1. Pub/sub-based Web Applications
Walter Wong
HIIT & NomadicLab

2. Agenda Current data delivery in the Web Pub/sub-based content delivery
Implementation
Evaluation
Conclusion

3. Pull-based model Client Server HTTP Get + Servers don’t save state
- Clients constantly poll
for data
- Entire page download
- No real time delivery
capabilities
HTTP 200 OK
HTTP Get
HTTP 200 OK :

4. Push-based HTTP long-polling
Client
Server
update!
+ Clients request and wait
+ Almost real-time delivery
+ Servers send just the
updated data (AJAX)
- Servers keep open TCP
connections
- Clients request again after
data delivery
HTTP Get
HTTP 200 OK
XHR Get (long poll)
HTTP 200 OK
XHR Get (long poll) :

5. Pub/sub-based for Web content delivery
Objectives
Real-time data delivery capabilities in the Web
Lower network bandwidth consumption (simple delivery channel - no TCP)
Lower hardware requirements (no connection maintenance)
Lower energy consumption (portable devices)

6. Pub/sub Model Subscriber Publisher Subscribe(data)
+ Servers don’t save state
+ Partial page download
+ Real time delivery
Capabilities
+ Consumes less energy
Publish(data)
Publish(data)
Publish(data)

7. Pub/sub-based for Web content delivery

8. PSIRP Firefox plug-in

9. Evaluation network

10. PSIRP Firefox plug-in vs. HTTP long-polling

11. Conclusion
Pull and push-based systems hinder real-time content delivery in the Web
Waste of resources mainly due to the host-centric client/server model
Publish/subscribe provides real-time content delivery with lower overhead
Implementation shows that pub/sub is simpler, requires lower hardware requirements and reduces the overall network traffic

12. Questions?
Comments?
Thanks!