IPv6
Click on the red underlined text to get to the source
... point to point service, sufficient to
interconnect IPv6 routers (and even IPv6 hosts, in certain
situations). At the other extreme, NBMA ...
... service, sufficient to
interconnect IPv6 routers (and even IPv6 hosts, in certain
situations). At the other extreme, NBMA networks ...
... Virtual Circuits (or functional
equivalents) may be used to emulate the service provided to the IPv6
layer by conventional broadcast ...
... this emulation requires complex convergence protocols, particularly
to support IPv6 multicast.
...
... architecture allows conventional
host-side operation of the IPv6 Neighbor Discovery protocol, while
also supporting the establishment of 'shortcut' NBMA forwarding paths
...
...
IPv6 developers opted to migrate away from a link layer specific
approach, chosing to combine a number of tasks into a protocol known
...
... protocol.) This document augments and optimizes the MARS protocol for
use in support of IPv6 Neighbor Discovery, generalizing the
applicability of RFC 2022prop beyond ATM ...
... VC are said to 'shortcut' the
routers that are in the logical IPv6 path between the VC's endpoints.
...
... NBMA networks capable of supporting dynamic
establishment of calls (SVCs or functional equivalent). For IPv6
over NBMA, shortcut discovery and management ...
... exactly two nodes and the use of Neighbor Discovery and other IPv6
features is limited. IPv6/NBMA ...
... Neighbor Discovery and other IPv6
features is limited. IPv6/NBMA interfaces have only one neighbor ...
... NBMA-specific companion documents MAY additionally specify the
concatenation of IPv6 over PPP and PPP over NBMA ...
... neighbors are discovered through
the use of messages multicast to members of an IPv6 interface's
local IPv6 ...
... flow was originally established through hop-
by-hop processing. This supports the existing ND ability for IPv6
destinations to perform their own dynamic interface ...
...
The remainder of this document is structured as follows: Section 2
explains the generalization of IPv6 Link to "Logical Link" when used
...
... the document. Appendix A provides some non-normative descriptive
text regarding the operation of Ipv6 Neighbor Discovery. Appendix B
describes some sub-optimal solutions for emulating the multicasting
...
...
It should be noted that whilst members of an LL are IPv6 Neighbors,
it is possible for Neighbors ...
...
Neighbor Discovery events can result in the expansion of an IPv6
interface's set of Neighbors ...
... of interfaces that make up its LL. This leads to three possible
relationships between any two IPv6 interfaces:
...
... IP
destination address. (IPv6 assumes that multicasting is an integral
part of the Internet service ...
... described in section 4.1, and SHALL send certain classes of outgoing
IPv6 packets directly to their local MARS as described in section
4.4.2.
...
... Redirect message
(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 ...
... host initiated trigger, and section 3.2.3 discusses the use of
NHRP to discover mappings for IPv6 targets in remote LLs.
...
...
SHALL only consider IPv6 packets with FlowID of zero for the
purposes of flow detection as defined in this section.
...
...
IPv6 routers that support the OPTIONAL flow detection behavior
described above SHALL support administrative mechanisms to switch ...
... flow-detection. They MAY provide mechanisms for adding additional
constraints to the categories of IPv6 packets that constitute a
'flow'.
...
...
The actual algorithm(s) for determining what sequence of IPv6 packets
constitute a 'flow' are outside the scope of this document. Appendix
...
... request for a host-triggered redirect. However, actual shortcut
discovery is OPTIONAL for IPv6 routers.
...
... router SHALL construct a Redirect message containing the IPv6
address of the transient neighbor, and the NBMA link layer address ...
... routers SHALL use NHRP in an NHS to NHS mode to establish
the IPv6 to link level address mapping of a better first hop.
...
... target protocol address, the scope of a shortcut request will be
automatically bounded to the scope of the IPv6 target address. (e.g.
resolution requests for site-local addresses ...
... NHRP specification [8],
covering those packet fields specifically utilized by the IPv6/NBMA
architecture ...
... NHRP resolution reply for a host-triggered shortcut
attempt is translated into an IPv6 Redirect message as follows:
...
... changes, or a target host going down or changing identity). Any IPv6
shortcut previously established on the basis of newly purged
information SHOULD be torn down.
...
... Link. The
application of these basic functions to the operation of the various
IPv6 protocols such as Neighbor Discovery is described in Appendix A.
...
... node can send or receive IPv6 datagrams its underlying
IPv6/NBMA interface(s) must first join ...
... interface will then be a member of the LL, have a
Cluster Member ID (CMI) assigned, and can begin supporting IPv6 and
IPv6 ND operations.
...
... This section describes the node's behavior when it gets a
JoinLocalGroup request from the IPv6 Layer. The details of how this
behavior is achieved are going to be implementation specific.
...
... node-local address is received, the
IPv6/NBMA driver SHALL return success indication to the caller and
...
... address with greater than
node-local scope, the IPv6/NBMA driver SHALL send an appropriate
single group ...
... This section describes the node's behavior when it gets a
LeaveLocalGroup request from the IPv6 Layer. The details of how this
behavior is achieved are going to be implementation specific.
...
... node-local address is received, the
IPv6/NBMA driver SHALL return success indication to the caller and
...
... address with greater than
node-local scope, the IPv6/NBMA driver SHALL send an appropriate
single group ...
... IP level 'next hop' for each outbound unicast IPv6 packet is used
to identify a pt-pt VC on which to forward the packet.
...
... (e.g. ATM or SMDS), the IPv6 packet SHALL be encapsulated with the
following LLC/SNAP header ...
... NBMA driver receives a unicast packet for
transmission the IPv6 layer will already have determined the link-
...
... IP level 'next hop' for each outbound multicast IPv6 packet is
used to identify a pt-pt or pt-mpt VC on which to forward the packet.
...
... alternative rule SHALL be specified in the NBMA-specific companion
document. Some mechanism for carrying the IPv6/NBMA driver's
Cluster Member ...
... If the packet's destination is one of the following multicast
addresses, it SHALL be sent over the IPv6/NBMA driver's direct pt-pt
VC ...
...
The MARS SHALL then redistribute the IPv6 packet as described in
section 3.1.1. (If the VC to the MARS ...
... MARS
client mechanisms are used by the IPv6/NBMA driver to select and/or
establish a pt-mpt VC ...
... encapsulation shown in section 4.4.1 SHALL
be de-encapsulated and passed up to the IPv6 layer. The IPv6 layer ...
... encapsulated and passed up to the IPv6 layer. The IPv6 layer
then determines how the incoming packet ...
... Packets received using the encapsulation specified in section 4.4.2
SHALL have their pkt$cmi field compared to the local IPv6/NBMA
driver's own CMI. If the pkt$cmi in the header ...
... the packet SHALL be silently dropped. Otherwise, the packet SHALL be
de-encapsulated and passed to the IPv6 layer. The IPv6 layer ...
... encapsulated and passed to the IPv6 layer. The IPv6 layer then
determines how the incoming packet ...
... NBMA driver SHALL NOT attempt to filter out multicast IPv6
packets arriving with encapsulation defined for unicast packets, nor
...
... attempt to filter out unicast IPv6 packets arriving with
encapsulation defined for multicast packets ...
... Neighbor Discovery on the intra-LL target.
This is done to resolve the IPv6 destination address into a link-
...
... unidirectional. Even after the source has reacted to a
redirect, the destination will continue to send IPv6 packets back to
the redirected node on the old path. This happens because the
...
... destination node has no way of determining the IPv6 address of the
other end of a new VC in the absence of Neighbor Discovery ...
... connection using the new
VC. IPv6 redirects are not intended to provide symmetrical
redirection. If the non-redirected node eventually receives a
...
...
However, IPv6/NBMA drivers can assume that they will always be
talking to another driver attached to the same type of NBMA ...
... NBMA network.
(For example, an IPv6/NBMA driver does not need to consider the
possibility of establishing a shortcut VC ...
... NBMA driver does not need to consider the
possibility of establishing a shortcut VC directly to an IPv6/FR
driver.)
...
... 10]. Refer to [19 - Appendix
A] for a description of creating IPv6 EUI-64 based interface
identifiers.
...
... interfaces will generally have some local identifier
that may be used to generate a unique IPv6/NBMA interface token ...
... NBMA interface MAY support an
independent IPv6 interface, two separate scenarios are possible:
...
... virtual hosts' (vhosts) sharing a common
NBMA driver. Each vhost is free to establish IPv6/NBMA
interfaces ...
... host will tag received packets in some locally
specific manner to identify what IPv6/NBMA interface they arrived on.
...
... NBMA interface they arrived on.
However, this is an issue generic to IPv6, and does not required
clarification in this document.)
...
... architecture allows conventional
host-side operation of the IPv6 Neighbor Discovery protocol, while
also supporting the establishment of 'shortcut' NBMA forwarding paths
...
... Link
multicasting of IPv6 packets, and distribution of Discovery messages.
Shortcut NBMA level paths are supported either through router ...
... new protocols, but depends on
existing protocols (NHRP, IPv6, ND, MARS) and is therefore subject ...
... While this proposal does not introduce any new security mechanisms
all current IPv6 security mechanisms will work without modification
for NBMA ...
... encryption for both
Neighbor Discovery protocols as well as the exchange of IPv6 data
packets. The MARS protocol is modified in a manner that does not
...
... solidify the architecture described here. Grenville Armitage's
original work on IPv6/NBMA occurred while employed at Bellcore.
Elements ...
... NBMA occurred while employed at Bellcore.
Elements of section 5 were borrowed from Matt Crawford's memo on IPv6
over Ethernet.
...
... Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", RFC 2460draft, December 1998. ...
... Crawford, M., "A Method for the Transmission of IPv6 Packets over Ethernet Networks", RFC 1972(-> 2464prop), August 1996. ...
... Narten, T., Nordmark, E. and W. Simpson, "Neighbor Discovery for IP Version 6 (IPv6)", RFC 2461draft, December 1998. ...
... Thomson, S. and T. Narten, "IPv6 Stateless Address Autoconfiguration", RFC 2462draft, December 1998. ...
... Armitage, G., Schulter, P. and M. Jork, "IPv6 over ATM Networks", RFC 2492prop, January 1999. ...
... C. Perkins, J. Bound, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", Work in Progress. ...
... Appendix A. IPv6 Protocol Operation Description ...
... NBMA model described in this document maintains the
complete semantics of the IPv6 protocols. No changes need to be made
to the IPv6 Network Layer ...
... semantics of the IPv6 protocols. No changes need to be made
to the IPv6 Network Layer. Since the concept of the security
association is not being changed for NBMA ...
... NBMA, this framework maintains
complete IPv6 security semantics and features. This allows IPv6 nodes ...
... IPv6 security semantics and features. This allows IPv6 nodes
to choose their responses to solicitations based on security
...
...
The remainder of this Appendix describes how the core IPv6 protocols
will operate within the model described here.
...
...
An IPv6 host performs address resolution by sending a Neighbor
Solicitation to the solicited-node ...
...
When the local node's IPv6/NBMA driver is passed the Neighbor
Solicitation message from the IPv6 network ...
... IPv6/NBMA driver is passed the Neighbor
Solicitation message from the IPv6 network layer, it follows the
steps described in section 4.4.2 Sending Multicast ...
... nodes will process the data as described in section 4.5 and pass
the de-encapsulated packets to the IPv6 network layer.
...
...
The solicited IPv6 host will respond to the Neighbor Solicitation
with a Neighbor Advertisement ...
... Neighbor Solicitation
with a Neighbor Advertisement message sent to the IPv6 unicast
address of the soliciting node. The Neighbor Advertisement ...
...
The solicited node's IPv6/NBMA driver will be passed the Neighbor
Advertisement and the soliciting node ...
... node's link-layer address from the
IPv6 network layer. It will then follow the steps described in
section section 4.4.1 to send the NA message ...
... VC, de-encapsulate the message, and pass it
to the IPv6 Network layer for processing as described in section 4.5.
The soliciting node ...
... nodes multicast address. When the local node IPv6/NBMA driver
is passed the Neighbor Advertisement ...
... NBMA driver
is passed the Neighbor Advertisement from the IPv6 network layer, it
follows the steps described in section 4.4.2 to send the NA message ...
... incoming packet as described in section 4.5 and then pass the packet
to the IPv6 network layer where it will be processed as described in
[7 ...
... all-routers multicast group address.
When the IPv6/NBMA driver gets the JoinLocalGroup request from the
IPv6 Network ...
... IPv6/NBMA driver gets the JoinLocalGroup request from the
IPv6 Network Layer, it follows the process described in section 4.2.
...
...
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 sends
an unsolicited Router Advertisement ...
... Router Advertisement, it sends a data packet addressed
to the IPv6 all-nodes multicast address. When the local node ...
... multicast address. When the local node
IPv6/NBMA driver gets the Router Advertisement message from the IPv6
network ...
... IPv6/NBMA driver gets the Router Advertisement message from the IPv6
network layer, it transmits the message by following steps described
in section 4.4.2. The MARS ...
... node on the LL will then process the incoming packet as
described in section 4.5 and pass the received packet to the IPv6
Network layer for processing as appropriate.
...
...
To perform Router Discovery, an IPv6 host sends a Router Solicitation
message to the all-routers ...
... multicast address. When the local node
IPv6/NBMA driver gets the request from the IPv6 Network Layer ...
... IPv6/NBMA driver gets the request from the IPv6 Network Layer to send
the packet, it follows the steps described in section 4.4.2. The RS ...
... RA message will process the message as described in section 4.5
and pass the RA message up to the IPv6 layer for processing. Only
those nodes ...
... router responds to a Router Solicitation by sending a Router
Advertisement addressed to the IPv6 all-nodes multicast address if
...
... Router Advertisement
as described in section 4.5 and will pass the RA message to the IPv6
network layer. The IPv6 network layer ...
... If a pt-pt VC is set up during Router Discovery, subsequent IPv6 best
effort unicast data between the soliciting node ...
... Neighbor Unreachability Detection (NUD) is the process by which an
IPv6 host determines that a neighbor is no longer reachable, as
described in [7 ...
... VC to a
neighbor (see section 4.4.1), are detected and handled at the IPv6
network layer, through Neighbor Unreachability Detection. The node ...
... Neighbor Unreachability Detection. The node's
IPv6/NBMA driver does not attempt to detect or recover from these
conditions.
...
... VC from the IPv6 host to one of its
IPv6 neighbors will be detected and handled through NUD. On each
...
... neighbors will be detected and handled through NUD. On each
attempt to send data from the IPv6 host to its neighbor, the node's
...
... VC to the neighbor, and
failing to do so, will drop the packet. IPv6 reachability
confirmation timers ...
... neighbor, which will be dropped by the local node's IPv6/NBMA driver
after again failing to setup the VC ...
... NBMA driver
after again failing to setup the VC. The IPv6 host will therefore
never receive the solicited Neighbor Advertisements needed for
...
... deleted
from the Neighbor cache. The next time the IPv6 host tries to send
data to that neighbor, address resolution ...
...
In the event that a VC from an IPv6 neighbor is released, the next
time a packet is sent from the IPv6 host ...
... IPv6 neighbor is released, the next
time a packet is sent from the IPv6 host to the neighbor, the node's
...
... VC
from the IPv6 host to one of its IPv6 neighbors). Depending on the
reason for the previous failure, connectivity to the neighbor ...
... tentative address (see 4.2. Joining a
Multicast Group). The IPv6 host initiates Duplicate Address Detection
by sending a Neighbor Solicitation ...
... tentative address as the target. When the local node's IPv6/NBMA
driver gets the Neighbor Solicitation ...
... NBMA
driver gets the Neighbor Solicitation message from the IPv6 network
layer, it follows the steps outlined in section 4.4.2. The NS ...
... filter out the message so that the sending node's
IPv6 network layer will not see the message. The IPv6 network layer ...
... Neighbor Solicitation. The processing will depend on whether or
not receiving IPv6 host considers the target address to be tentative.
...
... IPv6 router uses a Redirect Message to inform an IPv6 host of a
better first-hop for reaching a particular destination, as described
...
... host on the same LL, or to a transient neighbor on
another LL. The IPv6 router will unicast the Redirect to the IPv6 ...
... IPv6 router will unicast the Redirect to the IPv6
source address that triggered the Redirect. The router ...
... source address that triggered the Redirect. The router's IPv6/NBMA
driver will transmit the Redirect message ...
... The IPv6/NBMA driver of the IPv6 host that triggered the Redirect
will receive the encapsulated Redirect over one of it's pt-pt VCs ...
... encapsulate the packet, and pass the Redirect message
to the IPv6 Network Layer, as described section 4.5.
...
... NBMA hosts to be redirected off their LL to achieve
shortcut by using standard IPv6 protocols.
...
... 9] and [18].
The IPv6 auto-configuration process involves creating and verifying
the uniqueness of a link-local address on an LL, determining whether
...
... addresses, and determining if other (non- address) information is to
be autoconfigured. IPv6 addresses can also be manually configured, if
for example, auto-configuration fails because the autoconfigured
link-local address ...
... The following sections describe how stateless, stateful and manual
address configuration will work in an IPv6/NBMA environment.
...
... IPv6 stateless address configuration is the process by which an IPv6
host autoconfigures its interfaces, as described in [IPV6-ADDRCONF].
...
... address configuration is the process by which an IPv6
host autoconfigures its interfaces, as described in [IPV6-ADDRCONF].
...
... link-local address using Duplicate Address
Detection (DAD). If the IPv6 host detects that the link-local
address is not unique, the autoconfiguration process terminates. The
...
... link-local
address is not unique, the autoconfiguration process terminates. The
IPv6 host must then be manually configured.
...
...
After the IPv6 host determines that the link-local address is unique
and has assigned it to the interface ...
... and has assigned it to the interface on the Logical Link, the IPv6
host will perform Router Discovery to obtain auto-configuration
information. The IPv6 host ...
... IPv6
host will perform Router Discovery to obtain auto-configuration
information. The IPv6 host will send out a Router Solicitation and
will receive a Router Advertisement ...
... Router Advertisement, or it will wait for an
unsolicited Router Advertisement. The IPv6 host will process the M
and O bits of the Router Advertisement ...
... If there are no routers on the Logical Link, the IPv6 host will be
able to communicate with other IPv6 hosts on the Logical Link ...
... Link, the IPv6 host will be
able to communicate with other IPv6 hosts on the Logical Link using
link-local addresses ...
... layer address using Address Resolution. The IPv6 host will also
attempt to invoke stateful auto-configuration, unless it has been
explicitly configured not to do so.
...
... multicast group on the Logical Link. When the node's IPv6/NBMA
driver gets the JoinLocalGroup request from the IPv6 network ...
... IPv6/NBMA
driver gets the JoinLocalGroup request from the IPv6 network layer,
it follows the process described in section 4.2.
...
...
An IPv6 host will invoke stateful auto-configuration if M and O bits
of Router Advertisements ...
... routers are present
on the Logical Link. An IPv6 host that is obtaining configuration
information through the stateful mechanism will hereafter be referred
to as a DHCPv6 client ...
... Agent. When
the soliciting node's IPv6/NBMA driver gets the request from the IPv6
Network Layer ...
... node's IPv6/NBMA driver gets the request from the IPv6
Network Layer to send the packet, it follows the steps described in
section 4.4.2. This will result in one or more nodes ...
... node that receives the solicitation
packet will process it as described in section section 4.5. Only the
IPv6 network layer of the DHCPv6 server/relay-agent ...
... layer
will give the node's IPv6/NBMA driver the packet and link-layer
address of the DHCPv6 client ...
... Neighbor Discovery if
necessary). The node IPv6/NBMA driver will then transmit the packet
as described in section 4.4.1. This will result in a new pt-pt VC ...
...
The DHCP client's IPv6/NBMA driver will receive the encapsulated
packet from the DHCP Server ...
... encapsulate the multicast packet and then pass
it up to the IPv6 Network Layer for processing. The IPv6 network
...
... it up to the IPv6 Network Layer for processing. The IPv6 network
layer will deliver the DHCPv6 ...
... Agent. Prior to sending
the DHCPv6 message, the IPv6 network layer will perform Neighbor
Discovery (if necessary) to obtain the link-layer address ...
...
An IPv6 host will be manually configured if it discovers through DAD
that its link-local address ...
... DAD
that its link-local address is not unique. Once the IPv6 host is
configured with a unique interface token ...
... NBMA. While these protocols might not be the most
efficient in this environment, they will still work as described
below. However, IPv6 multicast routers connected to an NBMA LL could
...
... multicast group membership is an optional
enchancement and is not required for routers to determine IPv6
multicast group membership on a LL.
...
... Report and Group Membership Reduction messages. IGMPv6 will continue
to work unmodified over the IPv6/NBMA architecture described in this
...
... An IPv6 multicast router receives all IPv6 multicast packets on the
LL by joining all multicast groups in promiscuous mode [5 ...
... existing and future multicast VCs. The IPv6 multicast router will
thereafter be the recipient of all IPv6 multicast ...
... IPv6 multicast router will
thereafter be the recipient of all IPv6 multicast packets sent within
the Logical Link.
...
... multicast address. When the
local node's IPv6/NBMA driver gets the request from the IPv6 network
...
... NBMA drivers will receive the
packet, de-encapsulate it, and passed it up to the IPv6 Network
layer. If the originating node ...
... group
joined by the host. IPv6 hosts can also transmit a Group Membership
Report when the host ...
... address is
being reported. When the local node IPv6/NBMA driver gets the request
from the IPv6 network ...
... IPv6/NBMA driver gets the request
from the IPv6 network layer to send the packet, it follows the steps
described in 4.4.2. The node ...
... encapsulate the incoming packet and the packet will be passed to the
IPv6 network layer for processing. The MARS client ...
... Group Membership Reduction message when the host
leaves an IPv6 multicast group. The Group Membership Reduction is
...
... Group Membership Reduction is
sent to the multicast group the IPv6 host is leaving. The
transmission and receipt of Group Membership Reduction messages are
...
... interface on which it can transmit
all multicast IPv6 packets, including ICMPv6 packets. The IPv6
packets are then transmitted, and received by the intended
...
... multicast IPv6 packets, including ICMPv6 packets. The IPv6
packets are then transmitted, and received by the intended
destination set, using separate pt-mpt VCs ...
... VC is required to
actually carry the unicast IPv6 traffic that prompted the Neighbor
Solicitation.
...
... - performing aggregation on the basis of a packet's function rather
than its explicit IPv6 destination. The trade-off here is that the
aggregation ...
... (involving a trivial extension to the MARS itself.) This approach
recognizes that in any LL where IPv6 multicasting is supported:
...
... How these packets are considered to be related to each other (e.g.
through common header fields such as IPv6 destination addresses) is a
local configuration issue.
...
... NBMA shortcuts are for the benefit of 'the network' optimizing its
forwarding of IPv6 packets in the absence of any other guidance
from the host.
...
...
A non-zero FlowID has IPv6 semantics of "the source has previously
established some preferred, end to end hop by hop forwarding
...
... host,
and the network will provide default best effort forwarding (an IPv6
router defaults to providing best-effort forwarding for packets whose
...
... Neighbor
Discovery process than is currently available in Neighbor Discovery
packets. In these cases, the IPv6 Neighbor Discover protocols can be
extended to include new TLV ...
... MARS protocol. However, future support for
QoS on IPv6 multicast flows may require extensions. MARS control
messages ...