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[phazey]

Not really a bad thing, but (using True) about 95% of the usual ads are not showing/blocked. I get broken image links now. This is also happening to forum status icons etc,

Tried this on 3 different machines, same result. I've no proxy at my location, but i do know True is using Bluecoat transparent proxies somewhere in their network.....

[george]

You are using OpenDNS or other 3rd party DNS provider. Please use True own DNS instead, as they don't like OpenDNS etc.

[phazey]

Thanks, if it's not a problem with TV itself, then i'll stick with what i have......saves me a bunch on bandwidth.

[phazey]

I just want to revisit this. I just went to a site (facebook) using my HTPC and also found i had problems similar to what i experienced previously. Then i noticed that the browser i was using was stalling on URL's that had "static" in them - something i remembered from the problem above with some pictures being hosted on static.thaivisa.com when using True & a 3rd party DNS service.

Hope this helps...

[george]

Hi Phazey, hope this helps:

1. Customer is using a Thai ISP access method that is transparently cached (True ISP is notoriouis for this...)

2. Customer has the OpenDNS US based DNS servers configured

3. Customer attempts to access site that uses geographic load-balancing (via Akamai, thaivisa site for example)

Under the above circumstances, the customer was unlikely to be able to access the web site.

The explanation and root cause of the issue is as follows. Thaivisa.com uses a service similar to Akamai to serve its content:

1) Customer's PC looks up "thaivisa.com" against the OpenDNS DNS servers based in the US

2) thaivisa.com uses a similar service to Akamai, and Akamai DNS servers. Hence the customer's DNS lookup goes to the OpenDNS DNS servers in the US, and these servers recursively look up "thaivisa.com" from the Akamai DNS servers. As Akamai uses geographic load-balancing they attempt to return the IPs of servers that "are close to the customer". Akamai use the source IP of the querying recursive DNS server (= OpenDNS US based servers in this instance) to determine what "close to the customer is". Normally this works fine, as most people use recursive DNS servers that are close to where they are. However, when Thailand based customers from some Thai ISP's use US based DNS servers (like OpenDNS), things break down a little, as US based server IPs are returned. (And they are obviously not close to the customer!) Hence, the Akamai DNS returns IP addresses of US based Akamai servers for thaivisa.com .

3) The customer's PC attempts to establish an HTTP connection with the US based Akamai servers. (Using the IP addresses returned by OpenDNS.)

4) The Thai ISP's transparent caches intercept the HTTP traffic. The transparent caches look up thaivisa.com against local DNS servers. As these DNS servers are in Thailand, Akamai correctly returns the IP addresses of our load balance server in Bangkok.

5) The caches attempt to connect to the Akamai servers nearest to Thailand to retrieve the web objects.

6) The Akamai servers sends return packets to the customers PC's (as this is the source IP of the incoming traffic). This is where the problem is. The return traffic should have gone to the caches and not to the customer's PC.

7) Caches time out

8) Customer's browser times out

Thai ISP's caches are situated on the Thai side of the international circuits and only attempt to cache international traffic. They expect that egress international HTTP traffic has return traffic coming back on the international circuits.

The issue with OpenDNS and Thai ISP's transparent caching in conjunction with geographically load-balanced sites, is that the traffic is initially sent internationally (due to lookups against US based OpenDNS servers) and then the caches sends the traffic back domestically (due to lookups against Thai based DNS servers). Due to this asymmetry, return traffic from the target web site do not reach the caches.

The above is unfortunate, as OpenDNS is an _excellent_ service.

If you are based in Thailand and using OpenDNS, change back to your isp's dns.

[phazey]

Hi George, hope this helps;

The only issue I've found with True, Thaivisa.com, and i have tried to explain previously with Facebook is that the word "static" is being used, and filtered out, hence things not working 'quite right'.

Otherwise i can browse both sites fine - although i get no ads on TV, and FB gives me the mobile site..... If you want to take this to a PM level then please go ahead, i'd love to give my assistance based on my observations.