router
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... point to point service, sufficient to
interconnect IPv6 routers (and even IPv6 hosts, in certain
situations). At the other extreme, NBMA ...
... IP
endpoints that are logically separated by one or more routers at the
IP level. IPv6 packets ...
... IPv6 packets traversing this VC are said to 'shortcut' the
routers that are in the logical IPv6 path between the VC's endpoints ...
...
When appropriately configured, the egress router from a Logical
Link is responsible for detecting the existence of an IP packet ...
... While continuing to conventionally forward the flow's packets,
the router initiates an NHRP query for the flow ...
...
The originally querying router then issues a Redirect to the IP
source, identifying the flow ...
... Off-link nodes are considered to only be accessible through one of
the routers directly attached to the link.
...
... NBMA specific processing. The underlying
mechanism for distributing Neighbor Discovery and Router Discovery
messages then works as expected.
...
... (section 8 [7]). IPv6 allows a router to inform the members of an LL
that there is a better 'first hop' to a given destination (section
...
... destination (section
8.2 [7]). The advertisement itself is achieved through a Router
Redirect message, which may carry the link layer address ...
... A transmitting host only listens to Router Redirects from the router
that is currently acting as the default router ...
... transmitting host only listens to Router Redirects from the router
that is currently acting as the default router for the IP ...
... Router Redirects from the router
that is currently acting as the default router for the IP destination
...
... VC is torn down only if it no longer required
(since the old VC was to the router, it may still be required by
other packets from the host that are heading to the router ...
... router, it may still be required by
other packets from the host that are heading to the router).
...
... 12]. Responsibility for detecting
flows is placed into the routers, where packets cross the edges of IP
routing boundaries.
...
...
For the purpose of conformance with this document, a router MAY
choose to initiate the discovery of a better first-hop when it
determines that an identifiable flow ...
...
Such a router:
...
...
SHALL NOT use IP packets arriving from another router to
trigger the generation of a Router Redirect.
...
... better first-hop when a suitable flow is detected, and
advertise the information in a Router Redirect.
...
...
IPv6 routers that support the OPTIONAL flow detection behavior
described above SHALL support administrative mechanisms to switch ...
... neighbor.
To support host-triggered redirects, routers conforming to this
document SHALL recognize specific Neighbor Solicitation messages sent
...
... hop limit of the data flow
for which this trigger is being sent. This ensures that the router
is able to restrict the shortcut attempt to not exceed the reach
of the data flow ...
... request for a host-triggered redirect. However, actual shortcut
discovery is OPTIONAL for IPv6 routers.
...
...
When shortcut discovery is not supported, the router SHALL construct
a Redirect message identifying the router ...
... router SHALL construct
a Redirect message identifying the router itself as the best
'shortcut', and return it to the soliciting host.
...
...
If shortcut discovery is to be supported, the router's response SHALL
be:
...
...
Once the NHRP Reply is received by the originating router, the
router SHALL construct a Redirect message ...
... NHRP Reply is received by the originating router, the
router SHALL construct a Redirect message containing the IPv6
address of the transient neighbor ...
... VC (to the off-LL target itself,
or to the best egress router towards that neighbor as determined
by NHRP ...
... error indication is received for a host-triggered
shortcut attempt, the requesting router SHALL construct a Redirect
message identifying the router itself as the best 'shortcut', and
...
... shortcut attempt, the requesting router SHALL construct a Redirect
message identifying the router itself as the best 'shortcut', and
return it to the soliciting host.
...
... flow detection has occurred, or a host trigger has been
detected, routers SHALL use NHRP in an NHS to NHS mode to establish
the IPv6 ...
... IPv6/NBMA routers supporting shortcut discovery will need to perform
some or all of the following functions:
...
... target for resolution in a
NHRP Request. The router then forwards this NHRP Request to the next
closest NHS. The process continues (as it would for normal NHRP ...
... link-local scope of one of its interfaces. (This may
potentially occur within a single router.)
...
...
The last hop router SHALL resolve the NHRP Request from mapping
information contained in its neighbor cache ...
... destination is currently
considered unreachable, the last hop router SHALL perform Neighbor
Discovery on the local interface, and build the NHRP ...
... flow of packets going through the last hop router towards the target.
In this typical case the Neighbor cache ...
... If the discovery process was triggered through flow detection at the
originating router, the return of the NHRP Reply results in the
following events:
...
...
Any Redirect message sent by a router MUST conform to all the
rules described in [7] so that the packet is properly validated ...
... Address in the original
message. If the target of the short-cut is an egress router then
the ICMP Target Address ...
... Link Local address of the egress
router that is unique to the NBMA cloud to which the router ...
...
Also note that egress routers may subsequently redirect the source
host. To do so, the Link Local ...
... Source Address
The link-local address assigned to the router's interface
from which this message is sent.
...
... cache entries for which they have
issued Neighbor Advertisements or Router Redirects. If a NHRP Purge
is received that invalidates information previously issued to local
...
... is received that invalidates information previously issued to local
host, the router SHALL issue a Router Redirect specifying the router
...
... host, the router SHALL issue a Router Redirect specifying the router
itself as the new best next-hop ...
... host, the router SHALL issue a Router Redirect specifying the router
itself as the new best next-hop for the affected IPv6 ...
...
Routers SHALL keep track of Neighbor cache entries that have
previously been used to generate an NHRP ...
... Neighbor cache entry SHALL result in a NHRP Purge being sent
towards the router that originally requested the NHRP Reply.
...
... IPv6 packets, and distribution of Discovery messages.
Shortcut NBMA level paths are supported either through router based
flow detection, or host ...
... Neighbor
Discovery is used without modification for all intra-LL control
(including the initiation of NBMA shortcut discovery). Router to
router NHRP ...
... Katsube, Y., Nagami, K. and H. Esaki, "Toshiba's Router Architecture Extensions for ATM : Overview", RFC 2098 ...
... A.1.2. Performing Router Discovery ...
...
IPv6 routers periodically send unsolicited Router Advertisements
announcing their availability on the LL. When an IPv6 ...
...
IPv6 routers periodically send unsolicited Router Advertisements
announcing their availability on the LL. When an IPv6 router ...
... Router Advertisements
announcing their availability on the LL. When an IPv6 router sends
an unsolicited Router Advertisement, it sends a data packet ...
... IPv6 router sends
an unsolicited Router Advertisement, it sends a data packet addressed
to the IPv6 ...
... IPv6/NBMA driver gets the Router Advertisement message from the IPv6
network layer, it transmits the message by following steps described
...
... To perform Router Discovery, an IPv6 host sends a Router Solicitation
message to the all-routers multicast address ...
... IPv6 host sends a Router Solicitation
message to the all-routers multicast address. When the local node
...
... message will be sent to either those nodes which have joined the
all-routers multicast group or to all nodes. The nodes ...
... layer for processing. Only
those nodes which are routers will process the message and respond to
it.
...
...
An IPv6 router responds to a Router Solicitation by sending a Router
Advertisement addressed to the IPv6 ...
... An IPv6 router responds to a Router Solicitation by sending a Router
Advertisement addressed to the IPv6 all-nodes ...
... IPv6 router responds to a Router Solicitation by sending a Router
Advertisement addressed to the IPv6 all-nodes multicast address ...
... multicast address if
the source address of the Router Solicitation was the unspecified
address. If the source address ...
... address. If the source address in the Router Solicitation is not the
unspecified address, the the router ...
... Router Solicitation is not the
unspecified address, the the router will unicast the Router
Advertisement to the soliciting node ...
... address, the the router will unicast the Router
Advertisement to the soliciting node. If the router sends the Router
Advertisement ...
... unicast the Router
Advertisement to the soliciting node. If the router sends the Router
Advertisement to the all-nodes multicast address ...
... Router
Advertisement to the soliciting node. If the router sends the Router
Advertisement to the all-nodes multicast address then it follows the
...
... nodes multicast address then it follows the
steps described above for unsolicited Router Advertisements.
...
... will result in a new pt-pt VC being created between the router and
the soliciting node if one did not already exist.
...
...
The soliciting node will receive and process the Router Advertisement
as described in section 4.5 and will pass the RA message to the IPv6
network ...
... NBMA address, contained in the Router Advertisement message's Source
Link-Layer Address Option.
...
... effort unicast data between the soliciting node and the router will
be transmitted over the new PtP VC.
...
... 7]. This can be used to direct hosts to a better first hop
router, another host on the same LL, or to a transient neighbor on
...
... described in section 4.4.1. This will create a VC between the router
and the redirected host if one did not previously exist.
...
... hosts on an LL receive this
autoconfiguration information through Router Advertisement messages.
...
... interface on the Logical Link, the IPv6
host will perform Router Discovery to obtain auto-configuration
information. The IPv6 host will send out a Router Solicitation ...
... Router Discovery to obtain auto-configuration
information. The IPv6 host will send out a Router Solicitation and
will receive a Router Advertisement, or it will wait for an
...
... IPv6 host will send out a Router Solicitation and
will receive a Router Advertisement, or it will wait for an
unsolicited Router Advertisement. The IPv6 host ...
... will receive a Router Advertisement, or it will wait for an
unsolicited Router Advertisement. The IPv6 host will process the M
and O bits ...
... IPv6 host will process the M
and O bits of the Router Advertisement, as described in [9] and as a
result may invoke stateful address ...
... IPv6 host will invoke stateful auto-configuration if M and O bits
of Router Advertisements indicate it should do so, and may invoke
stateful auto-configuration if it detects that no routers are present
...
... of Router Advertisements indicate it should do so, and may invoke
stateful auto-configuration if it detects that no routers are present
on the Logical Link. An IPv6 host ...
... DHCPv6 client and a DHCPv6 Server on another LL
are sent either via a router or DHCPv6 Relay-Agent. Prior to sending
...
...
IPv6 multicast routers will use the IGMPv6 protocol to periodically
determine group memberships of local hosts ...
... efficient in this environment, they will still work as described
below. However, IPv6 multicast routers connected to an NBMA LL could
optionally optimize the IGMP ...
... MARS for multicast group membership is an optional
enchancement and is not required for routers to determine IPv6
multicast group membership on a LL.
...
...
An IPv6 multicast router receives all IPv6 multicast packets on the
LL by joining all multicast groups ...
... 5]. The MARS
server will then cause the multicast router to be added to all
existing and future multicast VCs ...
... multicast VCs. The IPv6 multicast router will
thereafter be the recipient of all IPv6 multicast packets sent within
...
...
A related sequence of IPv6 packets that the first hop router is
allowed to perform flow-detection on for the purposes of
...
... network will provide default best effort forwarding (an IPv6
router defaults to providing best-effort forwarding for packets whose
FlowID/source-address pair is not recognized).
...
... Non-zero FlowID
Best effort forwarding if the routers along the path have not
been otherwise configured with alternative processing rules for
...
... shortcut discovery is suspended.
If the routers along the path have been configured with
particular processing rules for this FlowID/source-address ...
... hop limit
from the host to the router. The use of this ND option is defined in
section 3.2.2 of this specification. Its binary representation
...
... The shortcut limit option is used by a host in a Neighbor
Solicitation message sent as a shortcut trigger to a default
router. It restricts the router's shortcut query to targets ...
... host in a Neighbor
Solicitation message sent as a shortcut trigger to a default
router. It restricts the router's shortcut query to targets
...