Internet Engineering Task Force P. Thubert
Internet-Draft Cisco
Intended status: Standards Track C. Bernardos, Ed.
Expires: March 16, 2009 UC3M
September 12, 2008
Network In Node Advertisement
draft-thubert-nina-03.txt
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Abstract
The Internet is evolving to become a more ubiquitous network, driven
by the low prices of wireless routers and access points and by the
users' requirements of connectivity anytime and anywhere. For that
reason, a cloud of nodes connected by wireless technology is being
created at the edge of the Internet. We refer to this cloud as a
Fringe Stub (FS). It is expected that networking in the FS will be
highly unmanaged and ad-hoc, but at the same time will need to offer
excellent service availability. The NEMO Basic Support protocol
could be used to provide global reachability for a mobile access
network within the FS and the Tree-Discovery mechanism could be used
to avoid the formation of loops in this highly unmanaged structure.
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Since Internet connectivity in mobile scenarios can be costly,
limited or unavailable, there is a need to enable local routing
between the Mobile Routers within a portion of the FS. This form of
local routing is useful for Route Optimization (RO) between Mobile
Routers that are communicating directly in a portion of the FS.
Network In Node Advertisement (NINA) is the second of a 2-passes
routing protocol; a first pass, Tree Discovery, builds a loop-less
structure -- a tree --, and the second pass, NINA, exposes the Mobile
Network Prefixes (MNPs) up the tree. The protocol operates as a
multi-hop extension of Neighbor Discovery (ND), to populate TD-based
trees with prefixes, and establish routes towards the MNPs down the
tree, from the root-MR towards the MR that owns the prefix, whereas
the default route is oriented towards the root-MR.
The NINA protocol introduces a new option in the ND Neighbor
Advertisement (NA), the Network In Node Option (NINO). An NA with
NINO(s) is called a NINA (Network In Node Advertisement). NINA is
designed for a hierarchical model, and by using this NA based
approach it abstracts the embedded network of a Mobile Router as a
host to the upper level of network abstraction. With NINA, a Mobile
Router presents its sub-tree to its parent as an embedded network and
hides the inner topology and movements.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Motivations . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Rationale for the proposed solution . . . . . . . . . . . . . 5
4.1. Why ND based . . . . . . . . . . . . . . . . . . . . . . . 5
4.2. Why NA based . . . . . . . . . . . . . . . . . . . . . . . 6
4.3. Relationship with TD . . . . . . . . . . . . . . . . . . . 6
4.4. Relationship with RRH . . . . . . . . . . . . . . . . . . 7
5. NINA Overview . . . . . . . . . . . . . . . . . . . . . . . . 8
6. Message Formats . . . . . . . . . . . . . . . . . . . . . . . 9
6.1. NINA message . . . . . . . . . . . . . . . . . . . . . . . 9
6.2. NINO IPv4 option . . . . . . . . . . . . . . . . . . . . . 12
7. Mobile Router Operation . . . . . . . . . . . . . . . . . . . 13
7.1. Multicast TD RA messages from parent . . . . . . . . . . . 15
7.2. Unicast NINA messages from child to parent . . . . . . . . 15
7.3. Other events . . . . . . . . . . . . . . . . . . . . . . . 16
7.4. Aggregation of prefixes on a same MR . . . . . . . . . . . 17
7.5. Aggregation of prefixes by a parent acting as mobile
Home . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
7.6. Default value . . . . . . . . . . . . . . . . . . . . . . 18
8. Privacy Considerations . . . . . . . . . . . . . . . . . . . . 18
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
10. Security Considerations . . . . . . . . . . . . . . . . . . . 19
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 19
12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19
12.1. Normative References . . . . . . . . . . . . . . . . . . . 19
12.2. Informative References . . . . . . . . . . . . . . . . . . 20
Appendix A. Contributors . . . . . . . . . . . . . . . . . . . . 21
Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 22
Intellectual Property and Copyright Statements . . . . . . . . . . 24
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1. Introduction
Mobile IP [3] allows transparent routing of IPv4 datagrams to mobile
nodes in the Internet. Mobile IPv6 (MIPv6) [4] extends this facility
for IPv6, and NEMO [5] enables it for mobile prefixes. In any case,
a mobile node is always identified by its Home Address (HoA),
regardless of its current point of attachment to the Internet. In
turn, MANET [11], [14] allows a set of unrelated nodes and routers to
discover their peers and establish communication.
Mobile Routers (MRs) may attach to other MRs and form a Care-of
Address (CoA) from a Mobile Network Prefix (MNP). As a result, MRs
are really MARs, Mobile Access Routers, because they can accept
connections from other MRs on their ingress interfaces. When Mobile
Routers attach to other Mobile Routers with a single Care-of Address
in a loop-less manner, they end up building trees. This process is
supported in Tree Discovery (TD) [6].
This draft provides a minimum extension to IPv6 Neighbor Discovery
(ND) Neighbors Advertisements (NA) - called NINA (Network In Node
Advertisement) - extending RFC 4861 [2] and RFC 4191 [7] to add the
capability to include a prefix option - called NINO (Network In Node
Option) - in the NAs of the MR. This enables an MR to learn the
prefixes of all other MRs down its sub-tree. Note that NINO is
pronounced NEE-GNO and NINA is pronounced NEE-GNA.
A NEMO Mobile Router has a double behavior. On its egress
interfaces, which are used to backhaul the traffic to the Home
Network and the rest of the Internet, it is seen as a Mobile Node
(MN), performing the IPv6 and MIPv6 host-required features such as
neighbor and router discovery [2]. On the (ingress) interfaces to
the Mobile Networks, the Mobile Router behaves as an IPv6 router with
support of the MIPv6 requirements on routers. This is why TD [6]
extends ND RA over the ingress interface of a Mobile Router whereas
NINA extends ND NAs to advertise over the egress interface the
prefixes that are reachable via the MR.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [1].
Readers are expected to be familiar with all the terms defined in the
RFC 3753 [10], the NEMO Terminology draft [19] and the MANEMO Problem
Statement draft [18].
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NINO (Network In Node Option): a new Neighbor Discovery (ND)
option that adds the capability to include a prefix option in
Neighbor Advertisements (NAs).
NINA (Network In Node Advertisement): a Neighbor Discovery (ND)
Neighbor Advertisement (NA) carrying a NINO. NINA is also used to
refer to the protocol itself (defined in this document).
3. Motivations
The Internet is evolving to become a more ubiquitous network, driven
by the low prices of wireless routers and access points and by the
users' requirements of connectivity anytime and anywhere. For that
reason, a cloud of nodes connected by wireless technology is being
created at the edge of the Internet. We refer to this cloud as a
Fringe Stub (FS). Examples of wireless technologies used within a FS
are wireless metropolitan and local area network protocols (WiMAX,
WLAN, 802.20, etc), short distance wireless technology (bluetooth,
IrDA, UWB), and radio mesh networks (e.g., 802.11s). It is expected
that networking in the FS will be highly unmanaged and ad-hoc, but at
the same time will need to offer excellent service availability.
The NEMO Basic Support protocol [5] could be used to provide global
reachability for a mobile access network within the FS. Analogously,
the Tree-Discovery mechanism [6] could be used to avoid the formation
of loops in this highly unmanaged structure. However, even with
these two technologies in place, packet delivery within the FS can
still be highly inefficient. Since Internet connectivity in mobile
scenarios can be costly, limited or unavailable, there is a need to
enable local routing between the Mobile Routers within a portion of
the FS. NINA can provide this form of local routing; it is an
example of Route Optimization (RO) between Mobile Routers that are
communicating directly in a portion of the Fringe Stub. This type of
solution can be considered to be a MANET for NEMO (MANEMO) approach
that aims to optimise the local routing in a Nested NEMO topology.
When a Fringe Stub is supported in this manner we refer to it as a
MANEMO Fringe Stub.
4. Rationale for the proposed solution
4.1. Why ND based
NINA extends the Neighbor Discovery protocol to address the MANEMO
requirements listed in [18], although MANET protocols [12], [15],
[16] provides similar features such as local routing and Internet
access over multihop.
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One of the drawbacks of MANET protocols is the question of which
protocol should be used. AODV, DSR, DYMO, OLSR, etc. are
standardized in IETF and each has distinct features, like proactive
and reactive. In MANEMO scenarios, Mobile Routers, mobile hosts, and
fixed access routers are involved, and therefore, it is highly
important to deploy a consistent protocol in the network. On the
other hand, ND is a core component of IPv6 and is supported by all
IPv6 nodes. All IPv6 nodes can process a NINO(s) in ND messages if
desired.
As opposed to most MANET scenarios, MANEMO scenarios do not typically
require to establish direct communication with other nodes in the
MFS. Instead their typical form of communication is with nodes
located in the Internet. Therefore the default route they are
interested in establishing is the one between themselves and their
respective Gateway. It should be noted however that communication
may consequently take place between two nodes in an MFS, in this case
the MANEMO protocol should optimise the delivery of packets to ensure
that they at least are not transmitted beyond the Gateway.
4.2. Why NA based
Since an MR appears as a host on the egress interface side, it is
legitimate to use NA in the visited network. There are two reasons
for that:
o If an MR advertises itself as a router in the visited network
using RA, it might get used as a default router by Local Fixed
Nodes (LFNs) attached to the visited network and cause trouble.
o By using NINA, the whole part of the fringe behind the MR has the
footprint of a single host from the visited network standpoint
(and moves as a single host).
By using NINA on top of a TD established tree, MANEMO can be made to
reproduce the NEMO behavior for a whole subtree by reducing to a
single host footprint, and retain NEMO compatibility by avoiding
spurious RAs. Thus, a whole subtree can move within the fringe as a
single host.
4.3. Relationship with TD
NINA exploits the loop-less cluster established by Tree Discovery, so
it does not need to provide loop avoidance.
With TD, MRs setup a default route up the tree via the parent Access
Router, and all the packets are directed by default towards the
clusterhead (Top Level Mobile Router or root-MR in NEMO terms). To
provide complete reachability, it is enough for NINA to expose the
prefixes down the tree from any given MR, while propagating prefixes
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information up the tree.
This allows an extreme conciseness of the routing information, with
no topological knowledge past the first hop. That conciseness
enables a high degree of movement within the nested structure; in
particular, a movement within a subtree is not seen outside of that
subtree, so most of the connectivity is maintained at all times while
there might never be such a thing as a convergence.
4.4. Relationship with RRH
The Reverse Routing Header (RRH) described in [17] operates in the
nested NEMO as a layer 3 Source Route Bridging (SRB) technique for
nested NEMO Route Optimization. It allows a quick reaction to inner
movements with the resolution of the packet; but the cost, an IPv6
address per packet per hop, might be deemed excessive.
Also, the Home Agent needs to cache the RRH in its binding cache, and
again, the overhead might be significant for a large deployment.
On the other hand, NINA establishes states in the intermediate nodes,
in a fashion similar to Transparent Bridging (TB), but at layer 3.
The integration of these 2 approaches allows switching between SRB to
TB models dynamically as the NINA states are populated or become
obsolete. To obtain this capability, the operation of an
intermediate MR described in [17] is altered in the following manner:
o If the MR has a (NINA) route to the upper entry in the RRH via the
source of the packet, it still updates the source of the packet
with its own Care-of Address, but does not save the previous
source as a new entry in the RRH.
o At best, if NINA has established states all along in a given
branch of the tree, the RRH for that branch has always 2 entries,
the first MR's Home Address, and its Care-of Address, regardless
of the depth of the first MR in the nested NEMO.
o When some MRs in the tree support NINA and some do not, the
resulting RRH will be only partly compressed. Also, if the NINA
route does not match the RRH, then the route is obsolete and the
source address is added to the RRH as described in [17], in order
to ensure a correct routing on the way back. When NINA catches
up, the entry will be saved again.
The integration of NINA and RRH can offer the best of 2 worlds: a
quick (per packet) resolution to the network changes, and the
transparent (stateful) operation when the NINA routing protocol
establishes the states in the nested NEMO.
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5. NINA Overview
This section provides an overview of the operation of NINA to set-up
MNP route state in a nested-NEMO scenario.
NINA requires the Tree Discovery protocol to build and maintain a
tree topology. It relies on TD to discover that a change occurs in a
sub-tree of the topology, and that change triggers a flow of route
updates for that sub-tree in the topology.
+---------------------+
| Internet |---CN
+---------------|-----+
/ Access Router
MR3_HA |
======?======
MR1
|
====?=============?==============?===
MR5 MR2 MR6
| | |
=========== ===?========= =============
MR3
|
==|=========?==
LFN1 MR4
|
=========
Figure 1: Nested NEMO scenario
Each tree that TD self-forms is considered a separate routing
topology. If a Mobile Router belongs to multiple of such topologies,
then it is expected that both the NINA signaling and the data packets
are flagged to follow the topology for which the packet was
introduced in the network.
NINA expects a Mobile Router to own one or more Mobile Network
Prefix(es) that move with the MR. With that model, it is assumed
that there is a single source for the advertisement of a given prefix
within a topology. If multiple MRs share a given MNP, some protocol
must take place between those MRs to make sure that one and only one
MR advertises a given prefix in a given tree.
Tree Discovery formats the nested NEMO into a loop-less logical
graph, thus providing loop avoidance for the NINA protocol. Each
time a movement occurs, TD restores the loop-less structure before
NINA can operate again and repaint the graph with prefixes.
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The root-MR of a nested NEMO is selected for a number of properties,
the primary one being an access to the wired infrastructure. It is
the default sink for every node in the tree.
More generally, the default gateway for a Mobile Router is its parent
up in the tree; the more specific routes, towards the Mobile Network
Prefixes, are always oriented down the tree, and NINA advertisements
flow up the tree towards the root-MR.
Each NINO contains a prefix and a sequence counter. The Mobile
Router that owns the prefix generates the NINO for that prefix,
including the sequence counter associated to that prefix and that is
incremented each time it generates a new NINO.
Due to a movement, a sub-tree can be temporarily out of sequence and
a NINO can be received from a sub-tree where the MR was but is no
more, until the parents realize it is gone. But by construction of
the tree, there can be a single route to a given prefix, so older
information is always invalid.
A parent-MR maintains a state for each prefix it learns from NINA.
In particular, the last sequence number is kept. An out-of-sequence
NINO must be disregarded. If the NINO appears valid, it is forwarded
to the parent's parent in the next burst, carried by a NINA, together
with the parent's own prefixes.
6. Message Formats
6.1. NINA message
NINA extends Neighbor Discovery [2] and RFC 4191 [7] to allow an MR
include a prefix option in the Neighbor Advertisements (NAs). The NA
is a necessary exchange that allows the AR to map the IPv6 address of
a node with its L2 address. The prefix option is normally present in
Router Advertisements (RAs) only. The meaning of such an option in a
NA is the concept of 'network in node', so we refer to this new ND
option as NINO (Network In Node Option) and we name the resulting
message NINA (Network In Node Advertisement).
When Tree Discovery is used to build a tree, there can be a single
route to a given prefix along that tree, so the freshest information
is always the best for unicast routes. In order to track that, the
NINO includes a sequence counter to the prefix advertisement.
The sequence counter is incremented by the source of the NINO, that
is the Mobile Router that owns the MNP, each time it issues a NINA,
and then forwarded as is up the tree. A depth is also added for
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tracking purposes; the depth is incremented at each hop as the NINO
is propagated up the tree.
On an egress interface, if NINA is configured, the MR:
o selects an Access Router (AR) as its point of attachment to the
network
o auto-configures a Care-of Address (CoA)
o acts as a host as opposed to a router. In particular, it refrains
from sending RAs
o sends NINAs, as unicast, to its AR only
o accepts unicast NINAs from any node BUT its AR
On an ingress interface, if NINA is configured, the MR:
o acts as a router, may accept visitors
o sends RAs with the Tree Information Option (RA-TIO)
o accepts NINAs from any node
Every NA to the AR contains a NINO. In particular, receiving a Tree
Discovery RA-TIO from the AR stimulates the sending of a delayed NINA
back, with the collection of all known prefixes (that is the prefixes
learned from NINO and the connected prefixes). A NINA is also sent
to the AR once it has been selected as new AR after a movement, or
when the list of advertised prefixes has changed.
NINA may advertise positive (prefix is present) or negative (removed)
NINOs. A no-NINO is stimulated by the disappearance of a prefix
below. This is discovered by timing out after a request (a RA-TIO)
or by receiving a no-NINO. A no-NINO is a NINO with a NINO Lifetime
of 0.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Prefix Length |L| Reserved1 |4|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NINO Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NINO Depth | Reserved3 | NINO Sequence |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Prefix (Variable Length) +
| |
+ +
| |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type:
NINO (number to be assigned by IANA).
Length:
8-bit unsigned integer. The length of the option (including the
Type and Length fields) in units of 8 octets.
Prefix Length:
Number of valid leading bits in the IPv6 Prefix.
Reserved1:
6-bit unused field. It MUST be initialized to zero by the sender
and MUST be ignored by the receiver.
'L' bit:
Indicates that the prefix or address is on-link as opposed to
another interface of the MR. This is useful for a child MR to
expose its IPv4 address on its egress interface. In that case,
the parent can set up forwarding to all the IPv4 prefixes in the
NINA via that address on this link.
'4' bit:
Indicates that the Prefix field carries an IPv4 mapped address.
NINO Lifetime:
32-bit unsigned integer. The length of time in seconds (relative
to the time the packet is sent) that the prefix is valid for route
determination. A value of all one bits (0xFFFFFFFF) represents
infinity. A value of all zero bits (0x00000000) indicates a loss
of reachability.
Reserved2:
32-bit unused field. It MUST be initialized to zero by the sender
and MUST be ignored by the receiver.
NINO Depth:
Set to 0 by the MR that owns the MNP and issues the NINO.
Incremented by all MRs that propagate the NINO.
Reserved3:
8-bit unused field. It MUST be initialized to zero by the sender
and MUST be ignored by the receiver.
NINO Sequence:
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Incremented by the MR that owns the MNP for each new NINO for that
prefix. Left unchanged by all MRs that propagate the NINO. A
lollipop mechanism is used to wrap from 0xFFFF directly to 10.
Prefix:
Variable-length field containing an IPv6 address or a prefix of an
IPv6 address. The Prefix Length field contains the number of
valid leading bits in the prefix. The bits in the prefix after
the prefix length (if any) are reserved and MUST be initialized to
zero by the sender and ignored by the receiver.
6.2. NINO IPv4 option
NINA is defined for both IPv4 and IPv6 address families.
For IPv4, a new NINO IPv4 option is introduced to be included in RA
and NA messages, for a node to advertise its IPv4 address on the
interface where the ND message is issued.
The NINO IPv4 option can be included in an RA by the sending router
to expose its IPv4 address to the attached visitors, so they can
install a default route via that address and use the sending router
as default gateway.
The option can also be included in a NA by a visiting node to expose
its IPv4 address to the Attachment Router; this address is used as
next hop by the AR as it installs routes via the visiting node
towards the IPv4 prefixes contained in the NINOs and passed as mapped
addresses in the NA message.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 address on sending interface |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type:
NINO IPv4 (number to be assigned by IANA).
Length:
8-bit unsigned integer. The length of the option (including the
Type and Length fields) in units of 8 octets.
Reserved:
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8-bit unused field. It MUST be initialized to zero by the sender
and MUST be ignored by the receiver.
IPv4 address on sending interface:
32-bit field containing the IPv4 address of the sending interface.
7. Mobile Router Operation
The Mobile Router operation is autonomous, based on the information
provided by the potential Access Routers in sight. Each MR selects
an AR (a MAR) in a loop-less and case-optimized fashion, and installs
a default route up the tree via the selected AR. The resulting tree
(the cluster) may never be globally stable enough to be mapped in a
global graph. So the adaptation to local movements must be rapid and
localized.
When the Reverse Routing Header (RRH) is used for NEMO flows, it
allows the update to the path on a per packet basis. Hopefully, the
root of the tree (the clusterhead) is connected to the infrastructure
where Home can be reached, and can be used as a gateway to discover
Home. When the NEMO tunnel is established, it becomes the default
route for the MR.
If the tree is not connected to the infrastructure or in any case if
Home can not be reached, MRs need an ad-hoc protocol to establish
local connectivity. This specification takes advantage of the TD
cluster and allows an MR to discover the prefixes below itself.
NINA information can be redistributed in a routing protocol, MANET or
IGP. But the MANET or the IGP SHOULD NOT be redistributed into NINA.
This creates a hierarchy of routing protocols where NINA routes stand
somewhere between connected and IGP routes.
NINA also allows a compression of the Reverse Routing header when the
routes match the topology as traced by RRH on a per packet basis. In
particular, if a NINA route exists to the first entry in the RRH via
the source of the packet, then the MR can override the source of the
packet with its own CoA without adding the original source to the
RRH. At that point, the RRH operation becomes loose, in other words
an hybrid between transparent (stateful) and source routing.
As a result:
o Tree Discovery establishes a tree using extended Neighbor
Discovery RS/RA flows.
o The NEMO Basic Support protocol exploits the tree to get optimally
out of a nested set of MRs and register Home.
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o RRH extends the NEMO Basic Support to provide Route Optimization
and faster path reestablishment.
o NINA also extends Neighbor Discovery in order to establish quickly
the routes down the cluster.
NINA maintains abstract lists of known prefixes. A prefix entry
contains the following abstract information: NINA maintains abstract
lists of known prefixes. NINA stores the prefix entries in either
one of 3 abstract lists; the Connected, the Reachable and the
Unreachable lists. A prefix entry contains the following abstract
information:
o A reference to the ND entry that was created for the advertiser
Neighbor.
o The IPv6 address of the advertiser Neighbor.
o The logical equivalent of the full NINA information.
o A reference to the interface of the advertiser Neighbor.
o A 'reported' Boolean to keep track whether this prefix was
reported already to the parent AR.
o A counter of retries to count how many RA-TIOs were sent on the
interface to the neighbor without reachability confirmation for
the prefix.
NINA stores the prefix entries in either one of 3 abstract lists; the
Connected, the Reachable and the Unreachable lists.
The Connected list corresponds to the MNP of the Mobile Router.
As long as an MR keeps receiving NINOs for a prefix timely, its
prefix entry is listed in the Reachable list.
Once scheduled to be destroyed, a prefix entry is moved to the
Unreachable list if the MR has a parent to which it sends NINOs,
otherwise the entry is cleaned up right away. The entry is removed
from the Unreachable list when the parent changes or when a no-NINO
is sent to the parent indicating the loss of the prefix.
NINA requires 2 timers; the DelayNA timer and the DestroyTimer.
o The DelayNA timer is armed upon a stimulation to send a NINA (such
as a TIO from the AR). When the timer is armed, all entries in
the Reachable list as well as all entries for Connected list are
set to not reported yet.
o The DelayNA timer has a duration that is DEF_NA_LATENCY divided by
2 with the tree depth.
o The DestroyTimer is armed when at least one entry has exhausted
its retries, which means that a number of RA-TIO were sent over
the ingress interface but that the entry was not confirmed with a
NINO. When the destroy timer elapses, for all exhausted entries,
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the associated route is removed, and the entry is scheduled to be
destroyed.
o The Destroy timer has a duration of min (MAX_DESTROY_INTERVAL,
RA_INTERVAL).
7.1. Multicast TD RA messages from parent
When ND sends a NA to the AR, NINA extends the message with prefix
options for:
o All the prefixes that are not 'DELETED' for all the ingress
interfaces.
o All the prefixes in the removed list as no-NINO.
o All the prefixes in the advertised list that are not reported yet.
The entries are set to reported.
When ND receives a NA from a visitor over an ingress interface, NINOs
are processed in a loop. For known prefixes, the sequence counter in
the NINO is checked against the last received and the update is used
only if the sequence is newer. This filters out obsolete
advertisements when a prefix has moved between 2 subtrees attached to
a same node.
If a prefix is advertised as a no-NINO, the associated route is
removed, and the entry is transferred to the removed list.
Otherwise, the route table is looked up:
o If a preferred route to that prefix from another protocol already
exists, the prefix is ignored.
o If a new route can be created, a new prefix entry is allocated to
track it, as CONFIRMED, but not reported.
o If a NINA route existed already via the same Neighbor, it is
CONFIRMED.
o If a NINA route existed via a different Neighbor, this is
equivalent to a no-NINO for the previous entry followed by a new
NINO for the new entry. So the old entry is scheduled to be
destroyed, whereas the new one is installed.
7.2. Unicast NINA messages from child to parent
When sending NINA to its parent, an MR includes the NINOs about not
already reported prefix entries in the Reachable and Connected lists,
as well as no-NINOs for all the entries in the Unreachable list.
Depending on its policy, the receiving MR SHOULD install a route to
the prefix in the NINO via the link local address of the source MR
and it SHOULD propagate the information, either as a NINO or by means
of redistribution into a routing protocol.
The RA-TIO from the root-MR is used to synchronize the whole tree.
Its period is expected to range from 500ms to hours, depending on the
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stability of the configuration and the bandwidth available.
When an MR receives a RA-TIO over an egress interface from the
current parent AR, the DelayNA is armed to force a full update. As
described in [6] the MR also issues a propagated RA-TIO over all its
ingress interfaces, after a small jitter that aims at minimizing
collisions of RA-TIO messages over the radio as it is propagated down
the tree.
The design choice behind this is NOT TO synchronize the parent and
children databases, but instead to update them regularly to cover
from the loss of packets. The rationale for that choice is movement.
If the topology can be expected to change frequently, synchronization
might be an excessive goal in terms of exchanges and protocol
complexity. This results in a simple protocol with no real peering.
When the MR sends a RA-TIO over an ingress interface, for all entries
on that interface:
o If the entry is CONFIRMED, it goes PENDING with the retry count
set to 0.
o If the entry is PENDING, the retry count is incremented. If it
reaches a maximum threshold, the entry goes ELAPSED If at least
one entry is ELAPSED at the end of the process: if the Destroy
timer is not running then it is armed with a jitter.
Since the DelayNA has a duration that decreases with the depth, it is
expected to receive all NINOs from all children before the timer
elapses and the full update is sent to the parent.
7.3. Other events
Finally, NINA listens to a series of events, such as:
o MR stopped or unable to run: NINA routes are cleaned up. NINA is
inactive.
o NINA operation stopped: All entries in the abstract lists are
freed. All the NINA routes are destroyed.
o Interface going down: for all entries in the Reachable list on
that interface, the associated route is removed, and the entry is
scheduled to be destroyed.
o Neighbor being removed from the ND list: if the entry is in the
Reachable list the associated route is removed, and the entry is
scheduled to be destroyed.
o Roaming: All entries in the Reachable list are set to not
'reported' and DelayNA is armed.
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7.4. Aggregation of prefixes on a same MR
When deploying an MR with multiple ingress interfaces, it makes sense
to affect an aggregation prefix (shorter than /64) to the MR and
partition it as /64 prefixes over the MR interfaces. An MR that owns
a contiguous set of prefixes should only report the aggregation of
these prefixes through NINA.
7.5. Aggregation of prefixes by a parent acting as mobile Home
There are also a number of cases where a mobile aggregation is shared
within a toon of Mobile Routers. For instance, a toon formed by
firefighters and their commander. In that case, it is still possible
to use aggregation techniques with NINA and improve its scalability.
In that case, the commander is configured as the NINA aggregator for
the group prefix. In run time, it absorbs the individual NINO
information it receives from the toon members down its subtree and
only reports the aggregation up the TD tree. This works fine when
the whole toon is attached within the commander's subtree.
But other cases might occur for which additional support is required:
1. the commander is attached within the subtree of one of its toon
members.
2. A toon member is somewhere else within the TD tree.
3. A toon member is somewhere else in the Internet.
In all those cases, a node situated above the commander in the TD
tree but not above the toon member will see the advertisements for
the aggregation owned by the commander but not that of the individual
toon member prefix. So it will route all the packets for the toon
member towards the commander, but the commander will have no route to
the toon and will fail to forward.
Section 8 'Mobile Home' of RFC 4887 [20] proposes a deployment model
where a Mobile Router would also act as Home Agent for a mobile
aggregation. This method can be used in the general case 3 to ensure
routability to the toon member. With that method, the Home Link for
a toon member should be one of the commander links. The Tree
Discovery plug-in should favor that link so that many toon members
actually attach at Home.
If a toon member is not at Home, then it will register to its Home
Agent using NEMO basic support (RFC 3963 [5]). Depending of the
location of a source, a packet to the toon member will either go
directly to it, or go to its commander. If the toon member as a
Mobile Router is registered to its commander as its Home Agent, the
commander can always encapsulate the packet to the CoA of the toon
member using NEMO, and ensure reachability to the MR.
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Section 2.7 of RFC 4888 [21] explains that in the specific case of
case 1), the commander will not be able to reach Home using plain
NEMO basic support, and an additional mechanism such as RRH ([17]) is
required to fix that issue.
Also specifically in case 1), the toon member will refrain from
adding the NINO options for its own prefixes that are aggregated in
the NINO option of its commander that it propagates up the TD tree.
7.6. Default value
DEF_NA_LATENCY = 150 ms
MAX_DESTROY_INTERVAL = 200ms
8. Privacy Considerations
It is already possible for a visiting Mobile Node (Mobile Router) to
autoconfigure an address that will not identify the visitor [22],
[13]. It is also possible for a visitor to roll its CoA periodically
even when it stays attached to a same point, and register the new
addresses as it forms them.
CIA (Capability, Innocuousness and Anonymity) properties demand also
that the visited party might not be identified by the visitor. To
achieve that, a Mobile Router should not advertise its MNPs on its
links open to untrusted visitors.
This draft recommends that the interface that is open for untrusted
visitors uses unique local addresses (RFC 4193 [8]) and rolls the
advertised prefixes with a short lifetime. This can be achieved for
instance by obtaining short lived leases from the Home Agent using
DHCP-PD [23].
Another possibility is to use strict RRH routing [17]; in that case,
the prefix that is presented on the link can be taken from anywhere
in the ULA range since it is not used for routing outside the link.
Alternatively, a global unique prefix obtained from an autoconf
solution [24], [25] or DHCPv6 prefix delegation [9] can be used as
well.
9. IANA Considerations
This document requires IANA to assign a number for a new ND option
type (NINO NA).
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10. Security Considerations
Exposing the MRs' MNPs within the MFS introduces several security
threats that should be carefully tackled, mainly derived from the
fact that MRs are distributing prefixes (i.e., their MNPs) that are
not topologically correct within the MFS.
To avoid these security issues -- that might enable malicious nodes
to steal traffic addressed to other nodes (by spoofing their
prefixes) -- Mobile Routers should be provided with some security
mechanisms, ensuring that an MR that is advertising a certain MNP is
actually authorized to do that.
The use of L2 trusts and policies, SeND or preconfigured security
relationships might help in securing the mechanism described in this
draft. Additionally, if MRs have connectivity with their Home
Agents, a modified Return Routability mechanism -- extended to
support prefix checks (such as [26] or [27]) -- may be used to
provide the required authorization, before starting to use the RO
shortcut within the MFS.
11. Acknowledgments
We would like to thank all the people who have provided comments on
this draft.
12. References
12.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
September 2007.
[3] Perkins, C., "IP Mobility Support for IPv4", RFC 3344,
August 2002.
[4] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in
IPv6", RFC 3775, June 2004.
[5] Devarapalli, V., Wakikawa, R., Petrescu, A., and P. Thubert,
"Network Mobility (NEMO) Basic Support Protocol", RFC 3963,
January 2005.
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[6] Thubert, P., Bontoux, C., Montavont, N., and B. McCarthy,
"Nested Nemo Tree Discovery", draft-thubert-tree-discovery-07
(work in progress), August 2008.
[7] Draves, R. and D. Thaler, "Default Router Preferences and More-
Specific Routes", RFC 4191, November 2005.
[8] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
Addresses", RFC 4193, October 2005.
[9] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic Host
Configuration Protocol (DHCP) version 6", RFC 3633,
December 2003.
12.2. Informative References
[10] Manner, J. and M. Kojo, "Mobility Related Terminology",
RFC 3753, June 2004.
[11] Corson, M. and J. Macker, "Mobile Ad hoc Networking (MANET):
Routing Protocol Performance Issues and Evaluation
Considerations", RFC 2501, January 1999.
[12] Johnson, D., Hu, Y., and D. Maltz, "The Dynamic Source Routing
Protocol (DSR) for Mobile Ad Hoc Networks for IPv4", RFC 4728,
February 2007.
[13] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure
Neighbor Discovery (SEND)", RFC 3971, March 2005.
[14] Chakeres, I., Macker, J., and T. Clausen, "Mobile Ad hoc
Network Architecture", draft-ietf-autoconf-manetarch-07 (work
in progress), November 2007.
[15] Clausen, T., Dearlove, C., and P. Jacquet, "The Optimized Link
State Routing Protocol version 2", draft-ietf-manet-olsrv2-07
(work in progress), July 2008.
[16] Clausen, T., Dearlove, C., and J. Dean, "MANET Neighborhood
Discovery Protocol (NHDP)", draft-ietf-manet-nhdp-07 (work in
progress), July 2008.
[17] Thubert, P. and M. Molteni, "IPv6 Reverse Routing Header and
its application to Mobile Networks",
draft-thubert-nemo-reverse-routing-header-07 (work in
progress), February 2007.
[18] Wakikawa, R., "Problem Statement and Requirements for MANEMO",
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draft-wakikawa-manemo-problem-statement-01 (work in progress),
July 2007.
[19] Ernst, T. and H-Y. Lach, "Network Mobility Support
Terminology", RFC 4885, July 2007.
[20] Thubert, P., Wakikawa, R., and V. Devarapalli, "Network
Mobility Home Network Models", RFC 4887, July 2007.
[21] Ng, C., Thubert, P., Watari, M., and F. Zhao, "Network Mobility
Route Optimization Problem Statement", RFC 4888, July 2007.
[22] Narten, T., Draves, R., and S. Krishnan, "Privacy Extensions
for Stateless Address Autoconfiguration in IPv6", RFC 4941,
September 2007.
[23] Droms, R. and P. Thubert, "DHCPv6 Prefix Delegation for NEMO",
draft-droms-nemo-dhcpv6-pd-02 (work in progress), April 2005.
[24] Baccelli, E., Mase, K., Ruffino, S., and S. Singh, "Address
Autoconfiguration for MANET: Terminology and Problem
Statement", draft-ietf-autoconf-statement-04 (work in
progress), February 2008.
[25] Bernardos, C., Calderon, M., and H. Moustafa, "Survey of IP
address autoconfiguration mechanisms for MANETs",
draft-bernardos-manet-autoconf-survey-03 (work in progress),
April 2008.
[26] Ng, C., "Extending Return Routability Procedure for Network
Prefix (RRNP)", draft-ng-nemo-rrnp-00 (work in progress),
October 2004.
[27] Bernardos, C., Soto, I., Maria, M., Fernando, F., and A.
Arturo, "VARON: Vehicular Ad hoc Route Optimisation for NEMO",
Computer Communications, vol. 30, pp. 1765-1784 , 2007.
Appendix A. Contributors
Ryuji Wakikawa
Toyota ITC
6-6-20 Akasaka, Minato-ku
Tokyo 107-0052
Japan
Phone: +81-3-5561-8276
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Fax: +81-3-5561-8292
Email: ryuji@jp.toyota-itc.com
Roberto Baldessari
NEC Europe Network Laboratories
Kurfuersten-anlage 36
Heidelberg 69115
Germany
Phone: +49 6221 4342167
Email: roberto.baldessari@netlab.nec.de
Jean Lorchat
Keio University and WIDE
5322 Endo Fujisawa Kanagawa
252-8520
JAPAN
Email: lorchat@sfc.wide.ad.jp
Ben McCarthy
Lancaster University
Computing Department
Infolab21, South Drive
Lancaster University
Lancaster LA1 4WA
UK
Phone: +44 1524 510 383
Email: b.mccarthy@lancaster.ac.uk
Appendix B. Change Log
Changes from -01 to -02:
o NINA IPv4 support: added IPv4 NINO ND option.
o References updated.
o Updated the location of the 'L' bit in the NINO NA option, to
match format of RFC 4861.
Changes from -00 to -01:
o Basic kiss (MR to MR over egress) sections removed.
o Added sections about aggregation of prefixes.
o Added Privacy consideration section.
o NINO NA message format changed.
o Some text cleanups.
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Authors' Addresses
Pascal Thubert
Cisco Systems
Village d'Entreprises Green Side
400, Avenue de Roumanille
Batiment T3
Biot - Sophia Antipolis 06410
FRANCE
Phone: +33 4 97 23 26 34
Email: pthubert@cisco.com
Carlos J. Bernardos (editor)
Universidad Carlos III de Madrid
Av. Universidad, 30
Leganes, Madrid 28911
Spain
Phone: +34 91624 6236
Email: cjbc@it.uc3m.es
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