Adapting Web Services for Limited Bandwidth Tactical Networks. Trude Hafsøe, Frank T. Johnsen, Ketil Lund, Anders Eggen - PDF

Description
Adapting Web Services for Limited Bandwidth Tactical Networks Trude Hafsøe, Frank T. Johnsen, Ketil Lund, Anders Eggen Outline Web Services Push vs pull communication Standardization efforts Optimizations

Please download to get full document.

View again

of 17
All materials on our website are shared by users. If you have any questions about copyright issues, please report us to resolve them. We are always happy to assist you.
Information
Category:

History

Publish on:

Views: 6 | Pages: 17

Extension: PDF | Download: 0

Share
Transcript
Adapting Web Services for Limited Bandwidth Tactical Networks Trude Hafsøe, Frank T. Johnsen, Ketil Lund, Anders Eggen Outline Web Services Push vs pull communication Standardization efforts Optimizations data representation data communication Summary Web Services and Network Based Defence Web Services is in widespread use on the Internet today. COTS products are readily available. Web Services is being considered as an enabling technology for NEC, and seem well suited. Web Services provides both synchronous and asynchronous communication. Push vs Pull communication Push: Push information to recipient. Asynchronous: No polling, which reduces communication overhead. Non-blocking. Example: Event service Good for wide-area distributed systems Pull: Actively fetch information from server. Synchronous: Polling; communication overhead and potential blocking of the application. Example: Remote procedure call An Event Service Asynchronous dissemination of information. Participants: publishers, that submit information to the system, and subscribers, that express their interest in specific types of information. Web Services pub/sub standardization efforts The asynchronous nature of the publish/subscribe paradigm makes it a very important mode of communications in NBD. Two standardization efforts regarding publish/subscribe: OASIS finished its Web Services Notification (WSN) standard late in W3C has a draft version of a similar framework called Web Services Eventing (WS-Eventing). WSN has most features. WS-Notification Three parts to the WSN specification: WS-BaseNotification The WS-Eventing specification provides similar functionality to that of WS-BaseNotification, but they are not compatible with each other. WS-BrokeredNotification defines the interface for notification intermediaries, i.e. notification brokers. WS-Topics enables users to specify the types of events in which they are interested. Web Services and Network Based Defence Pub/sub is well suited for use in a military context: track updates, building COP, and creating situational awareness. Challenges when using web services over tactical communications links Tactical networks Volatile medium low bandwidth high delay unstable connections Challenges when using Web Services Compression Information representation and encoding Optimizing transport (e.g. caching, multicast) Information representation Work by Gerz et al 1 Message based communication Referentially complete message, e.g., self-contained XML document. Replication based communication ( push ). Query based communication ( pull ). A combination may be most suited for Web Services Adapting the message representation Mainly status updates ( replication ) Retrieving missing data using queries. Standardization required for interoperability. 1 Gerz, M., Loaiza, F., and Chaum, E. An Object-Oriented XML Schema for the MIP Joint Command, Control, and Consultation Information Exchange Data model, CCRTS 2006 Optimizing transport Pub/Sub optimization by proxy content filtering deliver only relevant and necessary information unicast/multicast gateway utilize the underlying transmission medium subscriptions on behalf of clients reduce network traffic increase scalability Request/Response optimization by proxy caching of responses reduce network traffic increase scalability Subscription by proxy Server (S) Proxy (P) Clients A B subscribe(p,s) subscribe(a,s) ack(p) ack(a) subscribe(b,s) ack(b) Notification via proxy, unicast Server (S) Proxy (P) Clients A B notify(p) notify(a) notify(b) Notification via proxy, multicast Server (S) Proxy (P) Clients A B notify(p) multicast_notify(a,b) Caching Server (S) Proxy (P) Clients A B Low bandwidth Medium bandwidth request(a, object.x) object.x request(a, object.x) object.x request(b, object.x) object.x Other considerations COTS Web Services use HTTP over TCP as default not suited to tactical networks we are currently evaluating other means of transport What about security? More information available to the proxy means more ways to optimize data flow. (Security on link layer.) Little information available to the proxy, less ways to optimize data flow. (End-to-end application level security.) Summary Web Services well suited for implementing NEC, but verbose - based on XML, so inefficient in tactical networks Means to adapt Web Services compression proxy servers information representation optimization
Related Search
We Need Your Support
Thank you for visiting our website and your interest in our free products and services. We are nonprofit website to share and download documents. To the running of this website, we need your help to support us.

Thanks to everyone for your continued support.

No, Thanks