NBMA
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...
Non Broadcast Multiple Access (NBMA) networks may be utilized in a
variety of ways. At one extreme, they can be used to simply provide
...
... IPv6 routers (and even IPv6 hosts, in certain
situations). At the other extreme, NBMA networks that support dynamic
establishment and teardown of Virtual Circuits ...
... This document describes a general architecture for IPv6 over NBMA
networks. It forms the basis for companion documents that provide
...
... networks. It forms the basis for companion documents that provide
details specific to various NBMA technologies (for example, ATM [17]
...
... host-side operation of the IPv6 Neighbor Discovery protocol, while
also supporting the establishment of 'shortcut' NBMA forwarding paths
(when dynamically signaled NBMA links ...
... also supporting the establishment of 'shortcut' NBMA forwarding paths
(when dynamically signaled NBMA links are available).
...
... point to point and point to multipoint calls between
interfaces on an NBMA network. These will be generically referred to
as "SVCs" in the rest of the document. The use of administratively
...
... VC" shall be considered to
implicitly exist if the sender has an NBMA destination address to
which it can transmit packets whenever it desires.
...
... A key difference between this architecture and previous IP over NBMA
protocols is its mechanism for supporting IPv6 Neighbor Discovery.
...
... IP interface is capable of native multicasting. This is not
particularly true of most NBMA network services, and usually requires
convergence ...
... NBMA Shortcuts. ...
... VC's endpoints.
NBMA shortcuts are a mechanism for minimizing the consumption of
resources within an IP over NBMA ...
... NBMA shortcuts are a mechanism for minimizing the consumption of
resources within an IP over NBMA cloud (e.g. router hops and NBMA ...
... NBMA shortcuts are supported whenever IP is
deployed across NBMA networks capable of supporting dynamic
establishment of calls (SVCs or functional equivalent). For IPv6 ...
... establishment of calls (SVCs or functional equivalent). For IPv6
over NBMA, shortcut discovery and management is achieved through a
mixture of Neighbor Discovery ...
... NHRP protocols are NOT necessary, since
multicast and broadcast operations collapse down to an NBMA level
unicast operation. Dynamically discovered shortcuts are not
...
... link token generation SHALL
be covered by companion documents covering specific NBMA technology.
They SHALL conform to the following guidelines:
...
... MARS model, allowing emulation of general multicast using
multipoint calls provided by the underlying NBMA network. ...
... The NHRP service for seeking out the NBMA identities of IP
interfaces who are logically distant in an IP topological sense. ...
... IPv6 "Link" is generalized to "Logical Link" (LL) in NBMA
environments (analogous to the generalization of IPv4 IP Subnet ...
... flow is solicited as a transient
neighbor, the returned NBMA address will be the one chosen by the
destination ...
... interface at the NBMA level will be referred to as an "NBMA address".
(An example would be an ATM ...
... The call that, once established, is used to transfer IP packets from
one NBMA interface to another will be referred to as an SVC or PVC ...
... signaling mechanisms used to establish or tear down an SVC will be
defined in the NBMA-specific companion specifications. Certain NBMA
networks ...
... SVC will be
defined in the NBMA-specific companion specifications. Certain NBMA
networks may provide a form of connectionless service ...
... SVC" shall be considered to implicitly
exist if the sender has an NBMA destination address to which it can
transmit packets whenever it desires.
...
... Link to "Logical Link" when used
over NBMA networks, and introduces the notion of the Transient
Neighbor ...
...
The NBMA environment complicates the sense of the word 'link' in much
the same way as it complicated the sense of 'subnet ...
... Neighbors represent the 'shortcut' connections, where it has
been ascertained that direct connectivity at the NBMA level is
possible to a target that is not a member of the source's LL.
...
...
Note that section 1.3.1 applies when the NBMA network is being used
to provide only configured point to point ...
... multicast ICMPv6 packets down to the IPv6/NBMA driver
without any special, NBMA specific processing. The underlying
...
... IPv6/NBMA driver
without any special, NBMA specific processing. The underlying
mechanism for distributing Neighbor Discovery and Router Discovery ...
... destination, and supplies a link layer
(NBMA) address to use as the better first hop, the associated
Neighbor Cache ...
... context
involves building a new VC to the new NBMA address. If this is
successful, the old VC ...
... Redirect message containing the IPv6
address of the transient neighbor, and the NBMA link layer address
returned by the NHRP ...
...
IPv6/NBMA routers supporting shortcut discovery will need to perform
some or all of the following functions:
...
... router constructing the NHRP Reply does so using the
NBMA address returned by the target host when the target host ...
... NHRP messages are constructed and sent according to the rules in [8].
The value of the NBMA technology specific fields such as ar$afn,
ar$pro.type, ar$pro.snap and link layer address format are defined in
...
... ar$pro.type, ar$pro.snap and link layer address format are defined in
NBMA-specific companion documents. Source, destination or client
...
...
The majority of this section applies only to NBMA networks when used
to provide point to point ...
... to provide point to point and point to multipoint SVCs. Section 7
discusses the case where the NBMA network is being used to supply
only point to point ...
... control messages SHALL be defined in companion documents specific to
particular NBMA network technologies.
...
... local address is received, the
IPv6/NBMA driver SHALL return success indication to the caller and
take no additional action. (Packets sent to node ...
... local address is received, the
IPv6/NBMA driver SHALL return success indication to the caller and
take no additional action. (Packets sent to node ...
... LLC/SNAP encapsulation, an
alternative rule SHALL be specified in the NBMA-specific companion
document.
...
... destination.
Any time the IPv6/NBMA driver receives a unicast packet for
transmission the IPv6 ...
... address of the next hop. Thus, the information needed
to place the NBMA call to the next hop will be available.
...
... LLC/SNAP encapsulation, an
alternative rule SHALL be specified in the NBMA-specific companion
document. Some mechanism for carrying the IPv6/NBMA ...
... NBMA-specific companion
document. Some mechanism for carrying the IPv6/NBMA driver's
Cluster Member ID SHALL be provided.
...
... destination is one of the following multicast
addresses, it SHALL be sent over the IPv6/NBMA driver's direct pt-pt
VC to the MARS ...
... client mechanisms are used by the IPv6/NBMA driver to select and/or
establish a pt-mpt VC on which the packet is to be sent.
...
... encapsulation specified in section 4.4.2
SHALL have their pkt$cmi field compared to the local IPv6/NBMA
driver's own CMI. If the pkt$cmi in the header matches the local CMI
...
... LLC/SNAP encapsulation, alternative
rules SHALL be specified in the NBMA-specific companion document.
...
... concern itself where the new receiving node is located on the NBMA
network. The redirected node ...
...
This time limit MAY be reduced through configuration or as specified
in companion documents for specific NBMA networks.
...
... Mechanisms for signaling the establishment and teardown of pt-pt and
pt-mpt SVCs for different NBMA networks SHALL be specified in
companion documents.
...
...
Since any given IPv6/NBMA driver will not know if the remote end of a
VC is in the same LL, drivers SHALL implement NBMA ...
... NBMA driver will not know if the remote end of a
VC is in the same LL, drivers SHALL implement NBMA-specific
mechanisms to negotiate acceptable MTUs at the VC ...
...
However, IPv6/NBMA drivers can assume that they will always be
talking to another driver attached to the same type of NBMA network ...
... IPv6/NBMA drivers can assume that they will always be
talking to another driver attached to the same type of NBMA network.
(For example, an IPv6 ...
... network.
(For example, an IPv6/NBMA driver does not need to consider the
possibility of establishing a shortcut VC directly to an IPv6 ...
... Physical NBMA interfaces MAY be used to provide multiple logical NBMA
interfaces. Since each logical NBMA ...
... A set of 2 or more 'virtual hosts' (vhosts) sharing a common
NBMA driver. Each vhost is free to establish IPv6/NBMA
...
... NBMA driver. Each vhost is free to establish IPv6/NBMA
interfaces associated with different or common LLs. However,
...
...
In the first scenario, since each IPv6/NBMA interface is associated
with a different LL, each interface ...
... tag received packets in some locally
specific manner to identify what IPv6/NBMA interface they arrived on.
However, this is an issue generic to IPv6 ...
... interfaces over a single
physical NBMA interface, independent and unique identifiers SHALL be
...
... interface, independent and unique identifiers SHALL be
generated for each virtual NBMA interface to enable the construction
of unique IPv6 ...
... interface to enable the construction
of unique IPv6/NBMA interface tokens. The exact mechanism for
...
... [Type][Length][NTL][STL][..NBMA Number..][..NBMA
Subaddress..]
| Fixed || Link layer address ...
... STL] is a one octet 'SubAddress Type & Length' field.
[NBMA Number] is a variable length field. It is always present. This
contains the primary NBMA address ...
... [NBMA Number] is a variable length field. It is always present. This
contains the primary NBMA address.
...
... address.
[NBMA Subaddress] is a variable length field. It may or may not be
present. This contains any NBMA subaddress that may be required.
...
... [NBMA Subaddress] is a variable length field. It may or may not be
present. This contains any NBMA subaddress that may be required.
If the [NBMA ...
... NBMA subaddress that may be required.
If the [NBMA Subaddress] is not present, the option ends after the
[NBMA Number] ( and any additional padding for 8 byte ...
... If the [NBMA Subaddress] is not present, the option ends after the
[NBMA Number] ( and any additional padding for 8 byte alignment).
...
...
The contents and interpretation of the [NTL], [STL], [NBMA Number],
and [NBMA Subaddress] fields are specific to each NBMA ...
... NBMA Number],
and [NBMA Subaddress] fields are specific to each NBMA network, and
SHALL be specified in companion documents.
...
... This document describes a general architecture for IPv6 over NBMA
networks. It forms the basis for subsidiary companion documents that
...
... networks. It forms the basis for subsidiary companion documents that
provide details for various specific NBMA technologies (such as ATM
or Frame Relay ...
... host-side operation of the IPv6 Neighbor Discovery protocol, while
also supporting the establishment of 'shortcut' NBMA forwarding paths
(when dynamically signaled NBMA links ...
... also supporting the establishment of 'shortcut' NBMA forwarding paths
(when dynamically signaled NBMA links are available).
...
... multicasting of IPv6 packets, and distribution of Discovery messages.
Shortcut NBMA level paths are supported either through router based
flow ...
... host originated explicit requests. Neighbor
Discovery is used without modification for all intra-LL control
(including the initiation of NBMA shortcut discovery). Router to
router ...
... IPv6 security mechanisms will work without modification
for NBMA. This includes both authentication and encryption for both
...
... architecture described here. Grenville Armitage's
original work on IPv6/NBMA occurred while employed at Bellcore.
Elements of section 5 were borrowed from Matt Crawford's memo on IPv6 ...
... Luciani, J., Katz, D., Piscitello, D. Cole B and N. Doraswamy, "NBMA Next Hop Resolution Protocol (NHRP)", RFC 2332prop ...
...
The IPv6 over NBMA model described in this document maintains the
complete semantics of the IPv6 protocols ...
... IPv6 Network Layer. Since the concept of the security
association is not being changed for NBMA, this framework maintains
complete IPv6 ...
... node
that chooses what (and even if) to reply to the solicitation. Thus,
NBMA will be transparent to the network layer except in cases where
...
... When the local node's IPv6/NBMA driver is passed the Neighbor
Solicitation message from the IPv6 network layer ...
... update its Neighbor cache with the soliciting node's NBMA
address, contained in the Neighbor Solicitation ...
... The solicited node's IPv6/NBMA driver will be passed the Neighbor
Advertisement and the soliciting node's link-layer address ...
... node will then make the appropriate entries in it's
Neighbor cache, including caching the NBMA link-layer address of the
solicited node ...
... multicast address. When the local node IPv6/NBMA driver
is passed the Neighbor Advertisement from the IPv6 network ...
... multicast group address.
When the IPv6/NBMA driver gets the JoinLocalGroup request from the
IPv6 Network Layer ...
... Neighbor cache with the router's
NBMA address, contained in the Router Advertisement message's Source
Link-Layer Address Option ...
... Connectivity failures at the node's IPv6/NBMA driver, such as
released VCs (see section 4.6) and the inability to create ...
... neighbor, which will be dropped by the local node's IPv6/NBMA driver
after again failing to setup the VC. The IPv6 host ...
... target. When the local node's IPv6/NBMA
driver gets the Neighbor Solicitation message from the IPv6 network ...
... host will determine that the tentative address is not unique and
cannot be assigned to its NBMA interface.
...
... source address that triggered the Redirect. The router's IPv6/NBMA
driver will transmit the Redirect message using the procedure
...
...
The IPv6/NBMA driver of the IPv6 host that triggered the Redirect
will receive the encapsulated ...
... address specified in the Redirect Message. For
NBMA networks, the Redirect Message should contain the link-layer
address ...
... node to which it has been
redirected. Thus, the redirect can be to any node on the NBMA
network, regardless of the LL membership of the new target ...
... target node.
This allows NBMA hosts to be redirected off their LL to achieve
shortcut by using standard IPv6 protocols ...
... destination exists. If a pt-pt VC does not exist, then the IPv6/NBMA
driver will queue the data packet ...
... Link. When the node's IPv6/NBMA
driver gets the JoinLocalGroup request from the IPv6 network layer ...
... the soliciting node's IPv6/NBMA driver gets the request from the IPv6
Network Layer to send the packet, it follows the steps described in
...
... will give the node's IPv6/NBMA driver the packet and link-layer
address of the DHCPv6 client (obtained through Neighbor Discovery ...
... 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 or Relay Agent ...
... framework
described here, the IGMPv6 protocols can be used without any special
modifications for NBMA. While these protocols might not be the most
efficient in this environment, they will still work as described
below. However, IPv6 multicast ...
... below. However, IPv6 multicast routers connected to an NBMA LL could
optionally optimize the IGMP functions by sending
...
... Group Membership Reduction messages. IGMPv6 will continue
to work unmodified over the IPv6/NBMA architecture described in this
document.
...
... nodes in the LL. Each node's IPv6/NBMA drivers will receive the
packet, de-encapsulate it, and passed it up to the IPv6 Network ...
... being reported. When the local node IPv6/NBMA driver gets the request
from the IPv6 network layer ...
...
However, in connection oriented NBMA environments it becomes equally
(or more) important to minimize the number of independent VCs that a
...
... (or more) important to minimize the number of independent VCs that a
given NBMA interface is required to originate or terminate. If we
treat the MARS ...
... Quality of Service
guarantees, and optimal use of underlying IP and NBMA network
resources are still subjects ...
... document currently only describes the use of flow detection as a
means to optimize the use of NBMA network resources through the
establishment of inter-LL shortcuts.
...
...
NBMA shortcuts are for the benefit of 'the network' optimizing its
forwarding of IPv6 packets ...
...
It is desirable for an IPv6/NBMA host to have some mechanism for
overriding attempts by 'the network ...
... In the future, accurate mapping of IPv6 flows onto NBMA VCs may
require more information to be exchanged during the Neighbor
Discovery ...