Towards Distributed Protocol Stacks for Wireless Sensor Networks

Dipl.-Inf. Peter Rothenpieler
rothenpieler@itm.uni-luebeck.de
http://www.itm.uni-luebeck.de/users/rothenpieler

Towards Distributed Protocol Stacks
for Wireless Sensor Networks
IEEE International Conference on Cyber, Physical and Social Computing
November 20-23, 2012, Besançon, France

Peter Rothenpieler, Dennis Pfisterer
Institute of Telematics, University of Lübeck


Content
 Motivation
 Idea: Distributed Protocol Stacks
 (Short) Protocol Overview
 Design considerations & Limitations
 Evaluation
 Code size
 Round Trip Time
 Goodput
 Summary and Conclusion

2


Motivation: From WSNs to the Internet of Things
WSN: problem specific, custom tailored solutions  standardized protocol stacks

Application Application
Advantages:
 Layered Protocols: Divide and Conquer UDP ICMP UDP ICMP

 Interoperability & Heterogeneity IPv6 IPv6

6LoWPAN 6LoWPAN

Disadvantages: IEEE 802.15.4 IEEE 802.15.4
MAC & PHY MAC & PHY
 Additional protocols/layers increase code size
(+ adaptation layer?)

3


Motivation: Code Size of 6LoWPAN & IPv6
Cheap / Small Expensive / Big

OS Contiki Contiki iSense Contiki iSense
Platform MSP430 JN5139 JN5139 JN5148 JN5148
Flash 48 KB 96 KB 96 KB 128 KB 128 KB
6LoWPAN 4.6 8.0 7.8 5.9 5.1
IPv6 7.4 12.3 31.6 8.7 18.3
ND 6.8 13.3 7.6 9.3 5.0
ICMP 0.8 1.3 2.1 1.0 1.2
UDP 0.7 0.3 2.1 0.2 1.1
Routing (RPL) 9.0 12.9 N/A 8.4 N/A
Σ 29.3 48.1 51.2 33.5 30.6
% of Flash 61 % 50 % 53 % 26 % 24 %

Source: Instant Contiki 2.6, Jennisense (07/2012), iSense SVN (04/2012)

4


Idea: Distributed Protocol Stack
 Cooperation between layers  cooperation between nodes
 Share implementations of layers with neighboring nodes
 asynchronous RPC calls (“message passing”)

Application Application Application Application

UDP ICMP UDP ICMP UDP ICMP UDP ICMP

DPS DPS
IPv6 IPv6 IPv6 skeleton IPv6 stub

6LoWPAN 6LoWPAN 6LoWPAN

IEEE 802.15.4 IEEE 802.15.4 IEEE 802.15.4 IEEE 802.15.4
MAC & PHY MAC & PHY MAC & PHY MAC & PHY

RPC

Server Client

5


Protocol Overview

 Three phases
 Discovery & Advertise
 Three-way-Handshake Server
Server
 Exchange of RPC messages 1.Discovery

RPCAdvertise
2. Handshake
messages
2. Advertise
 Optionally supports the use of
 Acknowledgements
Client

6


Design considerations & Limitations
 DPS Covers only single-hop communication
 Clients need at least one Server within radio range
 Placement of nodes during deployment
 Certain fraction of nodes need to be Servers (topology/deployment)
 Clients can not communicate directly (need Server in-between)

7


Evaluation: Code Size
 Code size of native IPv6 implementation on JN5139 > 96 KB Flash
 Use of IPv6 on JN5139 now possible (26.5 KB reduction)

Client Server

Native IPv6 DPS Client Native IPv6 DPS Server
JN5139 JN5139 JN5148 JN5148
Application 5.5 KB 3.8 KB
Os 43.9 KB 36.4 KB
IPv6 Stack 50.2 KB 10.1 KB 27.6 KB 27.6 KB
DPS - 13.6 KB - 8.0 KB
Σ 99.6 KB 73.1 KB 67.8 KB 75.8 KB
100 % -27 % 100 % + 12 %
Relative
-26.5 KB +8.0 KB

8


Evaluation: Single-Hop Round Trip Time
Data based upon 100 ICMP echo request/reply packets for each payload size

Increase for additional fragments
6LoWPAN: 07 ms
DPS: 07 ms
DPS (ACK): 23 ms

(Un-)compressed IPv6 header
determines payload in first fragment

x ms

1 byte
Increase for additional payload
6LoWPAN: 0.068 ms/byte
DPS: 0.075 ms/byte (+10%)
DPS (ACK): 0.075 ms/byte (+10%)

9


Evaluation: Single-Hop Goodput
Data based upon 1000 UDP packets for each payload size and output speed

Decrease
1st Fragment: 32 %
Following Fragments: 4.2 % - 5.7 %

Native 6LoWPAN DPS

10


Summary & Conclusion
 Motivation and Introduction: Distributed Protocol Stacks
 Code size reduced by 27.5 KB for the DPS Client
 Increase of 8.0 KB for the DPS Server
 RTT increases by only 10 % (+ Offset of 6 ms)
 Goodput decreases only by 4.2 - 6.7 % (32% first fragment)
 Acknowledgements
 Increase RTT by additional 16ms / fragment
 Should be used
for DPS calls that change the state of the Server or Client
require reliability that is not offered by the protocol itself

11


Thank you for your attention!


Example
 Exchange of IP Address & Sending of IP Packet

Instead of receiving A, the Server
will forward it using IPv6/6LoWPAN,
if it is not the destination of the packet

Towards Distributed Protocol Stacks for Wireless Sensor Networks

Towards Distributed Protocol Stacks for Wireless Sensor Networks

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