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... IP version 6. The autoconfiguration
process includes creating a link-local address and verifying its
uniqueness on a link, determining what information should be
...
... uniqueness on a link, determining what information should be
autoconfigured (addresses, other information, or both), and in the
case of addresses, whether they should be obtained through the
...
... autoconfigured (addresses, other information, or both), and in the
case of addresses, whether they should be obtained through the
stateless mechanism, the stateful mechanism, or both. This document
...
... stateless mechanism, the stateful mechanism, or both. This document
defines the process for generating a link-local address, the process
for generating site-local and global addresses ...
... link-local address, the process
for generating site-local and global addresses via stateless address
autoconfiguration, and the Duplicate Address Detection procedure. The
...
... for generating site-local and global addresses via stateless address
autoconfiguration, and the Duplicate Address Detection procedure. The
details of autoconfiguration ...
... site-local and global addresses via stateless address
autoconfiguration, and the Duplicate Address Detection procedure. The
details of autoconfiguration using the stateful protocol are
...
...
IPv6 defines both a stateful and stateless address autoconfiguration
mechanism. Stateless autoconfiguration ...
... stateless mechanism allows a host to
generate its own addresses using a combination of locally available
information and information advertised by routers. Routers ...
... interface on a subnet. An address is formed by combining the two. In
the absence of routers, a host ...
... the absence of routers, a host can only generate link-local
addresses. However, link-local addresses are sufficient for allowing
communication among nodes ...
... routers, a host can only generate link-local
addresses. However, link-local addresses are sufficient for allowing
communication among nodes attached to the same link ...
... hosts obtain interface
addresses and/or configuration information and parameters from a
server. Servers maintain a database ...
... server. Servers maintain a database that keeps track of which
addresses have been assigned to which hosts. The stateful
autoconfiguration ...
... autoconfiguration protocol allows hosts to obtain addresses, other
configuration information or both from a server. Stateless ...
... can use stateless autoconfiguration to configure its own addresses,
but use stateful autoconfiguration to obtain other information.
...
... The stateless approach is used when a site is not particularly
concerned with the exact addresses hosts use, so long as they are
unique and properly routable. The stateful approach is used when a
...
... hosts use, so long as they are
unique and properly routable. The stateful approach is used when a
site requires tighter control over exact address assignments. Both
stateful and stateless address autoconfiguration may be used
...
... site requires tighter control over exact address assignments. Both
stateful and stateless address autoconfiguration may be used
simultaneously. The site administrator specifies which type of
...
...
IPv6 addresses are leased to an interface for a fixed (possibly
infinite) length of time. Each address ...
... IPv6 addresses are leased to an interface for a fixed (possibly
infinite) length of time. Each address has an associated lifetime
that indicates how long the address ...
... address has an associated lifetime
that indicates how long the address is bound to an interface. When a
lifetime ...
... lifetime expires, the binding (and address) become invalid and the
address may be reassigned to another interface ...
... binding (and address) become invalid and the
address may be reassigned to another interface elsewhere in the
Internet ...
... interface elsewhere in the
Internet. To handle the expiration of address bindings gracefully, an
address goes through two distinct phases while assigned to an
...
... Internet. To handle the expiration of address bindings gracefully, an
address goes through two distinct phases while assigned to an
interface. Initially, an address ...
... address goes through two distinct phases while assigned to an
interface. Initially, an address is "preferred", meaning that its use
in arbitrary communication is unrestricted. Later, an address becomes
...
... interface. Initially, an address is "preferred", meaning that its use
in arbitrary communication is unrestricted. Later, an address becomes
"deprecated" in anticipation that its current interface binding ...
... binding will
become invalid. While in a deprecated state, the use of an address is
discouraged, but not strictly forbidden. New communication (e.g.,
the opening of a new TCP connection ...
... discouraged, but not strictly forbidden. New communication (e.g.,
the opening of a new TCP connection) should use a preferred address
when possible. A deprecated address should be used only by
...
... TCP connection) should use a preferred address
when possible. A deprecated address should be used only by
applications that have been using it and would have difficulty
switching to another address ...
... deprecated address should be used only by
applications that have been using it and would have difficulty
switching to another address without a service disruption.
...
... duplicate address detection" algorithm on
addresses before assigning them to an interface. The Duplicate
Address Detection algorithm ...
... addresses before assigning them to an interface. The Duplicate
Address Detection algorithm is performed on all addresses,
...
... interface. The Duplicate
Address Detection algorithm is performed on all addresses,
independent of whether they are obtained via stateless or stateful
...
... stateless or stateful
autoconfiguration. This document defines the Duplicate Address
Detection algorithm.
...
... by some other means. However, it is expected that routers will
generate link-local addresses using the mechanism described in this
document. In addition, routers are expected to successfully pass the
...
... document. In addition, routers are expected to successfully pass the
Duplicate Address Detection procedure described in this document on
all addresses prior to assigning them to an interface ...
... Duplicate Address Detection procedure described in this document on
all addresses prior to assigning them to an interface.
...
... identifier for a single interface. A packet sent
to a unicast address is delivered to the interface identified by
that address ...
... interfaces (typically
belonging to different nodes). A packet sent to a multicast
address is delivered to all interfaces identified by that
address ...
... multicast
address is delivered to all interfaces identified by that
address.
anycast address ...
... interfaces (typically
belonging to different nodes). A packet sent to an anycast
address is delivered to one of the interfaces identified by that
address ...
... 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 [ADDR-ARCH ...
... solicited-node multicast address - a multicast address to which
Neighbor Solicitation messages are sent. The algorithm ...
... Neighbor Solicitation messages are sent. The algorithm for
computing the address is given in [DISCOVERY].
...
...
link-local address - an address having link-only scope that can be
used to reach neighboring nodes ...
... unicast address.
site-local address - an address having scope that is limited to the
local site.
...
...
site-local address - an address having scope that is limited to the
local site.
...
...
global address - an address with unlimited scope.
communication - any packet exchange among nodes ...
... 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 ...
...
tentative address - an address whose uniqueness on a link is being
verified, prior to its assignment to an interface ...
... 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 ...
... sense. An interface discards received packets addressed to a
tentative address, but accepts Neighbor Discovery packets
related to Duplicate Address Detection ...
... tentative address, but accepts Neighbor Discovery packets
related to Duplicate Address Detection for the tentative
address.
...
... Neighbor Discovery packets
related to Duplicate Address Detection for the tentative
address.
preferred address ...
... interface whose use by
upper layer protocols is unrestricted. Preferred addresses may
be used as the source (or destination) address ...
... 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 ...
... 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
...
... 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
...
... 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
...
... 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 ...
... 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
...
... 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 ...
... address - a preferred or deprecated address. A valid address
may appear as the source or destination address of a packet, and
...
... valid address
may appear as the source or destination address of a packet, and
the internet routing system ...
... routing system is expected to deliver packets sent
to a valid address to their intended recipients.
invalid address ...
... address to their intended recipients.
invalid address - an address that is not assigned to any interface. A
...
... valid lifetime expires.
Invalid addresses should not appear as the destination or source
address of a packet. In the former case, the internet ...
... 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 later case
...
... preferred lifetime - the length of time that a valid address is
preferred (i.e., the time until deprecation). When the preferred
lifetime ...
... preferred (i.e., the time until deprecation). When the preferred
lifetime expires, the address becomes deprecated.
valid ...
... that is (at least) unique per link [ADDR-ARCH]. Stateless
address autoconfiguration combines an interface identifier with
a prefix ...
... interface identifier with
a prefix to form an address. From address autoconfiguration's
perspective, an interface identifier ...
... a prefix to form an address. From address autoconfiguration's
perspective, an interface identifier is a bit string ...
... host to obtain or create
unique addresses for each of its interfaces. Address
autoconfiguration assumes that each interface ...
... unique addresses for each of its interfaces. Address
autoconfiguration assumes that each interface can provide a
unique identifier ...
... interface identifier
consists of the interface's link-layer address. An interface
identifier can be combined with a prefix to form an address ...
... link-layer address. An interface
identifier can be combined with a prefix to form an address.
...
... router as a prerequisite for communicating. Plug-and-play
communication is achieved through the use of link-local
addresses. Link-local addresses have a well-known prefix ...
... router as a prerequisite for communicating. Plug-and-play
communication is achieved through the use of link-local
addresses. Link-local addresses have a well-known prefix that
...
... nodes
attach. A host forms a link-local address by appending its
interface identifier to the link-local ...
... multiple networks and routers should not
require the presence of a stateful address configuration server.
In order to generate site-local or global addresses ...
... address configuration server.
In order to generate site-local or global addresses, hosts must
determine the prefixes ...
... Address configuration should facilitate the graceful renumbering
of a site's machines. For example, a site may wish to renumber
all of its nodes ...
... switches to a new network service
provider. Renumbering is achieved through the leasing of
addresses to interfaces and the assignment of multiple addresses
...
... addresses to interfaces and the assignment of multiple addresses
to the same interface. Lease lifetimes provide the mechanism
...
... through which a site phases out old prefixes. The assignment of
multiple addresses to an interface provides for a transition
period during which both a new address ...
... multiple addresses to an interface provides for a transition
period during which both a new address and the one being phased
out work simultaneously.
...
... routers) begin the autoconfiguration process by
generating a link-local address for the interface. A link-local
address is formed by appending the interface ...
... generating a link-local address for the interface. A link-local
address is formed by appending the interface's identifier to the
...
... used, however, a node must attempt to verify that this "tentative"
address is not already in use by another node on the link.
...
... Specifically, it sends a Neighbor Solicitation message containing the
tentative address as the target. If another node is already using
...
... target. If another node is already using
that address, it will return a Neighbor Advertisement saying so. If
another node ...
... Neighbor Advertisement saying so. If
another node is also attempting to use the same address, it will send
a Neighbor Solicitation for the target ...
...
If a node determines that its tentative link-local address is not
unique, autoconfiguration stops and manual configuration ...
... interface identifier. Alternatively, link-local
and other addresses will need to be configured manually.
...
...
Once a node ascertains that its tentative link-local address is
unique, it assigns it to the interface. At this point, the node ...
... Router
Advertisements contain two flags indicating what type of stateful
autoconfiguration (if any) should be performed. A "managed address
configuration" flag indicates whether hosts should use stateful
autoconfiguration ...
... hosts should use stateful
autoconfiguration to obtain addresses. An "other stateful
configuration" flag indicates whether hosts should use stateful
...
... autoconfiguration to obtain additional information (excluding
addresses).
...
... Router Advertisements also contain zero or more Prefix Information
options that contain information used by stateless address
autoconfiguration to generate site-local and global addresses. It
...
... options that contain information used by stateless address
autoconfiguration to generate site-local and global addresses. It
should be noted that the stateless and stateful address
autoconfiguration ...
... addresses. It
should be noted that the stateless and stateful address
autoconfiguration fields in Router Advertisements are processed
independently of one another, and a host ...
... independently of one another, and a host may use both stateful and
stateless address autoconfiguration simultaneously. One Prefix
Information option field, the "autonomous address ...
... stateless address autoconfiguration simultaneously. One Prefix
Information option field, the "autonomous address-configuration
flag", indicates whether or not the option even applies to stateless
...
... subnet prefix together with lifetime values indicating how long
addresses created from the prefix remain preferred and valid ...
...
For safety, all addresses must be tested for uniqueness prior to
their assignment to an interface. In the case of addresses ...
... addresses must be tested for uniqueness prior to
their assignment to an interface. In the case of addresses created
through stateless ...
... created
through stateless autoconfig, however, the uniqueness of an address
is determined primarily by the portion of the address formed from an
...
... stateless autoconfig, however, the uniqueness of an address
is determined primarily by the portion of the address formed from an
interface identifier. Thus, if a node ...
... interface identifier. Thus, if a node has already verified the
uniqueness of a link-local address, additional addresses created from
...
... node has already verified the
uniqueness of a link-local address, additional addresses created from
the same interface identifier ...
... the same interface identifier need not be tested individually. In
contrast, all addresses obtained manually or via stateful address
autoconfiguration should be tested for uniqueness individually. To
accommodate sites that believe the overhead ...
... interface identifier need not be tested individually. In
contrast, all addresses obtained manually or via stateful address
autoconfiguration should be tested for uniqueness individually. To
accommodate sites that believe the overhead of performing Duplicate
Address Detection ...
... stateful address
autoconfiguration should be tested for uniqueness individually. To
accommodate sites that believe the overhead of performing Duplicate
Address Detection outweighs its benefits, the use of Duplicate
Address Detection can be disabled through the administrative setting
of a per-interface ...
... accommodate sites that believe the overhead of performing Duplicate
Address Detection outweighs its benefits, the use of Duplicate
Address Detection can be disabled through the administrative setting
of a per-interface configuration flag.
...
... autoconfiguration process, a host may generate its
link-local address (and verify its uniqueness) in parallel with
waiting for a Router Advertisement. Because a router ...
...
Address leasing facilitates site renumbering by providing a mechanism
to time-out addresses assigned to interfaces ...
... Address leasing facilitates site renumbering by providing a mechanism
to time-out addresses assigned to interfaces in hosts. At present,
...
... TCP provide no support for changing
end-point addresses while a connection is open. If an end-point
...
... connection is open. If an end-point
address becomes invalid, existing connections break and all
communication to the invalid address ...
... address becomes invalid, existing connections break and all
communication to the invalid address fails. Even when applications
use UDP as a transport protocol ...
... use UDP as a transport protocol, addresses must generally remain the
same during a packet exchange.
...
...
Dividing valid addresses into preferred and deprecated categories
provides a way of indicating to upper layers that a valid ...
... provides a way of indicating to upper layers that a valid address may
become invalid shortly and that future communication using the
address ...
... address may
become invalid shortly and that future communication using the
address will fail, should the address's valid lifetime ...
... become invalid shortly and that future communication using the
address will fail, should the address's valid lifetime expire before
...
... lifetime expire before
communication ends. To avoid this scenario, higher layers should use
a preferred address (assuming one of sufficient scope exists) to
increase the likelihood that an address will remain valid ...
... a preferred address (assuming one of sufficient scope exists) to
increase the likelihood that an address will remain valid for the
duration of the communication. It is up to system administrators ...
... failed communication when renumbering takes place. The deprecation
period should be long enough that most, if not all, communications
are using the new address at the time an address becomes invalid.
...
... period should be long enough that most, if not all, communications
are using the new address at the time an address becomes invalid.
...
... IP layer is expected to provide a means for upper layers
(including applications) to select the most appropriate source
address given a particular destination and possibly other
constraints ...
... destination and possibly other
constraints. An application may choose to select the source address
itself before starting a new communication or may leave the address ...
... source address
itself before starting a new communication or may leave the address
unspecified, in which case the upper networking layers will use the
mechanism provided by the IP layer ...
... unspecified, in which case the upper networking layers will use the
mechanism provided by the IP layer to choose a suitable address on
the application's behalf.
...
...
Detailed address selection rules are beyond the scope of this
document.
...
... hosts, with two exceptions.
Routers are expected to generate a link-local address using the
procedure outlined below. In addition, routers perform Duplicate
Address Detection ...
... link-local address using the
procedure outlined below. In addition, routers perform Duplicate
Address Detection on all addresses prior to assigning them to an
interface ...
... procedure outlined below. In addition, routers perform Duplicate
Address Detection on all addresses prior to assigning them to an
interface.
...
... The number of consecutive Neighbor Solicitation
messages sent while performing Duplicate Address
Detection on a tentative address. A value of zero
indicates that Duplicate Address Detection ...
... Neighbor Solicitation
messages sent while performing Duplicate Address
Detection on a tentative address. A value of zero
indicates that Duplicate Address Detection is not
...
... Duplicate Address
Detection on a tentative address. A value of zero
indicates that Duplicate Address Detection is not
performed on tentative addresses. A value of one
...
... indicates that Duplicate Address Detection is not
performed on tentative addresses. A value of one
indicates a single transmission with no follow up
retransmissions ...
... specifies the delay between consecutive Neighbor
Solicitation transmissions performed during
Duplicate Address Detection (if
DupAddrDetectTransmits is greater than 1), as well
as the time a node ...
... node waits after sending the last
Neighbor Solicitation before ending the Duplicate
Address Detection process.
...
...
Beyond the formation of a link-local address and using Duplicate
Address Detection, how routers (auto)configure their interfaces ...
...
Beyond the formation of a link-local address and using Duplicate
Address Detection, how routers (auto)configure their interfaces is
...
... ManagedFlag Copied from the M flag field (i.e., the
"managed address configuration" flag) of the most
recently received Router Advertisement message.
...
... recently received Router Advertisement message.
The flag indicates whether or not addresses are
to be configured using the stateful
autoconfiguration ...
... Router Advertisement message.
The flag indicates whether or not information
other than addresses is to be obtained using the
stateful autoconfiguration mechanism. It starts ...
... valid configuration for
a host to use stateful address autoconfiguration
to request addresses only, without also accepting
...
... host to use stateful address autoconfiguration
to request addresses only, without also accepting
other configuration
information.
...
...
A host also maintains a list of addresses together with their
corresponding lifetimes. The address list contains both
...
... host also maintains a list of addresses together with their
corresponding lifetimes. The address list contains both
autoconfigured addresses and those configured manually.
...
... corresponding lifetimes. The address list contains both
autoconfigured addresses and those configured manually.
...
... Creation of Link-Local Addresses ...
... Duplicate Address Detection ...
...
Duplicate Address Detection is performed on unicast addresses prior
to assigning them to an interface ...
...
Duplicate Address Detection is performed on unicast addresses prior
to assigning them to an interface whose DupAddrDetectTransmits
...
... to assigning them to an interface whose DupAddrDetectTransmits
variable is greater than zero. Duplicate Address Detection MUST take
place on all unicast addresses, regardless of whether they are
...
... variable is greater than zero. Duplicate Address Detection MUST take
place on all unicast addresses, regardless of whether they are
obtained through stateful, stateless or manual configuration ...
... Duplicate Address Detection MUST NOT be performed on anycast
addresses.
...
... Duplicate Address Detection MUST NOT be performed on anycast
addresses.
...
... Each individual unicast address SHOULD be tested for uniqueness.
However, when stateless address autoconfiguration is used,
...
... Each individual unicast address SHOULD be tested for uniqueness.
However, when stateless address autoconfiguration is used,
address uniqueness is determined solely by the interface
identifier ...
... However, when stateless address autoconfiguration is used,
address uniqueness is determined solely by the interface
identifier, assuming that subnet prefixes are assigned correctly
...
... subnet prefixes are assigned correctly
(i.e., if all of an interface's addresses are generated from the
same identifier, either all addresses ...
... addresses are generated from the
same identifier, either all addresses or none of them will be
duplicates). Thus, for a set of addresses formed from the same
...
... identifier, either all addresses or none of them will be
duplicates). Thus, for a set of addresses formed from the same
interface identifier, it is sufficient to check that the link ...
... interface identifier, it is sufficient to check that the link-
local address generated from the identifier is unique on the
link ...
... identifier is unique on the
link. In such cases, the link-local address MUST be tested for
uniqueness, and if no duplicate address is detected, an
...
... link. In such cases, the link-local address MUST be tested for
uniqueness, and if no duplicate address is detected, an
implementation MAY choose to skip Duplicate Address Detection
...
... uniqueness, and if no duplicate address is detected, an
implementation MAY choose to skip Duplicate Address Detection
for additional addresses derived from the same interface
identifier ...
... implementation MAY choose to skip Duplicate Address Detection
for additional addresses derived from the same interface
identifier.
...
...
The procedure for detecting duplicate addresses uses Neighbor
Solicitation and Advertisement messages as described below. If a
...
... Neighbor
Solicitation and Advertisement messages as described below. If a
duplicate address is discovered during the procedure, the address
cannot be assigned to the interface ...
... Advertisement messages as described below. If a
duplicate address is discovered during the procedure, the address
cannot be assigned to the interface. If the address ...
... address
cannot be assigned to the interface. If the address is derived from
an interface identifier, a new identifier ...
... identifier will need to be assigned to
the interface, or all IP addresses for the interface will need to be
manually configured. Note that the method ...
... method for detecting duplicates
is not completely reliable, and it is possible that duplicate
addresses will still exist (e.g., if the link was partitioned while
Duplicate Address Detection ...
... addresses will still exist (e.g., if the link was partitioned while
Duplicate Address Detection was performed).
...
...
An address on which the duplicate Address Detection Procedure is
applied is said to be tentative until the procedure has completed
...
...
An address on which the duplicate Address Detection Procedure is
applied is said to be tentative until the procedure has completed
successfully. A tentative address ...
... duplicate Address Detection Procedure is
applied is said to be tentative until the procedure has completed
successfully. A tentative address is not considered "assigned to an
interface" in the traditional sense. That is, the interface ...
... Neighbor Solicitation and Advertisement messages containing
the tentative address in the Target Address field, but processes such
packets differently from those whose Target Address ...
... Advertisement messages containing
the tentative address in the Target Address field, but processes such
packets differently from those whose Target Address matches an
...
... tentative address in the Target Address field, but processes such
packets differently from those whose Target Address matches an
address assigned to the interface ...
... packets differently from those whose Target Address matches an
address assigned to the interface. Other packets addressed to the
tentative address ...
... address assigned to the interface. Other packets addressed to the
tentative address should be silently discarded.
...
...
It should also be noted that Duplicate Address Detection must be
performed prior to assigning an address to an interface ...
... It should also be noted that Duplicate Address Detection must be
performed prior to assigning an address to an interface in order to
prevent multiple nodes ...
... interface in order to
prevent multiple nodes from using the same address simultaneously.
If a node begins using an address ...
... address simultaneously.
If a node begins using an address in parallel with Duplicate Address
Detection, and another node is already using the address ...
... If a node begins using an address in parallel with Duplicate Address
Detection, and another node is already using the address, the node ...
... address in parallel with Duplicate Address
Detection, and another node is already using the address, the node
performing Duplicate Address Detection ...
... address, the node
performing Duplicate Address Detection will erroneously process
traffic intended for the other node ...
... The following subsections describe specific tests a node performs to
verify an address's uniqueness. An address is considered unique if
none of the tests indicate the presence of a duplicate address ...
... node performs to
verify an address's uniqueness. An address is considered unique if
none of the tests indicate the presence of a duplicate address within
...
... address's uniqueness. An address is considered unique if
none of the tests indicate the presence of a duplicate address within
RetransTimer milliseconds after having sent DupAddrDetectTransmits
Neighbor ...
... RetransTimer milliseconds after having sent DupAddrDetectTransmits
Neighbor Solicitations. Once an address is determined to be unique,
it may be assigned to an interface.
...
... nodes multicast address and the solicited-node multicast address
of the tentative address. The former insures that the node ...
... node multicast address
of the tentative address. The former insures that the node receives
Neighbor ...
... Neighbor Advertisements from other nodes already using the address;
the latter insures that two nodes attempting to use the same address ...
... address;
the latter insures that two nodes attempting to use the same address
simultaneously detect each other's presence.
...
... Neighbor
Solicitations, each separated by RetransTimer milliseconds. The
solicitation's Target Address is set to the address being checked,
the IP ...
... Solicitations, each separated by RetransTimer milliseconds. The
solicitation's Target Address is set to the address being checked,
the IP source is set to the unspecified address ...
... address being checked,
the IP source is set to the unspecified address and the IP
destination ...
... conditions when more than one node is trying to solicit for the same
address at the same time. In order to improve the robustness of the
Duplicate Address Detection algorithm ...
... address at the same time. In order to improve the robustness of the
Duplicate Address Detection algorithm, an interface MUST receive and
...
... process datagrams sent to the all-nodes multicast address or
solicited-node multicast address ...
... multicast address or
solicited-node multicast address of the tentative address while
delaying transmission of the initial Neighbor Solicitation ...
... solicited-node multicast address of the tentative address while
delaying transmission of the initial Neighbor Solicitation.
...
... interface,
node behavior depends on whether the target address is tentative or
not. If the target address is not tentative (i.e., it is assigned to
...
... node behavior depends on whether the target address is tentative or
not. If the target address is not tentative (i.e., it is assigned to
the receiving interface ...
... interface), the solicitation is processed as described
in [DISCOVERY]. If the target address is tentative, and the source
address is a unicast address, the solicitation's sender ...
... in [DISCOVERY]. If the target address is tentative, and the source
address is a unicast address, the solicitation's sender is performing
...
... DISCOVERY]. If the target address is tentative, and the source
address is a unicast address, the solicitation's sender is performing
address resolution ...
... unicast address, the solicitation's sender is performing
address resolution on the target; the solicitation should be silently
ignored. Otherwise, processing takes place as described below. In
...
... source address of the Neighbor Solicitation is the unspecified
address, the solicitation is from a node performing Duplicate Address
Detection. If the solicitation is from another node ...
... address, the solicitation is from a node performing Duplicate Address
Detection. If the solicitation is from another node, the tentative
address is a duplicate and should not be used (by either node ...
... node performing Duplicate Address
Detection. If the solicitation is from another node, the tentative
address is a duplicate and should not be used (by either node). If
the solicitation is from the node ...
... multicast packets), the solicitation does not indicate the presence
of a duplicate address.
...
... multicast packets.
The details of how such a facility is implemented may prevent
Duplicate Address Detection from working correctly. See the Appendix
for further discussion.
...
...
The following tests identify conditions under which a tentative
address is not unique:
...
... If a Neighbor Solicitation for a tentative address is
received prior to having sent one, the tentative address is a
...
... Neighbor Solicitation for a tentative address is
received prior to having sent one, the tentative address is a
duplicate. This condition occurs when two nodes run Duplicate
Address Detection ...
... tentative address is a
duplicate. This condition occurs when two nodes run Duplicate
Address Detection simultaneously, but transmit initial
solicitations at different times (e.g., by selecting different
random delay values before transmitting ...
... interface does not loopback packet, yet one or more
solicitations was received), the tentative address is a
duplicate. This condition occurs when two nodes run Duplicate
Address Detection ...
... tentative address is a
duplicate. This condition occurs when two nodes run Duplicate
Address Detection simultaneously and transmit solicitations at
roughly the same time.
...
... interface,
node behavior depends on whether the target address is tentative or
matches a unicast or anycast address ...
... target address is tentative or
matches a unicast or anycast address assigned to the interface. If
the target address ...
... anycast address assigned to the interface. If
the target address is assigned to the receiving interface, the
...
... interface, the
solicitation is processed as described in [DISCOVERY]. If the target
address is tentative, the tentative address is not unique.
...
... solicitation is processed as described in [DISCOVERY]. If the target
address is tentative, the tentative address is not unique.
...
... When Duplicate Address Detection Fails ...
...
A tentative address that is determined to be a duplicate as described
above, MUST NOT be assigned to an interface and the node ...
... node SHOULD log a
system management error. If the address is a link-local address
formed from an interface identifier ...
... system management error. If the address is a link-local address
formed from an interface identifier, the interface ...
... Creation of Global and Site-Local Addresses ...
...
Global and site-local addresses are formed by appending an interface
identifier to a prefix of appropriate length. Prefixes ...
... Prefix Information options contained in Router Advertisements.
Creation of global and site-local addresses and configuration of
other parameters as described in this section SHOULD be locally
configurable. However, the processing described below MUST be enabled
...
... Router Advertisements are sent periodically to the all-nodes
multicast address. To obtain an advertisement quickly, a host sends
out Router ...
... host MUST attempt to use stateful
autoconfiguration to obtain addresses and other configuration
information. An implementation MAY provide a way to disable the
invocation of stateful autoconfiguration ...
... into ManagedFlag. If the value of ManagedFlag changes from FALSE to
TRUE, and the host is not already running the stateful address
autoconfiguration protocol, the host should invoke the stateful
address autoconfiguration protocol, requesting both address
information ...
... host is not already running the stateful address
autoconfiguration protocol, the host should invoke the stateful
address autoconfiguration protocol, requesting both address
information and other information. If the value of the ManagedFlag
changes from TRUE to FALSE, the host ...
... stateful address
autoconfiguration protocol, the host should invoke the stateful
address autoconfiguration protocol, requesting both address
information and other information. If the value of the ManagedFlag
changes from TRUE to FALSE, the host should continue running the
...
... changes from TRUE to FALSE, the host should continue running the
stateful address autoconfiguration, i.e., the change in the value of
the ManagedFlag has no effect. If the value of the flag stays
unchanged, no special action takes place. In particular, a host ...
... unchanged, no special action takes place. In particular, a host MUST
NOT reinvoke stateful address configuration if it is already
participating in the stateful protocol as a result of an earlier
advertisement.
...
... invoke the stateful autoconfiguration protocol, requesting
information (excluding addresses if ManagedFlag is set to FALSE). If
the value of the OtherConfigFlag changes from TRUE to FALSE, the host
...
... the value of the OtherConfigFlag changes from TRUE to FALSE, the host
should continue running the stateful address autoconfiguration
protocol, i.e., the change in the value of OtherConfigFlag has no
effect. If the value of the flag stays unchanged, no special action
...
... d) If the prefix advertised does not match the prefix of an address
already in the list, and the Valid Lifetime ...
... Valid Lifetime is not 0, form an
address (and add it to the list) by combining the advertised
prefix with the link ...
... address is formed successfully, the host adds it to the
list of addresses assigned to the interface, initializing its
preferred and valid ...
... prefix matches the prefix of an autoconfigured
address (i.e., one obtained via stateless or stateful address
autoconfiguration) in the list of addresses ...
... address (i.e., one obtained via stateless or stateful address
autoconfiguration) in the list of addresses associated with the
interface ...
... address (i.e., one obtained via stateless or stateful address
autoconfiguration) in the list of addresses associated with the
interface, the specific action to perform depends on the Valid ...
... Lifetime in the received advertisement and the Lifetime
associated with the previously autoconfigured address (which we
call StoredLifetime in the discussion that follows):
...
... update the stored Lifetime of the
corresponding address.
2) If the StoredLifetime is less than or equal to 2 hours and the
...
... 3) Otherwise, reset the stored Lifetime in the corresponding
address to two hours.
The above rules address ...
... address to two hours.
The above rules address a specific denial of service attack in
which a bogus advertisement could contain prefixes ...
... options with short Lifetimes could cause all of a node's
addresses to expire prematurely. The above rules insure that
legitimate advertisements (which are sent periodically) will
"cancel" the short lifetimes before they actually take effect.
...
...
A preferred address becomes deprecated when its preferred lifetime
expires. A deprecated address ...
... preferred address becomes deprecated when its preferred lifetime
expires. A deprecated address SHOULD continue to be used as a source
address in existing communications, but SHOULD NOT be used in new
communications if an alternate (non-deprecated) address ...
... lifetime
expires. A deprecated address SHOULD continue to be used as a source
address in existing communications, but SHOULD NOT be used in new
communications if an alternate (non-deprecated) address is available
...
... deprecated address SHOULD continue to be used as a source
address in existing communications, but SHOULD NOT be used in new
communications if an alternate (non-deprecated) address is available
and has sufficient scope. IP and higher layers (e.g., TCP ...
... UDP) MUST
continue to accept datagrams destined to a deprecated address since a
deprecated address is still a valid ...
... datagrams destined to a deprecated address since a
deprecated address is still a valid address for the interface ...
... deprecated address is still a valid address for the interface. An
implementation MAY prevent any new communication from using a
...
... interface. An
implementation MAY prevent any new communication from using a
deprecated address, but system management MUST have the ability to
disable such a facility, and the facility MUST be disabled by
...
... when its valid lifetime expires. An invalid address MUST NOT be used
as a source address in outgoing communications and MUST NOT be
...
... lifetime expires. An invalid address MUST NOT be used
as a source address in outgoing communications and MUST NOT be
recognized as a destination on a receiving ...
...
It is possible for hosts to obtain address information using both
stateless and stateful protocols since both may be enabled at the
...
... physical attachment to
a network can generate an address (using a variety of ad hoc
techniques) that provides connectivity.
...
...
The use of Duplicate Address Detection opens up the possibility of
denial of service attacks. Any node ...
... node can respond to Neighbor
Solicitations for a tentative address, causing the other node to
reject the address ...
... tentative address, causing the other node to
reject the address as a duplicate. This attack is similar to other
attacks ...
... denial of service attack vulnerability; this document
incorporates changes that address this vulnerability.
...
... AUTHORS' ADDRESSES ...
... APPENDIX A: LOOPBACK SUPPRESSION & DUPLICATE ADDRESS DETECTION ...
... the same link happen to have the same identifier and link-layer
address, and they both send out packets with identical contents at
roughly the same time (e.g., Neighbor Solicitations for a tentative
address ...
... link-layer
address, and they both send out packets with identical contents at
roughly the same time (e.g., Neighbor Solicitations for a tentative
address as part of Duplicate Address Detection messages). Although a
receiver ...
... roughly the same time (e.g., Neighbor Solicitations for a tentative
address as part of Duplicate Address Detection messages). Although a
receiver will receive both packets, it cannot determine which packet
...
... was looped back and which was sent by another node; if one receives
more solicitations than were sent, the tentative address is a
duplicate. However, the situation may not always be this
straightforward.
...
... hardware itself suppresses
loopbacks, a node running Duplicate Address Detection simply counts
the number of Neighbor Solicitations received for a tentative address ...
... Duplicate Address Detection simply counts
the number of Neighbor Solicitations received for a tentative address
and compares them with the number expected. If there is a mismatch,
the tentative address ...
... tentative address
and compares them with the number expected. If there is a mismatch,
the tentative address is a duplicate.
...
... filter out unwanted loopbacks is
to discard any received packet whose link-layer source address is the
same as the receiving interface ...
... node using the same link-layer address. Duplicate Address
Detection will fail on interfaces that filter ...
... same link-layer address. Duplicate Address
Detection will fail on interfaces that filter received packets in
...
... If a node performing Duplicate Address Detection discards
received packets having the same source link-layer address as
...
... node performing Duplicate Address Detection discards
received packets having the same source link-layer address as
the receiving interface ...
... nodes also using the same link-layer address, including Neighbor
Advertisement and Neighbor Solicitation messages required to
...
... Neighbor
Advertisement and Neighbor Solicitation messages required to
make Duplicate Address Detection work correctly. This
particular problem can be avoided by temporarily disabling the
software suppression of loopbacks while a node ...
... software suppression of loopbacks while a node performs
Duplicate Address Detection.
...
... If a node that is already using a particular IP address discards
received packets having the same link-layer ...
... received packets having the same link-layer source address as
the interface, it will also discard Duplicate Address
Detection ...
... source address as
the interface, it will also discard Duplicate Address
Detection-related Neighbor Solicitation messages sent by another
node ...
... node also using the same link-layer address. Consequently,
Duplicate Address Detection will fail, and the other node ...
... layer address. Consequently,
Duplicate Address Detection will fail, and the other node will
configure a non-unique address ...
... Duplicate Address Detection will fail, and the other node will
configure a non-unique address. Since it is generally impossible
to know when another node is performing Duplicate Address
Detection ...
... address. Since it is generally impossible
to know when another node is performing Duplicate Address
Detection, this scenario can be avoided only if software
suppression of loopback is permanently disabled.
...
...
Thus, to perform Duplicate Address Detection correctly in the case
where two interfaces are using the same link ...
... interfaces are using the same link-layer address, an
implementation must have a good understanding of the interface's
...
... semantics, and the interface cannot discard
received packets simply because the source link-layer address is the
same as the interfaces.
...
... Clarified definition of deprecated address to make clear it is OK
to continue sending to or from deprecated addresses.
...
... Clarified definition of deprecated address to make clear it is OK
to continue sending to or from deprecated addresses.
...
... Added rules to Section 5.5.3 Router Advertisement processing to
address potential denial-of-service attack when prefixes are
...
... Clarified wording in Section 5.5.4 to make clear that all upper
layer protocols must process (i.e., send and receive) packets sent
to deprecated addresses.
...