sunday, october 15, 2000 jini pattern language workshop acm oopsla 2000 minneapolis, mn, usa...

Sunday, October 15, 2000

JINI Pattern Language WorkshopACM OOPSLA 2000

Minneapolis, MN, USA

Patterns in Bluetooth

Aniruddha [email protected] Labs Research,Lucent TechnologiesMurray Hill, NJ, USA

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Aniruddha S. Gokhale Patterns in Bluetooth

Design patterns capture the static & dynamic roles & relationships in solutions that occur repeatedly

Architectural patterns express a fundamental structural organization for software systems that provide a set of predefined subsystems, specify their relationships, & include the rules and guidelines for organizing the relationships between them

Optimization principle patterns document rules for avoiding common design & implementation mistakes that degrade performance

Patterns codify expert knowledge to help generate software architectures by capturing recurring structures & dynamics and resolving common design forces

Overview of Patterns

www.posa.uci.edu/

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Overview of Bluetooth• www.bluetooth.com• De facto standard for low-

cost, short range radio links between mobile devices

• Formed by a consortium of telecommunications

• Goal is to eliminate the need for cable connectivity and promote full scale ad hoc networking

• Operates in the unlicensed ISM band at 2.4 GHzPrimary components include a

radio unit, a link control unit, and a support unit for link management and host-terminal interface

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Layers PatternIntent

Helps to structure applications that can be decomposed into groups of subtasks in which each group of subtasks is at a particular level of abstraction

Bluetooth UsageDefines a protocol stack

Known UsesOSI Seven Layers, STREAMS

ForcesTasks independent of each other need to be decoupled

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Bluetooth Protocol Stack

Radio Specification• 2.4 GHz ISM band (2,400-

2,483.5 MHz)• Channels spaced 1MHz apart• Gaussian FSK modulation

Baseband Specification• Short range radio link• Uses slotted channel• channels point-to-point or point-

to-multipoint• Supports both circuit-switched

(SCO - synchronous connection-oriented) and packet-switched (ACL - asynchronous connectionless) links.

Link Manager Protocol (LMP)• Used for link setup, security,

and control

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Bluetooth Protocol Stack

Logical Link Control and Adaptation Protocol (L2CAP)

• Higher layer protocol multiplexing for SDP, TCS, RFCOMM

• Packet segmentation and reassembly

• Only for ACL links• Provides group abstractions• Provides the means to convey QoS

information• MTU = 64 Kbytes

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Multiplexor & Dispatcher PatternIntent

Multiplex messages from differing tasks into one task, and de-multiplex and dispatch messages from one task to one of several tasks

Forces

Support several tasks with differing message formats on top of a single task with its own message format

Known Uses• TCP/IP• System V STREAMS• ACE Reactor

Bluetooth UsageL2CAP Layer multiplexes packets from SDP, RFCOMM, TCS, and IP telephony protocol layers

L2CAP

SDP TCSRFCOMM

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SAR PatternIntent

Reassemble fragmented messages in the correct order before dispatching them to their destination task

Forces

Guarantee ordered delivery of messages to upper layers when lower layers fragment messages and can lose or reorder messages

Known Uses• TCP/IP• Reliable multicast over UDP

L2CAP

SDP TCSRFCOMM

Bluetooth Usage• L2CAP segments and reassembles

packets for SDP, RFCOMM, TCS, and IP telephony protocols

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Bluetooth Protocol StackService Discovery Protocol

(SDP)• Locating services and their

characteristics• Allows search based on attributes

or service classes• Allows discovery without consulting

a third device• Provides only information about the

service and not direct access to the service

RFCOMM• Provides emulation of serial ports

over L2CAP• Provides a unified interface for

communication medium between Bluetooth devices

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Lookup PatternIntent

Describes how to find and retrieve initial references to distributed objects and services

Forces

Discover services in an ad hoc network

Known Uses• JINI Lookup Service• CORBA Naming and Trading

Service

Bluetooth Usage• SDP allows discovery of services,

however, actual initial references must be obtained differentlySDP Client SDP Server

request

response

Client Server

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Service Browsing PatternIntent

Allows browsing all services offered by a Lookup Service

Forces

Ability to query based on class or characteristics of services

Known Uses• JINI Lookup Service• CORBA Trading Service

Bluetooth Usage• SDP allows discovering all services

based on attributes

SDP Client SDP Serverrequest

response

Client Server

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Bluetooth Protocol StackIrDA Interoperability (IrOBEX)• Protocol to function over both short

range RF and infra red (Ir) media• IrOBEX is a session protocol

mapped over RFCOMM, IrDA, or TCP/IP

• Provides a model for representing objects that follow a client/server request/response paradigm

Telephony Control (TCS)• Defines the call control signaling for

the establishment of speech and data calls between Bluetooth devices

• Defines mobility management issues

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Broker Pattern

Intent

Used to structure distributed systems with decoupled components that interact by remote method invocations

Forces

Request/response communication between Bluetooth devices

Known Uses• CORBA ORB• Java RMI• DCOM

Bluetooth Usage• OBEX (OBject EXchange) protocol

provides a model to represent objects using client/server paradigm

IrOBEX IrOBEXrequest

response

Client Server

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Facade PatternIntent

Provide a unified interface to a set of interfaces in a subsystem

Forces

Several disparate interfaces that must be unified

Known Uses• ACE


provides a unified interface for the underlying transport

• RFCOMM provides a unified interface over communication medium between Bluetooth devices

IrOBEX IrOBEXrequest

response

Client Server

BTDevice

ModemDevice

BTDevice

BTDevice

RFCOMM

RFCOMM Network

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Pluggable Protocol PatternIntent

To be able to use disparate subtasks to deliver messages belonging to a particular task

Forces

Unifying several disparate lower layers in a Layer pattern

Known Uses• TAO ORB supporting several

underlying transports such as TCP/IP, ATM, shared memory


can run on top of IrDA, RFCOMM, and TCP/IP

IrOBEX

TCP/IPRFCOMMIrDA

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Interoperability Requirements for Wireless Application Protocol (WAP)

• Many characteristics of Bluetooth devices shared with WAP target platforms

• Same device may be enabled for both protocols

• WAP clients and servers use PPP to use the physical and link control medium provided by Bluetooth

• Provide access to WAP’s value-added services using the ad hoc, dynamic characteristics of Bluetooth

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Bridge PatternIntent

Decouples an abstraction from its implementation so that the two can vary independently

Forces

Maintain independence between WAP and Bluetooth, however, allowing WAP applications to communicate over Bluetooth

Known Uses• ET++• libg++• ACE

Bluetooth UsagePPP serves as the bridge between WAP applications and the communication medium offered by Bluetooth

Bearer: e.g., PPP, CDMA

Application Layer (WAE)

Transport Layer (WDP)

Security Layer (WTLS)

Transaction Layer (WTP)

Session Layer (WSP)

WAP

Bluetooth

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Concluding Remarks• Bluetooth is the de facto standard for low cost, short range, wireless

communications between portable devices

• Bluetooth aims to eliminate the need for cables and promote full scale ad hoc networking

sunday, october 15, 2000 jini pattern language workshop acm oopsla 2000 minneapolis, mn, usa...

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