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2. Terminology

2. Terminology​

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].

This specification requires readers to be familiar with all the terms and concepts that are discussed in "Neighbor Discovery for IP version 6 (IPv6)" [RFC4861], "IPv6 Stateless Address Autoconfiguration" [RFC4862], "IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs): Overview, Assumptions, Problem Statement, and Goals" [RFC4919], "Transmission of IPv6 Packets over IEEE 802.15.4 Networks" [RFC4944], and "IP Addressing Model in Ad Hoc Networks" [RFC5889].

This specification makes extensive use of the same terminology defined in [RFC4861], unless otherwise defined below.

  • 6LoWPAN link: A wireless link determined by single IP hop reachability of neighboring nodes. These are considered links with undetermined connectivity properties as in [RFC5889].
  • 6LoWPAN Node (6LN): A 6LoWPAN node is any host or router participating in a LoWPAN. This term is used when referring to situations in which either a host or router can play the role described.
  • 6LoWPAN Router (6LR): An intermediate router in the LoWPAN that is able to send and receive Router Advertisements (RAs) and Router Solicitations (RSs) as well as forward and route IPv6 packets. 6LoWPAN routers are present only in route-over topologies.
  • 6LoWPAN Border Router (6LBR): A border router located at the junction of separate 6LoWPAN networks or between a 6LoWPAN network and another IP network. There may be one or more 6LBRs at the 6LoWPAN network boundary. A 6LBR is the responsible authority for IPv6 prefix propagation for the 6LoWPAN network it is serving. An isolated LoWPAN also contains a 6LBR in the network, which provides the prefix(es) for the isolated network.
  • Router: Either a 6LR or a 6LBR. Note that nothing in this document precludes a node being a router on some interfaces and a host on other interfaces as allowed by [RFC2460].
  • Mesh-under: A topology where nodes are connected to a 6LBR through a mesh using link-layer forwarding. Thus, in a mesh-under configuration, all IPv6 hosts in a LoWPAN are only one IP hop away from the 6LBR. This topology simulates the typical IP-subnet topology with one router with multiple nodes in the same subnet.
  • Route-over: A topology where hosts are connected to the 6LBR through the use of intermediate layer-3 (IP) routing. Here, hosts are typically multiple IP hops away from a 6LBR. The route-over topology typically consists of a 6LBR, a set of 6LRs, and hosts.
  • Non-transitive link: A link that exhibits asymmetric reachability as defined in Section 2.2 of [RFC4861].
  • IP-over-foo document: A specification that covers operating IP over a particular link type, for example, [RFC4944] "Transmission of IPv6 Packets over IEEE 802.15.4 Networks".
  • Header compression context: Address information shared across a LoWPAN and used by 6LoWPAN header compression [RFC6282] to enable the elision of information that would otherwise be sent repeatedly. In a "context", a (potentially partial) address is associated with a Context Identifier (CID), which is then used in header compression as a shortcut for (parts of) a source or destination address.
  • Registration: The process during which a LoWPAN node sends a Neighbor Solicitation message with an Address Registration Option to a router creating a Neighbor Cache Entry (NCE) for the LoWPAN node with a specific timeout. Thus, for 6LoWPAN routers, the Neighbor Cache doesn't behave like a cache. Instead, it behaves as a registry of all the host addresses that are attached to the router.
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