how do isp's work ?

i got bored so i started to look to see how the internet works. i have been looking at all the stuff to do with ip addresss, packets etc... but one thing i could find much on is how isp's work.

when you dial up to the net you dial up to ur isp but do all the files and infomationsyou request run throught your isp before it gets to you and all the information you submit gets sent to isp before going to its target ?

if so can they monitor what specfic people are doing and the information they are requesting and submiting ? can they get things like credit card deatails ? - i know its in https so its encrypted but if they can intercept the siginal cant they just decrypt it??

all i want its to just understand this a little bit - links to the relative info or answers would be apriciated

thanks

the internet is just a bunch of networks owned by different companies/people. internic assigned each major isp a block of ip addresses these large isp's give blocks to smaller isp's that they host ( yes ISPs have ISPs). all the isp's have an internal routing protocol ( IGP internal gateway protocol IS-IS, OSPF, etc) that their routers use and they redistribute the routes through their EGP (external gateway protocol) which is BGP for the most part. the networks each have an AS# (autonomous system number) that they registered (like AS#1 is BBN ) to seperate their BGP network from other BGP peers. the ISP's lease lines from telcos and/or each other. large ISPs will by buildings in each major city, usualy one ISP will own the building and the other ISPs rent rack space in the same building and connect their routers via fiber or CAT5 to other ISP routers in the same building. when you dial-up to an isp you go through what is known as a local loop provider (the telco that owns the wire outside your house) that will connect you to a modem bank that is in one of these buildings, the modem bank can be owned and sit on another ISPs network however. this is done by allowing you to connect to the modem bank which does the authentication on your isps radius server and your isp in return gives the isp that owns the modems a cut of the money( most small ISPs do this so they dont need to purchase modem banks up front just lease blocks of them from someone else). so to answer your question you may or may not be directly connecting to your isp just authenticating through them. the other part of your question is can they see the data? yes, if they wanted to they can capture the data as it passes through their network. but dont worry SSL is very secure and extremely hard and time consuming to decrypt.

OK, This is good info and if I understood what I read I think I knew most of it. The thing I don’t know is how do the blocks of IP addresses that are assigned get registered so other ISP’s know how to find them?

Example:
- I type in a Web address into my browser.
- Lets say this Web address is hosted by ISP A
- Lets also say that I subscribe to ISP B
- The address I typed gets sent to my ISP (B)

Question:

- How does ISP B know where to forward by request to in order to connect to ISP A?
- Is there some kind of central look up service, a phone book if you will, that ISP B uses to find ISP A?

I was always under the impression that there where a handful of central hubs around the world that provided this look up service for ISP’s. I thought these “central” places are where the ISP’s registered themselves so they could be seen on the internet. Is this correct? If not please explain further.

Thanks.

your not going to be able to get a full understanding by starting at this point.

u need to really start from the beginning,
read up on:
ip routing & dns servers

that will get you going in the right direction.

-SiX

read on how DNS works for the name resolution aspect of this, but if you are asking how ISP A knows how to get to ISP B then its quite simple. the internet is made up of a couple really big ISPs like global crossing, UUNET, BBN, QWEST, etc these ISPs have whats called an IGP (internal gateway protocol) that passes routes between their routers usualy OSPF but larger ones use IS-IS cause its more stable and scalable they redistribute the IGP routes to an EGP (external gateway protocol) which is BGP4. iBGP is their internal BGP running withing their network and eBGP is where they send their routes to other ISPs via BGP peering. think of it this way draw 4 circles each circle represents an isp whith several hundred routers running ospf to pass routes to each other (normal WAN stuff here) now draw a big circle around the 4 little ones this represents the BGP protocol passing network routes from one isp to another. the major isps dont charge each other for peering to each other but they do charge the little isps for peering with them which makes them the isps isp hehe. hope this helps.

what im wondering is if -

computer A sends info to computer b can computer c see it when computer C is not meant to eg. a hacker

.....A ----> b.....
..........^..........
..........|...........
..........C...........

or is it wen you say 'capture the data as it passes through their network.' do you mean LAN or a network such as one at a school or work place and someone uses a packet sniffer ? or netowrk as in part of the interent where it passes through some kind of isp's computer type thing ??

thanks

You seem like your pretty interested in Networking, I suguest going and getting your CCNA certification. You'll gain a better understanding of complicated computer networking, such as "the internet'.