Net etwork work Ke Kerne nel l Ar Archi chitect tectures ures an and d Im Impl plementa ementation tion (01 0120 20442 4423) ) Naming aming an and Ad Addressing ressing Chaiporn Jaikaeo Chaiporn.j@ku.ac.th Department of Computer Engineering Kasetsart University Materials taken from lecture slides by Karl and Willig
Name Na mes vs. . Add Addre resses Names: s: Refer to “things” Nodes, networks, data, transactions, … May or may not be globally unique Ad Addres esse ses: : Information needed to fi find these things Street address, IP address, MAC address May or may not be globally unique Services to map between names and addresses E.g., DNS Some names are also addresses 2
Na Nami ming ng in in WS WSN Nodes are not independent But collaborate to solve a given task Better to shift view from naming nodes to na naming ing data 3
Addre Add ress s Man Manage ageme ment nt Is Issue ues Address dress al allo loca catio ion: n: Assign an entity an address from a given pool of possible addresses Distributed address assignment (centralized like DHCP does not scale) Address dress deal allo locat cation: ion: Once address no longer used, put it back into the address pool Because of limited pool size Graceful or abrupt, depending on node actions 4
Add Addre ress s Man Manage ageme ment nt Is Issue ues Address representation Conflict detection & resolution (Duplicate Address Detection - DAD) What to do when the same address is assigned multiple times? Can happen e.g. when two networks merge Binding Map between addresses used by different protocol layers E.g., IP addresses are bound to MAC address by ARP 5
Un Unique iqueness ness of f Add Addre resses Globally unique Appears at most once all over the wo worl rld Network-wide unique Appears at most once in a given netwo work rk Locally unique Appears at most once in a defined neighbo borho rhood 6
Add Addre ressing sing Ov Overh rhead ead The fewer bits per address, the better Global > Network-wide > Local Tradeoffs Address length management overhead Typically, address negotiation runs only at the beginning Except when there is mobility 7
Di Distributed tributed Ad Addr dress ess As Assignment ignment Option ion 1: Random assignment Unacceptable high risk of duplicate addresses No-conflict probability for n addresses and k nodes is By Stirlings approximation Similar to the birthday paradox 8
Di Distributed tributed Ad Addr dress ess As Assignment ignment Option ion 2: Still random, but avoid addresses used in local neighborhood By overhearing exchanged packets Good enough in many WSN apps where data sent to a certain sink 9
Di Distributed tributed Ad Addr dress ess As Assignment ignment Option ion 3: Repair any observed conflicts Randomly pick a temporary address and a proposed fixed address Send an addres ess requ quest t to the proposed address, using temporary address If addres ess s reply y arrives, address already exists Collisions in temporary address unlikely, as only used briefly Option ion 4: Similar to 3, but use a neighbor that already has a fixed address to perform requests 10
Locally Lo cally Un Unique ique Add Addre resses Fewer bits are needed, due to Each address can be reused several times across the same network Lower-number addresses tend to be used more frequently Addresses can be compressed E.g., using Huffman coding 11
Is Issues ues wi with th As Asym ymme metr tric ic Li Link nks Assume nodes communicate with bidirectional neighbors only All bidirectional neighbors of each node must have distinct addresses The address of any inbound neighbor must be different from all bidirectional neighbors 12
Cont ntent ent-Base Based d Add Addre ressing ing Recall: Paradigm change from id-centric to data-centric networking in WSN Supported by content-based names/addresses Do not described involved nodes (not known anyway), but the co content nt itself the interaction is about Classical option: Put a naming scheme on top of IP addresses Done by some middleware systems 13
De Descr cribing ibing In Inte terests rests Inter eres ests ts describe relevant data/event Nodes match these interests with their locally observed data Format: Attribute-Value-Operation (AVO) E.g.: <TEMP, 20 ° C, GE> Operations: 14
Des Describing cribing In Inte tere rest/Sensor/Data st/Sensor/Data List of AVOs E.g., <type,temperature,IS> <x-coordinate,10,IS> <type,temperature,EQ> <y-coordinate,10,IS> <threshold-from-below,20,IS> <x-coordinate,20,LE> Sensor <x-coordinate,0,GE> <y-coordinate,20,LE> <y-coordinate,0,GE> <type,temperature,IS> <interval,0.05,IS> <x-coordinate,10,IS> <duration,10,IS> <y-coordinate,10,IS> <class,interest,IS> <temperature,20.01,IS> <class,data,IS> Interest Data 15
Mat Match ching ing Al Algo gorithm rithm Check whether an interest matches the locally available data 16
Di Dire rected cted Di Diffu ffusion ion An example of data-centric networking 17
Geographic Ge graphic addr addressing ing Express addresses by denoting physical position of nodes Considered a special case of content-based addresses Attributes for x and y (and z) coordinates Options Single point Circle or sphere centered around given point Rectangle by two corner points Polygon 18
Conclusion nclusion Addresses can be assigned distributedly Non-id-centric addresses give additional expressiveness, enables new interaction patterns than only using standard addresses These addresses have to be supported by specific protocols, in particular, routing protocols 19
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