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I have a ADSL broadband DHCP connection. I am using D-Link GLB-802C ADSL router. Now I want to know what actually happens when I access internet through browser or any other program. I know all http communication is handled via TCP. I have following questions.

  • while setting up the internet with the disk provided by router, I didn't made any setting of proxy so is the proxy not present, I just entered the username and password
  • If router handling connection to ISP proxy, Do I need to make special configuration for JAVA P2P applications to communicate with other peers.
  • My internet is working fine and when I checked network settings of Java they are configured to use browser settings.Are there any other settings required

I would also like to know do I need to forward a port for all P2P applications. I am currently trying JXTA and facing lot of problems to make it work over internet. I did started the thread here http://stackoverflow.com/questions/1371549/jxta-p2p-application-over-internet but not getting any answers so I am digging into this to make it work.

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migrated from stackoverflow.com Sep 3 '09 at 16:41

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Umm, you asked the other question 1 hour ago, give it some time –  Adam Batkin Sep 3 '09 at 7:10

1 Answer 1

Routers use NAT protocol to handle that. Making the long story short, routers relay TCP/IP packets directly between your computer and the destination server. There is no need to use proxies, the important setting is called ‘default gateway’ or ‘default route’.

But that method works that easy only for outgoing connections (as your router knows which computer from internal network has initiated the connection). When an incoming connection comes, it has only your external (router) IP and router can't know to which computer the packet is designated.

And there's where port forwarding comes. By setting it, you tell router that your computer is going to handle connections to that specific port, and all incoming connections to it should be relayed to your machine.

So, the answer may be a little ambiguous as it depends on how specific P2P protocol works. In most cases, you don't need to have the port forwarded as long as your peer has one (or external IP), or some proxy is used to relay your connections.

But I think it's a good idea to always have a port forwarded if it's possible as if you're going to use that on an Internet-wide basis, you can't guarantee that your peer will be able to forward him-/herself a port.

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Hi, I have some questions. * If our router is directly communicating to destination server how our ISP provider have all the records of sites we visited. * If ISP has no role to play between us and destination server how they control the speed with which we download. I mean, I have 256 kbps connection line I cannot download with higher speeds than this even if server provides high bandwidth connections. * I have heard of ports are also present in operating system are these same as that of router ports or it is a different concept. –  Xinus Sep 3 '09 at 8:31
    
well, the provider still might use some kind of transparent (i.e. running in such way that neither you or your router needs to set anything) proxy for your outgoing HTTP connections; you may try to use lagado.com/proxy-test to check if this applies to you. The ISP might also use some kind of network sniffer (a tool which ‘looks’ at the packets coming through the router) but that's less possible. –  Michał Górny Sep 3 '09 at 9:33
    
…and for the bandwidth thing, packets still go through ISP's routers and they can limit the rate at which they are relayed. It doesn't need to use proxy for that. And for the ‘ports’ — if you mean ports in network stack of your system, then that's the same thing. Your computer can also work as a router with appropriate hardware installed. –  Michał Górny Sep 3 '09 at 9:38
    
Note also that it is specific to IPv4. With IPv6, there are much more IP addresses and therefore no need for the NAT hack. –  bortzmeyer Sep 14 '09 at 8:10

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