Transparent Proxiy Cache And Ntl

codebreaker · 10-06-2006, 20:22

As far as my limited knowledge is concerned , i think that NTL uses a transparent proxy cache [ Inktomi and Apache ]. After your browser sends a request to fetch a website the DNS server of NTL tries to look into it's own proxy cache and then if unsuccessful to get the page , tries to look into the actual cloud [ internet or requested remote server ] .

Jon T · 10-06-2006, 20:31

Post deleted by author

original comments were aimed at NTL not the author of the first post(Codebreaker)

Chris W · 10-06-2006, 20:54

Quote:

Originally Posted by Jon T

No offence to you, but it doesn't inspire much confidence when NTL technical support operatives don't know how their product works.

In defence, i think it is very good that someone comes here to find out more about products

When I used to work in ntl the information available through the official channels which far inferior to what i learnt by googing and visiting this and other forums.

I also don't think it is a fundamental part of the technical support role to know how proxies work- in two and a half years of working there, no customers asked me to explain it.

codebreaker... feel free to post as many questions as you like on the forum, there are lots of knowledgable people around and if we can help you gain more knowledge this will help you, plus our member base who are ntl customers because they will be getting superior technical support from you

homealone · 10-06-2006, 21:08

Quote:

Originally Posted by Chris W

In defence, i think it is very good that someone comes here to find out more about products

<snip>

absolutely, well said.

codebreaker, much of what you need to know about proxies used by NTL can be found here

http://homepage.ntlworld.com/robin.d...trancache.html

and in the CF articles here

http://www.cableforum.co.uk/forum/article.php?c=16

codebreaker · 10-06-2006, 21:33

A big "thank U " to Chris . It's great to mate that u had been once with the technical support . But it is a matter of sheer disappointment that when a guy working with the ntl techsupport comes up with a new post , a guy who wants to know , wants to break the shackle of "SUPPORT BOUNDARIES" gets such kind of response from a fellow member who claims to be an IT technician .

cheers,

codebreaker

---------- Post added at 03:03 ---------- Previous post was at 02:49 ----------

This is what JonT send me as a PM
"I think it's good that you want to learn about the product that you are supporting. It's just a shame that you have to ask outside the organisation you wish to learn about"

I really wonder the level of frustration this guy has for his ISP . He indirectly calls me an outsider just because i have come up with a post on an unofficial forum . i can not believe it . I think i have to unsubscribe from cableforum ..

nffc · 10-06-2006, 22:51

Quote:

Originally Posted by Chris W

I also don't think it is a fundamental part of the technical support role to know how proxies work- in two and a half years of working there, no customers asked me to explain it.

Yes, just like most customers don't ask how their PCs work when it goes faulty. We know, that's so we can diagnose it, and we know "of" important things for that purpose - but the customers don't know, don't care and don't want to know.

They just want the product that they pay for / have paid for working. I'm sure NTL userbase is the same.

To codebreaker - no reason why you shouldn't further your knowledge and I don't see what's wrong with it, after all it is the customer who benefits in the long run. Do stay - we need tech support insiders!

To Jon T - you have a point and no need to over-react, if NTL haven't trained adequately in your view, that needs addressing with them, not an employee who just happens to be trying to further his knowledge by looking outside of NTL. It's wrong, but not his fault.

codebreaker · 11-06-2006, 15:26

I am back ... with some knowledge in my belly ...[ lol ]. Whenever an NTL customer tries to run an nslookup command from the DOS shell the following happens :
nslookup bbc.com
[the NTL dns first tries to resolve the address and pulls up the IP address associated with the specified web URL , if it fails to do so then it queries an external DNS server in an effort to resolve the IP address and the customer gets a message "non-authoritative answer" folloed by the web URL and it's corresponding ip address ]

Now the biggest question i have is , if NTL DNS servers [both primary and the secondary ] stops working ( u can recall the recent DNS outage ) will it be able to query an external DNS , is yes then how , if no then is it possible for the customer to specify an external DNS on his lan configuration . Will he be able to get access to the DNS server of bt or freeserve ?.....

cheers,
codebreaker

**Rob** · 11-06-2006, 15:56

It would appear that it's not easy to bypass the ntl proxy dns stuff.

I'm having appalling connections all day toady, except to CF, and using another ISPs DNS settings in my network connection TCP/IP settings made no difference whatsoever

codebreaker · 11-06-2006, 16:09

That's the point !!! the question is why ? , why i won't be able to specify the DNS addresses of btopenWORLD:
[Primary DNS Server: 194.73.73.94
Secondary DNS Server: 194.73.73.95 ] or Imperial Colleges in London [DNS: 155.198.20.20 ] etc if i specify them explicitely on my LAN connection . PLease can any1 come up with an answer ??

cheers,
codebreaker

melevittfl · 12-06-2006, 07:45

Quote:

Originally Posted by codebreaker

That's the point !!! the question is why ? , why i won't be able to specify the DNS addresses of btopenWORLD:

Because the transparent proxies perform their own DNS lookup as well. So, if there was a problem with NTL's DNS servers, you'd need to explicitly configure a different DNS server *and* bypass the NTL proxy caches (becuase they'd still try the NTL DNS server).

codebreaker · 12-06-2006, 15:06

Quote:

Originally Posted by melevittfl

So, if there was a problem with NTL's DNS servers, you'd need to explicitly configure a different DNS server *and* bypass the NTL proxy caches (becuase they'd still try the NTL DNS server).

well melvittf , i think to configure a different DNS server i have to get into the LAN properties , and put the DNS1 and DNS2 addresses of another ISP [ like btopen , freeserve ]. right ? . Now the question is can a customer use the NTL line to query a 3rd party DNS server ? . Will a freeserve DNS server do the job of resolving a web URL into an IP address for an NTL customer ? . If you open the command window and type nslookup [ after specifying the DNS addresses in lan connection ] , get into the nslookup shell and type : server [freeserve address] you can get the response from the server or the request will simply get timed_out. Now i want to know as whether a customer will get a reply from that freeserve DNS or will the DNS request will simply get TIMED_OUT ? .

cheers,
codebreaker

**Paul M** · 12-06-2006, 16:25

To quote from one of our articles ;

Transparent Proxy

Your PC does a dns lookup of the destination servers IP using its own (locally) defined dns servers.
It sends the http request on tcp port 80 to the destination servers IP address.
This request is intercepted by NTL's routers and re-directed to one of a group of transparent proxy [cache] servers - the decision on which proxy server gets used is based on the requested domains IP address.
The chosen proxy server checks if it has a valid copy of the requested page in its cache (using the domain name, not IP address).
If the proxy has the page it returns it directly back to the client, Job done.
If the proxy does not have the page it does a dns lookup of the requested domain using it's own defined dns servers.
The proxy sends the http request on tcp port 80 to the destination servers IP address.
This request is routed over the network direct to the destination servers IP.
The requested page is then returned, by the destination server, directly back to the proxy server.
The requested page is then returned, by the proxy server, direct to the client.

As you can see from point 6, they use their own DNS servers which are obviously the ntl dns servers, so if they are not working, your browsing will fail at that point, whatever dns servers *you* have set.

codebreaker · 12-06-2006, 17:08

[quote=Paul M]To quote from one of our articles ;

The requested page is then returned, by the destination server, directly back to the proxy server.

The requested page is then returned, by the proxy server, direct to the client.

just to add : A COPY OF THAT PAGE GETS STORED IN THE CACHE.

**Paul M** · 12-06-2006, 17:16

That depends on the headers with the page.

codebreaker · 12-06-2006, 17:27

Quote:

Originally Posted by Paul M

That depends on the headers with the page.

is that the cache-control tag u r talking about Paul ?