Network Kernel Architectures

and Implementation(01204423)

Naming and Addressing

Chaiporn JaikaeoChaiporn.j@ku.ac.th

Department of Computer EngineeringKasetsart University

Materials taken from lecture slides by Karl and Willig

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Names vs. Addresses Names: Refer to “things”

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

Addresses: Information needed to 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

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Naming in WSN Nodes are not independent

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

nodes to naming data

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Address Management Issues Address allocation: Assign an

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

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

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

actions

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Address Management Issues 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

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Uniqueness of Addresses Globally unique

Appears at most once all over the world

Network-wide unique Appears at most once in a given

network Locally unique

Appears at most once in a defined neighborhood

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Addressing Overhead 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

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Distributed Address Assignment Option 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

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Distributed Address Assignment Option 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

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Distributed Address Assignment Option 3: Repair any observed

conflicts Randomly pick a temporary address

and a proposed fixed address Send an address request to the

proposed address, using temporary address

If address reply arrives, address already exists

Collisions in temporary address unlikely, as only used briefly

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

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Locally Unique Addresses 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

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Issues with Asymmetric Links 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

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Content-Based Addressing 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 content itself the interaction is about

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

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Describing Interests Interests 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:

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

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

Interest

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

Sensor

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

Data

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Matching Algorithm Check whether an interest matches

the locally available data

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Directed Diffusion An example of data-centric

networking

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Geographic addressing 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

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Conclusion 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