Glossary
Symbols
_ISATAP name
See ISATAP name.
.NET Framework
The programming model of the .NET platform for building, deploying, and running Extensible Markup Language (XML) Web services and applications.
Numerics
6over4
An IPv6 coexistence technology that is used to provide IPv6 unicast and multicast connectivity across a multicast-enabled IPv4 infrastructure by treating the IPv4 network as a logical multicast link.
6over4 address
An address of the type [64-bit prefix]:0:0:WWXX:YYZZ, where WWXX:YYZZ is the colon hexadecimal representation of w.x.y.z (a public or private IPv4 address), which is used to represent a host for the 6over4 coexistence technology.
6to4
An IPv6 coexistence technology that is used to provide unicast IPv6 connectivity between IPv6 sites and hosts across the IPv4 Internet. 6to4 uses a public IPv4 address to construct a global IPv6 address prefix.
6to4 address
An address of the type 2002:WWXX:YYZZ:[SLA ID]:[Interface ID], where WWXX:YYZZ is the colon hexadecimal representation of w.x.y.z (a public IPv4 address), which is used to represent a node for the 6to4 coexistence technology.
6to4 host
An IPv6 host that is configured with at least one 6to4 address (a global address with the 2002::/16 prefix). 6to4 hosts do not require manual configuration and create 6to4 addresses by using standard address autoconfiguration mechanisms.
6to4 router
An IPv6/IPv4 router that supports the use of a 6to4 tunnel interface and is typically used to forward 6to4-addressed traffic between the 6to4 hosts within a site and other 6to4 routers or 6to4 relay routers on the IPv4 Internet.
6to4 relay router
An IPv6/IPv4 router that forwards 6to4-addressed traffic between 6to4 routers on the Internet and hosts on the IPv6 Internet.
A
AAAA record
The Domain Name System resource record type that is used to resolve a fully qualified domain name to an IPv6 address.
AAL5
See ATM Adaptation Layer 5.
AH
See Authentication header.
address
An identifier that is assigned at the IPv6 layer to an interface or set of interfaces and can be used as the source or destination of IPv6 packets.
address autoconfiguration
The process of automatically configuring IPv6 addresses on an interface. See also stateless address autoconfiguration and stateful address autoconfiguration.
address resolution
The process of resolving the link-layer address for a next-hop IP address on a link.
address selection rules
The address selection logic that is needed to decide which pair of addresses to use for communication.
aggregatable global unicast address
Also known as global addresses, aggregatable global unicast addresses are identified by the Format Prefix of 001 (2000::/3). IPv6 global addresses are equivalent to public IPv4 addresses and are globally routable and reachable on the IPv6 portion of the Internet.
anonymous address
See temporary address.
anycast address
An address assigned from the unicast address space that identifies multiple interfaces and is used for one-to-one-of-many delivery. With the appropriate routing topology, packets addressed to an anycast address are delivered to a single interface—the nearest interface that is identified by the address.
APIPA
See Automatic Private IP Addressing.
Asynchronous Transfer Mode
A cell-based packet-switching technology that supports both isochronous (time-dependent) and non-isochronous data types.
ATM
See Asynchronous Transfer Mode.
ATM Adaptation Layer 5
The ATM adaptation layer designed for LAN traffic and used to encapsulate IPv6 packets when they are sent across an ATM link.
Authentication header
An IPv6 extension header that provides data origin authentication, data integrity, and anti-replay services for the entire IPv6 packet, excluding changeable fields in the IPv6 header and extension headers.
Automatic Private IP Addressing
The automatic configuration of an IPv4 address in the 169.254.0.0/16 range and the subnet mask of 255.255.0.0 when an interface is configured for automatic configuration and a Dynamic Host Configuration Protocol (DHCP) server is not available.
automatic tunnel
An IPv6 over IPv4 tunnel in which the tunnel endpoints are determined by the use of logical tunnel interfaces, routes, and source and destination IPv6 addresses.
AutoNet
See Automatic Private IP Addressing.
B
binding acknowledgement
A message that contains the Binding Acknowledgement option in the Destination Options header. A binding acknowledgement is used in IPv6 mobility by correspondent nodes and home agents to confirm that a binding update was received and to indicate error conditions, if any.
binding cache
A table maintained by a correspondent node that maps the home address of mobile nodes that are away from home to their current care-of address.
binding request
A message that contains the Binding Request option in the Destination Options header. A binding request is used in IPv6 mobility by correspondent nodes and home agents to request a binding update from a mobile node that is away from home.
binding update
A message that contains the Binding Update option in the Destination Options header. A binding update is used in IPv6 mobility by a mobile node to update the binding cache entries of correspondent nodes and home agents for its current home address and care-of address.
binding update list
A list maintained by a mobile node that is away from home to record the most recent binding updates sent for the home agent and correspondent nodes.
C
care-of address
A global address used by a mobile node while it is connected to a foreign link.
CNA
See correspondent node address.
CoA
See care-of address.
coexistence
For IPv6, the use of technologies such as 6to4, ISATAP, and 6over4 to allow IPv6/IPv4 nodes to communicate while hosts and the routing infrastructure are being upgraded to support IPv6 or are being migrated from IPv4 to IPv6.
colon hexadecimal notation
The notation used to express IPv6 addresses. The 128-bit address is divided into 8 16-bit blocks. Each block is expressed as a hexadecimal number and adjacent blocks are delimited with colons. Within each block, leading zeros are suppressed. An example of an IPv6 unicast address in colon hexadecimal notation is 3FFE:FFFF:2A1D:48C:2AA:3CFF:FE21:81F9.
compatibility addresses
IPv6 addresses that are used when sending IPv6 traffic over an IPv4 infrastructure. Examples of compatibility addresses are IPv4-compatible addresses, 6to4 addresses, and ISATAP addresses.
configured tunnel
An IPv6 over IPv4 tunnel in which the tunnel endpoints are determined by manual configuration.
correspondent node
A node that is capable of communicating with a mobile node when it is away from home.
correspondent node address
The global address assigned to a correspondent node when it is communicating with a mobile node that is away from home.
critical router loop
The set of instructions that must be executed by a router to forward a packet.
D
DAD
See duplicate address detection.
default route
The route with the prefix ::/0. The default route matches all destinations and is the route used to determine the next-hop address if there are no other matching routes.
default router list
A list maintained by a host that lists all of the routers from which a router advertisement was received with the Router Lifetime field set to a nonzero value.
defending node
The node that is assigned a valid address set to a duplicate address being detected.
DELAY state
The state of the neighbor cache entry after it was in the STALE state and a packet is sent. The DELAY state is used to wait for an upper layer protocol to provide an indication that the neighbor is still reachable.
deprecated state
The state of an autoconfigured address in which the address is valid but its use is discouraged for new communication.
destination cache
A table maintained by IPv6 nodes that maps a destination address to a next-hop address and stores the path MTU.
Destination Options header
An IPv6 extension header that contains packet delivery parameters for either intermediate destinations or the final destination.
DHCP
See Dynamic Host Configuration Protocol.
distance vector
A routing protocol technology that propagates routing information in the form of a network ID and its "distance" (hop count).
DNS
See Domain Name System.
Domain Name System
A hierarchical namespace and protocol used for storing and querying name and address information.
double colon
The practice of compressing a single contiguous series of zero blocks of an IPv6 address to "::". For example, the multicast address FF02:0:0:0:0:0:0:2 is expressed as FF02::2. If there are two series of zero blocks of the same highest length, then by convention the left-most block is expressed as "::".
dual IP layer
The architecture of an IPv6/IPv4 node in which a single implementation of Transport layer protocols such as TCP and UDP operate over separate implementations of IPv4 and IPv6.
dual stack architecture
The architecture of an IPv6/IPv4 node that consists of two separate protocol stacks, one for IPv4 and one for IPv6, and each stack has its own implementation of the Transport layer protocols (TCP and UDP).
duplicate address detection
The process of using a Neighbor Solicitation message to confirm that a tentative address is not already assigned to an interface on the link.
Dynamic Host Configuration Protocol
A stateful address configuration protocol that provides an address and other configuration parameters.
E
Encapsulating Security Payload
An IPv6 extension header and trailer that provides data origin authentication, data integrity, data confidentiality, and anti-replay services for the payload encapsulated by the Encapsulating Security Payload header and trailer.
ESP
See Encapsulating Security Payload.
EUI
See Extended Unique Identifier.
EUI-64 address
A 64-bit link-layer address that is used as a basis for an IPv6 interface identifier.
Extended Unique Identifier
Link-layer addresses defined by the Institute of Electrical and Electronic Engineers (IEEE).
extension headers
Headers placed between the IPv6 header and the upper layer protocol data unit that provide IPv6 with additional capabilities.
F
FDDI
See Fiber Distributed Data Interface.
Fiber Distributed Data Interface
A desktop and backbone LAN technology specified by ANSI that uses token passing media access control, optical fiber, and operates at the bit rate of 100 Mbps.
flow
A series of packets exchanged between a source and a destination that requires special handling by intermediate IPv6 routers, as identified by the source and destination addresses and a non-zero value of the Flow Label field in the IPv6 header.
foreign link
A link that is not the mobile node's home link. A foreign link is identified by a foreign link prefix.
foreign link prefix
The global address prefix assigned to a foreign link and is used by a mobile node to obtain a care-of address.
Format Prefix
The high-order bits and their fixed values that define a type of IPv6 address.
FP
See Format Prefix.
fragment
A portion of an original IPv6 payload sent by a host. Fragments contain a Fragment header.
Fragment header
An IPv6 extension header that contains reassembly information for use by the receiving node.
fragmentation
The process of dividing an IPv6 payload into fragments by the sending host so that all the fragments are appropriately sized for the path MTU to the destination.
Frame Relay
A virtual circuit-based WAN technology designed to forward LAN data.
G
gateway
An IPv4 term for a router. IPv6 does not use the term "gateway" for a router.
global address
See aggregatable global unicast address.
Group ID
The last 112 bits or the last 32 bits (as per the recommendation of RFC 2373) of an IPv6 multicast address, which identifies the multicast group.
H
HA
See home address.
HAA
See home agent address.
home address
An address assigned to the mobile node when it is attached to the home link and through which the mobile node is always reachable, regardless of its location on the IPv6 Internet.
home agent
A router on the home link that maintains an awareness of the mobile nodes of its home link that are away from home and the care-of addresses that they are currently using. If the mobile node is on the home link, the home agent acts as an IPv6 router, forwarding packets addressed to the mobile node. If the mobile node is away from home, the home agent tunnels data sent to the mobile node's home address to the mobile node's current location on the IPv6 Internet.
home agent address
The global address of the home agent's interface on the home link.
Home Agent Address Discovery
An IPv6 mobility process in which a mobile node that is away from home discovers the list of home agents on its home link.
home agents list
A table maintained by home agents that contains the list of routers on the home link that can act as a home agent.
home link
The link that is assigned the home subnet prefix. The mobile node uses the home subnet prefix to create a home address.
Hop-by-Hop Options header
An IPv6 extension header that contains options that must be processed by every intermediate router and the destination.
host
A node that cannot forward IPv6 packets not explicitly addressed to itself (a nonrouter). A host is typically the source and a destination of IPv6 traffic, and silently discards traffic received that is not explicitly addressed to itself.
host group
The set of nodes listening for multicast traffic on a specific multicast address.
host route
A route to a specific IPv6 address. Host routes allow routing to occur on a per-IPv6 address basis. For host routes, the route prefix is a specific IPv6 address with a 128-bit prefix length.
Hosts file
A text file that is used to store name-to-address mappings. For computers running Windows XP or the Windows .NET Server 2003 family, the Hosts file is stored in the SystemRoot\System32\Drivers\Etc folder.
host-to-host tunneling
IPv6 over IPv4 tunneling where the tunnel endpoints are two hosts. For example, an IPv6/IPv4 node that resides within an IPv4 infrastructure creates an IPv6 over IPv4 tunnel to reach another host that resides within the same IPv4 infrastructure.
host-to-router tunneling
IPv6 over IPv4 tunneling where the tunnel begins at a sending host and ends at an IPv6/IPv4 router. For example, an IPv6/IPv4 node that resides within an IPv4 infrastructure creates an IPv6 over IPv4 tunnel to reach an IPv6/IPv4 router.
I
ICMPv6
See Internet Control Message Protocol for IPv6.
IEEE 802 address
A 48-bit link-layer address defined by the IEEE. Ethernet, Token Ring, and FDDI network adapters use IEEE 802 addresses.
IEEE 802.3 SNAP encapsulation
The encapsulation used when IPv6 packets are sent over an IEEE 802.3-compliant Ethernet link.
IEEE 802.5 SNAP encapsulation
The encapsulation used when IPv6 packets are sent over a Token Ring link.
IEEE EUI-64 address
See EUI-64 address.
INCOMPLETE state
The state of a neighbor cache entry in which a neighbor solicitation has been sent and no response has been received.
interface
The representation of a physical or logical attachment of a node to a link. An example of a physical interface is a network adapter. An example of a logical interface is a tunnel interface that is used to send IPv6 packets across an IPv4 network by encapsulating the IPv6 packet inside an IPv4 header.
interface ID
The last 64 bits of an IPv6 unicast or anycast address.
Internet Control Message Protocol for IPv6
A protocol that provides error messages for IPv6 packet routing and delivery and informational messages for diagnostics, Neighbor Discovery, Multicast Listener Discovery, and IPv6 mobility.
Internet Protocol Helper
An API that assists in the administration of the network configuration of the local computer. You can use Internet Protocol Helper (IP Helper) to programmatically retrieve information about the network configuration of the local computer, and to modify that configuration. IP Helper also provides notification mechanisms to ensure that an application is notified when certain aspects of the network configuration change on the local computer.
Internet Protocol security
A framework of open standards for ensuring private, secure communications at the Internet layer, through the use of cryptographic security services. IPSec supports network-level peer authentication, data origin authentication, data integrity, data confidentiality (encryption), and replay protection.
Intra-site Automatic Tunneling Addressing Protocol
A coexistence technology that is used to provide unicast IPv6 connectivity between IPv6 hosts across an IPv4 intranet. ISATAP derives an interface ID based on the IPv4 address (public or private) assigned to a host. The ISATAP-derived interface ID is used for automatic tunneling across an IPv4 infrastructure.
invalid state
The state of an autoconfigured address in which it can no longer be used to send or receive unicast traffic. An address enters the invalid state after the valid lifetime expires.
IP Helper
See Internet Protocol Helper.
IP6.INT
The DNS domain created for IPv6 reverse queries. Also called pointer queries, reverse queries determine a host name based on the address.
IPSec
See Internet Protocol security.
IPv4 multicast tunneling
See 6over4.
IPv4 node
A node that implements IPv4. It can send and receive IPv4 packets. It can be an IPv4-only node or an IPv6/IPv4 node.
IPv4-compatible address
An address of the form 0:0:0:0:0:0:w.x.y.z or ::w.x.y.z, in which w.x.y.z is the dotted decimal representation of a public IPv4 address. For example, ::131.107.89.42 is an IPv4-compatible address. IPv4-compatible addresses are used for IPv6 Automatic Tunneling.
IPv4-mapped address
An address of the form 0:0:0:0:0:FFFF:w.x.y.z or ::FFFF:w.x.y.z, in which w.x.y.z is an IPv4 address. IPv4-mapped addresses are used to represent an IPv4-only node to an IPv6 node.
IPv4-only node
A node that implements only IPv4 (and is assigned only IPv4 addresses). This node does not support IPv6. Most hosts and routers installed today are IPv4-only nodes.
IPv6 Automatic Tunneling
The automatic tunneling performed when using IPv4-compatible addresses.
IPv6 host address record
See AAAA record.
IPv6 in IPv4
See IPv6 over IPv4 tunneling.
IPv6 mobility
A set of messages and processes that allow an IPv6 node to arbitrarily change its location on the IPv6 Internet and still maintain existing connections.
IPv6 MTU
The maximum-sized IP packet that can be sent on a link.
IPv6 node
A node that implements IPv6. (It can send and receive IPv6 packets.) An IPv6 node can be an IPv6-only node or an IPv6/IPv4 node.
IPv6 over IPv4 tunneling
The encapsulation of IPv6 packets with an IPv4 header so that IPv6 traffic can be sent across an IPv4 infrastructure. In the IPv4 header, the Protocol field is set to 41.
IPv6 route table
See IPv6 route table.
IPv6 routing table
The set of routes used to determine the next-hop address and interface for IPv6 traffic sent by a host or forwarded by a router.
IPv6/IPv4 node
A node that has an implementation of both IPv4 and IPv6.
IPv6-only node
A node that implements only IPv6 (and is assigned only IPv6 addresses). It is able to communicate with IPv6 nodes and applications only.
ISATAP
See Intra-site Automatic Tunneling Addressing Protocol.
ISATAP address
An address of the type [64-bit prefix]:0:5EFE:w.x.y.z, where w.x.y.z is a public or private IPv4 address, that is assigned to an ISATAP host.
ISATAP host
A host that is assigned an ISATAP address.
ISATAP name
The name that is resolved by computers running Windows XP with Service Pack 1 or a member of the Windows .NET Server 2003 family to automatically discover the IPv4 address of the ISATAP router. Computers running Windows XP attempt to resolve the name "_ISATAP."
ISATAP router
An IPv6/IPv4 router that responds to tunneled router solicitations from ISATAP hosts and forwards traffic between ISATAP hosts and nodes on another IPv6 subnet or network.
J
join latency
The time between when a new member of a multicast group on a subnet that does not contain any group members sends a Multicast Listener Report message and when multicast packets for that multicast group are sent on the subnet.
jumbogram
An IPv6 packet that has a payload larger than 65,535 bytes. Jumbograms are indicated by setting the Payload Length field in the IPv6 header to 0 and including a Jumbo Payload option in the Hop-by-Hop Options header.
Jumbo Payload option
An option in the Hop-by-Hop Options header that indicates the size of a jumbogram.
L
LAN segment
A portion of a link consisting of a single medium that is bounded by bridges or Layer 2 switches.
leave latency
The time between when the last member of the multicast group on a subnet sends a Multicast Listener Done message and when multicast packets for that multicast group are no longer sent on the subnet.
link
One or more LAN segments bounded by routers.
link MTU
The maximum transmission unit (MTU)—the number of bytes in the largest IPv6 packet—that can be sent on a link. Because the maximum frame size includes the link-layer medium headers and trailers, the link MTU is not the same as the maximum frame size of the link. The link MTU is the same as the maximum payload size of the link-layer technology.
link state
A routing protocol technology that exchanges routing information consisting of a router's attached network prefixes and their assigned costs. Link state information is advertised upon startup and when changes in the network topology are detected.
link-local address
A local-use address identified by the FP of 1111 1110 10 (FE80::/10), whose scope is the local link. Nodes use link-local addresses to communicate with neighboring nodes on the same link. Link-local addresses are equivalent to Automatic Private IP Addressing (APIPA) IPv4 addresses.
local-use address
An IPv6 unicast address that is not reachable on the IPv6 Internet. Local-use addresses include link-local and site-local addresses.
longest matching route
The algorithm used by the route determination process to select the routes in the routing table that most closely match the destination address of the packet being sent or forwarded.
loopback address
The IPv6 address of ::1 that is assigned to the loopback interface.
loopback interface
An internal interface created so that a node can send packets to itself.
M
MAC
See media access control, MAC address.
MAC address
The link-layer address for typical LAN technologies such as Ethernet, Token Ring, and FDDI. Also known as the physical address, the hardware address, or the network adapter address.
maximum transmission unit
The largest protocol data unit that can be sent. Maximum transmission units are defined at the link layer (maximum frame sizes) and at the Internet layer (maximum IPv6 packet sizes).
media access control
An IEEE-defined sub-layer of the ISO Data Link layer, whose responsibilities include framing and managing access to the media.
migration
For IPv6, the conversion of all IPv4-only nodes to IPv6-only nodes.
MLD
See Multicast Listener Discovery.
mobile IP
See IPv6 mobility.
mobile node
An IPv6 node that can change links, and therefore addresses, and maintain reachability using its home address. A mobile node has awareness of its home address and care-of address, and indicates its home address/care-of address mapping to the home agent and IPv6 nodes with which it is communicating.
MTU
See maximum transmission unit.
multicast address
An address that identifies zero or multiple interfaces and is used for one-to-many delivery. With the appropriate multicast routing topology, packets addressed to a multicast address are delivered to all interfaces identified by the address.
multicast group
The set of hosts listening on a specific multicast address.
Multicast Listener Discovery
A set of three ICMPv6 messages used by hosts and routers to manage multicast group membership on a subnet.
N
name resolution
The process of resolving a name to an address. For IPv6, name resolution resolves a host name or fully qualified domain name (FQDN) to an IPv6 address.
NAT
See Network Address Translator.
NBMA
See non-broadcast multiple access link.
ND
See Neighbor Discovery.
neighbor
A node connected to the same link.
neighbor cache
A cache maintained by every IPv6 node that stores the on-link IP address of a neighbor, its corresponding link-layer address, and an indication of the neighbor's reachability state. The neighbor cache is equivalent to the ARP cache in IPv4.
Neighbor Discovery
A set of ICMPv6 messages and processes that determine relationships between neighboring nodes. Neighbor Discovery replaces ARP, ICMP router discovery, and the ICMP Redirect message used in IPv4. ND also provides neighbor unreachability detection.
Neighbor Discovery options
Options in Neighbor Discovery messages that indicate link-layer addresses, prefix information, MTU, redirect, routes, and IPv6 mobility configuration information.
neighbor unreachability detection
The Neighbor Discovery process that determines whether the IPv6 layer of a neighbor is no longer receiving packets. The reachability state of each neighbor with which a node is communicating is stored in the node's neighbor cache.
network
Two or more subnets connected by routers. Another term for network is internetwork.
Network Address Translator
An IPv4 router that translates addresses and ports when forwarding packets between a privately addressed network and the Internet.
network prefix
The portion of an address that is fixed and used to determine the subnet ID, the route, or the address range.
network segment
See subnet.
next-hop determination
The process of determining the next-hop address and interface for sending or forwarding a packet based on the contents of the routing table.
Next-Level Aggregation Identifier
A 24-bit field in the aggregatable global unicast address that allows ISPs to create multiple levels of addressing hierarchy within their networks to both organize addressing and routing for downstream ISPs and identify organization sites.
NLA ID
See Next-Level Aggregation Identifier.
NO ENTRY EXISTS state
The state of a neighbor cache entry before it is added to the neighbor cache.
node
For IPv6, any device that runs an implementation of IPv6, which includes both routers and hosts.
non-broadcast multiple access link
A link-layer technology that supports a link with more than two nodes, but with no facility to broadcast a single packet to multiple locations. For example, X.25, Frame Relay, and ATM are NBMA network types.
NUD
See neighbor unreachability detection.
O
offending node
The node that is performing duplicate address detection for an address that is already in use on the subnet.
P
packet
The protocol data unit (PDU) that exists at the Internet layer. For IPv6, a packet is composed of an IPv6 header and a payload.
parameter discovery
A Neighbor Discovery process that enables hosts to discover configuration parameters, including the link MTU and the default hop limit for outgoing packets.
path MTU
The maximum-sized IPv6 packet that can be sent without using host fragmentation between a source and destination over a path in an IPv6 network. The path MTU is the smallest link MTU of all the links in the path.
Path MTU Discovery
The use of the ICMPv6 Packet Too Big message to discover the highest IPv6 MTU for all links between two hosts.
path vector
A routing protocol technology that exchanges sequences of hop information indicating the path for a route. For example, BGP-4 exchanges sequences of autonomous system numbers. An autonomous system is a portion of the network under the same administrative authority.
PDU
See protocol data unit.
PMTU
See path MTU.
Point-to-Point Protocol
A standardized point-to-point network encapsulation method that provides frame delimitation, protocol identification, and bit-level integrity services.
pointer records
See PTR records.
PortProxy
A component of IPv6 for the Windows .NET Server 2003 family that enables TCP proxying to facilitate the communication between nodes or applications that cannot connect using a common Internet layer protocol (IPv4 or IPv6).
PPP
See Point-to-Point Protocol.
preferred lifetime
The amount of time in which a unicast address configured through stateless address autoconfiguration remains in the preferred state. The preferred lifetime is indicated by the Preferred Lifetime field in the Prefix Information option in a Router Advertisement message.
preferred state
The state of an autoconfigured address for which the address is valid, its uniqueness has been verified, and it can be used for unlimited communications.
prefix
See network prefix.
prefix discovery
A Neighbor Discovery process by which hosts discover the network prefixes for local link destinations and for stateless address configuration.
prefix length notation
The practice of expressing network prefixes as address/prefix-length, in which prefix-length is the number of high-order bits in the address that are fixed.
prefix list
A list of link-prefixes maintained by each host. Each entry in the prefix list defines a range of IP addresses for destinations that are directly reachable (neighbors).
PROBE state
The state of a neighbor cache entry that was in the STALE and DELAY states for which reachability confirmation is in progress.
protocol data unit
The entity that exists at any layer of a layered network architecture. The protocol data unit of layer n becomes the payload of layer n-1 (a lower layer).
pseudo-header
A temporary header constructed for the purposes of calculating a checksum to associate the IPv6 header with its payload. For IPv6, a new pseudo-header format is used for the ICMPv6, TCP, and UDP checksum calculations.
pseudo-periodic
Occurring at intervals for which the interval between successive events is not constant. For example, router advertisements sent by IPv6 routers occur pseudo-periodically; the next interval for advertising is chosen randomly between a maximum and minimum value.
PTR records
DNS resource records that resolve an address to a name.
Q
quad-A record
See AAAA record.
R
rate limiting
The practice of sending messages based on a timer or a percentage of bandwidth, rather than for each message that encounters the same error. For example, ICMPv6 error messages are rate limited.
REACHABLE state
The state of an entry in the neighbor cache for which reachability has been confirmed by receipt of a solicited unicast Neighbor Advertisement message.
reassembly
The process of reconstructing the original payload from a series of fragments.
redirect
The Neighbor Discovery process of informing a host of a better first-hop IPv6 address to reach a destination.
Remote Procedure Call
An API that is used for creating distributed client/server programs. The RPC run-time stubs and libraries manage most of the details relating to network protocols and communication. RPC functions are used to forward application function calls to a remote system across the network.
route cache
See destination cache.
route determination process
The process of determining which single route in the routing table to use for forwarding a packet.
route table
See IPv6 routing table.
router
A node that can forward packets not explicitly addressed to itself. On an IPv6 network, a router also typically advertises its presence and host configuration information.
router advertisement
A Neighbor Discovery message sent by a router either pseudo-periodically or in response to a Router Solicitation message. Router advertisements typically contain at least one Prefix Information option, from which hosts create stateless autoconfigured unicast IPv6 addresses.
router discovery
A Neighbor Discovery process in which a host discovers the local routers on an attached link.
router-to-host tunneling
IPv6 over IPv4 tunneling in which the tunnel begins at a forwarding router and ends at an IPv6/IPv4 host. For example, an IPv6/IPv4 router creates an IPv6 over IPv4 tunnel to reach an IPv6/IPv4 host that resides within an IPv4 infrastructure.
router-to-router tunneling
IPv6 over IPv4 tunneling in which the tunnel begins at a forwarding router and ends at an IPv6/IPv4 router. For example, an IPv6/IPv4 router on the edge of an IPv6 network creates an IPv6 over IPv4 tunnel to reach another IPv6/IPv4 router.
Routing header
An IPv6 extension header that is used to perform source routing over an IPv6 network. A source route is a list of intermediate destinations for the packet to travel to on its path to the final destination.
routing loop
A condition on a network in which traffic is forwarded in a loop, never reaching its destination.
routing protocols
A series of periodic or on-demand messages containing routing information that is exchanged between dynamic routers.
routing table
See IPv6 routing table.
RPC
See Remote Procedure Call.
S
scope
For IPv6 addresses, the scope is the region of the network over which the traffic is intended to propagate.
scope ID
See zone ID.
SLA ID
See Site-Level Aggregation Identifier.
Site-Level Aggregation Identifier
A 16-bit field within the aggregatable global unicast address that is used by an individual organization to identify subnets within its site.
site-local address
A local-use address identified by the FP of 1111 1110 11 (FEC0::/10). The scope of a site-local address is the site. Site-local addresses are equivalent to the IPv4 private address space. Site-local addresses are not reachable from other sites, and routers must not forward site-local traffic outside the site.
site prefix
Typically, a 48-bit prefix that is used to indicate all the addresses in the site. Site prefixes are stored in a local site prefix table, which is used to confine traffic to the site.
solicited-node address
A multicast address used by nodes for the address resolution process. The solicited-node address is constructed from the prefix FF02::1:FF00:0/104 and the last 24 bits of a unicast IPv6 address. The solicited-node address acts as a pseudo-unicast address for very efficient address resolution on IPv6 links.
STALE state
The state of a neighbor cache entry for which the reachable time (the duration since the last reachability confirmation was received) has elapsed. The neighbor cache entry goes into the STALE state after the value (milliseconds) in the Reachable Time field in the Router Advertisement message (or a host default value) elapses and remains in this state until a packet is sent to the neighbor.
stateful address autoconfiguration
The use of a stateful address configuration protocol, such as DHCPv6, to configure IPv6 addresses and configuration parameters.
stateless address autoconfiguration
The use of Neighbor Discovery Router Advertisement messages to configure IPv6 addresses and configuration parameters.
static routing
The use of manually configured routes in the routing tables of routers.
subnet
For IPv6, one or more links that use the same 64-bit IPv6 address prefix. Another term for subnet is network segment.
subnet route
For IPv6, a route with a 64-bit prefix that indicates a specific IPv6 subnet.
subnet-router anycast address
The anycast address [64-bit prefix]:: that is assigned to router interfaces.
T
temporary address
An address that uses a randomly derived temporary interface ID. Temporary addresses change over time, making it more difficult to track someone's Internet usage based on their IPv6 address.
tentative address
A unicast address whose uniqueness has not yet been verified.
tentative state
The state of an autoconfigured address in which uniqueness has not yet been verified.
TLA ID
See Top-Level Aggregation Identifier.
Top-Level Aggregation Identifier
A 13-bit field in the aggregatable global unicast address that is allocated by IANA to local Internet registries that, in turn, allocate individual TLA IDs to large, long-haul ISPs.
U
unicast address
An address that identifies a single interface within the scope of the type of address and is used for one-to-one delivery. The scope of an address is the region of the IPv6 network over which the address is unique. With the appropriate unicast routing topology, packets addressed to a unicast address are delivered to a single interface.
unspecified address
The address 0:0:0:0:0:0:0:0 (or ::) that is used to indicate the absence of an address. It is equivalent to the IPv4 unspecified address of 0.0.0.0. The unspecified address is typically used as a source address for packets attempting to verify the uniqueness of a tentative address.
upper-layer checksum
The checksum calculation performed by ICMPv6, TCP, and UDP that incorporates the new IPv6 pseudo-header.
upper-layer protocol
A protocol above IPv6 that uses IPv6 as its transport. Examples include ICMPv6 and Transport layer protocols such as TCP and UDP (but not Application layer protocols such as FTP and DNS, which use TCP and UDP as their transport).
V
valid lifetime
The amount of time in which a unicast address configured through stateless address autoconfiguration remains in the valid state, which includes both the preferred and deprecated states. The valid lifetime is indicated by the Valid Lifetime field in the Prefix Information option sent in a Router Advertisement message.
valid state
The state of an autoconfigured address for which the address can be used for sending and receiving unicast traffic. The valid state includes both the preferred and deprecated states.
virtual mobile node
A node that represents the logical connection of a mobile node that is away from home to its home link. Because the mobile node that is away from home is always assigned its home address, it always has a virtual connection to the home link.
W
Win32 Internet Extensions
An API used for creating an Internet client application. An Internet client application is a program that accesses information from a network data source (server) by using Internet protocols such as FTP or HTTP.
Windows Sockets
A Windows API based on Berkeley Sockets that applications use to access the network services of TCP/IP, IPv6, and other protocols.
WinInet
See Win32 Internet Extensions.
WinSock
See Windows Sockets.
X
X.25
A virtual circuit-based packet switching WAN technology originally designed in the 1970s to provide a reliable, connection-oriented service for LAN traffic.
Z
zone ID
An integer that specifies the zone of the destination for IPv6 traffic. In the Ping, Tracert, and Pathping commands, the syntax for specifying a zone ID is IPv6Address%ZoneID. Unless manually configured otherwise, the ZoneID value for link-local addresses is equal to the interface index. For site-local addresses, ZoneID is equal to the site number. If multiple sites are not being used, a zone ID for site-local addresses is not required. The ZoneID parameter is not needed when the destination is a global address.
