens, Jim" <[email protected]<mailto:[email protected]>>



Hello,



On Fri, Jul 18, 2025 at 12:12 AM Stevens, Jim

<[email protected]<mailto:[email protected]>> wrote:

>

> Some of the recent emails presume that MANET radios are IP routers and radios *only* route using IP, so that questions arise with whether you decrement TTL for each radio hop.  Similar questions arise with overlay/underlay networks and MANET wireless networking getting partitioned.  And, also multihop MANET networks that get partitioned lead to the issues raised in RFC 4903 about Multi-Link Subnet Issues.



MANET normally use only host routes (or routes to prefixes that are

reachable through a single router), so the subnet split is not that

important for them. It is also a good idea to NOT put a subnet on your

MANET interface but put a /32 address on it (or just a linklocal one).



There can be different MANET use cases.  Most of the different MANET networking waveforms (with their specific MANET protocols) that I work on have one or more IP stub subnets with host computers attached to the MANET radios and multiple MANET radios that also gateway to the rest of the internet.  So the MANET wireless networks can be transit wireless networks.  (Note that these are MANET networks other than standard 802.11, LoRaWAN, etc.)



I agree with the idea of either putting linklocal IP addresses on the wireless side of the MANET radios and/or using overlay/underlay IP addressing on the baseband interface(s) of the MANET radios (independent of whether the MANET routing is done at layer 3 or layer 2).



> So the MANET IETF working group also needs to consider MANET wireless networks where the wireless MANET routing is below IP – similar to how Ethernet switches route below IP.   This eliminates the TTL issues.  And overlay/underlay networks (whether MANET radios route using IP or below IP) can allow MANET radios in one IP subnet to transmit to another radio in that MANET wireless network that is in a different IP subnet.  And overlay/underlay can be adapted to solve Multi-Link Subnet issues as well



MANET can work with layer-2 forwarding below, but using two MANET

layers independently on top of each other can lead to all kinds of bad

side effects.



MANET protocols can also be working on layer-2 itself if you can

change the used address type to MAC addresses (and ignore the parts

being able to use a prefix).



Henning Rogge



Agree, we usually run our MANET protocols on the wireless layer-2 itself and standard IP routing to hosts/external routers to the MANET radios.



Also agree that having two MANET layers running independent of each other can lead to bad side effects.  This is reason for my comment about some wireless networks run MANET routing below IP and thus that it can be bad to include MANET functions in the IP routing above the layer-2 MANET layer, such as doing DLEP to ask for radio link information when the MANET radio radio can often do a better job of adapting to changes in the rf environment (such as changing modulation, frequency, channel access time slot allocations, etc).



But there can still be some special cases that IP routing needs to handle, such as the multi-link issues addressed in RFC 4903 that arise when the wireless networks are partitioned, especially if users wanted to have the IP subnet equivalent of a VPN above the wireless network(s).



Jim

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