6lowpan Working Group Z. Shelby, Ed.
Internet-Draft Sensinode
Intended status: Standards Track P. Thubert
Expires: August 27, 2009 Cisco
J. Hui
Arch Rock
S. Chakrabarti
IP Infusion
E. Nordmark
Sun
February 23, 2009
Neighbor Discovery for 6LoWPAN
draft-ietf-6lowpan-nd-01
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Abstract
This document specifies Neighbor Discovery optimized for 6LoWPAN.
The 6LoWPAN format allows IPv6 to be used over very constrained
wireless networks often making use of extended multihop topologies.
However, the use of standard IPv6 Neighbor Discovery over 6LoWPAN
networks has several problems. Standard Neighbor Discovery was not
designed for wireless links, and the standard IPv6 link concept and
heavy use of multicast makes it inefficient. This document spefies a
new mechanism allowing efficient Duplicate Address Detection over
entire 6LoWPAN networks. In addition it specifies context
dissemination for use with router advertisements, claim and defend
addressing, and the support of extended LoWPANs over backbone links.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1. Goals & Assumptions . . . . . . . . . . . . . . . . . . . 6
1.2. Why not standard IPv6 ND? . . . . . . . . . . . . . . . . 7
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 8
3. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 10
3.1. Bootstrapping . . . . . . . . . . . . . . . . . . . . . . 13
3.2. Basic operation . . . . . . . . . . . . . . . . . . . . . 14
3.3. Optional features . . . . . . . . . . . . . . . . . . . . 15
4. 6LoWPAN ND Messages . . . . . . . . . . . . . . . . . . . . . 15
4.1. Router Registration/Confirmation Message . . . . . . . . . 16
4.2. Router Advertisement Message . . . . . . . . . . . . . . . 18
4.3. NS/NA Messages . . . . . . . . . . . . . . . . . . . . . . 19
4.4. 6LoWPAN ND Message Options . . . . . . . . . . . . . . . . 20
4.4.1. Address Option . . . . . . . . . . . . . . . . . . . . 20
4.4.2. 6LoWPAN Prefix Information Option . . . . . . . . . . 21
4.4.3. Multihop Information Option . . . . . . . . . . . . . 23
4.4.4. Owner Interface Identifier Option . . . . . . . . . . 23
5. LoWPAN Subnet . . . . . . . . . . . . . . . . . . . . . . . . 24
6. LoWPAN Node Specification . . . . . . . . . . . . . . . . . . 25
6.1. Forming addresses . . . . . . . . . . . . . . . . . . . . 25
6.2. Registration process . . . . . . . . . . . . . . . . . . . 26
6.3. Next-hop determination . . . . . . . . . . . . . . . . . . 28
6.4. Address lookup . . . . . . . . . . . . . . . . . . . . . . 28
7. LoWPAN Router Specification . . . . . . . . . . . . . . . . . 29
7.1. Router Configuration Variables . . . . . . . . . . . . . . 29
7.2. Becoming an Advertising Interface . . . . . . . . . . . . 29
7.3. Router Advertisement Message Content . . . . . . . . . . . 29
7.4. Sending Unsolicited Router Advertisements . . . . . . . . 31
7.5. Ceasing To Be an Advertising Interface . . . . . . . . . . 31
7.6. Processing Router Solicitations . . . . . . . . . . . . . 31
7.7. Router Advertisement Consistency . . . . . . . . . . . . . 31
7.8. Relaying a Router Registration Message . . . . . . . . . . 31
7.9. Relaying a Router Confirmation Message . . . . . . . . . . 31
8. LoWPAN Edge Router Specification . . . . . . . . . . . . . . . 31
8.1. Registration process . . . . . . . . . . . . . . . . . . . 32
8.2. Exposing the Edge Router . . . . . . . . . . . . . . . . . 34
8.3. Forwarding packets . . . . . . . . . . . . . . . . . . . . 35
8.4. Address collision detection and resolution . . . . . . . . 35
8.5. Duplicate OII detection . . . . . . . . . . . . . . . . . 37
8.6. Fault tolerance . . . . . . . . . . . . . . . . . . . . . 38
9. Ad-hoc LoWPAN Operation . . . . . . . . . . . . . . . . . . . 39
10. Message Examples . . . . . . . . . . . . . . . . . . . . . . . 39
10.1. Basic RR/RC message exchange . . . . . . . . . . . . . . . 39
10.2. Relayed RR/RCC message exchange . . . . . . . . . . . . . 40
10.3. Router advertisement . . . . . . . . . . . . . . . . . . . 41
11. Security Considerations . . . . . . . . . . . . . . . . . . . 42
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12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 42
13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 43
14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 43
14.1. Normative References . . . . . . . . . . . . . . . . . . . 43
14.2. Informative References . . . . . . . . . . . . . . . . . . 44
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 45
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1. Introduction
The IPv6 over IEEE 802.15.4 [RFC4944] document has specified IPv6
headers carried over an IEEE 802.15.4 and similar network with the
help of an adaptation header which comes before the IP header. A
LoWPAN link is characterized as lossy, low-power, low bit-rate, short
range, with long deep sleep periods. Multicast as used in IPv6
Neighbor Discovery [RFC4861] is not desirable in such a wireless low-
power, lossy network.
Moreover, LoWPAN links are transient in nature; they are not always
considered to be in a fixed network nor they are bounded by our
standard definition of a wired-link. The link is in reality defined
by reachability and radio strength. The standard IPv6 Neighbor
Discovery [RFC4861] control messages and their default frequency also
attribute to unnecessary loss of power in 6LoWPAN networks.
Neighbor discovery for 6LoWPAN provides for basic bootstrapping and
network operation, along with advanced features such as claim and
defend addressing and extended LoWPANs over backbone links, while
avoiding the use of multicast and providing both mesh under and route
over support. Unlike standard IPv6 ND [RFC4861], this document takes
the characteristics of low-power, lossy wireless networks and links
into account.
A LoWPAN network is composed of a potentially large amount of radio
links, eventually federated by a backbone or a backhaul link.
Although a given link has broadcast capabilities, the aggregation of
links is a complex Non-Broadcast MultiAccess (NBMA, [RFC2491])
structure with no multicast capabilities. This specification
introduces a registration mechanism over the radio edge of the NBMA
network and proxy operation over the federating backbone or backhaul.
That registration mechanism provides a service somewhat similar to
MARS ([RFC2022]) for the limited purpose of ND NS/NA, and in a lot
simpler and less generic fashion. For those link scope multicast
that could not be avoided, such as ND RAs, Trickle may be used to
optimize the dissemination of the information in the Low Power
network.
The concept of a LoWPAN whiteboard located at Edge Routers is
introduced, which allows for duplicate address detection and claim
and defend addressing for the entire LoWPAN. Address resolution
simplifications are included to make LoWPAN operation efficient and
reduce LoWPAN Node complexity. A new registration/confirmation
message sequence is specified, allowing nodes to register their IPv6
addresses with an Edge Router whiteboard.
The ER whiteboard makes use of soft bindings, thus nodes send
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periodic registration messages in order to maintain their bindings.
Changes in network topology, and mobility between ERs and subnets are
supported. The dissemination of RA information throughout multihop
route over networks is also discussed.
This document also specifies the seamless integration of an extended
LoWPAN and multiple Edge Routers on a shared backbone link (e.g.
Ethernet) to form a single IPv6 subnet. This allows nodes to keep
the same IPv6 address throughout a large network, and allows for easy
communications with backbone link IPv6 hosts.
The document defines two new ICMPv6 messages: Router Registration and
Router Confirmation. In addition a new 6LOWPAN_ER anycast address is
introduced, allowing for nodes to send register without knowing the
specific Edge Router's or Router's unicast address.
1.1. Goals & Assumptions
This document has the following main goals and makes several
assumptions.
Goals:
o Avoid the use of multicast for ND messages inside the LoWPANs.
o Disseminate context information throughout the LoWPAN.
o Minimize the complexity of LoWPAN nodes.
o Interconnect LoWPANs with backbone links seamlessly.
o Provide a mechanism for claim and defend addressing.
Assumptions:
o Either [RFC4944] or [I-D.ietf-6lowpan-hc] 6LoWPAN header
compression used.
o Link layer technology may be IEEE 802.15.4 as in [RFC4944], or
any other suitable link-layer.
o Link-local addresses are derived from an EUI-64 identifier.
o The use of optimistic DAD.
o Mesh-under nodes know the edge router link-layer addresses of
their mesh network from some L2 mechanism.
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o A subnet includes all the LoWPAN nodes and their backbone link.
1.2. Why not standard IPv6 ND?
IPv6 Neighbor Discovery [RFC4861] provides several important
functions such as Router Discovery, Address Resolution, Duplicate
Address Detection, Redirect, Prefix and Parameter Discovery.
Following power-on and initialisation of the network in IPv6 ethernet
networks, a node joins the solicited-node multicast address on the
interface and then it performs duplicate address detection (DAD) for
the acquired link-local address by sending solicited-node multicast
message to the link. After that it sends multicast messages to all-
router address to solicit router advertisements. Once the host
receives a valid router advertisement with the "A" flag, it
autoconfigures the IPv6 address with the advertised prefix in the
rotuer advertisement (RA). Besides this, the IPv6 routers usually
send router advertisements periodically on the network. It sends the
RA to all-node multicast address. Nodes send Neighbor Solicitation/
Neighbor Advertisement messages to resolve the IPv6 address of the
destination on the link. These NS/NA messages are also often
multicast messages and it assumes that the node is on the same link
and relies on the fact that the destination node is always powered
and generally reliable.
A LoWPAN network typically uses two types of L2 addresses - 16-bit
short addresses and 64-bit unique addresses as defined in [RFC4944].
Moreover, the link bandwidth is often on the order of less than 100
bytes where we often might need to use header compression and use a
minimum payload. The network is lossy and low-powered, and it does
not provide multicast capability at the link-layer, thus simulating
multicast behavior by both using broadcast or sending a number of
unicast messages, both expensive for the low-powered network and the
low-processing capable nodes. Often these low-powered nodes conserve
energy by using sleep schedules; waking them up to receive IPv6
signaling messages such as multicast messages for NS, and periodic RA
is not practical. Nor they are capable of processing address-
resolution for its neighbors effectively. Due to radio strength of
its neighboring router or its own strength, a node may often move
from one router to another without physically moving from one place
to another. Considering the above characteristics in a LoWPAN, and
IPv6 Neighbor Discovery [RFC4861] base protocol requirements, it was
concluded that standard Neighbor Discovery is not suitable as it is
and a 6lowpan-specific ND definition would be useful and efficient
for the wide deployment of IPv6 over low-powered wireless networks of
embedded devices.
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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 [RFC2119].
Readers are expected to be familiar with all the terms and concepts
that are discussed in "Neighbor Discovery for IP version 6"
[RFC4861], "IPv6 Stateless Address Autoconfiguration" [RFC4862],
"IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs):
Overview, Assumptions, Problem Statement, and Goals" [RFC4919] and
"Transmission of IPv6 Packets over IEEE 802.15.4 Networks" [RFC4944].
Readers would benefit from reading "Mobility Support in IPv6"
[RFC3775], "Neighbor Discovery Proxies (ND Proxy)" [RFC4389] and
"Optimistic Duplicate Address Detection" [RFC4429] prior to this
specification for a clear understanding of state of the art in ND
proxy and binding.
This document defines additional terms:
LoWPAN Host
A node that only sources or sinks IPv6 datagrams. Referred to as
a host in this document. The term node is used when the the
differentiation between host and router is not important.
LoWPAN Edge Router
An IPv6 router that interconnects the LoWPAN to another network.
Referred to as an Edge Router in this document.
LoWPAN Router
A node that forwards datagrams between arbitrary source-
destination pairs using a single 6LoWPAN/802.15.4 interface. A
LoWPAN Router may also serve as a LoWPAN Host - both sourcing and
sinking IPv6 datagrams. Refered to as a router in this document.
All LoWPAN Routers perform ND message relay on behalf of other
nodes.
Mesh Under
A LoWPAN configuration where the link-local scope is defined by
the boundaries of the LoWPAN and includes all nodes within.
Forwarding is achieved at L2 between mesh nodes.
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Route Over
A LoWPAN configuration where the link-local scope is defined by
those nodes reachable over a single radio transmission. Due to
the time-varying characteristics of wireless communication, the
neighbor set may change over time even when nodes maintain the
same physical locations. Multihop is achieved using IP routing.
Backbone Link
This is an IPv6 link that interconnects two or more Edge Routers.
It is expected to be deployed as a high speed backbone in order to
federate a potentially large set of LoWPANS.
Backhaul Link
This is an IPv6 link that connects a single Edge Router to another
network.
Extended LoWPAN
This is the aggregation of multiple LoWPANs as defined in
[RFC4919] interconnected by a backbone link via Edge Routers and
forming a single subnet.
LoWPAN Link
In a LoWPAN, a link can be a very instable set of nodes, for
instance the set of nodes that can receive a packet that is
broadcast over the air. Such a set may vary from one packet to
the next as the node moves or as the radio propagation conditions
change.
LoWPAN Subnet
A subnet including a LoWPAN or Extended LoWPAN, together with the
backbone link with the same subnet prefix and prefix length.
Binding
The association of the LoWPAN node IPv6 address and Interface ID
with associated whiteboard and ND states including the remaining
lifetime of that association.
Registration
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The process during which a LoWPAN node sends a Router Registration
ND message to an Edge Router causing a binding for the LoWPAN node
to be registered.
3. Protocol Overview
Neighbor discovery for 6LoWPAN provides additions and optimizations
to IPv6 ND [RFC4861] specifically supporting 6LoWPAN networks. Basic
bootstrapping and network maintenenace mechanisms are provided, and
the use of multicast is avoided. Duplicate address detection and
claim and defend addressing are supported as part of bootstrapping.
This is achieved using a whiteboard located on the 6LoWPAN Edge
Routers of the LoWPAN network. Extended LoWPANs over backbone links
are optionally supported.
Multihop route-over networks are supported by routers relaying ND
messages. ND for 6LoWPAN is designed to work with many network
topologies, including isolated ad-hoc networks, single ER networks,
and networks with multiple ERs interconnected by a backbone link.
The use of both IEEE 802.15.4 and other suitable 6LoWPAN link-layer
technologies is considered. Both the use of mesh under forwarding
and route over routing are supported.
|
|
|
+-----+
| | Edge
| | router
+-----+
m m
m m
m m m m m: Mesh node
m m m m
m m m
LoWPAN
Figure 1: A Mesh under LoWPAN.
In a mesh under network, shown above, multihop forwarding is dealt
with below layer 3. Thus the entire LoWPAN forms a link-layer mesh.
This means that the IPv6 link-local scope includes all the nodes of
the LoWPAN. Link-local scope stops however at the ER, and does not
include any backbone link. The implication of this regarding ND for
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6LoWPAN, is that it can always be assumed that the ER and hosts are
on the same link. In these networks only LoWPAN Node and Edge Router
functionalities are needed. Multicast with mesh under technologies
most often induces flooding, and therefore it is avoided.
|
|
|
+-----+
| | Edge
| | router
+-----+
r h
r r r
h r h r h h: Host
h r r h r: Router
h h h
LoWPAN
Figure 2: A Route over LoWPAN.
A route over network performs multihop using standard layer 3 IP
routing. The link-local scope is defined by a LoWPAN link, which
includes nodes reachable over a single radio transmission at each
instant. The implication for ND for 6LoWPAN is that if the ER is out
of radio range of a host, the ND messages require relaying by
intermediate routers. In these networks also LoWPAN Router
functionality needs to be implemented by all routers in the LoWPAN.
Multicast may also involve flooding in such networks and often does
not work, and thus is avoided.
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Infrastructure
Cloud
z
z
z Backhaul link
z
z
+-----+
| | Edge
| | router
+-----+
o o
o o o
o o o o o o: Any node
o o o o
o o o
LoWPAN
Figure 3: A LoWPAN connected to a backhaul link.
The simplest topology is a LoWPAN connected by a single Edge Router
to another network, over a so-called backhaul link. The Edge Router
maintains a whiteboard of all hosts in the network. The Edge Router
terminates 6LoWPAN framing from the LoWPAN, and forwards packets.
The LoWPAN subnet covers all the interfaces in the LoWPAN, which have
the same prefix and prefix length.
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Infrastucture Cloud
|
|
+-----+ +-----+
| | Gateway | | Host
| | | |
+-----+ +-----+
| |
| Backbone link |
+--------------------+------------------+
| | |
+-----+ +-----+ +-----+
| | Edge | | Edge | | Edge
| | router | | router | | router
+-----+ +-----+ +-----+
o o o o o o o o
o o o o o o o o o o o o o o o o o
o o o o o o o o o o o o o o o o
o o o o o o o o o o o o
o o o o o o o o o
Extended LoWPAN OII
Figure 4: Backbone link and edge routers with a 6LoWPAN subnet
In the backbone link topology, a backbone link federates multiple
LoWPANs into a single LoWPAN Subnet, the Extended LoWPAN. Each
LoWPAN is anchored at one or more Edge Router. The Edge Routers
interconnect the LoWPANs over the backbone link. A node can move
freely from a LoWPAN anchored at an Edge Router to a LoWPAN anchored
at another Edge Router on the same backbone link and conserve all
IPv6 address it has formed.
The following sections summarizes how ND for 6LoWPAN works, starting
with bootrapping on the network, maintenance of the network, and
finally optional features.
3.1. Bootstrapping
A Host first performs stateless autoconfiguration of its link-local
unicast address for each LoWPAN interface from its EUI-64 as in
[RFC4944]. When a LoWPAN Host wants to join a LoWPAN network, it
does so by listening for Route Advertisements from Edge Routers or
routers, or by broadcasting a Router Solicitations. If a valid
prefix is advertised in the RA, the host may form an optimistic
global unique address with stateless autoconfiguration.
Next the Host registers with an on-link Edge Router or router by
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sending a Router Registration (RR) message to it, either unicast or
using the 6LOWPAN_ER anycast address. These message exchanges are
illustrated below. The RR contains the addresses the node wants to
register. If the network is configured to support whiteboard claim
and defend, e.g., generating short addresses for nodes, this is
indicated in the RA message with the M flag. In such networks a node
may request an address to be generated on its behalf by including an
Address Option with the A flag and an address of length 0 in the RR.
Note that registration must be performed separately for each
interface of a Host.
The Edge Router replies either directly with a Router Confirmation
(RC), or through a router by relaying. Note that routers only exist
in route over networks, and in mesh under networks nodes are on the
same link with Edge Routers. This confirmation includes the set of
addresses now bound to the whiteboard of the ER. The Host is now
capable of using the LoWPAN, and the ER forwards on its behalf.
Node Edge Router
| |
| ---------- Router Registration --------> |
| |
| <--------- Router Confirmation --------- |
| |
Figure 5: Basic ND registration exchange when the Node and Edge
Router are on the same link.
Node Router (relay) Edge Router
| | |
| ---- RR ---> | ---- RR ---> |
| | |
| <---- RC ---- | <---- RC ---- |
| | |
Figure 6: Relay ND registration exchange in route over networks.
3.2. Basic operation
The whiteboard address bindings and assignments are soft, and thus
must be renewed periodically as indicated by the lifetime of the
binding. This is achieved by periodically sending a new RR to the
ER. If a host moves, or the network topology changes, and the
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current ER is no longer available, the host then starts the
registration process with another ER. If the host is still in the
same Extended LoWPAN (same prefix), its IPv6 addresses remain the
same. Claim and defend addresses generated by the whiteboard must be
remembered by the host and refreshed in order to keep the address.
If the host moves to a different LoWPAN, with a different prefix, the
bootstrapping process is initiated again. In route over networks,
Routers that act as relays must disseminate RAs to their neighbors.
The Edge Router initiates RAs, and this information is included in
the RAs of each router.
3.3. Optional features
This documents specifies a method for forming Extended LoWPAN
networks with multiple ERs on a backbone link. This optional feature
allows for DAD across the entire Extended LoWPAN and backbone links,
seen as a single subnet. The method uniquely identifies the LoWPAN
Host on the backbone, and overrides the claim on an address on behalf
of a LoWPAN Host. Thus a Host can keep the same address, and appears
the same to other hosts on the backbone link, regardless of moving
its binding from one ER to another.
4. 6LoWPAN ND Messages
This section introduces message formats for all messages used in this
document. The new messages are all ICMPv6 messages and extend the
capabilities of "The IPv6 Neighbor Discovery Protocol" [RFC4861]. In
addition the ICMPv6 Router Advertisement is updated with new options.
The following new ICMPv6 message types are defined:
Router Registration
Router Confirmation
In addition, the following new ICMPv6 options are defined:
Address Option
6LoWPAN Prefix Information Option
Multihop Information Option
Owner Interface Identifier Option
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4.1. Router Registration/Confirmation Message
The Router Registration (RR) and Router Confirmation (RC) messages
are used by a Host to register with an ER, and for the ER to confirm
the binding. Any option that is not recognized MUST be skipped
silently. The Router Registration message is sent by the LoWPAN Node
to an on-link ER or router, and may be sent unicast or to the
6LOWPAN_ER anycast address. This same message format is also used
for relayed RR/RC messages, with an alternative code that is set when
the message has been relayed.
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 | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TID | Status |P| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Owner Interface Identifier +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Binding option(s)...
+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: Router Registration/Confirmation message format
IP Fields:
Source Address: The IPv6 address of the source. This address may
be an optimistic address.
Destination Address: The destination IPv6 address of an on-link
Edge Router or Router. May be the 6LOWPAN_ER anycast address.
Hop Limit: 255
ICMP Fields:
Type: TBD1 for Router Registration, TBD2 for Router Confirmation.
Code: 0 indicates a message sent directly from the orginating
host. 1 indicates that the message has been relayed by a
router.
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Checksum: The ICMP checksum.
TID: A unique Transaction ID assigned by the host and used to
match replies. A lollypop mechanism is used to increment the
TID at each new message. TID is set to 0 upon booting, and is
incremented with each RR message. After reaching 0xFFFF, the
value loops to 16 (0xFF) and is incremented from there. Thus
the values between 0-16 MUST only used after a boot or reboot.
P: 1-bit Primary flag. Set to indicate that the router is primary
and MAY represent the node if used in a backbone link setup.
If the flag is not set then the router MUST not represent the
node on the backbone. Flag is echoed in a confirmation.
Status: 8-bit unsigned integer. Values TBD. 0 means unqualified
success. Any value below 128 is a positive status that means
that the binding was created or is being created
optimistically.
Lifetime: 32-bit unsigned integer. The amout of time in units of
seconds remaining before the binding of this owner interface
identifier, and all associated address options and
configuration options, MUST be considered expired. A value of
zero indicates that the Binding Cache entries for the
registered owner interface identifier MUST be deleted.
Reserved: This field is unused. It MUST be initialized to zero
by the sender and MUST be ignored by the receiver.
Owner Interface Identifier: A globally unique identifier for the
requesting host's interface. Typically the EUI-64 dervied IID.
Possible Options:
Address Option(s): An Address Option is included for each address
the host wants to bind for this interface.
Configuration options: Other configuration information requests
and configuration settings may be carried in options of RR/RC
messages. Such options are not defined in this document.
Source link-layer address: Included in a Relay RR message in case
the Owner Interface Identifier is not the same as the link-
layer address of the host interface. Format as defined in
[RFC4861] and [RFC4944]. If the RR was relayed, then this
option MAY be added to the RC by the relaying router to
indicate the identity of the ER for use by a host.
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Target link-layer address: Included in a relayed RC message in
case the Owner Interface Identifier is not the same as the
link-layer address of the host interface. Format as defined in
[RFC4861] and [RFC4944]. MAY be included in an RR message from
a host to a router to indicate the prefered Edge Router to
relay the message to.
Future versions of this protocol may define new option types.
Receivers MUST silently ignore any options they do not recognized
and continue processing the message.
4.2. Router Advertisement Message
The RA message for 6LoWPAN is identical to the [RFC4861] RA message.
The use of flags is defined in the 6LoWPAN context, and additional
new options are identified.
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 | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cur Hop Limit |M|O|H|Prf|P|R|R| Router Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reachable Time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Retrans Timer |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options ...
+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: Router Advertisement Message Format
IP Fields:
Source Address: MUST be the link-local address assigned to the
interface from which this message is sent.
Destination Address: Typically the Source Address of an invoking
Router Solicitation or the all-nodes multicast address.
Hop Limit: 255
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ICMP Fields:
Type: 134
Code: 0
Checksum: The ICMP checksum.
Cur Hop Limit: As specified in [RFC4861].
M: As specified in [RFC4861] with the exception that managed mode
here refers to the claim and defend address mechanism specified
in this document, not DHCPv6 as in [RFC4861].
O: As specified in [RFC4861].
Prf: 2-bit signed integer. Default Router Preference as defined
in [RFC4191]. Indicates whether to prefer this router over
other default routers. LoWPAN Routers SHOULD set the
preference to (00) for normal, and LoWPAN Edge Routers SHOULD
set the preference to (01) for high.
Router Lifetime: As specified in [RFC4861].
Reachable Time: As specified in [RFC4861].
Possible Options:
6LoWPAN Prefix Information Option: This option includes
information about the prefixes of the LoWPAN along with other
context information.
Multihop Information Option: This option provides a sequence
number associated with the current prefix options. It allows
the prefix options themselves to be sent only periodically in
unsolicited RAs.
Future versions of this protocol may define new option types.
Receivers MUST silently ignore any options they do not recognized
and continue processing the message.
4.3. NS/NA Messages
Neighbor Solicitation and Neighbor Advertisement messages are
employed between ERs on the backbone link. A unique identifier is
required in the message as an option to uniquely identify a host's
interface. The standard NS/NA message is used in this document is as
per [RFC4861] with the an additional Owner Interface Identifier
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Option defined in this document. The Owner Interface Identifier is
the same as that carried in RR/RC messages and associated with
bindings.
4.4. 6LoWPAN ND Message Options
This section defines the new ND for 6LoWPAN message options.
4.4.1. Address Option
The Address Option is used to indicate the address which a node wants
to register with an ER in an RR, and to indicate the success or
failure of that binding in an RC. Multiple Address Options can be
included in a message. In order to be as compact as possible, fields
are used to indicate the compression of the IPv6 address. The
Address Option also allows for duplicate addresses (e.g. anycasts),
the request of a generated address for claim and defend, or for an
address to be removed.
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 | Status | P | S |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|D|A|R| Reserved | IPv6 Address ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9: Address Option format
Type: TBD3
Length: 8-bit unsigned integer. The length of the option (including
the type and length fields) in units of 8 octets.
Status: 8-bit unsigned integer. Values TBD. 0 means unqualified
success. Any value below 128 is a positive status that means that
the binding for this address was created or is being created
optimistically. Only used in a confirmation.
D: 1-bit Duplicate flag. When set, indicates that duplicates are
allowed for this address (to support anycast) in a request.
A: 1-bit Address Generation flag. Set to indicate that the host is
requesting a generated address for claim and defend addressing.
In a request when A is set the IPv6 address length is 0. Set to
indicate that an address has been assigned in a confirmation. P
and S are set to indicate the type of address requested and
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assigned when A is set. Otherwise must be 0.
R: 1-bit Removal flag. When set, indicates that this particular
address binding MUST be removed from a whiteboard (in a request)
or MUST not be used any longer (in a confirmation).
P: 4-bit unsigned integer. Identifies prefix compression or type, if
any.
0: Prefix is carried inline.
1: Prefix compressed and link-local (fe80:/10) is assumed.
2: Prefix compressed and the default prefix is assumed.
3-15: Reserved.
S: 4-bit unsigned integer. Identifies suffix compression or type, if
any.
0: Suffix carried inline.
1: Suffix compressed and assumes the same value as the Owner
Interface Identifier field in the RR/RC message header.
2: Suffix compressed and is derived from the 6LoWPAN short address
option as defined in RFC 4944.
3: Suffix is a 6LoWPAN 16-bit short address as defined in RFC 4944
or as appropriate for the link-layer of the LoWPAN.
4-15: Reserved.
IPv6 Address: The IPv6 address to be registered with the ER, or
confirmed by the ER. Parts of the address may be elided as per
the P and S fields.
4.4.2. 6LoWPAN Prefix Information Option
This option carries prefix information for LoWPANs, and is similar in
use to the Prefix Information Option of [RFC4861]. However this
option allows for the dissemination of multiple contexts identified
by a Context Identifier (CID) for use in 6LoWPAN address compression.
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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|A| CID | r |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Valid Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. Prefix .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 10: 6LoWPAN Prefix Information Option format
Type: TBD4
Length: 8-bit unsigned integer. The length of the option (including
the type and length fields) in units of 8 octets.
Prefix Length: 8-bit unsigned integer. The number of leading bits
in the Prefix that are valid. The value ranges from 0 to 128.
The prefix length field provides necessary information for on-link
determination (when combined with the L flag in the prefix
information option). It also assists with address
autoconfiguration as specified in [RFC4862], for which there may
be more restrictions on the prefix length.
L: 1-bit on-link flag. This flag MUST be unset for for route over
LoWPANs and backbone link LoWPANs, and MAY be set for mesh-under
LoWPANs without a backbone.
A: 1-bit autonomous address-configuration flag. When set indicates
that this prefix can be used for stateless address configuration
as specified in [RFC4861].
CID: 4-bit Context Identifier for this prefix information. The use
of this Context Identifier is not specified in this document.
Valid 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 the purpose of on-link determination. A value of all
one bits (0xffffffff) represents infinity.
Prefix: The IPv6 Prefix indicated for this context. This may be a
partial prefix, or even an entire IPv6 address for use as a
context for compression.
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4.4.3. Multihop Information Option
This option identifies the set of prefix information options by a
sequence number. This allows for the full set of prefix information
options to be sent only periodically in unsolicited RAs. If a host
detects a difference in the sequence number of this option, then the
prefix information has likely changed, and is then requested with an
RS.
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 | Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|V| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 11: Multihop Information Option
Type: TBD5
Length: 1
Sequence Number: 16-bit signed integer. Indicates the freshness of
the information advertised by the RA.
V: 1-bit flag. Indicates if the sequence number is valid and the
router is advertising information obtained from another router.
Reserved: This field is unused. It MUST be initialized to zero by
the sender and MUST be ignored by the receiver.
4.4.4. Owner Interface Identifier Option
This option is for use with standard NS and NA messages between ERs
over a backbone link. By using this option, the binding in question
can be uniquely identified and matched with the whiteboard entries of
each ER.
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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 | TID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Owner Interface Identifier +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 12: Owner Interface Identifier Option
Type: TBD6
Length: 2
TID: A unique Transaction ID assigned by the host in the associated
RR and used to match RC replies.
Reserved: This field is unused. It MUST be initialized to zero by
the sender and MUST be ignored by the receiver.
Owner Interface Identifier: A globally unique identifier for the
host's interface associated with the binding for the NS/NA message
in question.
5. LoWPAN Subnet
In a LoWPAN, a link can be a very unstable set of nodes, for instance
the set of nodes that can receive a packet that is broadcast over the
air at that instant. Such a set may vary from one packet to the next
as the node moves or as the radio propagation conditions change. In
addition, a LoWPAN is an NBMA network. As a result, a link does not
define the proper set of nodes to perform ND operations such as
Duplicate Address Detection and Address Resolution, nor is it stable
enough to be assigned a prefix usable for routing or address
configuration. Therefore in ND for 6LoWPAN, those operations are
performed over the entire LoWPAN or Extended LoWPAN. In LoWPANs it
is critical that IP routing, homogeneous addressing across the
LoWPAN, and the mobility of nodes are supported.
In this document, a LoWPAN subnet is defined to be a collection of
LoWPAN links interconnected by routers that have the same subnet
prefix. In particular, DAD is performed over a LoWPAN subnet for all
types of addresses, inclucing link-local. Thus a LoWPAN subnet
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differs from the IPv6 subnet defined in [RFC4291] as the LoWPAN
subnet is associated with a collection of links and is a multi-link
subnet. In a LoWPAN, setting the hop-limit to 1 limits a packet to
the link, but hop limit assumptions MUST NOT be made about the
subnet. Multi-link subnet issues are discussed in [RFC4903]. The
issues pointed out in [RFC4903] are not relevant in 6LoWPAN where
existing applications do not exist, and the network is a variation of
NBMA.
In the backhaul model, the Edge Router's interface and all the LoWPAN
Node interfaces registered to that Edge Router form a subnet. In
that model, the Edge Router serves all the prefixes that are defined
on the subnet and can be connected to an IP routed infrastructure.
With the backhaul model, in a mesh under network the link and subnet
are equivalent as the link spans the entire LoWPAN.
In the backbone model, a Backbone Link federates multiple LoWPANs
into a single subnet. Each LoWPAN is a collection of links anchored
at an Edge Router. The Edge Routers interconnect the LoWPANs over
the Backbone Link. A node can move freely from a LoWPAN anchored at
an Edge Router to a LoWPAN anchored at another Edge Router in the
same subnet and conserve its link-local and any other IPv6 address it
has formed.
6. LoWPAN Node Specification
Instead of relying on multicast ND messages for DAD and neighbor
address resolution, LoWPAN Nodes make use of an Edge Router in the
LoWPAN which keeps a whiteboard of all bound addresses from nodes
attached to the same ER. In addition, ERs may support a backbone
link, creating an extended LoWPAN sharing the same subnet prefix.
This allows a node to change its point of attachment without changing
its IPv6 addresses. This specification simplifies address resolution
compared to standard IPv6 ND. Claim and defend addressing is also
specified as part of the binding process. This section specifies
LoWPAN node operations.
6.1. Forming addresses
All nodes are required to autoconfigure at least one address, a link-
local address, which is derived from the IEEE 64-bit extended MAC
address that is globally unique to the interface as in [RFC4944]. As
a result, knowledge of the 64-bit address of another LoWPAN Node is
enough to derive its link-local address and reach it if on the same
link. Another consequence is that the link-local address is
presumably unique on the Extended LoWPAN, which enables the use of
Optimistic Duplicate Address Detection (oDAD) [RFC4429] over the
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Transit Link and the LoWPAN. The address SHOULD be created as
optimistic to enable its use in the binding process with the Edge
Router.
Nodes MAY learn the address of Edge Routers or Routers using
traditional means such as L2 configuration or Router Advertisement
messages. This specification also introduces a new anycast address
6LOWPAN_ER that the node can use to reach any Edge Router or router
on the link. This specification tolerates movement within the LoWPAN
so the node does not have to stick with a given router and MAY keep
using the 6LOWPAN_ER anycast address for all its registrations.
The node SHOULD also form a global unicast address, for routing
inside the LoWPAN and reachability from outside of the Extended
LoWPAN. If a valid prefix is available from an RA ('A' flag is set),
then a global unicast address can be derived using SAA. This address
is marked optimistic until confirmed by the ER.
This specification includes a method for requesting a unique
stateless address from the Edge Router by setting the 'A' flag in an
Address Option during registration. This is useful for receiving a
unique short address and, and works in a claim and defend fasion.
The node can tell if address generation is available if the 'M' flag
of the RA from that router is set. Address generation using the
RR/RC mechanism is stateless. Although the address is generated by
the ER and checked for uniqueness across the subnet using DAD, it is
just like any other address binding in the whiteboard of the ER after
assignment. Thus in order to keep using the assigned address the
host must keep refreshing the address binding, including when moving
to another ER in the same subnet.
To simplify address resolution it is assumed that nodes within a
LoWPAN use addresses in a homogeneous way and that the unicast IPv6
address IIDs resolve directly to a corresponding link-layer address.
Thus avoiding address resolution whenever possible.
6.2. Registration process
The binding process is very similar to that of a MIPv6 mobile node,
though the messages used are new Neighbor Discovery ICMP messages. A
LoWPAN Node address is tentative or optimistic as long as the binding
is not confirmed by the Edge Router.
The LoWPAN Node uses unicast Router Registrations to perform the
binding. The destination address is that of an on-link Edge Router
or router, or the 6LOWPAN_ER anycast address. Registration SHOULD be
preferred with on-link ERs rather than Routers. The Preference Flag
of the RA is used to differentiate between ERs and routers. The
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source address is the link local address of the node. A unique Owner
Interface Indentifier is included in the Router Registration so the
binding can be identified throughout the subnet. This is usually the
EUI-64 identifier of the interface. The RR message includes an
Address Option for each address to be bound. Thus the message is
structured as follows.
ICMPv6 (Router Registration (Address Option[0], Address Option[1],
Address Option[n]))
A unique Transaction ID (TID) is included by the host in the RR
message and used to match replies. A lollypop mechanism is used.
TID is set to 0 upon booting, and is incremented with each RR
message. After reaching 0xFFFF, the value loops to 16 (0xFF) and is
incremented from there. Thus the values between 0-16 MUST only used
after a boot or reboot.
The acknowledgment to a Router Registration is a unicast Router
Confirmation message that contains the status of the binding. The
source of the packet is the link-local address of the Edge Router or
Router. The destination address is the link-local address of the
node. An Address Option for each confirmed or assigned address is
included. Upon successful completion in the Router Confirmation
message, the LoWPAN Node sets the address from optimistic or
tentative to preferred. See Section 10 for detailed message
examples.
If no Router Confirmation is received within an implementation
specific timeout and number of retries, then there may be no Edge
Routers in the LoWPAN. In this case the hosts and routers SHOULD
continue to operate using the optimistic address generated by SAA.
See Section 9 for more information on ad-hoc network operation.
This specification also introduces the concept of a secondary
binding. For redundancy, a node might place a secondary binding with
one or more other Edge Routers on the same or different LoWPANs. The
'P' flag in the Router Registration Indentity Request Option
indicates whether the binding is primary. The use of this mechanism
for fault tolerance is explained in Section 8.6.
ER bindings have a timeout associated with them, therefore nodes must
periodically send a new Router Registration message to renew the
bindings. If a node no longer receives RCs from any router in the
current subnet, the registration process begins from the beginning.
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6.3. Next-hop determination
Next-hop determination is performed as in Section 5.2 of [RFC4861]
with the following exceptions. All prefixes are assumed to be off-
link as the LoWPAN subnet with that prefix may be larger than the
link in route over topologies, unless the destination address exists
in the neighbor cache. Link-layer information should be used to
maintain the neighbor cahce whenever possible rather than using ND
traffic. The ERs and routers used for registration are kept in the
default router List. Multicast addresses resolve to a broadcast as
specified in [RFC4944].
6.4. Address lookup
A LoWPAN node does not use multicast for its Neighbor Solicitation as
prescribed by the IPv6 ND [RFC4861] and oDAD [RFC4429]. When lookup
is necessary, all NS messages are sent in unicast to the Edge Router,
that answers in unicast as well. The message is a standard Neighbor
Solicitation but for the destination is set to the Edge Router
address or the well known 6LOWPAN_ER anycast address as opposed to
the solicited-node multicast address for the destination address. A
LoWPAN Node SHOULD retain a small queue for packets to neighbors
awaiting to be delivered while address lookup is being performed.
The size of the queue should be suitable to the available RAM of the
node, and is not required to be a minimum of one buffer per neighbor
as in [RFC4861].
The Target link-layer address in the response is either that of the
destination if a short cut is possible over the LoWPAN, or that of
the Edge Router if the destination is reachable over the Transit
Link, in which case the Edge Router will terminate 6LoWPAN and relay
the packet.
A LoWPAN Node does not need to join the solicited-node multicast
address for its own addresses and SHOULD NOT have to answer a
multicast Neighbor Solicitation. It MAY be configured to answer a
unicast NS but that is not required by this specification.
Care must be used with the 6LOWPAN_ER and other anycast addresses, as
anycast resolution is normally performed with a multicast NS/NA
exchange. As nodes are not required to answer NS messages, the next
hop determination process SHOULD map the anycast address to the link
layer address of a neighbor using available L2 or other ND
information.
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7. LoWPAN Router Specification
LoWPAN Routers are used in a route over configuration where the
network is composed of overlapping link-local scopes. As a result,
we extend ND as specified in [RFC4861] to operate over an entire
LoWPAN subnet, rather than a single IP link. This section describes
ND for 6LoWPAN router operations. Note that this section does not
apply to mesh under LoWPANs.
Network configuration parameters carried in Router Advertisements
originate at Edge Routers and must disseminate to all routers and
hosts within the LoWPAN. The Multihop Information Option is used to
support information dissemination from one or more Edge Routers to
all other nodes in the LoWPAN. The option includes a "V" flag which
indicates that the information contained in the Router Advertisement
is valid. The option also includes a sequence number to ensure that
all nodes converge on the same settings.
Because Router Registration/Confirmation exchanges only occur over
link-local scope, such messages must be relayed between hosts and
Edge Routers when separated by multiple IP hops. Every LoWPAN Router
MUST also serve as a relay to ensure that any neighboring node can
successfully participate in the LoWPAN.
7.1. Router Configuration Variables
A router MUST allow conceptual variables as defined in Section 6.2.1
of [RFC4861].
7.2. Becoming an Advertising Interface
An interface may become an advertising interace as specified in
Section 6.2.2 of [RFC4861].
A LoWPAN Router's interface MAY become an advertising interface
before all of its router variables have been initializes. The router
MUST learn these variables (e.g. AdvCurHopLimit, AdvReachableTime,
prefix information, etc.) from neighboring routers. While the
variables are not initialized, the router MAY send Router
Advertisement with the "Solicit" flag set to solicit Router
Advertisements from neighboring routers. However, the router MUST
set the Router Lifetime field to zero while one or more of its
variables are uninitialized.
7.3. Router Advertisement Message Content
A router sends periodic as well as solicited Router Advertisements
out its advertising interface. Outgoing Router Advertisements are
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filled with the following values constistent with the message format
given in this document.
- In the Router Lifetime field: if the router has a default route,
the interface's configured AdvDefaultLifetime. If the router does
not have a default route, zero.
- In the M and O flags: the current value of AdvManagedFlag and
AdvOtherConfigFlag, respectively.
- In the Preference flag: this flag is set to 00 to indicate that
the sender is a LoWPAN Router.
- In the Cur Hop Limit field: the current value of CurHopLimit.
- In the Reachable Time field: the current value of
AdvReachableTime.
- In the Retrans Timer field: the current value of
AdvRetransTimer.
- In the options:
- Multihop Information option: to indicate if the information
contained in the Router Advertisement is valid and, if so, the
freshness of the information contained in the Router
Advertisement message. The option fields are set as follows:
- In the "valid" flag: the current value of
AdvInformationValid.
- In the Sequence Number field: the current value of
AdvInformationSequence.
- 6LoWPAN Prefix Information options: one 6LoWPAN Prefix
Information option for each prefix listed in AdvPrefixList with
the option fields set from the information in the AdvPrefxList
entry as follows:
- In the "on-link" flag: the entry's AdvOnLinkFlag.
- In the "Autonomous address configuration" flag: the
entry's AdvAutonomousFlag.
- In the Valid Lifetime field: the entry's AdvValidLifetime.
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7.4. Sending Unsolicited Router Advertisements
As specified in Section 6.2.4 of [RFC4861].
7.5. Ceasing To Be an Advertising Interface
As specified in Section 6.2.5 of [RFC4861].
7.6. Processing Router Solicitations
As specified in Section 6.2.6 of [RFC4861].
7.7. Router Advertisement Consistency
TBD
7.8. Relaying a Router Registration Message
When a router receives a Router Registration message from a LoWPAN
Node, it sets the Code field to 1 indicating that the message has
been relayed. The IPv6 source address is set to that of the router.
By default, the router relays Router Registration messages to the
6LOWPAN_ER anycast address. However, the router MAY be configured to
use a list of destination addresses, which MAY include unicast
addresses, the 6LOWPAN_ER anycast address, or other addresses
selected by the network administrator. If the RR includes a Target
link-layer address option, then that SHOULD be used to form the
desination address as it indicates the ER which the LoWPAN node
prefers.
7.9. Relaying a Router Confirmation Message
When the router receives a Relay Router Confirmation message from an
Edge Router, the Code field is set to 1. The Owner Interface
Identifier is used to form the IPv6 Destination Address for the
Router Confirmation message. If a Target link-layer address option
is included in the message, then that is used to form the IPv6
destination address instead of the Owner Interface Identifier. The
IPv6 source address is set to that of the Router. The Hop Limit of
the Router Confirmation message is set to 255.
8. LoWPAN Edge Router Specification
Edge Routers are introduced to scale the Neighbor Discovery
Operations by reducing the amount of costly multicast ND messages
over a LoWPAN subnet that may cover hundreds or thousands of nodes.
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Instead of multicasting ND messages, a LoWPAN Node performs unicast
exchanges with an Edge Router to claim and lookup addresses using
unicast and anycast addresses, and the Edge Router performs ND
operations on its behalf over the Backbone Link when necessary, for
example DAD.
This specification documents the extensions to IPv6 Neighbor
Discovery that enables a LoWPAN Node to claim and lookup addresses
using an Edge Router as an intermediate proxy. The draft also
documents the use of EUI-64 based link-local addresses and the way
they are claimed by the Edge Routers over the Backbone link.
This specification documents the LoWPAN whiteboard, a conceptual data
structure that is similar to the MIPv6 binding cache.
Another function of the Edge Router is to perform 6LoWPAN compression
and uncompression between the LoWPAN and the Backbone Link and ensure
MTU compatibility. Packets flow uncompressed over the Backbone Link
and are routed normally towards a Gateway or an Application sitting
on the Backbone link or on a different link that is reachable via IP.
8.1. Registration process
Upon a new registration for a link-local or global unicast address
based on an IEEE 64-bit extended MAC address, the Edge Router MAY use
Optimistic DAD on the Transit Link. A positive acknowledgement can
be sent to the 6LoWPAN node right away if oDAD is used on the Transit
Link.
A LoWPAN Node should be able to join a different Edge Router at any
time without the complexities of terminating a current registration
and renumbering. To enable this, the ND operation on the backbone
link upon a Router Registration/Confirmation flow wins the address
ownership over an ND operation that is done asynchronously, on behalf
of the same LoWPAN Node, upon a prior registration. So an Edge
Router that would happen to have a binding for that same address for
the same LoWPAN Node identified by its EUI-64 address will yield and
deprecate its binding.
The new Owner Interface Identifier Option in NS/NA messages that
carries the node EUI-64 address and the lollypop mechanism on the TID
help differentiate an address collision over the backbone from a
movement of a node from one Edge Router to the next. More details on
collision detection and resolution are provided in Section 8.4.
The override (O) bit is used to differentiate a registration flow
from the asynchronous defense of an address by an edge router acting
as a proxy. Upon a registration flow, an edge router doing DAD or
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accepting a reregistration SHOULD set the override (O) bit in its NA
messages. Asynchronously to the registration, the edge router SHOULD
NOT set the override (O) bit in its NA messages and should yield to
an NA message with the override (O) bit set.
So the Edge Router operation on the transit link is similar to that
of a Home Agent as specified in "Mobility Support for IPv6" [RFC3775]
yet different. In particular, the Neighbor Advertisement message is
used as specified in section "10.4.1. Intercepting Packets for a
Mobile Node" with the exception that the override (O) bit is not set,
indicating that this Edge Router acts as a proxy for the LoWPAN and
will yield should another Edge Router claim that address on the
Backbone Link.
This specification also introduces the concept of a secondary
binding. Upon a secondary binding, the Edge Router will not announce
or defend the address on the backbone link, but will be able to
forward packets to the node over its LoWPAN interface. This feature
is used for fault tolerance, explained in Section 8.6.
The Edge Router responds to a Router Registration with a Router
Confirmation. The source address is a link-local address of the
router and the destination is the optimistic address of the node from
which the RR was received. The ER responds to relayed RR messages
with an RC message, where the destination address is the address of
the Router which sent the relayed RR message.
If the Edge Router is primary for a registration as indicated by the
'P' flag and it is connected to a Backbone, then it SHOULD perform ND
operations on the backbone. In particular the Egde Router SHOULD
reject the registration if DAD fails on the backbone. When oDAD is
used over the backbone the Edge Router MAY issue the Router
Confirmation right away with a positive code, but if a collision is
finally detected, it cancels the registration with an asynchronous
Router Confirmation and a negative completion code on the same TID.
If the RR message includes an Address Option with the 'A' flag set,
this indicated the request of stateless address generation. If the
ER supports managed address mode ('M' flag set in its RAs), then the
ER aquires an appropriate, unique link-layer address for the network
either by generating it and performing DAD, or with some other
method. If successful, this address is returned in an Address Option
of the RC with the 'A' flag set and the assigned IPv6 address formed
from the generated link-layer address with the defualt prefix inline.
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8.2. Exposing the Edge Router
The Backbone link is used as reference for Neighbor Discovery
operations. When an Edge Router does not have an entry in its
registration table for a target node, it looks it up over the
backbone using ND an operation in place for that medium. Edge
Routers also represent the LoWPAN Nodes that are proactively
registered to them. That way, a lookup over the backbone is not
propagated over the LoWPANs, but answered by the Edge Router that has
the registration for the target, if any.
To enable proxying over the backbone Link, an Edge Router must join
the solicited-node multicast address on that link for all the
registered addresses of the nodes in its LoWPANs. The Edge Router
answers the Neighbor Solicitation with a Neighbor Advertisement that
indicates its own link-layer address in the Target link-layer address
option.
An Edge Router expects and answers unicast Neighbor Solicitations for
all nodes in its LoWPANs. It answers as a proxy for the real target.
The target link-layer address in the response is either that of the
destination if a short cut is possible over the LoWPAN, or that of
the Backbone Router if the destination is reachable over the Transit
Link, in which case the Backbone Router will terminate 6LoWPAN and
relay the packet.
The Edge Router forms a link-local address in exactly the same way as
any other node on the LoWPAN.
The Edge Router configures the well known 6LOWPAN_ER anycast address
on the LoWPAN interfaces where it serves as Edge Router. Note that
the Edge Router will accept registration packets with a hop limit
that is lower than 255 on that specific address.
The Edge Router announces itself using Router Advertisement (RA)
messages that are broadcasted periodically over the LOWPAN and the
backbone link. The Edge Router MAY also announce any prefix that is
configured on the transit link, and serve as the default gateway for
any node on the Transit Link or on the attached LoWPANs.
The transit link Maximum Transmission Unit serves as base for Path
MTU discovery and Transport layer Maximum Segment Size negotiation
(see section 8.3 of [RFC2460]) for all nodes in the LoWPANs. To
achieve this, the Edge Router announces the MTU of the transit link
over the LoWPAN using the MTU option in the RA message as prescribed
in section "4.6.4. MTU" of IPv6 Neighbor Discovery [RFC4861].
LoWPAN Nodes SHOULD form IPv6 packets that are smaller than that MTU.
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As a result, those packets should not require any fragmentation over
the transit link though they might be intranet-fragmented over the
LoWPAN itself as prescribed by [RFC4944].
More information on the MTU issue with regard to ND-proxying can be
found in Neighbor Discovery Proxies [RFC4389] and
[I-D.van-beijnum-multi-mtu].
8.3. Forwarding packets
Upon receiving packets on one of its LoWPAN interfaces, the Edge
Router checks whether it has a binding for the source address. If it
does, then the Edge Router can forward the packet to another LoWPAN
Node or over the Backbone link. The hop limit is decremented upon
forwarding. Otherwise, the Edge Router MUST discard the packet. If
the packet is to be transmitted over the Transit link, then the
6LoWPAN sublayer is terminated and the full IPv6 packet is
reassembled and expanded.
When forwarding a packet from the Backbone Link towards a LoWPAN
interface, the Edge Router performs the 6LoWPAN sublayer operations
of compression and fragmentation and passes the packet to the lower
layer for transmission.
8.4. Address collision detection and resolution
The assumption in this section is that the OII that is carried in the
registration messages and in the NS/NA messages is globally unique.
When this assumption fails, and additional collision resolution
mechanism takes place, as detailed in Section 8.5.
The address collision can be detected within the edge router if the
edge router already has a registration for a given address, or over
the transit link using Duplicate Address Detection. The edge router
in charge of the resolution is the edge router that handles the
registration.
The general principles are as follows:
Mobility is included and welcome. A node may migrate its
registration to a new edge router transparently and at any time.
The protocol is designed to recognize the mobility and silently
cleanup the registration states.
A synchronous operation wins against a delayed proxy operation.
An edge router that processes a router registration normally takes
over an existing registration maintained by a defendant edge
router.
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The decision to migrate the registration from an edge router to
another is made by the edge router that processes a Router
Registration message based on its own states for that registration
and ND exchanges over the transit link.
A registration is identified by the (OII, IPv6 address) pair. A
conflict occurs when a Router Registration is received for an IPv6
address that is already registered with a different OII at the
same or another edge router. The resolution of such conflict is
explained below.
A conflict may also occur with a node that is already present on
the transit link when the registration occurs, or with a node
appears on the transit link while a registration already exists
for its claimed address. The resolution of such conflict is done
using standard Duplicate Address Detection as prescribed by
[RFC4862].
Upon a Router Registration message, an edge router looks up an
existing registration for that IPv6 address in its LoWPAN whiteboard.
If the entry does not exist then the edge router looks up the address
over the transit link using the NS (DAD) mechanism. The edge router
SHOULD include an Owner Interface Identifier Option in the NS
message. An edge router that defends that address for an existing
registration MUST include an Owner Interface Identifier Option in the
NA message and SHOULD NOT set set the Override (O) bit.
If no entry is found for that address and DAD times out, the edge
router accepts the registration: it creates an entry on the
whiteboard, sends a positive Router Confirmation Message to the node,
and advertises the address on the transit link. Since this happens
asynchronously to the Router Registration, the edge router SHOULD NOT
set set Override (O) bit in the NA message.
If an entry is found in the whiteboard for the same (OII, IPv6
address) pair, additional checking is performed for duplicate OII
detection as detailed in Section 8.5. If no duplication is detected,
then the edge router accepts the update of the reservation: it
updates a entry on the whiteboard, sends a positive Router
Confirmation Message to the node, and advertises the address on the
transit link. Since this happens synchronously to the Router
Registration, the edge router SHOULD set set Override (O) bit in the
NA message.
If the address is already present on the transit link and defended by
a remote edge router, then that edge router defends the address with
the Override (O) bit reset and the Owner Interface Identifier Option
in the NA message.
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If the edge router receives an NA message during the DAD period, it
checks for an Owner Interface Identifier Option in the NA message.
If there is no OII or the (O) bit is set then this is a duplicate
address, DAD fails and the registration is rejected. If there is an
Owner Interface Identifier Option in the NA message and the OII is
different, then DAD fails and the registration is rejected. If the
OII is the same, additional checking is performed for duplicate OII
detection as detailed in Section 8.5. If there is no duplication
then the NA is ignored and the DAD timer keeps going.
If the edge router receives an NS (DAD) message from another node
during the DAD period, it checks for a Owner Interface Identifier
Option in the NS message. If there is no OII then DAD fails and the
registration is rejected. If there is an Owner Interface Identifier
Option in the NA message and the OII is different, then DAD fails and
the registration is rejected. If the OII is the same, then the
greatest TID wins. In other words, if the TID in the registration is
smaller than or equal to the TID in the OII Option then DAD fails and
the registration is rejected. Otherwise the NS is ignored and the
DAD timer keeps going.
Other edge routers are informed of a take over decision by an NA with
the Override (O) bit set and silently set their own state to non-
operational. An edge router that looses ownership should attempt to
keep the registration entry in the whiteboard till the end of the
registration lifetime for the purpose of duplicate OII detection if
memory capacity allows. The TID in the whiteboard entry is updated
with that in the OII option in the NA.
8.5. Duplicate OII detection
The TID is a sequential number that is used to control the normal
operation of a registration and detect a duplicate Owner Interface
Identifier during the Neighbor Discovery operations. The TID is set
by a node in its Router Registration message and echoed by the edge
router in the Router Confirmation message. At least the 4 most
recent values for a TID are also kept by the edge router in the
whiteboard entry for validation purpose.
The TID is maintained using the lollypop mechanism. When a node
starts or restarts, the TID is reset to zero. After that, it is
incremented with each Router Registration. When the TID reaches its
maximum value (0xFFFF) it wraps directly to its looping value at the
base of the lollypop that is 16. So a value in the straight part of
the lollypop (between 0 and 0xFF) is only used after a reboot and
before the circular part of the lollypop is entered.
Upon a positive Registration Confirmation, if the current TID is less
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than 16, then the node sets it to 16. So a TID in the straight part
denotes a node that just started/restarted and did not get registered
yet.
To compare TID1 and TID2, the following rules apply:
If at least one of TID1 and TID2 is in the straight part of the
lollipop (smaller than 16) then they compare directly.
If both TID1 and TID2 are in the circular part then TID2 is
greater than TID1 if (TID2 - TID1) is smaller than (TID1 - TID2).
A TID value is consistent with the preceeding one if it is a small
increment or decrement (more or less 16) from it. During normal
operations, the TIDs saved in the white board entry should be
consistent. As long as a TID is consistent with the previous one, it
appears that the new message is coming from the same source as the
previous one and there is no OII collision. If the TID is a small
decrement then the registration messages crossed and that message
should be ignored, but still there's no collision.
If the TID jumps to a low value in the lollypop this can be
interpreted as either a new node competing for the OII and a reboot
by the node owning the registration. With this specification, this
situation is optimistically interpreted as a reboot and not reported
as a collision, but an actual collision will be detected and filtered
out next.
Otherwise, if an inconsistent TID value is detected between the new
TID and the most recently accepted value, then the edge router
compares with the older TID values that are saved in the whiteboard
entry for that registration. This might occur for instance with an
entry that was rendered non-operational when the address was taken
over by another edge router.
If the new value is consistent with a recent value then it appears
that 2 sources are competing for the same OII and an OII collision
should be logged. In that case the greater TID wins, that is if the
new TID is greater than the previous one it is accepted, otherwise it
is reported as a collision.
If the new value is not consistent with a recent value saved in the
whiteboard entry then it is rejected as a collision.
8.6. Fault tolerance
This specification allows for a secondary registration. The
secondary registration enables the node to prepare states within the
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network and make the move quicker between primary and secondary.
If an external keep alive mechanism is in place between the primary
and the secondary edge routers, then the secondary registration
enables the secondary edge router to start intercepting packets on
the backbone and forwarding them to the node before the node even
knows that the primary is no longer operational.
The secondary registration also enables the node to bicast a packet
for extra reliability, that is send a copy of a packet to both edge
routers without being subject to ingress filtering. The mechanism
that enables this filtering is not specified here.
9. Ad-hoc LoWPAN Operation
LoWPAN networks by nature may often work in an ad-hoc fasion.
Neighbor Discovery for 6LoWPAN may still be applied in such ad-hoc
networks. If a router in the LoWPAN implements the Edge Router
whiteboard functionality, then ND for 6LoWPAN can be applied in
routers and nodes as specified in this document. The election of
such an edge router in an ad-hoc network is not specified here. The
Edge Router does not implement forwarding or backbone features, and
must generate a prefix to advertise.
If no Edge Router is available in the LoWPAN, then the whiteboard
features specified in this draft are unavailable. The nodes in the
LoWPAN SHOULD however continue to operate using SAA optimistic
addresses after timing out on Router Registrations.
10. Message Examples
This section provides basic examples of messages and options from
this document.
10.1. Basic RR/RC message exchange
In the basic case, when a host wanting to register to the whiteboard
is on the same link with an Edge Router, a simple RR/RC message
exchange occurs. In this example a host wants to register its
address generated with SAA, and in addition requests a generated
short address.
First the Host sends an RR message to the Edge Router or to the
6LOWPAN_ER Anycast address. In this example the host wants to use
the Edge Router as primary, uses a 600s lifetime, and its EUI-64 as
the Owner Interface Indentifier. The message has two Address
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Options. The host has just booted, therefore the TID starts with 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 = TBD | Code = 0 | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TID = 0 | Status = 0 |1| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Lifetime = 600 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Owner Interface Identifier = +
| EUI-64 of the interface |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 13: Basic RR 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 = TBD | Length = 1 | Status = 0 | P=2 | S=1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0|0|0| Reserved | Padding = 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 14: Address Option 1, for the SAA address.
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 = TBD | Length = 1 | Status = 0 | P=2 | S=3 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0|1|0| Reserved | Padding = 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 15: Address Option 2, for the requested address.
10.2. Relayed RR/RCC message exchange
In case an Edge Router is not on-link, then the RR message from the
previous example is sent to any on-link Router in exactly the same
format. This Router in turn relays the message to an Edge Router.
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As the OII of the Host is the same as its IID, the Router simply sets
Code = 1 to indicate that the message was relayed. The destination
IPv6 address is that of an Edge Router or the 6LOWPAN_ER Anycast
address and the source IPv6 address that of the relaying router. The
Address Options are not modified.
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 = TBD | Code = 1 | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TID = 0 | Status = 0 |1| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Lifetime = 600 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Owner Interface Identifier = +
| EUI-64 of the interface |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 16: Relayed RR message.
10.3. Router advertisement
Routers and Edge Routers in LoWPAN networks periodically send RA
messages. In the following example is of an RA message sent by a
Router. The only difference if an Edge Router would send the message
is that the Preference flag would be 01 for high.
In the example the M flag is set to indicate that generated addresses
are available, the Preference flag is 00 for normal, and a 1200s
Route Lifetime is advertised. A 6LoWPAN Prefix Information Option is
included.
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 = 134 | Code = 0 | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cur Hop Limit |1|0|0|00 |Rsrvd| Router Lifetime = 1200 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reachable Time = 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Retrans Timer = 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Figure 17: RA message example.
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 = TBD | Length = 2 | PL = 60 |0|1| CID=0 | r |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Valid Lifetime = 3000 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. Prefix = 2001:DB8::/60 .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 18: 6LoWPAN Prefix Information Option example.
11. Security Considerations
This specification expects that the link layer is sufficiently
protected, either by means of physical or IP security for the
backbone link or MAC sublayer cryptography. In particular, it is
expected that the LoWPAN MAC provides secure unicast to/from Routers
and secure broadcast from the Routers in a way that prevents
tempering with or replaying the RA messages. However, any future
6LoWPAN security protocol that applies to Neighbor Discovery for
6LoWPAN protocol, is out of scope of this document.
The use of EUI-64 for forming the Interface ID in the link local
address prevents the usage of Secure ND ([RFC3971] and [RFC3972]) and
address privacy techniques. Considering the envisioned deployments
and the MAC layer security applied, this is not considered an issue
at this time.
12. IANA Considerations
This document requires two new ICMPv6 message types:
Router Registration (TBD1)
Router Confirmation (TBD2)
The document also requires four new ND option types under the
subregistry "IPv6 Neighbor Discovery Option Formats":
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Address Option (TBD3)
6LoWPAN Prefix Information Option (TBD4)
Multihop Information Option (TBD5)
Owner Interface Identifier Option (TBD6)
[TO BE REMOVED: This registration should take place at the following
location: http://www.iana.org/assignments/icmpv6-parameters]
There is also the need for a new link local anycast address,
6LOWPAN_ER for 6LoWPAN Edge Routers and Routers; used as a functional
address.
[TO BE REMOVED: This registration should take place at the following
location: http://www.iana.org/assignments/ipv6-anycast-addresses]
13. Acknowledgments
The authors thank Carsten Bormann, Geoff Mulligan and Julien Abeille
for useful discussions and comments that have helped shaped and
improve this document.
14. References
14.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.
[RFC2491] Armitage, G., Schulter, P., Jork, M., and G. Harter, "IPv6
over Non-Broadcast Multiple Access (NBMA) networks",
RFC 2491, January 1999.
[RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
in IPv6", RFC 3775, June 2004.
[RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and
More-Specific Routes", RFC 4191, November 2005.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006.
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[RFC4429] Moore, N., "Optimistic Duplicate Address Detection (DAD)
for IPv6", RFC 4429, April 2006.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
September 2007.
[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", RFC 4862, September 2007.
[RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler,
"Transmission of IPv6 Packets over IEEE 802.15.4
Networks", RFC 4944, September 2007.
14.2. Informative References
[I-D.ietf-6lowpan-hc]
Hui, J. and P. Thubert, "Compression Format for IPv6
Datagrams in 6LoWPAN Networks", draft-ietf-6lowpan-hc-04
(work in progress), December 2008.
[I-D.van-beijnum-multi-mtu]
Beijnum, I., "Extensions for Multi-MTU Subnets",
draft-van-beijnum-multi-mtu-02 (work in progress),
February 2008.
[RFC2022] Armitage, G., "Support for Multicast over UNI 3.0/3.1
based ATM Networks", RFC 2022, November 1996.
[RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure
Neighbor Discovery (SEND)", RFC 3971, March 2005.
[RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)",
RFC 3972, March 2005.
[RFC4389] Thaler, D., Talwar, M., and C. Patel, "Neighbor Discovery
Proxies (ND Proxy)", RFC 4389, April 2006.
[RFC4903] Thaler, D., "Multi-Link Subnet Issues", RFC 4903,
June 2007.
[RFC4919] Kushalnagar, N., Montenegro, G., and C. Schumacher, "IPv6
over Low-Power Wireless Personal Area Networks (6LoWPANs):
Overview, Assumptions, Problem Statement, and Goals",
RFC 4919, August 2007.
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Authors' Addresses
Zach Shelby (editor)
Sensinode
Kidekuja 2
Vuokatti 88600
FINLAND
Phone: +358407796297
Email: zach@sensinode.com
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
Jonathan W. Hui
Arch Rock Corporation
501 2nd St. Ste. 410
San Francisco, California 94107
USA
Phone: +415 692 0828
Email: jhui@archrock.com
Samita Chakrabarti
IP Infusion
1188 Arquest Street
Sunnyvale, California
USA
Phone:
Email: samitac@ipinfusion.com
Shelby, et al. Expires August 27, 2009 [Page 45]
Internet-Draft Neighbor Discovery for 6LoWPAN February 2009
Erik Nordmark
Sun Microsystems, Inc.
17 Network Circle
Menlo Park, California 94025
USA
Phone:
Email: Erik.Nordmark@Sun.COM
Shelby, et al. Expires August 27, 2009 [Page 46]
