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Routing MANET The BABEL routing protocol (RFC 8966) is well applicable (RFC 8967) to networks with unstable link metrics such as wireless networks. Wi-Fi (IEEE Std 802.11-2024) is an example of such a network and the Wi-Fi standard includes a mesh feature which was specified to be configurable for different routing protocols and link metrics. This document specifies how, in Wi-Fi mesh, to use BABEL and/or the delay based link metric specified in RFC 9616.

Introduction [[[This is an incomplete early draft.]]] The BABEL routing protocol (RFC 8966) is well applicable (RFC 8967) to networks with unstable link metrics such as wireless networks. Wi-Fi (IEEE Std 802.11-2024) is an example of such a network and the Wi-Fi standard includes a mesh feature which was specified to be configurable for different routing protocols and link metrics. This document specifies how, in Wi-Fi mesh, to use BABEL and/or the delay based link metric specified in RFC 9616. Not only is the Wi-Fi mesh protocol explicitly designed to allow the specification of other Path Selection Protocols (routing protocols) and Path Selection Metrics (link metrics), but has sent the IETF a stating that it has no objection to this work.

Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 when, and only when, they appear in all capitals, as shown here.

Clause

Parts of are referred to as Clauses which are hierarchically numbered. These can be nested multiple levels.

Frame

Roughly the Layer 2 term equivalent to packet.

MAC

Media Access Control, not message authentication code.

Path Selection Metric

The Wi-Fi mesh term for a link cost metric.

Path Selection Protocol

The Wi-Fi mesh term for a routing protocol.

Station

A logical Wi-Fi entity that is a singly addressable instance of a medium access control and physical layer interface to the wireless medium.

Wi-Fi

The IEEE Std 802.11-2024 wireless communication standard.

IEEE Std 802.11 Specifics

Mesh Discovery and Formation Mesh Stations generally discover each other through the transmission and reception of mesh beacon frames. (A mesh Station can also transmit a Probe with the intent of soliciting a Probe Response from a potential peer.) While the interval between beacons is configurable, the common value used is 100 milliseconds. For two Stations to peer, there are a number of fields, called the mesh profile ( Clause 14.2.3), that have to match between the stations which are included in a mesh beacon. These fields include the Mesh ID, Path Selection Protocol ID, and Link Metric ID. In particular, mesh beacon frames include the Mesh Configuration element ( Clause 9.4.2.97) which in turn contains an Active Path Selection Protocol Identifier (Clause 9.4.2.97.2) and Active Path Selection Metric Identifier (Clause 9.4.2.97.3). (The Mesh Configuration element is also included in Probe Response, Mesh Peering Open, and Mesh Peering Confirm Wi-Fi control frames.) The Path Selection and Path Metric identifiers are one-byte fields for which the value 255 (0xFF) indicates that a "vendor specific" protocol or metric, respectively, is in use by the transmitting Station. The vendor specifics are indicated in one or more Vendor Specific elements (Clause 9.4.2.25) included in the same Wi-Fi frame with the Mesh Configuration element. shows such an element where IANA is the "vendor".

IETF "Vendor Specific" Wi-Fi Element 1 1 1 1 1 1 1 1 1 1 2 2 2 2 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 +----------------+---------------+ | Element ID=221 | Length | +----------------+---------------+---------------+ | IANA OUI = 0x00000E | +----------------+---------------+---------------+ | Subtype | Content +----------------+-------------

Element ID

221 (0xDD).

Length

Length of the element in bytes excluding the Element ID and Length field as a one-byte unsigned integer.

IANA OUI

0x00005E

Subtype

Type of content.

Content

Subtype specific information. May be null.

If the Babel path selection protocol is in use, but not the delay-based path metric, then the Active Path Selection Protocol Identifier field MUST be set to 255 (0xFF) and there MUST be an IANA OUI Vendor Specific element present with a subtype of 1. If the delay based path metric in use, but not the Babel path selection protocol is, then the Active Path Selection Metric Identifier field MUST be set to 255 (0xFF) and there MUST be an IANA OUI Vendor Specific element present with a subtype of 2. To indicate that both the Bable path selection protocol and the delay based path metric are in use, the Active Path Selection Protocol Identifier field and the Active Path Selection Metric Identifier in the Mesh Configuration element MUST be set to 255 (0xFF) and there MUST be an IANA OUI Vendor Specific element present with a subtype of 3. The use of a single Vendor Specific element for this case is to minimize the burden of increased beacon size. The Content portion of the Vendor Specific element can be null or can be a Babel routing message such as a Hello.

Babel Specifics

Addresses Wi-Fi operates on Layer 2 of the OSI model using 48-bit MAC addresses which form a flat rather than a hierarchical address space. Thus frames are routed based on a destination MAC address. TBD is assigned as the Babel Address Encoding type for 48-bit MAC addresses

Router ID Each mesh Station (router) using Babel has an arbitrary 8 byte router-id that must be unique within the routing domain. It is RECOMMENDED that this be derived from the MAC addresses of the Station's interfaces by treating them as 48-bit unsigned integers, selecting the one with the least magnitude, and padding it 16 low order zero bits.

Babel Messages More TBD. If a mesh Station using Babel is sending beacons, it may be convenient to include a Hello message in the contents of the beacon's IANA Vendor Specific Element being used to announce that the Station is using Babel. More TBD.

Multicast and Broadcast Wi-Fi mesh can inherently handle multicase and broadcast data traffic independent of routing by numbering such messages, flooding them inside the mesh, and deleting duplicates.

IANA Considerations This section is to be interpreted as provided in .

Babel Address Encoding IANA is requested to assign a codepoint in the Babel Address Encoding registry as follows:

AE	Name	Reference
TBD	48-Bit MAC Address	[this document]

IANA Parameters for Wi-Fi (IEEE 802.11) In conformance with Section 4 of IANA is requested to create a registry in the "IANA OUI Ethernet Numbers" Registry Group as follows:

Name:

IETF Parameters for Wi-Fi (IEEE Std 802.11)

References:

[this document]

Note:

This registry provides subtypes, under the IANA OUI, for the "vendor specific" elements that may be used in the IEEE Std 802.11-2024 protocol.

The initial contents of the registry are as follows:

Subtype	Description	Reference
0	Reserved	[this document]
1	Babel Path Selection	[this document]
2	Delay Based Link Metric	[this document]
3	Babel Path Selection and Delay Based Link Metric	[this document]
4-41	Unassigned
42	Example for use in documentation	[this document]
43-254	Unassigned

Security Considerations For IEEE Std 802.11 security considerations, see . When Wi-Fi mesh Stations peer, they negotiate security and keys. For Babel security considerations, see [RFC8966].

Normative References IEEE Informative References IEEE 802 LMSC IEEE 802.11 Working Group

Acknowledgements The comments and suggestions of the following are gratefully acknowledged: