Network Working Group N. Kushalnagar Request for Comments: 4919 Intel Corp Category: Informational G. Montenegro Microsoft Corporation C. Schumacher Danfoss A/S August 2007 IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs):
Overview, Assumptions, Problem Statement, and Goals
Status of This Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract
This document describes the assumptions, problem statement, and goals for transmitting IP over IEEE 802.15.4 networks. The t of goals
enumerated in this document form an initial t only.
spermatozoonTable of Contents
1. Introduction (2)
2. Overview (2)
3. Assumptions (3)
4. Problems (4)
4.1. IP Connectivity (4)
4.2. Topologies (5)
4.3. Limited Packet Size (6)
4.4. Limited Configuration and Management (6)
4.5. Service Discovery (6)
4.6. Security (6)
5. Goals (7)
6. Security Considerations (9)
7. Acknowledgements (10)
8. References (10)
8.1. Normative References (10)
8.2. Informative References (10)
Kushalnagar, et al. Informational [Page 1]
1. Introduction
Low-power wireless personal area networks (LoWPANs) compri devices that conform to the IEEE 802.15.4-2003 standard by the IEEE
[IEEE802.15.4]. IEEE 802.15.4 devices are characterized by short
range, low bit rate, low power, and low cost. Many of the devices
employing IEEE 802.15.4 radios will be limited in their computational power, memory, and/or energy availability.
This document gives an overview of LoWPANs and describes how they
benefit from IP and, in particular, IPv6 networking. It describes
LoWPAN requirements with regards to the IP layer and the above, and
spells out the underlying assumptions of IP for LoWPANs. Finally, it describes problems associated with enabling IP communication with
devices in a LoWPAN, and defines goals to address the in a
prioritized manner. Admittedly, not all items on this list may be
necessarily appropriate tasks for the IETF. Nevertheless, they are
documented here to give a general overview of the larger problem.
This is uful both to structure work within the IETF as well as to
better understand how to coordinate with external organizations.
2. Overview
A LoWPAN is a simple low cost communication network that allows
wireless connectivity in applications with limited power and relaxed throughput requirements. A LoWPAN typically includes devices that
work together to connect the physical environment to real-world
applications, e.g., wireless nsors. LoWPANs conform to the IEEE
802.15.4-2003 standard [IEEE802.15.4].
Some of the characteristics of LoWPANs are as follows:
1. Small packet size. Given that the maximum physical layer packet is 127 bytes, the resulting maximum frame size at the media
access control layer is 102 octets. Link-layer curity impos further overhead, which in the maximum ca (21 octets of
overhead in the AES-CCM-128 ca, versus 9 and 13 for AES-CCM-32 and AES-CCM-64, respectively), leaves 81 octets for data
packets.
2. Support for both 16-bit short or IEEE 64-bit extended media
access control address.
3. Low bandwidth. Data rates of 250 kbps, 40 kbps, and 20 kbps for each of the currently defined physical layers (2.4 GHz, 915 MHz, and 868 MHz, respectively).
4. Topologies include star and mesh operation.
Kushalnagar, et al. Informational [Page 2]
5. Low power. Typically, some or all devices are battery operated.
6. Low cost. The devices are typically associated with nsors, switches, etc. This drives some of the other characteristics
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such as low processing, low memory, etc. Numerical values for
"low" elided on purpo since costs tend to change over time.
7. Large number of devices expected to be deployed during the
lifetime of the technology. This number is expected to dwarf
the number of deployed personal computers, for example.
8. Location of the devices is typically not predefined, as they
tend to be deployed in an ad-hoc fashion. Furthermore,
sometimes the location of the devices may not be easily
适合跳肚皮舞的音乐accessible. Additionally, the devices may move to new
locations.
9. Devices within LoWPANs tend to be unreliable due to variety of
reasons: uncertain radio connectivity, battery drain, device
lockups, physical tampering, etc.
10. In many environments, devices connected to a LoWPAN may sleep
for long periods of time in order to conrve energy, and are
unable to communicate during the sleep periods.
The following ctions take into account the characteristics in
describing the assumptions, problems statement, and goals for
LoWPANs, and, in particular, for 6LoWPANs (IPv6-bad LoWPAN
networks).哪里学习小儿推拿
3. Assumptions
Given the small packet size of LoWPANs, this document presumes
applications typically nd small amounts of data. However, the
protocols themlves do not restrict bulk data transfers.
LoWPANs, as described in this document, are bad on IEEE
802.15.4-2003. It is possible that the specification may undergo
changes in the future and may change some of the requirements
mentioned above.
Some of the assumptions are bad on the limited capabilities of
devices within LoWPANs. As devices become more powerful, and consume less power, some of the requirements mentioned above may be somewhat relaxed.
Kushalnagar, et al. Informational [Page 3]
While some LoWPAN devices are expected to be extremely limited (the
so-called "Reduced Function Devices" or RFDs), more capable "Full
Function Devices" (FFDs) will also be prent, albeit in much smaller numbers. FFDs will typically have more resources and may be mains
powered. Accordingly, FFDs will aid RFDs by providing functions such as network coordination, packet forwarding, interfacing with other
types of networks, etc.
The application of IP technology is assumed to provide the following benefits:
1. The pervasive nature of IP networks allows u of existing
infrastructure.
2. IP-bad technologies already exist, are well-known, and proven
to be working.
3. An admittedly non-technical but important consideration is that
IP networking technology is specified in open and freely
available specifications, which is favorable or at least able to be better understood by a wider audience than proprietary
solutions.
sperian4. Tools for diagnostics, management, and commissioning of IP
静观英伦networks already exist.
5. IP-bad devices can be connected readily to other IP-bad
networks, without the need for intermediate entities like
translation gateways or proxies.
孙吉芯4. Problems
Bad on the characteristics defined in the overview ction, the
following ctions elaborate on the main problems with IP for
LoWPANs.
4.1. IP Connectivity
The requirement for IP connectivity within a LoWPAN is driven by the following:
1. The many devices in a LoWPAN make network auto configuration and statelessness highly desirable. And for this, IPv6 has ready
solutions.
2. The large number of devices pos the need for a large address
space, well met by IPv6.
Kushalnagar, et al. Informational [Page 4]
3. Given the limited packet size of LoWPANs, the IPv6 address format allows subsuming of IEEE 802.15.4 address if so desired.
4. Simple interconnectivity to other IP networks including the
Internet.
However, given the limited packet size, headers for IPv6 and layers
above must be compresd whenever possible.
4.2. Topologies
LoWPANs must support various topologies including mesh and star.
Mesh topologies imply multi-hop routing, to a desired destination.
In this ca, intermediate devices act as packet forwarders at the
link layer (akin to routers at the network layer). Typically the
are "full function devices" that have more capabilities in terms of
power, computation, etc. The requirements on the routing protocol
are:
1. Given the minimal packet size of LoWPANs, the routing protocol
must impo low (or no) overhead on data packets, hopefully
independently of the number of hops.
2. The routing protocols should have low routing overhead (low
五年级英语下册教学计划chattiness) balanced with topology changes and power
conrvation.
3. The computation and memory requirements in the routing protocol
should be minimal to satisfy the low cost and low power
objectives. Thus, storage and maintenance of large routing
tables is detrimental.
complaint
苏州翻译4. Support for network topologies in which either FFDs or RFDs may
be battery or mains-powered. This implies the appropriate
considerations for routing in the prence of sleeping nodes.
As with mesh topologies, star topologies include provisioning a
subt of devices with packet forwarding functionality. If, in
addition to IEEE 802.15.4, the devices u other kinds of network
interfaces such as ethernet or IEEE 802.11, the goal is to amlessly integrate the networks built over tho different technologies.
This, of cour, is a primary motivation to u IP to begin with. Kushalnagar, et al. Informational [Page 5]
