RFC 8415
Dynamic Host Configuration Protocol for IPv6 (DHCPv6)
Pages: 154
Proposed Standard
→ Errata
Obsoletes: 3315 3633 3736 4242 7083 7283 7550
Proposed Standard
→ Errata
Obsoletes: 3315 3633 3736 4242 7083 7283 7550
Part 2 of 14 – Pages 9 to 15
4. Terminology
This section defines terminology specific to IPv6 and DHCP used in this document.4.1. IPv6 Terminology
IPv6 terminology from [RFC8200], [RFC4291], and [RFC4862] relevant to this specification is included below. address An IP-layer identifier for an interface or a set of interfaces. GUA Global unicast address (see [RFC4291]). 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 it is necessary to avoid ambiguity. 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 are Ethernet (simple or
bridged); Point-to-Point Protocol (PPP) and
PPP over Ethernet (PPPoE) links; and
Internet-layer (or higher) "tunnels", such
as tunnels over IPv4 or IPv6 itself.
link-layer identifier A link-layer identifier for an interface --
for example, IEEE 802 addresses for
Ethernet or Token Ring network interfaces.
link-local address An IPv6 address having a link-only scope,
indicated by having the prefix (fe80::/10),
that can be used to reach neighboring nodes
attached to the same link. Every IPv6
interface on which DHCPv6 can reasonably be
useful has a link-local address.
multicast address An identifier for a set of interfaces
(typically belonging to different nodes).
A packet sent to a multicast address is
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 a prefix.
router A node that forwards IP packets not
explicitly addressed to itself.
ULA Unique local address (see [RFC4193]).
unicast address An identifier for a single interface. A
packet sent to a unicast address is
delivered to the interface identified by
that address.
4.2. DHCP Terminology
Terminology specific to DHCP can be found below. 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 policies. binding A binding (or client binding) is a group of server data records containing the information the server has about the addresses or delegated prefixes in an Identity Association (IA) or configuration information explicitly assigned to the client. Configuration information that has been returned to a client through a policy, such as the 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 lease in the IA -- for example, temporary). A binding containing configuration information for a client is indexed by <DUID>. See below for definitions of DUID, IA, and IAID. configuration parameter An element of the configuration information set on the server and delivered to the client using DHCP. Such parameters may be used to carry information to be used by a node to configure its network subsystem and enable communication on a link or internetwork, for example. container option An option that encapsulates other options (for example, the IA_NA option (see Section 21.4) may contain IA Address options (see Section 21.6)).
delegating router The router that acts as a DHCP server and
responds to requests for delegated
prefixes. This document primarily uses the
term "DHCP server" or "server" when
discussing the "delegating router"
functionality of prefix delegation (see
Section 1).
DHCP Dynamic Host Configuration Protocol for
IPv6. The terms "DHCPv4" and "DHCPv6" are
used only in contexts where it is necessary
to avoid ambiguity.
DHCP client Also referred to as "client". A node that
initiates requests on a link to obtain
configuration parameters from one or more
DHCP servers. The node may act as a
requesting router (see below) if it
supports prefix delegation.
DHCP domain A set of links managed by DHCP and operated
by a single administrative entity.
DHCP relay agent Also referred to as "relay agent". A node
that acts as an intermediary to deliver
DHCP messages between clients and servers.
In certain configurations, there may be
more than one relay agent between clients
and servers, so a relay agent may send DHCP
messages to another relay agent.
DHCP server Also referred to as "server". A node that
responds to requests from clients. It may
or may not be on the same link as the
client(s). Depending on its capabilities,
if it supports prefix delegation it may
also feature the functionality of a
delegating router.
DUID A DHCP Unique Identifier for a DHCP
participant. Each DHCP client and server
has exactly one DUID. See Section 11 for
details of the ways in which a DUID may be
constructed.
encapsulated option A DHCP option that is usually only
contained in another option. For example,
the IA Address option is contained in IA_NA
or IA_TA options (see Section 21.5). See
Section 9 of [RFC7227] for a more complete
definition.
IA Identity Association: a collection of
leases assigned to a client. Each IA has
an associated IAID (see below). A client
may have more than one IA assigned to it --
for example, one for each of its
interfaces. Each IA holds one type of
lease; for example, an identity association
for temporary addresses (IA_TA) holds
temporary addresses, and an identity
association for prefix delegation (IA_PD)
holds delegated prefixes. Throughout this
document, "IA" is used to refer to an
identity association without identifying
the type of a lease in the IA. At the time
of writing this document, there are three
IA types defined: IA_NA, IA_TA, and IA_PD.
New IA types may be defined in the future.
IA option(s) At the time of writing this document, one
or more IA_NA, IA_TA, and/or IA_PD options.
New IA types may be defined in the future.
IAID Identity Association Identifier: an
identifier for an IA, chosen by the client.
Each IA has an IAID, which is chosen to be
unique among IAIDs for IAs of a specific
type that belong to that client.
IA_NA Identity Association for Non-temporary
Addresses: an IA that carries assigned
addresses that are not temporary addresses
(see "IA_TA"). See Section 21.4 for
details on the IA_NA option.
IA_PD Identity Association for Prefix Delegation:
an IA that carries delegated prefixes. See
Section 21.21 for details on the IA_PD
option.
IA_TA Identity Association for Temporary
Addresses: an IA that carries temporary
addresses (see [RFC4941]). See
Section 21.5 for details on the IA_TA
option.
lease A contract by which the server grants the
use of an address or delegated prefix to
the client for a specified period of time.
message A unit of data carried as the payload of a
UDP datagram, exchanged among DHCP servers,
relay agents, and clients.
Reconfigure key A key supplied to a client by a server.
Used to provide security for Reconfigure
messages (see Section 7.3 for the list of
available message types).
relaying A DHCP relay agent relays DHCP messages
between DHCP participants.
requesting router The router that acts as a DHCP client and
is requesting prefix(es) to be assigned.
This document primarily uses the term "DHCP
client" or "client" when discussing the
"requesting router" functionality of prefix
delegation (see Section 1).
retransmission Another attempt to send the same DHCP
message by a client or server, as a result
of not receiving a valid response to the
previously sent messages. The
retransmitted message is typically modified
prior to sending, as required by the DHCP
specifications. In particular, the client
updates the value of the Elapsed Time
option in the retransmitted message.
RKAP The Reconfiguration Key Authentication
Protocol (see Section 20.4).
singleton option An option that is allowed to appear only
once as a top-level option or at any
encapsulation level. Most options are
singletons.
T1 The time interval after which the client is
expected to contact the server that did the
assignment to extend (renew) the lifetimes
of the addresses assigned (via IA_NA
option(s)) and/or prefixes delegated (via
IA_PD option(s)) to the client. T1 is
expressed as an absolute value in messages
(in seconds), is conveyed within IA
containers (currently the IA_NA and IA_PD
options), and is interpreted as a time
interval since the packet's reception. The
value stored in the T1 field in IA options
is referred to as the T1 value. The actual
time when the timer expires is referred to
as the T1 time.
T2 The time interval after which the client is
expected to contact any available server to
extend (rebind) the lifetimes of the
addresses assigned (via IA_NA option(s))
and/or prefixes delegated (via IA_PD
option(s)) to the client. T2 is expressed
as an absolute value in messages (in
seconds), is conveyed within IA containers
(currently the IA_NA and IA_PD options),
and is interpreted as a time interval since
the packet's reception. The value stored
in the T2 field in IA options is referred
to as the T2 value. The actual time when
the timer expires is referred to as the
T2 time.
top-level option An option conveyed in a DHCP message
directly, i.e., not encapsulated in any
other option, as described in Section 9 of
[RFC7227].
transaction ID An opaque value used to match responses
with replies initiated by either a client
or a server.
(next page on part 3)