Page 127 - ITU Kaleidoscope 2016

ICTs for a Sustainable World

Resource
controller (RC)

Resource Load statistics
provisioning

Authorized public
Replication directory

RC Record
caching Record registration
Resource
provisioning Record update Private directory

Load statistics
Replication Record
Record caching owners -
Record lookup On-demand IoT devices
record caches (red cars)
IoT application
clients On-demand
(yellow cars) allocated resource

Figure 1. Components and processes of the proposed IoT directory service.

so is received from the resource controller. In
3. IOT DIRECTORY SERVICE ARCHITECTURE addition, if some replica servers are no longer in use
due to lack of queries for the copies of records stored
Figure 1 shows the components and processes involved in in them, these copies are deleted and resources
the proposed IoT directory service. The major components allocated to them are returned to the resource pool.
(shown by boxes in the figure) are: (1) Authorized public (2) On-demand record caches: They store copies of
directory, (2) On-demand record caches, (3) Resource records distributed from the authorized public
controller, (4) Private directory, (5) Record owners, and (6) directory to the network edges closer to clients or IoT
Record clients. Similarly, the processes involved (shown by applications. They accept record lookup requests from
arrows in the figure) are: (a) Record registration, (b) Record IoT applications and provide relevant records in the
caching, (c) Record replication, (d) Record lookup, (e) response. They are tracked by the authorized public
Record update, (f) Load statistics monitoring, and (g) On- directory, i.e. the authorized public directory stores the
demand resource provisioning. The components and reachability information of all record caches in a list
processes are described below. and uses the list to access them when any change in
the authorized public directory records needs to be
3.1. Architectural Components reflected immediately in the trackable caches as well.
(1) Authorized public directory: It contains the required Similarly, to reduce the record update latency, some
database management functions to store, lookup, cache servers, called anchor cache server, are
update, and delete records, and replication functions to delegated by the authorized directory to accept and
copy the whole database, or some records, to process record update requests. Similar to the
designated replica servers. It is called “authorized authorized public directory, the cache can also make
public directory” because it stores records of its replicas to reduce its load and thus record access
authorized IoT devices or things only and provides the latency. Moreover, any anchor cache server can
records to authorized clients that are eligible to obtain distribute records to other replica servers created by
them (i.e. each record contains its access policy). Each the resource controller as the record owner moves
record in the database is composed of various from one network to the other. This process is
attributes (e.g. ID, location, data types, security key regulated by the distribution policies provided by
and certificate) linked to the IoT device name. The record owners and initiated by the authorized public
names may be of heterogeneous types, and can be directory, so all caches are able to provide
written in different formats (e.g. text, binary). “authoritative” answers to client queries, which can be
However, they are unique in the database so that each totally trusted as long as the records (or their cache
record is uniquely identified by the name. To reduce copies) have not expired.
the workload and lookup latency of the authorized (3) Resource controller: It allocates, adjusts, and adapts
public directory, the replication function creates a resources of the authorized directory, cache servers as
copy of specified records and stores them in the well as of their replica servers on the basis of regular
designated replica servers when a command for doing monitoring of their performance and load statistics.

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