WAP/ WML : Wireless Protocol wireless protocol

Transcription

1 Device Connectivity

2 Device Connectivity Pervasive computing devices do not develop their full potential unless they are connected to applications and services through the Internet. Device connectivity covers protocols for device-to-device and device to server interactions that are relevant in the pervasive computing domain, including wireless protocols, mobile phone technologies, Bluetooth, the Mobile IP, synchronization protocols such as SyncML, and transaction protocols and protocols enabling distributes services such as Jini.

3 Wireless Protocols Used for normal communication choice for hand held devices like PDAs and mobile phones. Following gives an overview of wireless protocols. 1. WAP/ WML : Wireless Application Protocol (WAP) is a technical standard for accessing information over a mobile wireless network. A WAP browser is a web browser for mobile devices such as mobile phones that uses the protocol. It is similar to HTTP. Wireless equivalent of HTML is WML. There is no end to end security provided in WAP. There are listed some of the key features offered by WAP: A programming model similar to the Internet's Wireless Markup Language (WML) WMLScript Wireless Telephony Application Interface (WTAI)

4 Wireless Protocols OBEX : OBJECT EXCHANGE PROTOCOL 1. Also termed IrOBEX is a communications protocol that facilitates the exchange of binary objects between devices 2. HTTP has only pull command while it has pull and push command for bidirectional communication. 3. It is maintained by the Infrared Data Association (IrDA) but has also been adopted by the Bluetooth Special Interest Group and the SyncML wing of the Open Mobile Alliance (OMA). 4. It consists of two models: 1. The session model structures the dialog between two decides and uses a binary packet based client/server request and response model. 2. The object model carries information about the objects being sent as well as containing the objects themselves. Object consists of a sequence of headers which describes the name, length, descriptive text of the object.

5 Wireless Protocols Bluetooth: Bluetooth is a wireless technology standard for exchanging data over short distances. Bluetooth is managed by the Bluetooth Special Interest Group (SIG), which has more than 25,000 member companies in the areas of telecommunication, computing, networking, and consumer electronics Characteristics of Bluetooth are : Frequency band: 2.4 GHz ISM(industrial-scientific-medical) band that is 83 MHz-wide. Security: authentication based on private keys and encryption Transmitting capabilities : omnidirectional and has range of 10m Bandwidth : data transfer rate up to 1 Mbps. Cost : relatively expensive with an expected price of $ 5 to 10 per Bluetooth module.

6 Wireless Protocols IrDA : specifies several infrared communication standards. Important standard for pervasive computing devices afe IrDA-Data nd IrMC (infrared mobile communications). IrDA is perfectly suited for high speed data connections like connecting a device to a wired network Characteristics of IrDA: Frequency band: infrared light is used as the physical trqansport medium Security: IrDA has no security concept Transmitting capabilities : point to point connection between sender and receiver. Designed for short distance communication (0-30 cm); Bandwidth : data transfer rate upto 4 Mbps. Cost : very cheap as senders and receivers are mass-produced ($1to2)

7 Mobile Phone Technologies Type 1G 2G 2+G 3G Protocol AMPS, C-Net GSM, TDMA, CDMA Technology Analog, Circuits- Switched Digital, Circuit Switched GPRS, HSCSD, EDGE Digital, Circuit or Packet Switched Speech Quality Poor High High High Bandwidth Low Low Medium High UTMS,W- CDMA Digital, Packet Switched Security None Depending on Protocol, Low to high Suitable Applications Data transmission and Fax Send short alphanumeric messages High GPRS Applications High Video conferencing and full motion video

8 Mobile Internet Protocol IP Protocol (IPv4, IPv6): IP has the task of delivering packets from the source host to the destination host solely based on the IP addresses in the packet headers. For this purpose, IP defines packet structures that encapsulate the data to be delivered. It also defines addressing methods that are used to label the datagram with source and destination information.

9 Mobile IP : Mobile IP is an Internet Engineering Task Force (IETF) standard communications protocol that is designed to allow mobile device users to move from one network to another while maintaining their permanent IP address. Mobile IP is an enhancement of the Internet Protocol (IP) that adds mechanisms for forwarding Internet traffic to mobile devices (known as mobile nodes) when they are connecting through other than their home network.

10 Steps of connection establishment in mobile IP : 1) Discover care-of-address 2) register care of address 3) tunnel care of address

11 Synchronization and Replication Protocol Client Server Used For AvantGo from AvantGo Inc PalmOS, Windows CE AvantGo Server Retrieving Content Channels (E.g Web Pages) Mobile connect from IBM PalmOS, Windows CE EPOC Lotus Notes, MS Exchange,RDBS PIM Applications, Databases Intellisync from Puma Technologies PalmOS, Windows CE Lotus Notes, MS Outlook PIM Applications Truesync from Starfish Technologies Mobile Phones, PalmOS, Windows CE Lotus Notes, MS Outlook,Sidekick etc PIM Applications

12 Synchronization can be device to server and device to device (where one device acts as server) like one client and one server sync, multiple client and one server sync, multiple client and multiple server sync. To avoid out of sync situations, Synchronization Principles are used: Pre-synchronization : Authentication, Authorization and determination of device capabilities. Synchronization : synchronization data exchange of new, deleted and updated entries Post-Synchronization : clean up tasks like updating mapping tables and reporting unresolved conflicts Example - SyncML

13 SyncML SyncML (Synchronization Markup Language) is the former name for a platform-independent information synchronization standard. The project is currently referred to as Open Mobile Alliance Data Synchronization and Device Management. The purpose of SyncML is to offer an open standard as a replacement for existing data synchronization solutions, which have mostly been somewhat vendor-, application- or operating system specific. SyncML works by exchanging commands, which can be requests and responses. As an example: the mobile sends an Alert command for signaling the wish to begin a refreshonly synchronization the computer responds with a Status command for accepting the request the mobile sends one or more Sync command containing an Add subcommand for each item (e.g., phonebook entry); if the number of entries is large, it does not include the <Final/> tag; in the latter case, the computer requests to continue with an appropriate Alert message, and the mobile sends another chunk of items; otherwise, the computer confirms it received all data with a Status command

14 Distributed Services Sun s Jini : Uses Java RMI between the different Jini participants 5 Key Concepts : Discovery :finds other members in the jini community and joins them Look-up : a directory that understands the java type hierarchy Leasing : ensures that the jini network is stable and self healing. Remote Events :allow jini services to send notification to participants in a jini Community. Transactions : same as database transactions

15 Distributed Services Microsoft's Universal Plug and Play (UPnP) Build on XML standards such as Simple Service Description Protocol (SSDP) for Service Discovery, General Event Notification Architecture (GENA) for events, and SOAP (Simple Object Access Protocol) for remote procedure calls. Services provided by UPnP : IP Addressing : A device that will join an UPnP network must get an IP address, can be achieved using DHCP or Auto IP from reserved IP Discovery : allows devices to advertise their services to control points and to use new control points to search for devices of interest Description : tell the control point what kind of service it is offering Control : send request to the device for service Events : control points can subscribe to events on devices. When an event occurs, device will send a notification to all subscribed control points Presentation : presentation URL under which the device can be configured remotely via a browser.

16 Message and Transaction Based Protocols : It ensures the delivery and atomic operations in the pervasive computing space, where communication breakdowns or devices being switched on and off while attempting to transmit data. 1. Message and Transaction Technology is the technology available for Guaranteed Message Delivery and atomic operations 1. Messaging and queuing system to allow asynchronous delivery of messages. 2. One to one, one to many, many to one queue 2. Message and Transaction Products Message Queuing Systems (ExpressQ,MQE,MSMQ) Relational Databases for Pervasive Computing Devices (DB2e,Oracle Lite)

17 Security Security Concepts Identification Authentication Authorisation Digital Signatures endorsed by passwords Non-repudiation Device Security WAP Phones PDAs

18 Server Side Security Inner Firewall (Web Application Security) Outer Firewall (Authentication and access Control) Connected to Gateways through SSL (WAP,Voice,PDA,ISP)

19 Cryptographic Algorithms Symmetric Cryptographic Algorithms Data Encryption Standard (DES) Triple DES AES Encryption Standard Public Key Algorithms RSA (Rivest, Shamir,adleman) Digital Signature Elliptic Curve

20 Device Management Challenges of Device Management Tracking the device locations Device user relationship Version control of devices and software Software updates of existing devices Installations of new software devices on existing devices Provide Secure access to device information

21 Device Management Software Distribution Issues and approches in Device management Hardware Capabilities Hardware Version Management Software Version Management Library Management Devices are not always connected Insecure Connections Unstable Connections Operating system Updates