One document matched: draft-wu-convergence-internet-wsn-00.txt
Independent Submission Wu,Xu
Internet Draft CEDRI
Intended status: Informational July 31, 2010
Expires: January 2011
Convergence framework of Internet and WSN
draft-wu-convergence-internet-wsn-00.txt
Abstract
This Internet Draft provides a detailed description of the
convergence framework of Internet and WSN so far, including 4 main
solutions and 2 additional technologies. The main aim of this
document is to serve as a general reference for the convergence
solution space, to take advantage of the two networks the advantages
of diversity and meet the needs of network users. Furthermore, each
solution is analyzed based on a number of evaluation considerations.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
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This Internet-Draft will expire on January 31, 2009.
Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Internet-Draft WSN convergence framework July 2010
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Table of Contents
1. Introduction ................................................ 2
2. Conventions used in this document............................ 2
2.1. WSN .................................................... 2
2.2. DTN .................................................... 3
3. Proxy ....................................................... 3
4. Protocol Overlay ............................................ 4
5. Delay Tolerant Network....................................... 5
6. Full IP ..................................................... 6
7. Other technologies .......................................... 8
8. Security Considerations...................................... 8
9. IANA Considerations ......................................... 8
10. References ................................................. 8
10.1. Normative References................................... 8
10.2. Informative References................................. 9
11. Acknowledgments ............................................ 9
1. Introduction
With large-scale, integrated, flat Internet and small-scale, diverse,
mobile wireless sensor network, a converged network is coming into
existence, which is efficient, flexible and secure [1]. Network
adopting the integration of mutual collaboration and effective
management of resources and rational allocation can effectively
improve network throughput ,reduce the energy consumption of wireless
devices , reduce the information transmission delay, and provide
technical support for rapid decision-making; we can take advantage of
the two networks the advantages of diversity and meet the needs of
network users better, effectively improve network security, provide a
basis for the reliable platform for access to information and expand
the network coverage, so the network is more scalable.
2. Conventions used in this document
2.1. WSN
A wireless sensor network (WSN) consists of spatially distributed
autonomous sensors to cooperatively monitor physical or environmental
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conditions, such as temperature, sound, vibration, pressure, motion
or pollutants [2].
2.2. DTN
A disruption-tolerant network (DTN) is a network designed so that
temporary or intermittent communications problems, limitations and
anomalies have the least possible adverse impact.
3. Proxy
Proxy nodes between heterogeneous networks are mounted in this mode,
which can simultaneously implement WSN protocols and TCP / IP, and
translate protocols at the different levels. Communications between
Internet and WSN need the proxy. So a WSN can use different protocols
with respect to the requirements and environment. This is the
simplest mode of network convergence, as shown in Figure 1.
+--------+ +-------+ +-----+
|Internet|-------| Proxy |-----| WSN |
+--------+ +-------+ +-----+
Figure 1 Proxy mode
Proxy mode includes two different operating sub-modes: relay agent
and front-end.
Relay agent simply forwards the packets between the WSN and Internet,
equivalent to a special router at application and network levels.
Agents can also act as the front-end of WSN. Sensor nodes push data
to the proxy, periodically or event-driven based. The proxy stored
the information into a database, with capacity of large database and
powerful processing. Internet users can query all kinds of
information in various ways, through SQL or Web-based interface.
Without the required information, an agent can start the collection
of information. As the front-end, an agent can integrate the
processing and storage of data, and can return data to the user as
quickly as possible, with key management, user authentication, data
encryption and other security measures at the same time.
A proxy node can be integrated by user agent, application agent,
register agent and resource manager, acting as the bridge between
Internet and WSN, with resource storage and access control functions,
and provides a quick query of WSN information services. WSN can
access Internet through a proxy node, and Internet users can easily
visit the WSN.
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In contrast, proxy mode has an obvious disadvantage of single point
failure. Most functions are concentrated in the proxy node, such as
network protocol conversion, information processing and storage. Once
the agent fails, the Internet can not communicate with the WSN. In
addition, an agent is application-oriented, usually dedicated to
specific tasks and agreement. Applications need special agent design.
Without proper routing mechanism, Internet and WSN can not converged;
result in lack of flexibility and scalability.
4. Protocol Overlay
Instead of protocol conversion, heterogeneous networks with different
protocol stacks use protocol overlay for the protocol interconnection.
There are two modes of WSN and Internet overlay: WSN over TCP / IP
and TCP / IP over WSN.
WSN over TCP / IP mode is similar to the private network implemented
on the Internet via VPN (virtual private network). In this mode,
Internet computers communicating with the WSN are called virtual WSN
nodes (virtual node), so are the gateway nodes connecting
heterogeneous networks. A network composite of virtual nodes is
called WSN virtual network, which is an extension of WSN over the
Internet. Each WSN node has its own private protocols dedicated to
the characteristics of WSN, and communication between nodes is based
on the private protocols. In the virtual part of the networks, WSN
traffic is carried over TCP / UDP / IP as protocol payload. TCP / UDP
/ IP transfer data in a tunnel between the virtual nodes. WSN over
TCP / IP protocol stack is shown in Figure 2.
Internet Overlay gateway WSN
+--------+ +-----------------+ +--------+
| APP-S | | APP-S | | APP-S |
+--------+ +-----------------+ +--------+
|Trans-S | | Trans-S | |Trans-S |
+--------+ +-----------------+ +--------+
| NET-S | | NET-S | | NET-S |
+--------+ +--------+--------+ +--------+
|TCP/UDP | |TCP/UDP | LLC-S | | LLC-S |
+--------+ +--------+--------+ +--------+
| IP | | IP | MAC-S | | MAC-S |
+--------+ +--------+--------+ +--------+
^ ^ ^ ^
| | | |
+----------+ +-----------+
Figure 2 WSN over TCP / IP
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Internet users may need to access and control some special nodes in
the WSN, like nodes with the execution (actuator) or performing
certain important functions as cluster head nodes. These special
nodes support TCP / IP protocol. Because of communication capacity
constraints, these nodes and gateway nodes can not reach each other
in one hop. For data transfer between them, a tunnel over WSN is
introduced, that is TCP/IP over WSN. The private protocols are used
by the majority of WSN, and IP is only extended to the special nodes.
So it is not proposed that all WSN nodes support TCP / IP protocol.
Protocol stacks and data flows of this mode are shown in Figure 3.
Internet WSN
host TCP/IP node
+--------+ +--------+
| APP | | APP |
+--------+ Common +--------+
|TCP/UDP | Tunnel node |TCP/UDP |
+--------+ +--------+--------+ +--------+ +--------+
| IP | | IP | | APP-S | | APP-S |
+--------+ +--------+--------+ +--------+ +--------+
^ ^ |Trans-S | |Trans-S | |Trans-S |
| | +--------+ +--------+ +--------+
+-----------+ ^ ^ ^ ^
| | | |
+---------+----+---------+
Figure 3 TCP / IP over WSN
5. Delay Tolerant Network
Internet protocols are inefficient in the environment of long
communication path, variable delay, frequent network structure, high
error rate and asynchronous transfer. Delay tolerant network (DTN) is
proposed for this kind of network environment, as shown in figure 4.
+--------+ +-------+ +-----+
|Internet| | DTN | | WSN |
| host |<----->|Gateway|<--->| node|
+--------+ +-------+ +-----+
Figure 4 DTN gateway
A bundle layer is introduced at the top layer of DTN, to achieve
interoperability for heterogeneous network domains. DTN is suitable
for WSN, and every node has storage function. Due to node sleep or
failure, WSN will frequently change its division structures, breaking
all end to end paths through the network. Packet loss rate is very
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high in WSN, and the data routes are asymmetric too. DTN system is
more powerful than the simple agent-based approach. When a DTN
gateway is in a WSN, the WSN is mapped to multiple DTN regions. In a
WSN with frequent network division change and less end to end
communications, this network design is more appropriate to ensure the
communication reliability in the DTN layer.
There are one or more DTN gateways in each DTN region, which are
responsible for message forwarding between the regions, and message
transfer from other regions to the local area, without single point
failure like in the proxy system. With one or more DTN gateways
connecting to Internet, the WSN can easily be extended to the
Internet via DTN.
More cost is needed to deploy Bundle in the existing network protocol
stack, which is the disadvantage of the DTN mode.
6. Full IP
Adoption of TCP / IP protocols for all WSN nodes is a direct approach
for seamless convergence of WSN and Internet, result in the same
network layer protocol for heterogeneous networks, and protocol
conversion or overlay through special nodes is not needed. With one
or more WSN nodes connecting to the Internet, two networks can
exchange information by any node, through direct physical connection
(Ethernet cable) or wireless link (GPRS). In the network we can use
the network link to communicate through the and so on. This kind of
convergence is more flexible. WSN nodes can access the Internet nodes
closely, relaying real-time data to the end user with minimal delay,
and the Internet users can visit any WSN node.
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+-----+
| WSN |TCP/IP
| node|
+-----+
|
| TCP/IP
+--------+ +-----+ +-----+
|Internet|<--->| WSN |------| WSN |TCP/IP
| | | node| | node|
+--------+ +-----+ +-----+
^ | |
| | |
v | |
+-----+ +-----+ +-----+
| WSN |------| WSN |------| WSN |
| node| | node| | node|
+-----+ +-----+ +-----+
TCP/IP TCP/IP TCP/IP
Figure 5 Full IP mode
The data transmitted between WSN nodes is small-sized, usually a few
dozen bytes or even a few bytes. The header of TCP / IP protocol is
at least 40 bytes, 20 bytes for TCP protocol and 20 bytes for IP
protocol, which seriously affect the data transmission efficiency and
waste node's energy. To use WSN TCP / IP protocol efficiently, a
protocol header compression algorithm must be used. In addition, TCP
/ IP protocol is also too complicated for WSN nodes with limited
resource. Many enhanced algorithms have been proposed, such as
protocol mapping, homeostasis, and probability searching methods, but
these methods cost great time and space complexity.
IP address auto-configuration for WSN nodes is also an important
research area, which is useful for WSN with dispersion and the static
structure, but there are still some obstacles for the dense nodes and
mobile nodes.
With the introduction of protocol header compression, the new model
of two nodes and two stacks is presented for WSN nodes TCP / IP
protocol, containing a small amount of additional super nodes in
addition to ordinary nodes. The ordinary nodes use compressed TCP /
IP protocol. The super nodes achieve conversion between the
compressed and standard TCP / IP protocol, and interact with the
external Internet seamlessly and efficiently. However, without
efficient routing mechanism, the super node does not have universal
applicability. IPv6 protocol is brought to WSN after efficient
simplification, which is basis of WSN routing protocol. The algorithm
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of protocol stack has a good scalability, but not a best routing
algorithm to solve energy problems and slow convergence. The network
has primary nodes with large storage capacity and powerful processing
capabality, and other nodes cluster around the primary node. The
primary node is assigned with fixed IP address, and has a mapping
table of member ID and IP address. This approach is only suitable for
heterogeneous WSN, and the scalability is not good.
7. Other technologies
There are other modes for the convergence of Internet and WSN, such
as virtual IP and mobile agent technologies [3].
Virtual IP is an IP address mapping technology. For computer network
users, only the gateway is assigned with a virtual IP address, and
the sensor node does not have one. This technology can realize the
address mapping between sensor node ID / location and gateway IP
address.
Mobile agent is encapsulated in the WSN node, capable of interacting
with Internet. When running out of energy, the agent disconnects from
the Internet, and travels to the appropriate neighbor with useful
information, which is then an access node. Internet user can pack the
required data for long-term interaction in the mobile agent. The
agent moves to WSN with the information, and interacts with the
gateway or access node. Connection failure between the Internet and
WSN will not affect the mobile agent. After the connection's resuming,
the proxy will return the results to Internet user.
8. Security Considerations
Due to the open wireless environment of WSN, the convergence
framework mechanisms are susceptible to a number of information
attacks.
9. IANA Considerations
This document includes no IANA actions.
10. References
10.1. Normative References
[1] S. Corson, J. Macker, " Mobile Ad hoc Networking (MANET):
Routing Protocol Performance Issues and Evaluation
Considerations ", RFC 2501, January 1999.
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10.2. Informative References
[2] Kay; Friedemann Mattern, "The Design Space of Wireless Sensor
Networks", IEEE Wireless Communications 11 (6): 54-61,
doi:10.1109/MWC.2004.1368897.
[3] Thomas Haenselmann. Sensor networks. GFDL Wireless Sensor
Network textbook. Retrieved 2006-08-29.
11. Acknowledgments
The author wishes to acknowledge the following for their review and
constructive criticism of this document: Zhiwei Cai.
This document was prepared using 2-Word-v2.0.template.dot.
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Authors' Addresses
Zuoshun Wu
China Electronic Device Research Insititue(CEDRI)
No.13 Road Dacheng, District Fengtai, Beijing, China
Phone: +86 010 68693712
Email: wuzuoshun@163.com
Qijian Xu
China Electronic Device Research Insititue(CEDRI)
No.13 Road Dacheng, District Fengtai, Beijing, China
Phone: +86 010 68693730
Email: xuqijian@sina.com
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