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# 39516 15-Aug-2009 18:39
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Website owners can force telecom's cache to not cache their website. It works for apache and iis servers:

http://en.wikipedia.org/wiki/List_of_HTTP_headers#Avoiding_Caching

http://support.microsoft.com/kb/247404
 
http://www.i18nguy.com/markup/metatags.html
 
It just involves putting some html code into your apache or iis server and into your website and this will tell telecom's cache to not cache your website so visitors get a fresh up to date version of your website all the time.

Here is an example of youtube using the no cache header:

http://url-info.appspot.com

Type in www.youtube.com and click 'headers' once the scan is finish. You will see this:

Cache-Control no-cache

So i don't know how telecom is caching youtube videos.


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  # 247016 15-Aug-2009 18:50
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you realise that its up to the cache software to choose whether to implement and respect the cache control and expiry headers?  some providers may be caching content regardless of the headers.

In the case of telecom though, their cache's are apparently configured to respect those settings.  An
excerpt from the NOG list regarding telecom's cache implementation:


"If you don't want it cached or want to control the time we keep it in cache then you can use cache control directives and expiry meta tags in the page.

At this point in time we have not enabled caching of streaming media."




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  # 247339 16-Aug-2009 20:28
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i think there may be some legal copyright issues around cache's not respecting the no cache headers:

http://news.cnet.com/2100-1038_3-1024234.html

i also read cache's don't cache ssl pages so if websites use https then i don't think you can cache them.

 
 
 
 


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  # 247343 16-Aug-2009 20:35
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Why do you have such a vendetta against caching?




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  # 247407 16-Aug-2009 23:02
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How dare they cache static content, it lowers latency and increases download speeds - outrageous... even worse they international bandwidth savings allow them to offer an unlimited plan for $59.95 /month... those bastards

OH WAIT...

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  # 247640 17-Aug-2009 13:17
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Because they are storing a copy of your content and serving it without your permission if they violate the no-cache directive.

Why should ISPs be treated any differently to a kid distributing pre-release material via bittorrent to people - they are both violations of copyright.




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  # 247643 17-Aug-2009 13:18
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  # 247659 17-Aug-2009 13:35
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richms: Because they are storing a copy of your content and serving it without your permission if they violate the no-cache directive.

Why should ISPs be treated any differently to a kid distributing pre-release material via bittorrent to people - they are both violations of copyright.


Well for one they are awarded "Common Carrier Status" which means that as long as they treat all traffic the same, they can be held liable for none of it, much the same as the post office are not liable for any content they carry through their network.

FYI If the post office started to 'screen' mail for content, then they would lose their common carrier status and become liable for any content they failed to correctly screen/block.

Oh, and it's not like someone's ripped your content from another medium and uploaded it without permission to teh internets and removed all the copy protection.

They are simply speeding up the transmission of your data, in it's original format, in it's original medium.

Sure they should not ignore the no-cache directive, but you shouldn't be such a drama queen :-)




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  # 247682 17-Aug-2009 14:18
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Do anti-caching people turn off the cache in their browser as well? Why stop there, you could ignore TTL on DNS records and do a DNS lookup each time adding latency. ;)

Seriously tho, there is nothing wrong with a well configured cache - I run Squid 3.1 under FreeBSD and it makes a huge improvement - while the byte hit ratio is only around 20% the request hit ratio is closer to 45% - that's 45% of the http requests that didn't need to leave my internal network giving me a significant improvement in page loading times.

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  # 247699 17-Aug-2009 14:54
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The whole "ISPs have common carrier status" thing is a myth. And caching by an ISP is explicitly allowed under the copyright law under section 92E.

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  # 247704 17-Aug-2009 15:04
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freitasm: But that's only if they are not following the directives. AFAIK there isn't any indication of this happening.

Or do you know for sure it's happening?



It was me that suggested that a cache has to implement and respect the directives.  I was stating a technical fact rather than pointing out the Telecom caching (or ISP-X caching) behaviour.

I also pointed out (in my first reply on this thread) that Telecom have publically (via NZNOG) stated that they do respect these settings and currently do not cache streaming media.




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  # 247706 17-Aug-2009 15:07
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It's easy to fit in by yelling out, and far more difficult to actually read and consider the facts. Anytime you hear, "I don't have the time to understand this issue, I'm too busy being upset," you know that something is wrong.
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  # 247712 17-Aug-2009 15:11
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i just checked www.twitter.com at http://url-info.appspot.com and it uses a no cache header too.

section 92E of the nz copyright act says:

An Internet service provider does not infringe copyright in a work by caching material if the Internet service provider:
(b) complies with any conditions imposed by the copyright owner of the material for access to that material.

So if a website(copyright owner) is using the no cache code in their header then that is a condition imposed by the copyright owner so telecom has to comply with it or they will be breaching copyright.

here is a list i have made of popular websites that use the no cache header so telecom can't cache:
twitter.com
facebook.com
youtube.com
digg.com

So if telecom thinks they are going to save money by caching youtube videos, they will be breaking the law. Heck i would love to know what websites telecom caches on their unlimited plan. Anyone know?

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  # 247724 17-Aug-2009 15:24
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the youtube cache at telecom is a google server (ie if you are a telecom broadband customer using their DNS) you will be pointed to it. This is slightly different to pushing youtube traffic via an http cache.  Obviously Google are sweet with it since their DNS points to it.

There are also plenty of sites that might use the no-cache header but are akamised or similar.
The no-cache directive applies to each html object served up, so unless you've checked every single page on those above sites you can't say for sure that they are entirely uncacheable.

So I doubt the no-cache header own it's own is a clearcut way of saying telecom can't cache something.

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  # 247732 17-Aug-2009 15:36
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How does the DNS stuff work to point at their cache? Does it look at the IP doing the lookup or something?




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  # 247736 17-Aug-2009 15:43
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you need to be using Telecom/Xtra's DNS servers to get the response that points you to the youtube cache. I've noticed it serves up some static google content as well.

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