Caching in Pervasive web Monday, November 27 2006
Why web caching in Pervasive web is so important?
Caching in pervasive web fundamentally improves the performance by avoiding redundant data transfers and avoids long roundtrip to servers by cached data anywhere close to the client (proxies).
Client side caching: Generally data can be cashed anywhere in the network, in clients, servers or proxies. But I did not say the client side cache, I don't think it make much sense in pervasive web, typically mobile Devices are having less storage, may be some personal information could be cached or less amount data which is not application specific could be stored in clients.
Client side caching: Generally data can be cashed anywhere in the network, in clients, servers or proxies. But I did not say the client side cache, I don't think it make much sense in pervasive web, typically mobile Devices are having less storage, may be some personal information could be cached or less amount data which is not application specific could be stored in clients.
Server Side Caching: Server side caching improves response time, not the bandwidth, still it’s not completely solving the actual problem, There is still long round trip between client and server.
Proxy Caching: When caching pushed away from both client and server thereby freeing the two ends, so that both ends could do some other useful work. For example, server could do some computational work rather than delivering the same content repeatedly. Anyways it’s a design decision about where to store what.
Proxy Caching: When caching pushed away from both client and server thereby freeing the two ends, so that both ends could do some other useful work. For example, server could do some computational work rather than delivering the same content repeatedly. Anyways it’s a design decision about where to store what.
Caching may be an option in classic web but for constrained mobile environment caching is almost a must than an option for resource-intensive computation.
Advantages...
The main advantages are reduced network traffic, server load and response time (avoids World Wide Wait).
The reduction of response time directly reduces the communication cost in pervasive web, it may not be true in the classic web, but in pervasive web the communication cost is very important, (telecommunication services cost still much expensive in lot of countries). For example, if I browse 30 minutes daily in my mobile device and if it reduces 10 minutes by caching techniques, totally I could save 300 minutes monthly for my wireless connection. This makes me to think one important question though, what is cost of building and maintaining such infrastructure?
Though the wireless communication costs are going down as competition increases, but it will never reach zero (I hope that Google don't offer any free internet connection with add's) in my point of view, business Wants to maximize the ROI and caching could stay along with it.
Caching is not just improving scalability, its also improving reliability and user experience; it’s also zero code deployment using off-the-shell components.
Techniques:
There are different techniques developed for caching, such as proxy caching, hierarchical caching, inter cache communication, distributed caching, adaptive web caching etc
In recent years networked proxy caching - CDN widely used.
The future:
Caching can be a powerful technique when pervasive web uses semantic web where agents/bots hosted at client or servers may require frequent data for mining or doing some AI work.
Challenges
Clearly there should be a scheme to implement such system where we could define the administration controls and cache replacement policies
Few months back I have noted how caching opens up vulnerabilities in one way, caching data in proxies is very vulnerable. So each and every content should be scanned.
I previously mentioned that data could be cached "anywhere close to the client". it means not storing statically in intermediate proxies, In pervasive web mobility introduced few other challanges, what if users moves to new location? for example if I use my device at home, then The Home proxy could cache my data, if I move to new location the cached content should also be moved relative to my new location, again its design question what content needs to be moved and also depends on the longevity of the users stays at the new location. I heard there is new protocol to implement this called x-ICP
Questions I have in mind
what type of data has to be cached? (Note: One of the study estimates that 77% content delivered on the internet are multimedia objects such as images, audio etc)
what type of data has to be cached? (Note: One of the study estimates that 77% content delivered on the internet are multimedia objects such as images, audio etc)
What about the real time data or streaming content?
What caching techniques are standardized and how to implement device independent caching?
Content has to be cached for each device?
Content has to be cached for each device?
Since information increasing rapidly, how those replications maintain integrity?
What about the privacy of those cached contents?
And finally the Architectural challenges will be in top of all the above challenges I listed
