Technical Specs

EAP messages between the CGR and a joining interface because the joining interface might be multiple mesh hops away from
the CGR. CGRs communicate with a standard AAA server using the RADIUS protocol.
• Evicting nodes—To evict nodes from a network, the CGR must communicate a new Group Temporal Key (GTK) to all nodes
in the PAN except those being evicted. The new GTK has a valid lifetime that begins immediately. After the new GTK is
distributed to all allowed nodes, the CGR invalidates the old GTK. After the old GTK is invalidated, those nodes that did not
receive the new GTK can no longer participate in the network and are considered evicted.
• Security mode—All data-and-acknowledgment traffic are protected using the IEEE 802.15.4 Counter with CBC-MAC (CCM)
security mode.
• AES-128 keys—All nodes in a PAN share the same AES-128 keys for use with CCM.
• Device authentication—EAP-TLS, where the CGR serves as the authenticator and communicates with a standard AAA server
using RADIUS.
• Handshake protocol—A handshake protocol similar to 802.11i is used to establish a Pairwise Temporal Key (PTK) between
a device and a CGR. The PTK is used to securely distribute the GTK. The same handshake messages might be used to refresh
the GTK.
Because communication modules might not be within direct communication range of a CGR, RMEs also implement an EAP proxy
service so that communication modules can proxy messages between a joining device and the CGR.
6LoWPAN Adaptation
The 6LoWPAN adaptation layer adapts IPv6 to operate efficiently over low-power and lossy links such as defined by IEEE 802.15.4
(low-rate WPAN (LR-WPANs)). The adaptation layer sits between the IPv6 and IEEE 802.15.4 layers and provides IPv6 header
compression, IPv6 datagram fragmentation, and optimized IPv6 Neighbor Discovery.
The 6LoWPAN adaptation feature uses packet-header filtering for packet transmission when transporting IPv6 datagrams within
IEEE 802.15.4e frames.
RMEs implement the 6LoWPAN header compression format: >RFC 6282 on Compression Format for IPv6 Datagrams over IEEE
802.15.4-Based Networks . For each IPv6 datagram submitted to the mesh interface for transmission, an RME attempts to compress
the IPv6 header to the smallest encoding supported by the header compression mechanism.
Initial 6LoWPAN RFC 4944 also includes an IPv6 header compression scheme that is now deprecated and replaced by RFC
6282 6LoWPAN header compression. The Cisco CGR implementation for 6LoWPAN header compression implements only
RFC 6282.
Note
For more information on RFC 6282, see http://datatracker.ietf.org/doc/rfc6282/ .
The 6LoWPAN adaptation feature uses 800-byte IEEE802.15.4 MTU with MAC layer fragmentation, and has 800-byte IEEE 802.1X
MTU with no MAC layer fragmentation support.
RMEs perform hop-by-hop packet fragmentation and reassembly, where a communication module must receive all 6LoWPAN
fragments for an IPv6 datagram before it can begin forwarding the datagram to the next hop. However, whereas the IEEE
802.15.4e/g PHY supports a 1500-byte MTU, the Cisco implementation of the 6LoWPAN layer does not generate link frames
larger than 800 bytes.
Note
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