Transmission of IPv6 Packets over Digital Enhanced Cordless Telecommunications (DECT) Ultra Low Energy (ULE)
Extracted elements (30)
DECT ULE's star topology with no mesh networking capability means the Multi-Link Subnet / NBMA model was chosen to avoid the complexity of implementing a separate /64 subnet per DECT ULE link, while still supporting 6LN-to-6LN communication via the 6LBR.
IP multicast is mapped to unicast replication by the 6LBR because the DECT MAC layer broadcast service does not support the 1280-octet MTU required by IPv6, making native multicast unsuitable.
The DECT ULE DLC's native segmentation and reassembly capability eliminates the need for RFC 4944 fragmentation at the 6LoWPAN layer, simplifying the stack. The default 500-octet MTU is raised to 1280 octets to support full IPv6 packets.
The TPUI (20-bit Temporary Portable User Identity assigned during location registration) is not used for IID construction because many implementations assign the same TPUI repeatedly, making it unsuitable for stable unique addressing per RFC 8065.
A significant difference from IEEE 802.15.4 is that DECT ULE in its primary configuration does not support mesh topology or multihop networks at the link layer, so the RFC 4944 mesh header and the 6LR role are not defined for DECT ULE.
DECT device addresses (IPEI, RFPI) and IEEE MAC-48 addresses belong to different address spaces, so IIDs derived from DECT addresses via the RFC 4291 Appendix A procedure cannot be considered globally unique within the IEEE address space.
A DECT ULE 6LN MUST NOT register its link-local address because the IIDs used in link-local addresses are derived from DECT addresses, ensuring a unique mapping between link-local and Layer 2 addresses already exists.
A DECT ULE 6LN MUST register its non-link-local addresses with the 6LBR by sending an NS with the Address Registration Option (ARO), irrespective of the IID generation method.
Because DECT ULE does not support multihop networks at the link layer, the mesh header defined in RFC 4944 for mesh-under routing MUST NOT be used.
For link-local header compression, both IPv6 source and destination addresses MUST be elided (CID=0, SAC=0, SAM=11, DAC=0, DAM=11) since IIDs map uniquely to DECT link end-point addresses.
For non-link-local addresses, 6LNs SHOULD NOT use IIDs derived from MAC-48 or DECT device addresses; schemes such as CGAs, privacy extensions, HBAs, DHCPv6, or static semantically opaque addresses SHOULD be used by default.
The 6LBR MUST include the 6LoWPAN Context Option (6CO) for all prefixes advertised in Router Advertisements to enable efficient non-link-local header compression.
The 6LBR MUST keep track of multicast listeners at DECT ULE link-level granularity and MUST NOT forward multicast packets to 6LNs that have not registered for the relevant multicast groups.
The 6LBR MUST set the 'on-link' (L) flag to zero in the Prefix Information Option, causing 6LNs to always send packets to the 6LBR including when the destination is another 6LN on the same prefix.
The DECT device addresses IPEI and RFPI MUST be used to derive the IPv6 link-local 64-bit Interface Identifiers (IIDs) for 6LN and 6LBR respectively, by expanding the 40-bit addresses to 48-bit with leading zeros and setting the MSB to 1 (RFPI) or 0 (IPEI).
The DECT ULE DLC layer SHALL be configured with an MTU size of 1280 octets, ensuring complete IPv6 packets can be carried without requiring RFC 4944 fragmentation/reassembly.
The IPv6 header compression format specified in RFC 6282 MUST be used; all headers MUST be compressed according to encoding formats described in RFC 6282.
The PP SHALL specify <<IWU-ATTRIBUTES>> in a service-change message setting the ULE Application Protocol Identifier to 0x06 and the MTU size to 1280 octets or larger before IPv6 transmission can begin.
The RFC 4944 fragmentation and reassembly function MUST NOT be used since DECT ULE DLC already implements fragmentation and reassembly functionality.
When generated IIDs are not globally unique, Duplicate Address Detection (DAD) MUST be used. Non-link-local addresses generated by a 6LN MUST be registered with the 6LBR.
IPv6 link-local address configuration reveals no new information to the 6LBR beyond what it already knows from the link layer connection. For non-link-local addresses, 6LNs SHOULD use randomly generated IIDs or privacy-preserving schemes such as CGAs, privacy extensions, HBAs, or semantically opaque addresses.
DECT ULE uses a Permanent Virtual Circuit (PVC) established via a DECT service call between PP and FP. The PP specifies <<IWU-ATTRIBUTES>> in a service-change (other) message, followed by service-change (resume); the FP responds with service-change-accept (resume) containing a valid paging descriptor.
The 6LBR (implemented by the DECT Fixed Part) uses a Multi-Link Subnet / Non-Broadcast Multi-Access (NBMA) model, forwarding packets between 6LNs since PPs cannot directly communicate with each other in the star topology.
The DECT ULE Application Protocol Identifier is set to 0x06 for 6LoWPAN, as negotiated in the service-change procedure defined in ETSI TS 102.939-1. This identifier is exchanged when the Permanent Virtual Circuit (PVC) is established.
The IPEI (International Portable Equipment Identity) is a 40-bit globally unique DECT identity assigned to each PP during manufacturing, used to derive the IID for link-local address formation.
The RFPI (Radio Fixed Part Identity) is a 40-bit globally unique DECT identity assigned to each FP during manufacturing, used to derive the IID for the 6LBR link-local address.
DECT ULE communications are secured at the link layer (DLC) using CCM mode (Counter with CBC-MAC) with AES-128 for per-message encryption and authentication. Session security keys are individual per FP-PP binding; no shared encryption key is used among PPs.
Even though DECT ULE offers link layer security, it is still recommended to use secure transport or application protocols above 6LoWPAN for end-to-end protection.
The DECT ULE pairing procedure generates a master User Authentication Key (UAK) via the DSAA2 algorithm using AES-128. Session security keys derived during location registration may be renewed regularly.
IPv6 link-local addresses are formed by appending the 64-bit IID (derived from 40-bit DECT address expanded to 48 bits, then processed per RFC 4291 Appendix A) to the FE80::/64 prefix. The U/L bit (7th bit) is zero, indicating the IID is not globally unique.