Pcdwarf.net

Extraits de la RFC4862

• IP – Internet Protocol Version 6. The terms IPv4 and IPv6 are used only in contexts where necessary to avoid ambiguity.
• node – a device that implements IP.
• router – a node that forwards IP packets not explicitly addressed to itself.
• host – any node that is not a router.
• upper layer – a protocol layer immediately above IP. Examples are transport protocols such as TCP and UDP, control protocols such as ICMP, routing protocols such as OSPF, and Internet or lower-layer protocols being « tunneled » over (i.e., encapsulated in) IP such as IPX, AppleTalk, or IP itself.
• link – a communication facility or medium over which nodes can communicate at the link layer, i.e., the layer immediately below IP. Examples are Ethernets (simple or bridged); PPP links; X.25, Frame Relay, or ATM networks; and Internet (or higher) layer « tunnels », such as tunnels over IPv4 or IPv6 itself.
• interface – a node’s attachment to a link.
• address – an IP-layer identifier for an interface or a set of interfaces.
• unicast address – an identifier for a single interface. A packet sent to a unicast address is delivered to the interface identified by that 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.
• anycast address – an identifier for a set of interfaces (typically belonging to different nodes). A packet sent to an anycast address is delivered to one of the interfaces identified by that address (the « nearest » one, according to the routing protocol’s measure of distance). See [RFC4291].
• solicited-node multicast address – a multicast address to which Neighbor Solicitation messages are sent. The algorithm for computing the address is given in [RFC4291].
• link-layer address – a link-layer identifier for an interface. Examples include IEEE 802 addresses for Ethernet links and E.164 addresses for Integrated Services Digital Network (ISDN) links.
• link-local address – an address having link-only scope that can be used to reach neighboring nodes attached to the same link. All interfaces have a link-local unicast address.
• global address – an address with unlimited scope.
• communication – any packet exchange among nodes that requires that the address of each node used in the exchange remain the same for the duration of the packet exchange. Examples are a TCP connection or a UDP request-response.
• tentative address – an address whose uniqueness on a link is being verified, prior to its assignment to an interface. A tentative address is not considered assigned to an interface in the usual sense. An interface discards received packets addressed to a tentative address, but accepts Neighbor Discovery packets related to Duplicate Address Detection for the tentative address.
• preferred address – an address assigned to an interface whose use by upper-layer protocols is unrestricted. Preferred addresses may be used as the source (or destination) address of packets sent from (or to) the interface.
• deprecated address – An address assigned to an interface whose use is discouraged, but not forbidden. A deprecated address should no longer be used as a source address in new communications, but packets sent from or to deprecated addresses are delivered as expected. A deprecated address may continue to be used as a source address in communications where switching to a preferred address causes hardship to a specific upper-layer activity e.g., an existing TCP connection).
• valid address – a preferred or deprecated address. A valid address may appear as the source or destination address of a packet, and the Internet routing system is expected to deliver packets sent to a valid address to their intended recipients.
• invalid address – an address that is not assigned to any interface. A valid address becomes invalid when its valid lifetime expires. Invalid addresses should not appear as the destination or source address of a packet. In the former case, the Internet routing system will be unable to deliver the packet; in the latter case, the recipient of the packet will be unable to respond to it.
• preferred lifetime – the length of time that a valid address is preferred (i.e., the time until deprecation). When the preferred lifetime expires, the address becomes deprecated.
• valid lifetime – the length of time an address remains in the valid state (i.e., the time until invalidation). The valid lifetime must be greater than or equal to the preferred lifetime. When the valid lifetime expires, the address becomes invalid.
• interface identifier – a link-dependent identifier for an interface that is (at least) unique per link [RFC4291]. Stateless address autoconfiguration combines an interface identifier with a prefix to form an address. From address autoconfiguration’s perspective, an interface identifier is a bit string of known length. The exact length of an interface identifier and the way it is created is defined in a separate link-type specific document that covers issues related to the transmission of IP over a particular link type (e.g., [RFC2464]). Note that the address architecture [RFC4291] also defines the length of the interface identifiers for some set of addresses, but the two sets of definitions must be consistent. In many cases, the identifier will be derived from the interface’s link-layer address.