One document matched: draft-ietf-6lowpan-routing-requirements-01.xml
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<!DOCTYPE rfc SYSTEM "rfc2629.dtd" [
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<!ENTITY RFC4919 PUBLIC "" "http://xml.resource.org/public/rfc/bibxml/reference.RFC.4919.xml">
]>
<!-- IPR changed, Mar 5,2009 -->
<rfc ipr="trust200902" docName="draft-ietf-6lowpan-routing-requirements-01">
<?rfc toc="yes"?>
<?rfc sortrefs="yes"?>
<?rfc symrefs="no" ?>
<front>
<title abbrev="6LoWPAN Routing Requirements">
Problem Statement and Requirements for 6LoWPAN Routing
</title>
<author initials="E." surname="Kim" fullname="Eunsook Eunah Kim">
<organization>ETRI</organization>
<address>
<postal>
<street>161 Gajeong-dong</street>
<street>Yuseong-gu</street>
<city>Daejeon</city>
<code>305-700</code>
<country>Korea</country>
</postal>
<phone>+82-42-860-6124</phone>
<email>eunah.ietf@gmail.com</email>
</address>
</author>
<author initials="D." surname="Kaspar" fullname="Dominik Kaspar">
<organization>Simula Research Laboratory</organization>
<address>
<postal>
<street>Martin Linges v 17</street>
<city>Snaroya</city>
<code>1367</code>
<country>Norway</country>
</postal>
<phone>+47-6782-8223</phone>
<email>dokaspar.ietf@gmail.com</email>
</address>
</author>
<author initials="C." surname="Gomez" fullname="Carles Gomez">
<organization>Tech. Univ. of Catalonia/i2CAT</organization>
<address>
<postal>
<street>Escola Politecnica Superior de Castelldefels</street>
<street>Avda. del Canal Olimpic, 15</street>
<city>Castelldefels</city>
<code>08860</code>
<country>Spain</country>
</postal>
<phone>+34-93-413-7206</phone>
<email>carlesgo@entel.upc.edu</email>
</address>
</author>
<author initials="C." surname="Bormann" fullname="Carsten Bormann">
<organization>Universität Bremen TZI</organization>
<address>
<postal>
<street>Postfach 330440</street>
<city>Bremen</city>
<code>D-28359</code>
<country>Germany</country>
</postal>
<phone>+49-421-218-63921</phone>
<facsimile>+49-421-218-7000</facsimile>
<email>cabo@tzi.org</email>
</address>
</author>
<date year="2009" />
<area>General</area>
<workgroup>6LoWPAN Working Group</workgroup>
<keyword>Internet-Draft</keyword>
<abstract>
<t>
This document provides the problem statement for 6LoWPAN routing.
It also defines the requirements for 6LoWPAN routing considering
IEEE 802.15.4 specificities and the low-power characteristics of the network
and its devices.
</t>
</abstract>
</front>
<middle>
<section anchor="problems" title="Problem Statement">
<t>
In the context of this document, low-power wireless personal area networks
(LoWPANs) are formed by devices that are compatible with the IEEE 802.15.4
standard <xref target="refs.IEEE802.15.4"/>. Most of the LoWPAN devices
are distinguished by their low bandwidth, short range, scarce memory
capacity, limited processing capability and other attributes of
inexpensive hardware. The characteristics of nodes
participating in LoWPANs are assumed to be those described in RFC 4919 <xref target="RFC4919"/>.
</t>
<t>
IEEE 802.15.4 networks support star and mesh topologies.
However, neither the IEEE 802.15.4 standard nor the 6LoWPAN format
specification ("IPv6 over IEEE 802.15.4" <xref target="RFC4944"/>) define
how mesh topologies could be obtained and maintained. Thus, the 6LoWPAN
formation and multi-hop routing should be supported by higher layers,
either the 6LoWPAN adaptation layer or the IP layer. A number
of IP routing protocols have been developed in various
IETF working groups. However, these existing routing protocols may not
satisfy the requirements of multi-hop routing in 6LoWPANs, for the following
reasons:
<list style="symbols">
<!--t>
6LoWPAN nodes have special types and roles, such as primary battery-operated RFDs,
battery-operated and mains-powered FFDs,
possibly various levels of RFDs and FFDs, mains-powered and high-performance gateways, data aggregators, etc. 6LoWPAN
routing protocols should support multiple device types and roles.
</t-->
<t> <!-- Eunah's proposal to change the above paragraph. Feb. 17, 2009 -->
6LoWPAN nodes have special types and roles, such as primary battery-operated nodes,
power-affluent nodes, mains-powered and high-performance gateways,
data aggregators, etc. 6LoWPAN routing protocols should support multiple device types
and roles.
</t>
<t>
The more stringent requirements apply to LoWPANs, as opposed
to higher performance or non-battery-operated networks. <!--may not suffice.-->
6LoWPAN nodes are characterized by small memory sizes,
low processing power, and are running on very limited power supplied
by primary non-rechargeable batteries (a few KBytes of RAM,
a few dozens of KBytes of ROM/flash memory, and a few MHz of CPU is
typical). A node's lifetime is usually defined by the lifetime of
its battery.
</t>
<t>
Handling sleeping nodes is very critical in LoWPANs, more than in
traditional ad-hoc networks. LoWPAN nodes might stay in sleep-mode
for most of the time. Time synchronization is important for efficient
forwarding of packets.
</t>
<t> <!-- Eunah deleted ND example in(as imply.. ), as ND has been changed. feb. 17, 2009 -->
Routing in 6LoWPANs might possibly translate to a simpler problem
than routing in higher-performance networks. LoWPANs might be either
transit networks or stub networks. Under the assumption that LoWPANs
are never transit networks (as implied by <xref target="RFC4944"/>),
routing protocols may be
drastically simplified. This document will primarily focus on stub
networks. Based on the necessity, this document may be extended
with 6LoWPAN network configurations that include transit networks.
</t>
<t>
Routing in LoWPANs might possibly translate to a harder problem
than routing in higher-performance networks. Routing in LoWPANs
requires power-optimization, stable operation in harsh environments,
data-aware routing, etc. These requirements are not easily
satisfiable all at once.
</t>
</list>
This creates new challenges on obtaining robust and reliable routing within LoWPANs.
</t>
<t>
The 6LoWPAN problem statement document ("6LoWPAN Problems and Goals" <xref target="RFC4919"/>)
briefly mentions four requirements on routing protocols;
<list>
<t>(a) low overhead on data packets</t>
<t>(b) low routing overhead</t>
<t>(c) minimal memory and computation requirements</t>
<t>(d) support for sleeping nodes considering battery saving</t>
</list>
<!-- eunah deleted 'only low overhead and energy saving' from the first sentence. feb. 17,2009-->
These four high-level requirements describe the basic need for 6LoWPAN routing.
Based on the fundamental features of 6LoWPAN, more detailed routing requirements
are presented in this document,
which can lead to further analysis and protocol design.
</t>
<t>
Using the 6LoWPAN header format <xref target="RFC4944"/>, there are two layers
routing protocols can be defined at, commonly referred to
as "Mesh Under" and "Route Over". The Mesh Under approach supports routing under the IP link
and is directly based on the link-layer IEEE 802.15.4 standard in 6LoWPAN,
therefore using (64-bit or 16-bit short) MAC addresses. On the other hand,
the Route Over approach relies on IP routing and therefore supports
routing over possibly various types of interconnected links
(see also <xref target="NetworkStack"/>). Most statements in this document consider
both the Mesh Under and Route Over cases.
<vspace/>
<!-- Eunah proposes changes, feb 17, 2009>
[Note] The ROLL WG is now working on the protocol survey for Low power
and Lossy Networks (LLNs), not specifically for 6LoWPAN.
After that survey, it will be decided whether new solutions will be
developed or not. This document is focused on 6LoWPAN specific requirements,
in alignment with the ROLL WG.
<-- Eunah's proposal-->
Note: The ROLL WG is now working on Route Over approaches for Low power
and Lossy Networks (LLNs), not specifically for 6LoWPAN.
This document is focused on 6LoWPAN-specific requirements,
in alignment with the ROLL WG.
</t>
<t>
Considering the problems above, detailed 6LoWPAN routing requirements
must be defined. Application-specific features affect the design of
6LoWPAN routing requirements and the corresponding solutions.
However, various applications can be profiled by similar technical
characteristics, although the related detailed requirements might differ
(e.g., a few dozens of nodes for home lighting system need appropriate
scalability for the applications, while billions of nodes for a
highway infrastructure system also need appropriate scalability).
This document states the routing requirements of 6LoWPAN applications
in general, while trying to give examples for different cases of routing.
This routing requirements document does not imply that a single
routing solution may be the best one for all 6LoWPAN applications.
</t>
</section><!-- end of Chapter 1:problem statement-->
<!-- ----------------------------------------------->
<!-------------------------------------------------->
<section anchor="terminology" title="Terminology">
<t>
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 <xref target="RFC2119"/>.
</t>
<t>
Readers are expected to be familiar with all the terms and concepts
that are discussed in <xref target="RFC4919">"IPv6 over Low-Power
Wireless Personal Area Networks (6LoWPANs): Overview, Assumptions,
Problem Statement, and Goals"</xref>, and
<xref target="RFC4944">" Transmission of IPv6 Packets over IEEE 802.15.4 Networks"</xref>.
</t>
<t>
This document defines additional terms:
<list style="hanging">
<t hangText="LoWPAN Coordinator Node"></t>
<t>
A logical functional entity that performs the special role of coordinating its child nodes
for local data aggregation, status management of local nodes, etc.
Thus, the Coordinator Node does not need to coincide with a link-layer PAN coordinator
and there may be multiple instance in a LoWPAN. <!-- DK090305 -->
</t>
<t hangText="LoWPAN Mesh Node"></t>
<t>
A LoWPAN node that forwards data between arbitary source-destination pairs
in 6LoWPAN adaptation layer using link address (and thus only exist in Mesh Under LoWPANs).
A Mesh Node may also serve as a LoWPAN Host.
</t>
</list>
</t>
<t>
Additionally, in alignment with all other 6LoWPAN drafts, this document uses the same
terms and definitions as provided by the 6LoWPAN ND draft <xref target="refs.6lowpan.nd"/>:
<!-- ?rfc include='../6lowpan/6lowpan-terminology.xml'?-->
<list style="hanging">
<t hangText="LoWPAN Host"></t>
<t>A node that only sources or sinks IPv6
datagrams. Referred to as a host in this document. The term
node (see LoWPAN Node) is used when the the differentiation between host and router
is not important.</t>
<t hangText="LoWPAN Edge Router"></t>
<t>An IPv6 router that interconnects the LoWPAN to another network. Referred to as an edge router in this document.
</t>
<t hangText="LoWPAN Router"></t>
<t>A node that forwards datagrams between arbitrary source-destination pairs using a single
6LoWPAN interface performing IP routing (and thus only exist in route over LoWPANs).
A LoWPAN Router may also serve as a LoWPAN Host - both sourcing and sinking IPv6
datagrams. Refered to as a router in 6LoWPAN documents. All LoWPAN Routers
perform ND message relay on behalf of other nodes.
</t>
<t hangText="LoWPAN Node"></t>
<t>A node that composes a LoWPAN.
In mesh under, each intermidiate node performs multi-hop forwarding at L2.
In route over, each intermidiate node serves as a LoWPAN router performing IP routing.
</t>
<t hangText="Mesh Under"></t>
<t>A LoWPAN configuration where the link-local
scope is defined by the boundaries of the LoWPAN and
includes all nodes within. Forwarding and multihop routing functions are achieved at L2
between mesh nodes.
</t>
<t hangText="Route Over"></t>
<t>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.
</t>
<t hangText="Backbone Link"></t>
<t>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.
</t>
<t hangText="Extended LoWPAN"></t>
<t>This is the aggregation of multiple LoWPANs as defined in
<xref target="RFC4919"/> interconnected
by a backbone link via Edge Routers and forming a single subnet.
</t>
<t hangText="LoWPAN Link"></t>
<t>
A low-power wireless link which is shared by a link-local scope in a LoWPAN.
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 in a route over LoWPAN, or the set of nodes currently reachable in an L2 mesh
in a mesh under LoWPAN. Such a set may vary from one packet to the next as the
nodes move or as the radio propagation conditions change.
</t>
<t hangText="LoWPAN Subnet"></t>
<t>A subnet including a LoWPAN or an Extended LoWPAN, together with the backbone link with
the same subnet prefix and prefix length.
</t>
</list>
</t>
</section> <!-- end of terminology definitions -->
<!-------------------------------------------------->
<!-------------------------------------------------->
<section title="Design Space">
<t>
Apart from a wide variety of routing algorithms possible for 6LoWPAN,
the question remains as to whether routing should be performed Mesh Under
(in the adaptation layer defined by the 6lowpan format document <xref target="RFC4944"/>), or
by the IP-layer using a Route Over approach.
<!-- text modification to meet Alex question
The most significant consequence of mesh-under routing is that routing would
be directly based on the IEEE 802.15.4 standard, <-->
The most significant consequence of Mesh Under routing is that
the inherited stringent characteristics of IEEE 802.15.4 would directly affect
the 6LoWPAN routing mechanisms,
<!-- suggested changes until here-->
therefore using (64-bit or 16-bit short) MAC addresses instead of IP
addresses, and a 6LoWPAN would be seen as a single IP link.
In case a Route Over mechanism is to be applied to a 6LoWPAN it
must also support 6LoWPAN's unique properties using global IPv6 addressing.
</t>
<figure anchor='NetworkStack' title="Mesh-under (left) and route-over routing (right)">
<preamble>
<xref target="NetworkStack"/> shows the place of 6LoWPAN routing in the entire network stack.
</preamble>
<artwork>
+-----------------------------+ +-----------------------------+
| Application Layer | | Application Layer |
+-----------------------------+ +-----------------------------+
| Transport Layer (TCP/UDP) | | Transport Layer (TCP/UDP) |
+-----------------------------+ +-----------------------------+
| Network Layer (IPv6) | | Network +---------+ |
+-----------------------------+ | Layer | Routing | |
| 6LoWPAN +---------+ | | (IPv6) +---------+ |
| Adaptation | Routing | | +-----------------------------+
| Layer +---------+ | | 6LoWPAN Adaptation Layer |
+-----------------------------+ +-----------------------------+
| IEEE 802.15.4 (MAC) | | IEEE 802.15.4 (MAC) |
+-----------------------------+ +-----------------------------+
| IEEE 802.15.4 (PHY) | | IEEE 802.15.4 (PHY) |
+-----------------------------+ +-----------------------------+
</artwork>
<postamble/>
</figure>
<t>
In order to avoid packet fragmentation and the overhead for reassembly,
routing packets should fit into a single IEEE 802.15.4 physical frame
and application data should not be expanded to an extent that they
no longer fit.
</t>
<!---------------------------------->
<section title="6LoWPAN Headers for Routing">
<!-- Eunah on Mar.4 -->
<t>
In the simplest case for a Mesh Under where predefined layer two forwarding is appropriate,
the mesh-header defined in RFC 4944 <xref target="RFC4944"/> is sufficient.
Frame Delivery in a Link-Layer Mesh is described in the Section 11 in RFC 4944.
The mesh type and header defined in RFC 4944 are as follows:
</t>
<!-- eunah added on Mar. 4-->
<figure anchor='6LoWPANmesh' title="6LoWPAN Mesh Header">
<preamble>A 6LoWPAN Mesh Header:</preamble>
<artwork>
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1 0|V|F|HopsLft| originator address, final address
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
</artwork><postamble/>
</figure>
<!-- -->
<t>
However, the mesh header is not sufficient when it needs full
routing functionalities applying more routing metrics and functions.
If a Mesh Under routing protocol is built for operation in 6LoWPAN's
adaptation layer, routing control packets with MAC addresses are placed after the
6LoWPAN Dispatch. A new Dispatch value is REQUIRED to be assigned for Mesh Under routing.
As shown in <xref target="6LoWPANMeshRoutingHeader"/>,
multiple routing protocols can be supported by the usage of different
Dispatch bit sequences.
</t>
<!-- Eunah inserts this figure on feb. 17,2009 -->
<figure anchor='6LoWPANMeshRoutingHeader' title="6LoWPAN packet format and Mesh Under routing">
<preamble>A 6LoWPAN encapsulated Mesh Under Routing packet:</preamble>
<artwork>
+---------------------+----------------+---------+----
| Dispatch (new val.) | Routing header | ...
+---------------------+----------------+---------+----
</artwork><postamble/>
</figure>
<!-- give ur opinion on this figure-. if it's better to insert or not -->
<t>
<!-- please check the text change , eunah on feb.17,2009-->
When a Route Over protocol is built over the IPv6 layer, the Dispatch value
can be chosen as one of the Dispatch patterns for 6LoWPAN, followed by a compressed
or uncompressed IPv6 header, and Route Over routing header will be included in the payload of IPv6 packet.
</t>
<!-- Eunah inserts this figure on feb. 17,2009 -->
<figure anchor='6LoWPAN-HC1RouteOverHeader' title="6LoWPAN HC1 packet format and Route Over routing">
<preamble>
<xref target="6LoWPAN-HC1RouteOverHeader"/> depicts an example of
6LoWPAN encapsulated Route Over routing packets for HC1 defined in RFC 4944:</preamble>
<artwork>
+----------------+-------------+------------------------+---
| Dispatch + HC1 | IPv6 Header | Payload(Routing packet)| ...
+----------------+-------------+------------------------+---
</artwork><postamble/>
</figure>
<figure anchor='6LoWPAN-IPHCRouteOverHeader' title="6LoWPAN IPHC packet format and Route Over routing">
<preamble>
<xref target="6LoWPAN-HC1RouteOverHeader"/> depicts an example of
6LoWPAN encapsulated Route Over routing packets for IPHC defined in
the ongoing packet format work in 6LoWPAN <xref target="refs.6lowpan.IPHC"/>:</preamble>
<artwork>
+----------------------+-------------+------------------------+--
|Dispatch + LOWPAN_IPHC| IPv6 Header | Payload(Routing packet)|...
+----------------------+-------------+------------------------+--
</artwork><postamble/>
</figure>
<!-- give ur opinion on this figure-. if it's better to insert or not -->
</section>
<!------------------------------------->
<section title="Reference Network Model">
<t> <!--some text changes, feb 17,2009-->
When a 6LoWPAN follows the Mesh Under configuration,
the LoWPAN Edge Router (ER) is the only IPv6 router in the 6LoWPAN (see <xref target="6LoWPAN-mesh-conf"/>).
This means that the IPv6 link-local scope includes all nodes in the LoWPAN.
A Mesh Under routing mechanism MUST be provided to support multi-hop transmission.
</t>
<t>
If a Route Over routing is used in the stub-network, not only the ER but
also other intermediate nodes become LoWPAN Routers and perform standard layer 3 routing (see <xref target="6LoWPAN-rover-conf"/>).
The link-local scope is defined by one radio hop.
</t>
<figure anchor='6LoWPAN-mesh-conf' title="An example of a Mesh Under LoWPAN">
<preamble></preamble>
<artwork>
h h
/ | ER: Edge Router
ER --- m --- m --- h m: Mesh Node
/ \ h: LoWPAN Host
h m --- h
|
/ \
m - m -- h
</artwork>
</figure>
<figure anchor='6LoWPAN-rover-conf' title="An example of a Route Over LoWPAN">
<preamble></preamble>
<artwork>
h h
/ | ER: Edge Router
ER --- r --- r --- h r: LoWPAN Router
/ \ h: LoWPAN Host
h r --- h
|
/ \
r - r -- h
</artwork>
</figure>
<t>
When multiple 6LoWPANs are formed with globally unique IPv6 addresses
in the 6LoWPANs, and node (a) of 6LoWPAN [A] wants to communicate
with node (b) of 6LoWPAN [B], the normal IPv6 mechanisms can be employed.
For Mesh Under, there is one IP hop from a node (a) to ER of [A],
no matter how many radio hops stay apart from each other. This, of course, assumes
the existence of a Mesh Under routing protocol in order to reach the ER.
For Route Over, the IPv6 address of (b) is set as the destination of the packets, and
the nodes perform IP routing to the ER for these outgoing packets.
In this case, one radio hop is one IPv6 link.
Additionally, a default route to the ER could be inserted into the 6LoWPAN routing system.
</t>
</section>
</section> <!-- end of Chapter2:Design space-->
<!------------------------------------------------------------>
<!------------------------------------------------------------>
<!-- start of section 3.scenario and parameters -->
<section anchor="scenarios" title="Scenario Considerations and Parameters for 6LoWPAN Routing">
<t>
IP-based LoWPAN technology is still in its early stage of
development, but the range of conceivable usage scenarios is
tremendous. The numerous possible applications of sensor networks
make it obvious that mesh topologies will be prevalent in LoWPAN
environments and robust routing will be a necessity for expedient
communication. Research efforts in the area of sensor networking
have put forth a large variety of multi-hop routing algorithms
<xref target="refs.bulusu"/> and <xref target="refs.cctc"/>.
Most related work focuses on optimizing
routing for specific application scenarios, which can largely be categorized
into several models of communication, including the following ones:
<list style="symbols">
<!-- changes to meet Misha Dohler's comment , feb 17,2009>
<t>Flooding (in very small networks)</t>
<t>Data-aware routing (dissemination vs. gathering)</t>
<t>Event-driven vs. query-based routing</t>
<t>Geographic routing</t>
<t>Probabilistic routing</t>
<t>Hierarchical routing</t>
<-->
<t>Flooding (in very small networks)</t>
<t>Hierarchical routing</t>
<t>Geographic routing</t>
<t>Self-organizing coordinate routing</t>
</list>
Depending on the topology of a 6LoWPAN and the application(s) running over it,
different types of routing may be used. However, this document abstracts from
application-specific communication and describes general routing requirements
valid for overall routing in 6LoWPANs.
</t>
<t>
The following parameters can be used to describe specific scenarios
in which the candidate routing protocols could be evaluated.
</t>
<list style="letters">
<t>Network Properties:</t>
<list style="symbols">
<t>
Number of Devices, Density and Network Diameter: <vspace/>
These parameters usually affect the routing state directly
(e.g. the number of entries in a routing table or neighbor
list). Especially in large and dense networks, policies must
be applied for discarding "low-quality" and stale routing
entries in order to prevent memory overflow.
</t>
<t>
Connectivity: <vspace/>
Due to external factors or programmed disconnections, a 6LoWPAN
can be in several states of connectivity; anything in the
range from "always connected" to "rarely connected". This
poses great challenges to the dynamic discovery of routes
across a 6LoWPAN.
</t>
<t>
Dynamicity (including mobility): <vspace/>
Location changes can be induced by unpredictable external
factors or by controlled motion, which may in turn cause route
changes. Also, nodes may dynamically be introduced into a
6LoWPAN and removed from it later. The routing state and the
volume of control messages may heavily dependent on the number
of moving nodes in a LoWPAN and their speed.
</t>
<t>
Deployment: <vspace/>
In a 6LoWPAN, it is possible for nodes to be scattered randomly
or to be deployed in an organized manner. The deployment can
occur at once, or as an iterative process, which may also
affect the routing state.
</t>
<t>
Spatial Distribution of Nodes and Gateways: <vspace/>
Network connectivity depends on the spatial distribution of the nodes,
and on other factors like device number, density and transmission
range. For instance, nodes can be placed on a grid, or can be randomly placed in
an area (bidimensional Poisson distribution), etc.
In addition, if the 6LoWPAN is connected to other networks through
infrastructure nodes called gateways, the number and spatial
distribution of gateways affects network congestion and available
<!--bandwidth-->data rate<!-- Mischa Dohler's comment-->, among others.
</t>
<t>
Traffic Patterns, Topology and Applications: <vspace/>
The design of a LoWPAN and the requirements on its application
have a big impact on the network topology and the most efficient routing type to be
used. For different traffic patterns (point-to-point,
multipoint-to-point, point-to-multipoint) and network
architectures, various routing mechanisms have been
introduced, such as data-aware, event-driven, address-centric,
and geographic routing.
</t>
<t>
Classes of Service: <vspace/>
For mission-critical applications, support of multiple classes of
service may be required in resource-constrained LoWPANs and may
require a certain degree of routing protocol overhead.
</t>
<t>
Security: <vspace/>
LoWPANs may carry sensitive information and require a high
level of security support where the availability, integrity,
and confidentiality of data are primordial. Secured messages
cause overhead and affect the power consumption of LoWPAN
routing protocols.
</t>
</list> <!-- end of network parameters-->
<t>Node Parameters:</t>
<list style="symbols">
<t>
Processing Speed and Memory Size: <vspace/>
These basic parameters define the maximum size of the routing
state. LoWPAN nodes may have different performance
characteristics. <!-- suggesting to delete the following text ==> beyond the common RFD/FFD distinction -->
</t>
<t>
Power Consumption and Power Source: <vspace/>
The number and topology of battery- and mains-powered nodes in
a LoWPAN affect routing protocols in their selection of
optimal paths for network lifetime <!-- maximization--> optimization.
</t>
<t>
Transmission Range: <vspace/>
This parameter affects routing. For example, a
high transmission range may cause a dense network, which in
turn results in more direct neighbors of a node, higher
connectivity and a larger routing state.
</t>
<t>
Traffic Pattern:
This parameter affects routing since high-loaded nodes (either
because they are the source of packets to be transmitted or due
to forwarding) may incur a greater contribution to delivery
delays and may consume more energy than lightly loaded nodes.
This applies to both data packets and routing control messages.
</t>
</list> <!--end of node parameters-->
<t>Link Parameters:
<vspace/> <vspace/>
This section discusses link parameters that apply
to IEEE 802.15.4 legacy mode (i.e. not making use of improved schemes).
</t>
<list style="symbols">
<t>
Throughput:
<vspace/>
<vspace/>
The maximum user data throughput of a bulk data transmission between a single sender and
a single receiver through an unslotted IEEE 802.15.4 2.4 GHz channel in ideal conditions is
as follows <xref target="refs.Latre"/>:
<list style="symbols">
<t>16-bit MAC addresses, unreliable mode: 151.6 kbps </t>
<t>16-bit MAC addresses, reliable mode: 139.0 kbps </t>
<t>64-bit MAC addresses, unreliable mode: 135.6 kbps </t>
<t>64-bit MAC addresses, reliable mode: 124.4 kbps </t>
</list>
<vspace/>
<vspace/>
In the case of 915 MHz band:
<list style="symbols">
<t> 16-bit MAC addresses, unreliable mode: 31.1 kbps </t>
<t> 16-bit MAC addresses, reliable mode: 28.6 kbps </t>
<t> 64-bit MAC addresses, unreliable mode: 27.8 kbps </t>
<t> 64-bit MAC addresses, reliable mode: 25.6 kbps </t>
</list>
<vspace/>
<vspace/>
In the case of 868 MHz band:
<list style="symbols">
<t> 16-bit MAC addresses, unreliable mode: 15.5 kbps </t>
<t> 16-bit MAC addresses, reliable mode: 14.3 kbps </t>
<t> 64-bit MAC addresses, unreliable mode: 13.9 kbps </t>
<t> 64-bit MAC addresses, reliable mode: 12.8 kbps </t>
</list>
</t>
<t>
Latency: <vspace/>
The range of latencies of a frame transmission between a single sender and
a single receiver through an unslotted IEEE 802.15.4 2.4 GHz channel in ideal conditions
are as shown next <xref target="refs.Latre"/>. For unreliable mode, the actual latency is provided. For reliable mode,
the round-trip-time including transmission of a layer two acknowledgment is provided:
<list style="symbols">
<t> 16-bit MAC addresses, unreliable mode: [1.92 ms, 6.02 ms] </t>
<t> 16-bit MAC addresses, reliable mode: [2.46 ms, 6.56 ms] </t>
<t> 64-bit MAC addresses, unreliable mode: [2.75 ms, 6.02 ms] </t>
<t> 64-bit MAC addresses, reliable mode: [3.30 ms, 6.56 ms] </t>
</list>
<vspace/>
In the case of 915 MHz band:
<list style="symbols">
<t> 16-bit MAC addresses, unreliable mode: [5.85 ms, 29.35 ms] </t>
<t> 16-bit MAC addresses, reliable mode: [8.35 ms, 31.85 ms] </t>
<t> 64-bit MAC addresses, unreliable mode: [8.95 ms, 29.35 ms] </t>
<t> 64-bit MAC addresses, reliable mode: [11.45 ms, 31.85 ms] </t>
</list>
<vspace/>
In the case of 868 MHz band:
<list style="symbols">
<t> 16-bit MAC addresses, unreliable mode: [11.7 ms, 58.7 ms] </t>
<t> 16-bit MAC addresses, reliable mode: [16.7 ms, 63.7 ms] </t>
<t> 64-bit MAC addresses, unreliable mode: [17.9 ms, 58.7 ms] </t>
<t> 64-bit MAC addresses, reliable mode: [22.9 ms, 63.7 ms] </t>
</list>
</t>
</list> <!-- end of link parameters-->
</list> <!-- end of parameter list-->
</section> <!-- end of Chapter3: Scenarios and Parameters-->
<!-------------------------------------------------->
<!-------------------------------------------------->
<!-- start of section 4.routing requirements -->
<section anchor="Requirements" title="6LoWPAN Routing Requirements">
<t>
This section defines a list of requirements for 6LoWPAN routing. The
most important design property unique to low-power networks is that 6LoWPANs
have to support multiple device types and roles, for example:
<list style="symbols">
<t>primarily battery-operated host nodes (called "power-constrained nodes" in the following)</t>
<t>mains-powered host nodes (an example for what we call "power-affluent nodes")</t>
<t>power-affluent (but not necessarily mains-powered) high-performance gateway(s)</t>
<!-- <t>possibly various levels of nodes (data aggregators, relayers, etc.)</t> -->
<t>nodes with various functionality (data aggregators, relays, local manager/coordinators, etc.)</t>
</list>
<t>
Due to these unique device types and roles LoWPANs need to consider
the following two primary attributes:
</t>
<list style="symbols">
<t>
Power conservation: some devices are mains-powered, but most are
battery-operated and need to last several months to a few years
with a single AA battery. Many devices are mains-powered most of
the time, but still need to function for possibly extended periods
from batteries (e.g. on a construction site before building power
is switched on for the first time).
</t>
<t>
Low performance: tiny devices, small memory sizes, low-performance
processors, low bandwidth, high loss rates, etc.
</t>
</list>
These fundamental attributes of LoWPANs affect the design of routing
solutions, so that existing routing specifications should be
simplified and modified to the smallest extent possible when there are appropriate solutions to adapt,
otherwise, new solutions should be introduced in order to
fit the low-power requirements of LoWPANs, meeting the requirements
described in the following.
</t>
<!---------------------------------------->
<!-- start of Section 4.1: Device -->
<section anchor="reqs1" title="Support of 6LoWPAN Device Properties">
<t>
The general objectives listed in this section should be followed
by 6LoWPAN routing protocols. The importance of each requirement is
dependent on what node type the protocol is running on and what
the role of the node is. The following requirements are based on battery-powered LoWPAN nodes.
</t>
<t>
[R01] 6LoWPAN routing protocols SHOULD allow to be implemented with small code size
and require low routing state to fit the typical 6LoWPAN node capacity
(e.g., code size considering its typical flash memory size, and routing table less than 32 entries).
</t>
<list>
<t> <!-- R01: small code-->
A 6LoWPAN routing protocol solution should consider the limited memory size
typically starting at 4KB.
RAM size of LoWPAN nodes often ranges between 2KB and 10KB,
and program flash memory normally consists of 48KB to 128KB.
(e.g., in the current market, MICAz has 128KB program flash,
4KB EEPROM, 512KB external flash ROM; TIP700CM has 48KB program
flash, 10KB RAM, 1MB external flash ROM).
</t>
<t>
Due to these hardware restrictions, code length should be considered to
fit within a small memory size; no more than 48KB to 128KB of flash memory including
at least a few tens of KB of application code size.
A routing protocol of low complexity helps to achieve
the goal of reducing power consumption, improves robustness,
requires lower routing state, is easier to analyze, and may be
implicitly less prone to security attacks.
</t>
<t>
In addition, operation with low routing state (such as routing tables and neighbor lists)
SHOULD be maintained since some typical memory sizes preclude to store
state of a large number of nodes. For instance, industrial monitoring applications
need to support at maximum 20 hops <xref target="refs.roll.industry"/>.
Small networks can be designed to support a smaller number of hops.
It is highly dependent on the network architecture,
but considering the 6LoWPAN device properties, there should be at least one mode of operation that can
function with 32 forwarding entries or less.
</t>
</list> <!-- end of R01-->
<t> <!-- R02: minimal power -->
[R02] 6LoWPAN routing protocols SHOULD cause minimal power
consumption by the efficient use of control packets
(e.g., minimize expensive IP multicast which causes link broadcast to the entire
LoWPAN) and by the efficient routing of data packets.
</t>
<list>
<t>
One way of battery lifetime optimization is by achieving a minimal
control message overhead. Compared to functions such as
computational operations or taking sensor samples, radio communications
is by far the dominant factor of power consumption <xref target="refs.SmartDust"/>.
Power consumption of transmission and/or reception depends linearly
on the length of data units and on the frequency of transmission
and reception of the data units <xref target="refs.Shih"/>.
</t>
<t>
The energy consumption of two
example RF controllers for low-power nodes is shown in <xref target="refs.Hill"/>.
The TR1000 radio consumes 21mW when transmitting at 0.75mW,
and 15mW on reception (with a receiver sensitivity of -85dBm).
The CC1000 consumes 31.6mW when transmitting 0.75mW, and 20mW for receiving (with a receiver sensitivity
of -105dBm). The power continuation under the concept of
an idealized power source is explained in <xref target="refs.Hill"/>.
Based on the energy of an idealized AA battery,
the CC1000 can transmit for approximately 4 days straight or receive
for 9 consecutive days. Note that availability for reception consumes
power as well.
</t>
<t>
Multicast may causes flooding in the LoWPAN. On consideration this, 6LoWPAN routing
protocol SHOULD minimize the control cost by the routing packets.
Another document discusses control cost of routing protocols in low power and lossy networks <xref target="refs.roll.survey"/>.
</t>
</list> <!-- end of R03-->
</section> <!-- end of section 4.1 -->
<!-------------------------------------->
<!-- start of section 4.2 : Link -->
<section anchor="reqs2" title="Support of 6LoWPAN Link Properties">
<t>
6LoWPAN links have the characteristics of low <!--bandwidth --> data rate and possibly high loss rates.
The routing requirements described in this section are derived from
the link properties.
</t>
<t> <!-- R03: no fragmentation-->
<!-- Proposed text change , eunah, feb 17,2009>
[R03] 6LoWPAN routing protocol control messages SHOULD not create
fragmentation of physical layer (PHY) frames.</t>
<-->
[R03] 6LoWPAN routing protocol control messages SHOULD NOT exceed a single IEEE 802.15.4 frame size
in order to avoid packet fragmentation and the overhead for reassembly.
<!-- give ur opinion on this text changes. i think we need better wording..-->
</t>
<list>
<t>
In order to save energy, routing overhead should be minimized to
prevent fragmentation of frames.
Therefore, 6LoWPAN routing should not cause packets to exceed the
IEEE 802.15.4 frame size. This reduces the energy required for
transmission, avoids unnecessary waste of bandwidth, and prevents
the need for packet reassembly. As calculated in RFC4944
<xref target="RFC4944"/>, the maximum size of a 6LoWPAN frame,
in order not to cause fragmentation, is 81 octets.
This may imply the use of semantic fragmentation and/or algorithms
that can work on small increments of routing information.
</t>
</list> <!-- end of R03: no fragmentation-->
<t> <!-- start of R04: NEWLY added on Nov. 3, by EUNAH-->
[R04] The design of routing protocols for LoWPANs must consider the fact that
packets are to be delivered with sufficient probability according to application requirements.
</t>
<list>
<t>
Requirements on successful end-to-end packet delivery ratio
(where delivery may be bounded within certain latency) vary depending
on applications. In industrial applications, some non-critical monitoring
applications may tolerate successful delivery ratio of less than 90%
with hours of latency; in some other cases, a delivery ratio of 99.9%
is required <xref target="refs.roll.industry"/>. In building automation applications,
application layer errors must be below 0.01% <xref target="refs.roll.building"/>.
</t>
<t>
Successful end-to-end delivery of packets in a IEEE 802.15.4 mesh
depends on the quality of the path selected by the routing protocol and
on the ability of the routing protocol to cope with short-term and long-term quality variation.
The metric of the routing protocol strongly influences performance of
the routing protocol in terms of delivery ratio.
</t>
<t>
The quality of a given path depends on the individual qualities of the links
(including the devices) that compose that path. IEEE 802.15.4 settings affect
the quality perceived at upper layers. In particular, in IEEE 802.15.4 reliable mode,
if an acknowledgment frame is not received after a given period,
the originator retries frame transmission up to a maximum number of times.
If an acknowledgment frame is still not received by the sender
after performing the maximum number of transmission attempts,
the MAC layer assumes the transmission has failed and notifies the next
higher layer of the failure. Note that excessive retransmission may be detrimental,
see RFC 3819 <xref target="RFC3819"/>.
</t>
</list>
<t> <!-- start of R05: NEWLY added on Nov. 17 -->
[R05] The design of routing protocols for LoWPANs must consider the
<!-- deleted by Alex comment, Carles suggestion on it---end-to-end -->latency requirements of applications and IEEE 802.15.4 link latency characteristics.
</t>
<list>
<t>
Latency requirements may differ from a few hundreds milliseconds to minutes,
depending on the type of application.
Real-time building automation applications usually need response times
below 500 ms between egress and ingress, while
forced entry security alerts must be routed to one or more fixed or mobile user devices
within 5 seconds <xref target="refs.roll.building"/>.
Non-critical closed loop applications for industrial automation
have latency requirements that can be as low as 100 ms but many control loops are
tolerant of latencies above 1s <xref target="refs.roll.industry"/>. In contrast to this,
urban monitoring applications allow latencies smaller than the typical intervals used for
reporting sensed information; for instance, in the order of seconds to
minutes <xref target="refs.roll.urban"/>.
</t>
<t>
The range of latencies of a frame transmission between a single
sender and a single receiver through an ideal unslotted IEEE 802.15.4
2.4 GHz channel is between 2.46ms and 6.02ms in 64 bit MAC address
unreliable mode and 2.20 ms to 6.56ms in 64 bit address reliable
mode. The range of latencies of 868 MHz band is from 11.7 ms to
63.7 ms, depending on the address type and reliable/unreliable
mode used. Note that the latencies may be larger than that depending
on channel load, MAC layer settings <!-- deleted by Carles suggestion== that regulate medium access
procedure-->, and reliable/unreliable mode choice. <!-- deleted by carles suggestion == and nodes sleeping.-->
<!-- Carles inserted for -01 issue tracker #3 -->
Note that other MAC approaches than the legacy 802.15.4 may be used (e.g. TDMA).
Duty cycling may further affect latency (see [R08 ]).
</t>
<!-- t deleted by Carles suggeston for -01>
Some routing protocols are aware of the hop count of a path. This
parameter may be used as an input to select paths on an end-to-end latency basis if necessary.
</t -->
<t>
Note that a tradeoff exists between [R05] and [R04].
</t>
</list> <!-- end of R05-->
<t> <!-- start of R06-->
[R06] 6LoWPAN routing protocols SHOULD be robust to dynamic loss
caused by link failure or device unavailability either in short-term
(e.g. due to RSSI variation, interference variation, noise and asynchrony)
or in long-term (e.g. due to a depleted power source, hardware breakdown,
operating system misbehavior, etc).
</t>
<list>
<t>
An important trait of 6LoWPAN devices is their unreliability due to
limited system capabilities, and also because they might be closely
coupled to the physical world with all its unpredictable variation.
In harsh environments, LoWPANs easily suffer from
link failure. Collision or link failure easily increases Send
Queue/Receive Queue (SQ/RQ) and it can lead to queue overflow and
packet losses.
</t>
<t>
For home applications, where users expect feedback after carrying out actions
(such as handling a remote control while moving around),
routing protocols must converge
within 2 seconds if the destination node of the packet has moved
and must converge within 0.5 seconds if only the sender has moved <xref target="refs.roll.home"/>.
The tolerance of the recovery time can vary depending on the application,
however, the routing protocol must provide the detection of short-term unavailability
and long-term disappearance.
The routing protocol has to exploit network resources (e.g. path redundancy)
to offer good network behavior despite of node failure.
</t>
</list> <!-- end of R06-->
<t>
[R07] 6LoWPAN routing protocols SHOULD be designed to correctly operate in the presence of link asymmetry.
</t>
<list>
<t>
Link asymmetry occurs when the probability of successful transmission
between two nodes is significantly higher in one direction than in
the other one. This phenomenon has been reported in a large number of
experimental studies and it is expected that 6LoWPANs will exhibit
link asymmetry.
</t>
</list>
</section>
<!-- end of section 4.2: link -->
<!------------------------------------------->
<!-- start of section 4.3 : Network-->
<section anchor="reqs3" title="Support of 6LoWPAN Network Characteristics">
<t>
6LoWPANs can be deployed in different sizes and topologies,
adhere to various models of mobility, tolerate various levels of interference, etc.
In any case, LoWPANs must maintain low energy consumption.
The requirements described in the following subsection are derived
from the network attributes of 6LoWPANs.
</t>
<t> <!-- R08: sleep node-->
[R08] 6LoWPAN routing protocols SHOULD be reliable despite unresponsive nodes
due to periodic hibernation.
</t>
<list>
<t>
Many nodes in LoWPAN environments might periodically hibernate
(i.e. disable their transceiver activity) in order to save energy.
Therefore, routing protocols must ensure robust packet
delivery despite nodes frequently shutting off their radio
transmission interface. Feedback from the lower IEEE 802.15.4 layer may be considered
to enhance the power-awareness of 6LoWPAN routing protocols.
</t>
<t>
CC1000-based nodes must operate at a duty cycle
of approximately 2% to survive for one year from idealized AA battery power source
<xref target="refs.Hill"/>.
For home automation purposes, it is suggested that
that the devices have to maximize the sleep phase with a duty cycle lower
than 1% <xref target="refs.roll.home"/>, while in building automation applications,
batteries must be operational
for at least 5 years when the sensing devices are transmitting data (e.g. 64 bytes) once
per minute <xref target="refs.roll.building"/>.
</t>
<t>
Dependent on the application in use, packet rates differ from 1/sec to 1/day.
Routing protocols need to know the cycle of the packet transmission
and utilize the information to calculate routing paths.
</t>
</list> <!-- end of R08-->
<t> <!-- R09: metrics -->
[R09] The metric used by 6LoWPAN routing protocols MAY utilize
a combination of the inputs provided by the lower layers and other measures
to obtain the optimal path considering energy balance and link qualities.
</t>
<list>
<t>
In homes, buildings, or infrastructure, some nodes will be installed
with mains power. Such power-installed nodes MUST be considered
as a relay points for more roles in packet delivery.
6LoWPAN routing protocols MUST know the power constraints of the nodes.
</t>
<t>
Simple hop-count-only mechanisms may be inefficient in 6LoWPANs.
There is a Link Quality Indication (LQI), or/and RSSI from
IEEE 802.15.4 that may be taken into account for better metrics.
The metric to be used (and its goal) may depend on
applications and requirements.
</t>
<t>
The numbers in <xref target="LDR"/> represent the Link Delivery Ratio (LDR)
of each pair of nodes. There are studies that show a piecewise linear dependence between LQI and
LDR <xref target="refs.Chen"/>.
</t>
<figure anchor='LDR' title="An example network">
<preamble></preamble>
<artwork>
0.6
A-------C
\ /
0.9 \ / 0.9
\ /
B
</artwork>
</figure>
<t>
In this simple example, there are two options in routing from node A
to node C, with the following features:
</t>
<list style="letters">
<t>Path AC:</t>
<list style="symbols">
<t>(1/0.6) = 1.67 avg. transmissions needed for each packet</t>
<t>one-hop path</t>
<t>good in energy consumption and end-to-end latency of data packets, bad in delivery ratio (0.6)</t>
<t>bad in probability of route reconfigurations</t>
</list>
<t>Path ABC</t>
<list style="symbols">
<t>2*(1/0.81) = 2.47 avg. transmissions needed for each packet</t>
<t>two-hop path</t>
<t>bad in energy consumption and end-to-end latency of data packets, good in delivery ratio (0.81)</t>
</list>
</list>
<t>
If energy consumption of the network must be minimized,
path AC is the best (this path would be chosen based on a hop count
metric). However, if the delivery ratio in that case is not sufficient,
the best path is ABC (it would be chosen by an LQI based metric).
Combinations of both metrics can be used.
</t>
<t>
The metric also affects the probability of route reconfiguration.
Route reconfiguration, which may be triggered by packet losses,
may require transmission of routing protocol messages.
It is possible to use a metric aimed at selecting the path with low route
reconfiguration rate by using LQI as an input to the metric.
Such a path has good properties, including stability and low control message overhead.
</t>
</list> <!-- end of R09:metrics-->
<t> <!-- R10-->
[R10] 6LoWPAN routing protocols SHOULD be designed to achieve both
scalability from a few nodes to millions of nodes and minimality in terms of used system resources.
</t>
<list>
<t>
A LoWPAN may consist of just a couple of nodes (for instance in
a body-area network), but may expand to much higher numbers of
devices (e.g. monitoring of a city infrastructure or a highway).
For home automation applications it is envisioned that the routing protocol
must support 250 devices in the network <xref target="refs.roll.home"/>,
while routing protocols for metropolitan-scale sensor networks must be capable of clustering
a large number of sensing nodes into regions
containing on the order of 10^2 to 10^4 sensing nodes each <xref target="refs.roll.urban"/>.
It is therefore necessary that routing mechanisms are designed
to be scalable for operation in various network sizes. However,
due to a lack of memory size and computational power, 6LoWPAN
routing might limit forwarding entries to a small number, such
as at maximum 32 routing table entries.
</t>
</list> <!--end of R10-->
<t> <!--R11 -->
[R11] The procedure of route repair and related control messages
should not harm overall energy consumption from the routing protocols.
</t>
<list>
<t>
Local repair improves throughput and end-to-end latency, especially
in large networks. Since routes are repaired quickly, fewer data
packets are dropped, and a smaller number of routing protocol
packet transmissions are needed since routes can be repaired without
source initiated Route Discovery <xref target="refs.Lee"/>.
One important consideration here may be to avoid premature
depletion, even in case that impairs other requirements.
</t>
</list> <!-- end of R11-->
<t> <!-- R12-->
[R12] 6LoWPAN routing protocols SHOULD allow for dynamically adaptive
topologies and mobile nodes. When supporting dynamic topologies and
mobile nodes, route maintenance should keep in mind the goal of
a minimal routing state and routing protocol message overhead.
</t>
<list>
<t>
Building monitoring applications, for instance, require that the mobile devices
SHOULD be capable of leaving (handing-off) from an old network joining
onto a new network within 15 seconds <xref target="refs.roll.building"/>.
More interactive applications such as used in home automation systems, where users are giving input
and expect instant feedback, mobility requirements are also stricter and
a convergence time below 0.5 seconds is commonly required <xref target="refs.roll.home"/>.
In industrial environments, where mobile equipment such as cranes
move around, the support of vehicular speeds of up to 35 km/h are
required to be supported by the routing protocol <xref target="refs.roll.industry"/>.
Currently, 6LoWPANs are not being used for such a fast mobility,
but dynamic association and disassociation MUST be supported in 6LoWPAN.
</t>
<t>
There are several challenges that should be addressed by a 6LoWPAN
routing protocol in order to create robust routing in dynamic
environments:
<list style="symbols">
<t> Mobile nodes changing their location inside a LoWPAN:
<vspace/>
If the nodes' movement pattern is unknown, mobility cannot
easily be detected or distinguished by the routing protocols.
Mobile nodes can be treated as nodes that disappear and re-appear
in another place. Movement pattern tracking increases complexity and can be
avoided by handling moving nodes using reactive route updates.
</t>
<t> Movement of a LoWPAN with respect to other (inter)connected LoWPANs:
<vspace/>
Within stub networks, more powerful gateway nodes need to be
configured to handle moving LoWPANs.
</t>
<t> Nodes permanently joining or leaving the LoWPAN:
<vspace/>
In order to ease routing table updates, reduce their size, and minimize error
control messages, nodes leaving the network may announce their
disassociation to the closest edge router
<!-- eunah inserted the following . feb.18,2009 -->or if any, to a specific node which takes charge of
local association and disassociation.
</t>
</list> <!--end of symbol list-->
</t>
</list> <!-- end of R12-->
<t> <!-- R13: traffic pattern -->
[R13] 6LoWPAN routing protocol SHOULD support various traffic patterns;
point-to-point, point-to-multipoint, and multipoint-to-point,
while avoid excessive multicast traffic in a LoWPAN.
</t>
<list>
<t>
6LoWPANs often have point-to-multipoint or multipoint-to-point
traffic patterns. Many emerging applications include point-to-point
communication as well. 6LoWPAN routing protocols should
be designed with the consideration of forwarding packets from/to
multiple sources/destinations. Current WG drafts in the ROLL working group
explain that the workload or traffic pattern of use cases for
LoWPANs tend to be highly structured, unlike the any-to-any data
transfers that dominate typical client and server workloads. In many
cases, exploiting such structure may simplify difficult problems
arising from resource constraints or variation in connectivity.
</t>
</list> <!-- end of R13-->
</section>
<!-- end of section 4.3-->
<!------------------------------------------>
<!-- start of section :4.4 security -->
<section anchor="reqs4" title="Support of Security">
<t>
The routing requirement described in this subsection allows secure
transmission of routing messages. Solutions may take into account the
specific features of IEEE 802.15.4 MAC layers.
</t>
<t> <!-- R14: security-->
[R14] 6LoWPAN protocols SHOULD support secure delivery of control messages.
A minimal security level can be achieved by utilizing AES-based mechanism
provided by IEEE 802.15.4.
</t>
<list>
<t>
Security threats within LoWPANs may be different from existing
threat models in ad-hoc network environments. Neighbor Discovery
in IEEE 802.15.4 links may be susceptible to threats as listed in
RFC3756 <xref target="RFC3756"/>. Bootstrapping may also impose additional threats.
Security is also very important for designing robust routing
protocols, but it should not cause significant transmission
overhead. While there are applications which require very high security,
such as in traffic control, other applications are less easily harmed by
wrong node behavior, such as a home entertainment system.
</t>
<t>
The IEEE 802.15.4 MAC provides an AES-based security mechanism. Routing
protocols need to define how this mechanism can be used to obtain
the intended security. Byte overhead of the mechanism, which depends
on the security services selected, must be considered. In the worst
case in terms of overhead, the mechanism consumes 21 bytes of MAC
payload.
</t>
<t> <!-- This is inserted to resolve Issue Tracker #4. Suggested by Carles, Feb. 18.2009 -->
IEEE 802.15.4 does not specify protection for acknowledgement frames.
Since the sequence numbers of data frames are sent in the clear,
an adversary can forge an acknowledgement for each data frame.
This weakness can be combined with targeted jamming to prevent delivery of
selected packets. In consequence, IEEE 802.15.4 acknowledgements cannot be relied upon.
In applications that require high security, the routing protocol must not exploit
feedback from acknowledgements (e.g. to keep track of neighbor connectivity, see [R16]).
</t>
</list> <!-- end of R14 --->
</section>
<!-- end of section: 4.4 secuirty -->
<!---------------------------------------------->
<!-- start of section: 4.5 mesh-under -->
<section anchor="reqs5" title="Support of Mesh-under Forwarding">
<!-- The following text is deleted by Carles, Feb.18.2009 >
Reception of an acknowledgement after a frame transmission may
render unnecessary the transmission of explicit Hello messages, for example.
</t -->
<t> <!-- The following text is inserted instead of the above text -->
One LoWPAN may be built as one IPv6 link. In this case, Mesh Under
forwarding/routing mechanisms must be supported. The routing requirements
described in this subsection allow optimization and correct operation
of routing solutions taking into account the specific features of the mesh-under configuration.
</t>
<t>
[R15] In case a routing protocol operates in 6LoWPAN's adaptation layer,
routing tables and neighbor lists MUST support 16-bit short and
64-bit extended addresses.
</t>
<t>
[R16] In order to perform discovery and maintenance of neighbors, LoWPAN Nodes SHOULD avoid sending
"Hello" messages <!-- following text is inserted by Alex comment--> of NS, NA, RS or RA messages.
Instead, link-layer mechanisms (such as
acknowledgments) MAY be utilized to keep track of
active neighbors.
</t>
<list>
<t>
Reception of an acknowledgement after a frame transmission may render
unnecessary the transmission of explicit Hello messages, for example.
<!-- the following text is inserted by Carles, Feb. 18,2009-->
In a more general view, any frame received by a node may be used as an input
to evaluate the connectivity between the sender and receiver of that frame.
</t>
</list>
<t>
[R17] In case there are one or more nodes allocated <!--eunah changed, feb. 18, 2009-->for the
specific role of local management, the nodes MAY take the role of keeping track of node association and
de-association within the charging area of the LoWPAN.
</t>
<t>
[R18] If the routing protocol functionality includes enabling IP multicast,
then it may want to employ relay points of group-targeting messages instead
of using link-layer multicast (broadcast).
</t>
</section>
<!-- end of mesh-under req -->
</section>
<!-- end of Requirement section-->
<!-------------------------------------------->
<!-------------------------------------------->
<section title="Security Considerations">
<t>Security issues are described in Section 4.4. Security considerations
of RFC 4919 <xref target="RFC4919"/> and RFC 4944
<xref target="RFC4944"/> apply as well. More security considerations will result
from the 6LoWPAN security analysis work.
</t>
</section>
<section title="Acknowledgements">
<t>The authors thank Myung-Ki Shin for giving the idea of writing this draft.
The authors also thank to S. Chakrabarti who gave valuable comments for mesh-under requirements.</t>
</section>
</middle>
<back>
<references title='Normative References'>&RFC2119;&RFC3756;&RFC4919;&RFC4944;&RFC3819;
<reference anchor="refs.IEEE802.15.4">
<front>
<title>IEEE Std. 802.15.4-2006 (as amended)</title>
<author><organization>IEEE Computer Society</organization></author>
<date month="" year="2007"/>
</front>
</reference>
<!-- previously used references to IEEE 802.15.4 standard (before draft-dokaspar-6lowpan-routreq-07)
<reference anchor="refs.IEEE802.15.4">
<front>
<title>IEEE Std. 802.15.4-2003</title>
<author><organization>IEEE Computer Society</organization></author>
<date month="October" year="2003"/>
</front>
</reference>
<reference anchor="refs.IEEE802.15.4-2006">
<front>
<title>IEEE Std. 802.15.4-2006</title>
<author><organization>IEEE Computer Society</organization></author>
<date month="September" year="2006"/>
</front>
</reference>-->
</references>
<references title='Informative References'>
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<front>
<title>Wireless Sensor Networks</title>
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<date month="July" year="2005"/>
</front>
</reference>
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<front>
<title>LoWPAN Neighbor Discovery Extensions, draft-ietf-6lowpan-nd-01 (work in progress)</title>
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<author initials="P." surname="Thubert" fullname=""></author>
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<date month="February" year="2009"/>
</front>
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<date month="December" year="2008"/>
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</front>
</reference>
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<front>
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<front>
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<date month="July" year="2001"/>
</front>
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<front>
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</front>
</reference>
<reference anchor="refs.roll.home">
<front>
<title>Home Automation Routing Requirement in Low Power and Lossy Networks, draft-ietf-roll-home-routing-reqs-06 (work in progress)</title>
<author initials="A." surname="Brandt" fullname="Anders Brandt"></author>
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<date month="November" year="2008"/>
</front>
</reference>
<reference anchor="refs.roll.industry">
<front>
<title>Industrial Routing Requirements in Low Power and Lossy Networks, draft-ietf-roll-indus-routing-reqs-04 (work in progress)</title>
<author initials="K." surname="Pister" fullname="Kris Pister"></author>
<author initials="P." surname="Thubert" fullname="Pascal Thubert"></author>
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<date month="January" year="2009"/>
</front>
</reference>
<reference anchor="refs.roll.urban">
<front>
<title>Urban WSNs Routing Requirements in Low Power and Lossy Networks, draft-ietf-roll-urban-routing-reqs-03 (work in progress)</title>
<author initials="M." surname="Dohler" fullname="Mischa Dohler"></author>
<author initials="T." surname="Watteyne" fullname="Thomas Watteyne"></author>
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</front>
</reference>
<reference anchor="refs.roll.building">
<front>
<title> Building Automation Routing Requirements in Low Power and Lossy Networks, draft-ietf-roll-building-routing-reqs-05 (work in progress)</title>
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</front>
</reference>
<reference anchor="refs.roll.survey">
<front>
<title> Overview of Existing Routing Protocols for Low Power and Lossy Networks
, draft-ietf-roll-protocols-survey-06 (work in progress)</title>
<author initials="P." surname="Levis" fullname=""></author>
<author initials="A." surname="Tavakoli" fullname=""></author>
<author initials="S." surname="Dawson-Haggerty" fullname=""></author>
</front>
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<reference anchor="refs.Latre">
<front>
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<date month="May" year="2006"/>
</front>
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<front>
<title>Quantifying Organization by Means of Entropy</title>
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<date year="2008"/>
</front>
</reference>
</references>
</back>
</rfc>| PAFTECH AB 2003-2026 | 2026-04-24 01:37:09 |