Architectures and Architectures and Applications for Applications for Wireless Sensor Wireless Sensor

Networks (204525)Networks (204525)

Naming and AddressingNaming and Addressing

Chaiporn JaikaeoChaiporn JaikaeoChaiporn.j@ku.ac.thChaiporn.j@ku.ac.th

Department of Computer EngineeringDepartment of Computer EngineeringKasetsart UniversityKasetsart University

Materials taken from lecture slides by Karl and Willig

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Names vs. AddressesNames vs. Addresses Names: Names: Refer to “things”Refer to “things”

Nodes, networks, data, transactions, …Nodes, networks, data, transactions, … May or may not be globally uniqueMay or may not be globally unique

Addresses: Addresses: Information needed to Information needed to find find these thingsthese things Street address, IP address, MAC addressStreet address, IP address, MAC address May or may not be globally uniqueMay or may not be globally unique

Services to map between names and Services to map between names and addressesaddresses E.g., DNSE.g., DNS

Some names are also addressesSome names are also addresses

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Naming in WSNNaming in WSN Nodes are not independentNodes are not independent

But collaborate to solve a given taskBut collaborate to solve a given task Better to shift view from naming Better to shift view from naming

nodes to nodes to naming datanaming data

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Address Management Address Management IssuesIssues Address allocation:Address allocation: Assign an Assign an

entity an address from a given pool entity an address from a given pool of possible addressesof possible addresses Distributed address assignment Distributed address assignment

(centralized like DHCP does not scale)(centralized like DHCP does not scale) Address deallocation:Address deallocation: Once Once

address no longer used, put it back address no longer used, put it back into the address poolinto the address pool Because of limited pool sizeBecause of limited pool size Graceful or abrupt, depending on node Graceful or abrupt, depending on node

actionsactions

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Address Management Address Management IssuesIssues Address representationAddress representation Conflict detection & resolution Conflict detection & resolution

(Duplicate Address Detection - DAD)(Duplicate Address Detection - DAD) What to do when the same address is What to do when the same address is

assigned multiple times? assigned multiple times? Can happen e.g. when two networks Can happen e.g. when two networks

mergemerge BindingBinding

Map between addresses used by Map between addresses used by different protocol layersdifferent protocol layers

E.g., IP addresses are bound to MAC E.g., IP addresses are bound to MAC address by ARPaddress by ARP

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Uniqueness of Uniqueness of AddressesAddresses Globally uniqueGlobally unique

Appears at most once all over the Appears at most once all over the worldworld

Network-wide uniqueNetwork-wide unique Appears at most once in a given Appears at most once in a given

networknetwork Locally uniqueLocally unique

Appears at most once in a definedAppears at most once in a defined neighborhoodneighborhood

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Addressing OverheadAddressing Overhead The fewer bits per address, the The fewer bits per address, the

betterbetter Global > Network-wide > LocalGlobal > Network-wide > Local TradeoffsTradeoffs

Address length Address length management management overheadoverhead

Typically, address negotiation runs Typically, address negotiation runs only at the beginningonly at the beginning Except when there is mobilityExcept when there is mobility

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Distributed Address Distributed Address AssignmentAssignment Option 1:Option 1: Random assignment Random assignment

Unacceptable high risk of duplicate Unacceptable high risk of duplicate addressesaddresses

No-conflict probability for No-conflict probability for nn addresses addresses and and kk nodes is nodes is

By Stirlings approximationBy Stirlings approximation

Similar to the Similar to the birthday paradoxbirthday paradox

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Distributed Address Distributed Address AssignmentAssignment Option 2:Option 2: Still random, but avoid Still random, but avoid

addresses used in local addresses used in local neighborhoodneighborhood By overhearing exchanged packetsBy overhearing exchanged packets Good enough in many WSN apps where Good enough in many WSN apps where

data sent to a certain sinkdata sent to a certain sink

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Distributed Address Distributed Address AssignmentAssignment Option 3:Option 3: Repair any observed conflicts Repair any observed conflicts

Randomly pick a temporary address and a Randomly pick a temporary address and a proposed fixed addressproposed fixed address

Send an Send an address request address request to the proposed to the proposed address, using temporary address address, using temporary address

If If address reply address reply arrives, address already arrives, address already existsexists

Collisions in temporary address unlikely, as Collisions in temporary address unlikely, as only used brieflyonly used briefly

Option 4:Option 4: Similar to 3, but use a Similar to 3, but use a neighbor that already has a fixed neighbor that already has a fixed address to perform requestsaddress to perform requests

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Locally Unique Locally Unique AddressesAddresses Fewer bits are needed, due toFewer bits are needed, due to

Each address can be reused several Each address can be reused several times across the same networktimes across the same network

Lower-number addresses tend to be Lower-number addresses tend to be used more frequentlyused more frequently Addresses can be compressedAddresses can be compressed E.g., using Huffman codingE.g., using Huffman coding

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Issues with Asymmetric Issues with Asymmetric LinksLinks Assume nodes communicate with Assume nodes communicate with

bidirectional neighborsbidirectional neighbors All bidirectional neighbors of each node must All bidirectional neighbors of each node must

have distinct addresseshave distinct addresses The address of any inbound neighbor must be The address of any inbound neighbor must be

different from all bidirectional neighborsdifferent from all bidirectional neighbors

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Content-Based Content-Based AddressingAddressing Recall: Paradigm change from id-Recall: Paradigm change from id-

centric to data-centric networking in centric to data-centric networking in WSN WSN

Supported by content-based Supported by content-based names/addressesnames/addresses Do not described involved nodes (not Do not described involved nodes (not

known anyway), but the known anyway), but the content content itself itself the interaction is aboutthe interaction is about

Classical option: Put a naming Classical option: Put a naming scheme on top of IP addressesscheme on top of IP addresses Done by some middleware systemsDone by some middleware systems

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Describing Describing InterestsInterests Interests Interests describe relevant data/event describe relevant data/event

Nodes match these interests with their locally Nodes match these interests with their locally observed dataobserved data

Format: Attribute-Value-Operation (AVO)Format: Attribute-Value-Operation (AVO) E.g.: <TEMP, 20°C, GE> E.g.: <TEMP, 20°C, GE> Operations: Operations:

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Describing Describing Interest/Sensor/DataInterest/Sensor/Data List of AVOsList of AVOs E.g.,E.g.,

<type,temperature,EQ><type,temperature,EQ><threshold-from-below,20,IS><threshold-from-below,20,IS><x-coordinate,20,LE><x-coordinate,20,LE><x-coordinate,0,GE><x-coordinate,0,GE><y-coordinate,20,LE><y-coordinate,20,LE><y-coordinate,0,GE><y-coordinate,0,GE><interval,0.05,IS><interval,0.05,IS><duration,10,IS><duration,10,IS><class,interest,IS><class,interest,IS>

InterestInterest

<type,temperature,IS><type,temperature,IS><x-coordinate,10,IS><x-coordinate,10,IS><y-coordinate,10,IS><y-coordinate,10,IS>

SensorSensor

<type,temperature,IS><type,temperature,IS><x-coordinate,10,IS><x-coordinate,10,IS><y-coordinate,10,IS><y-coordinate,10,IS><temperature,20.01,IS><temperature,20.01,IS><class,data,IS><class,data,IS>

DataData

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Matching AlgorithmMatching Algorithm Check whether an interest matches Check whether an interest matches

the locally available datathe locally available data

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Directed DiffusionDirected Diffusion An example of data-centric An example of data-centric

networkingnetworking

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Geographic addressingGeographic addressing Express addresses by denoting Express addresses by denoting

physical position of nodesphysical position of nodes Considered a special case of content-Considered a special case of content-

based addressesbased addresses Attributes for x and y (and z) coordinatesAttributes for x and y (and z) coordinates

OptionsOptions Single pointSingle point Circle or sphere centered around given Circle or sphere centered around given

pointpoint Rectangle by two corner pointsRectangle by two corner points PolygonPolygon

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ConclusionConclusion Addresses can be assigned Addresses can be assigned

distributedlydistributedly Non-id-centric addresses give Non-id-centric addresses give

additional expressiveness, enables additional expressiveness, enables new interaction patterns than only new interaction patterns than only using standard addressesusing standard addresses

These addresses have to be These addresses have to be supported by specific protocols, in supported by specific protocols, in particular, routing protocolsparticular, routing protocols