How Isp works

aljugan

hi Dear users i have one question about connection of ISP. how an ISP connects us to the rest of the world.can anybody explain it or share any link. and 2nd part of the question is this that when we are connected to the isp through a adsl (router/modem).this connection between me and my ISP in which category of networking falls?.
Thanks

xXErebuS

Take a look at the routing protocol BGP - this is the "internet" routing protocol.

Medium doesn't matter if that is what you're asking about the ADSL?

theodoxa

You connect to your ISP's Central Office (CO) using a variety of methods (xDSL, Cable, etc...) If its DSL, the CO has something called a DSLAM which separates the Voice (Phone Calls) and Data (Internet). Then, using BGP (Border Gateway Protocol), each router decides where to forward your data packet next to reach its destination. If the destination is in the same Autonomous System as your ISP, it will be routed through their network until it reaches its destination. While iBGP (BGP within a single AS) has its peculiarities (all beyond the scope of CCNA), what it does is really no different than IGPs such as EIGRP, OSPF, and RIP - It determines the best way to reach a destination.

If the destination is on another provider's network (a different Autonomous System), then BGP helps determine the best path to get it out of your provider's AS and to the destination AS. BGP has an obscenely [and unnecessarily] long list of path attributes which it uses to determine which route is best. For Cisco routers, Cisco added their own proprietary attribute called weight which is considered first. After that, thing such as how many ASes are crossed (think RIP's hop count, but using ASes instead of hops), whether the route was locally originated or was learned from somewhere else, Ingress/Egress, etc...are considered. It's really complicated, but in the end it does the same thing as any other routing protocol - Determines the best route to place in the routing table of each router to reach each destination subnet.

If your ISP is large enough (Tier 1), they may have their own backbone [covering the US or even other countries] and connections to other ISPs. If not, then they will likely have their own ISP (e.g. Level 3 Communications | The Reliable Partner of Choice) who can provide them with connectivity to their backbone and other ISPs. All Tier 1 ISPs are interconnected. Tier 2 and Tier 3 (Smaller) ISPs purchase service through larger (Tier 1) ISPs to reach other areas of the internet.

Tier 1 network - Wikipedia, the free encyclopedia

aljugan

Thanks a lottt for such explanation .....just one thing explain me please how one country connects to another country is it via satellite or via cable??(through sea)....thanks

aljugan

i means that when i am connected with my ISP it will call al LAN or which type of network is this???

Magic Johnson

aljugan wrote: »

i means that when i am connected with my ISP it will call al LAN or which type of network is this???

Wide Area Network (WAN)

kj0

aljugan wrote: »

Thanks a lottt for such explanation .....just one thing explain me please how one country connects to another country is it via satellite or via cable??(through sea)....thanks

Hopefully this will help. You can click on the lines and it will tell you what they are.

Submarine Cable Map

CoolAsAFan

kj0 wrote: »

Hopefully this will help. You can click on the lines and it will tell you what they are.

Submarine Cable Map

Thank you for sharing this link, very cool!