4. Terminology

4. Terminology

This section defines terminology specific to IPv6 and DHCP used in this document.

4.1. IPv6 Terminology

The following contains IPv6 terminology from the IPv6 protocol [RFC 2460], IPv6 addressing architecture [RFC 2373], and IPv6 stateless address autoconfiguration [RFC 2462] that is relevant to this specification.

address
An IP layer identifier for an interface or a set of interfaces.

host
Any node that is not a router.

IP
Internet Protocol version 6 (IPv6). The terms IPv4 and IPv6 are used only in contexts where ambiguity needs to be avoided.

interface
A node's attachment to a link.

link
A communication facility or medium over which nodes can communicate at the link layer (i.e., the layer immediately below IP). Examples include: Ethernet (simple or bridged); Token Ring; PPP links, X.25, Frame Relay, or ATM networks; and Internet (or higher) layer "tunnels", such as tunnels over IPv4 or IPv6 itself.

link-layer identifier
A link-layer identifier for an interface. Examples include IEEE 802 addresses for Ethernet or Token Ring network interfaces, and E.164 addresses for ISDN links.

link-local address
An IPv6 address with link-only scope, indicated by the prefix (FE80::/10), that can be used to reach neighboring nodes attached to the same link. Each interface has a link-local address.

multicast address
An identifier for a set of interfaces (typically belonging to different nodes). Packets sent to a multicast address are delivered to all interfaces identified by that address.

neighbor
A node attached to the same link.

node
A device that implements IP.

packet
An IP header plus payload.

prefix
The initial bits of an address, or a set of IP addresses that share the same initial bits.

prefix length
The number of bits in the prefix.

router
A node that forwards IP packets not explicitly addressed to itself.

unicast address
An identifier for a single interface. Packets sent to a unicast address are delivered to the interface identified by that address.

4.2. DHCP Terminology

The following can be found for DHCP-specific terminology.

appropriate to the link
An address is "appropriate to the link" when the address is consistent with the DHCP server's knowledge of the network topology, prefix assignment, and address assignment policy.

binding
A binding (or client binding) is a collection of server data records containing information the server has about addresses in an IA or configuration information explicitly assigned to the client. Configuration information returned to the client through policy (for example, information returned to all clients on the same link) does not require a binding. A binding containing information about an IA is indexed by the tuple <DUID, IA-type, IAID> (where IA-type is the type of address in the IA; for example, temporary addresses). A binding containing client configuration information is indexed by <DUID>.

configuration parameter
An element of configuration information set on a server and passed to a client using DHCP. Such parameters can be used to carry information that a node uses to configure its network subsystem and enable communication on a link or the Internet.

DHCP
Dynamic Host Configuration Protocol for IPv6. The terms DHCPv4 and DHCPv6 are used only in contexts where ambiguity needs to be avoided.

DHCP client (or client)
A node that initiates requests to obtain configuration parameters from one or more DHCP servers on a link.

DHCP domain
A collection of links managed by DHCP and operated by a single administrative entity.

DHCP realm
A name used to identify a DHCP administrative domain for selecting DHCP authentication keys.

DHCP relay agent (or relay agent)
A node that acts as an intermediate node to pass DHCP messages between clients and servers, and is on the same link as the client.

DHCP server (or server)
A node that responds to requests from clients, and may or may not be on the same link as the client.

DUID
A DHCP Unique Identifier for a DHCP participant; each DHCP client and server has exactly one DUID. For details on ways in which a DUID can be constructed, see section 9.

Identity association (IA)
A collection of addresses assigned to a client. Each IA has an associated IAID. A client may have multiple IAs assigned; for example, one per interface. Each IA holds one type of address; for example, an Identity Association for Temporary Addresses (IA_TA) holds temporary addresses (see "Identity Association for Temporary Addresses"). In this document, "IA" is used to refer to an identity association, without identifying the type of address in the IA.

Identity association identifier (IAID)
An identifier for an IA, chosen by the client. Each IA has an IAID, which is chosen to be unique among the IAIDs for all IAs on that client.

Identity association for non-temporary addresses (IA_NA)
An IA that carries assigned addresses that are not temporary addresses (see "Identity Association for Temporary Addresses").

Identity association for temporary addresses (IA_TA)
An IA that carries temporary addresses (see RFC 3041 [RFC 3041]).

message
A data unit carried as the payload of a UDP datagram, exchanged between DHCP servers, relay agents, and clients.

Reconfigure key
A key provided by a server to a client for providing security for Reconfigure messages.

relaying
A DHCP relay agent relays DHCP messages between DHCP participants.

transaction ID
An opaque value used to match responses and replies with messages initiated by clients or servers.