Transcript Terminal Bridge Extension Over Distributed Architecture

Terminal Bridge Extension
Over Distributed Architecture
MSc. Sami Saalasti
Agenda
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Overview of Current Situation
Service Distribution
CORBA
Wireless CORBA
Terminal Bridge Extension
Use-Cases
Conclusions
Overview of Current Situation
• Wireless networks have become common
varying from small Bluetooth networks to
large-scale GSM networks
• Combining different networks provides a
situation where we can use “best features
from every technology”
• However, no general model for using
these different wireless technologies
together
Service Distribution
• Distributed Service Architecture describes a
network environment which offers shared
services to network users
• Services can be distributed by using different
approaches over CORBA or the Wireless
CORBA
• Both CORBA architectures can support several
wireless networking technologies such as
Bluetooth, WLAN and GPRS
• The idea is to provide access to a shared
service from different kinds of mobile networks
CORBA 1/2
• Common Object Request Broker Architecture (CORBA),
OMG's open architecture and infrastructure that computer
applications use to work together over networks to perform
remote invocations
• Using the standard protocol Internet Inter-ORB Protocol
(IIOP), vendor independent interoperability can be reached
CORBA 2/2
• Network layer is completely hidden from
applications, argument marshalling,
connection handling, flow control handled
by the Object Request Broker (ORB)
• Underlying network must be reliable
because no connection failures are
expected
Wireless CORBA 1/3
• New evolution of CORBA, the Wireless
CORBA has been developed to specially
operate on wireless networks
• Wireless CORBA offers a software
middleware solution for communication on
several platforms with capability of
performing flexible change of network
access point (handoff)
Wireless CORBA 2/3
• New components: Terminal Bridge (TB), Access
Bridge (AB) and Home Location Agent (HLA)
• Wireless CORBA utilizes centralized service model
which provides one centralized service which can be
accessed through several Access Bridges
Home Location Agent
Access Bridge
Backbone
network
B
Terminal Bridge
Service
wired link
wireless link
Access Bridge
Wireless CORBA 3/3
• There may be multiple wireless networks
available and the Wireless CORBA lacks
methods to detect possible new networks
if the current connection drops.
• No implementation for monitoring the
connection status
• No implementation for handoff automation
when connection weakens
Terminal Bridge Extension 1/2
• Extension automates the handoff process
and guards the connection state by
monitoring signalling level
• If the current connection seems to be too
weak, the Terminal Bridge extension
selects another available access point and
commands Terminal Bridge to perform a
handoff
Terminal Bridge Extension 2/3
Terminal Bridge Extension 3/4
• Extension was used over the underlying
Wireless CORBA architecture which was
operating over TCP/IP (WLAN and GPRS)
and L2CAP (Bluetooth)
• The task of the extension was to guide the
Terminal Bridge to select always the most
suitable network
Terminal Bridge Extension 4/4
Use-Cases 1/3
Use-Cases 2/3
Use-Cases 3/3
Conclusions 1/2
• Wireless CORBA and Terminal Bridge
Extension provides very flexible
architecture to use distributed services in
changing wireless environment
• Using very different wireless technologies
together provides new possibilities for
creating and using services
Conclusions 2/2
• Currently, Bluetooth is problematic technology: inquiry
and connection times can kill usability very effectively if
user moves a lot from one network area to other
• If plain Bluetooth network is used, it should be designed
very precisely because one gap in the network coverage
area breaks the link.
• Better solution would be to use WLAN in the background
and then decide what kind of Bluetooth network can be
built
• GPRS creates completely different possibilities to use
services on a wider area because network coverage is
no more as restricting factor