Network Kernel Architectures and Implementation ( ) Naming and Addressing Chaiporn Jaikaeo Department of Computer Engineering Kasetsart University Materials taken from lecture slides by Karl and Willig

2 Names vs. Addresses Names: Refer to “things” Names: Refer to “things”  Nodes, networks, data, transactions, …  May or may not be globally unique Addresses: Information needed to find these things 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 Services to map between names and addresses  E.g., DNS Some names are also addresses Some names are also addresses

3 Naming in WSN Nodes are not independent Nodes are not independent  But collaborate to solve a given task Better to shift view from naming nodes to naming data Better to shift view from naming nodes to naming data

4 Address Management Issues Address allocation: Assign an entity an address from a given pool of possible addresses 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 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

5 Address Management Issues Address representation Address representation Conflict detection & resolution (Duplicate Address Detection - DAD) 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 Binding  Map between addresses used by different protocol layers  E.g., IP addresses are bound to MAC address by ARP

6 Uniqueness of Addresses Globally unique Globally unique  Appears at most once all over the world Network-wide unique Network-wide unique  Appears at most once in a given network Locally unique Locally unique  Appears at most once in a defined neighborhood

7 Addressing Overhead The fewer bits per address, the better The fewer bits per address, the better Global > Network-wide > Local Global > Network-wide > Local Tradeoffs Tradeoffs  Address length  management overhead Typically, address negotiation runs only at the beginning Typically, address negotiation runs only at the beginning  Except when there is mobility

8 Distributed Address Assignment Option 1: Random 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

9 Distributed Address Assignment Option 2: Still random, but avoid addresses used in local neighborhood 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

10 Distributed Address Assignment Option 3: Repair any observed conflicts 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 Option 4: Similar to 3, but use a neighbor that already has a fixed address to perform requests

11 Locally Unique Addresses Fewer bits are needed, due to 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

12 Issues with Asymmetric Links Assume nodes communicate with bidirectional neighbors only 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

13 Content-Based Addressing Recall: Paradigm change from id-centric to data-centric networking in WSN Recall: Paradigm change from id-centric to data-centric networking in WSN Supported by content-based names/addresses 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 Classical option: Put a naming scheme on top of IP addresses  Done by some middleware systems

14 Describing Interests Interests describe relevant data/event Interests describe relevant data/event  Nodes match these interests with their locally observed data Format: Attribute-Value-Operation (AVO) Format: Attribute-Value-Operation (AVO)  E.g.:  E.g.:  Operations:

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

16 Matching Algorithm Check whether an interest matches the locally available data Check whether an interest matches the locally available data

17 Directed Diffusion An example of data-centric networking An example of data-centric networking

18 Geographic addressing Express addresses by denoting physical position of nodes 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 Options  Single point  Circle or sphere centered around given point  Rectangle by two corner points  Polygon

19 Conclusion Addresses can be assigned distributedly Addresses can be assigned distributedly Non-id-centric addresses give additional expressiveness, enables new interaction patterns than only using standard addresses 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 These addresses have to be supported by specific protocols, in particular, routing protocols