A Review of Internet Technology Part 2 – Internet Infrastructure

Based on RFC 2026 of the Internet Engineering Task force (IETF), the internet is a loosely organized international collaboration of autonomous, interconnected networks.

Usually you get connected to the Internet through an ISP (Internet Service Provider), and you are assigned a unique temporary IP address from a DHCP (Dynamic Host Configuration Protocol), permanent one if you are connected through LAN (Local Area Network). If you like to send a message to another computer on the Internet you use Protocol Stack, The TCP (Transmission Control Protocol) and IP (Internet Protocol), are the two major communication protocols.

Protocol Stack Used on the Internet
1.      Internet Protocol Layer2.      Hardware Layer 3.      Network Protocol Layer 4.      Hardware Layer

So how it works? ISP maintains a pool of modems for dial in customers, and a port server controls the data flow, billing and usage and your packets routed to the ISP Backbone and from here usually the packets go through several routers, several backbones, dedicated lines, and other networks until they reach the destination. If you want to trace route to reach to Yahoo for example, from windows command line you can do something like this and therefore see the route that it takes to reach to Yahoo, this is the route from my pc to reach to Yahoo over the network:

Internet Infrastructure is built upon many large networks which interconnected with each other. These networks are known as Network Service Providers or NSPs. Here are some of the well-known NSPs: AT&T, Verizon, Sprint, and IBM.

These networks peer with each other to exchange packet traffic. Each NSP is required to be connected to at least three Network Access Points or NAPS. NSPs also interconnect at Metropolitan Area Exchanges or MAEs. MAEs serve the same purpose as NAPs, but privately owned. MAEs or NAPs are referred as Internet Exchange Points or IXs. Here is some hierarchy of the infrastructure:

So how does a packet find its way through the network? Through a router, a router is connected between networks to route packets between them. Each router is aware of its sub-networks and IP addresses. When a packet reaches a router, the router examines the IP address and check with its routing table if it finds it, direct the packet to the destination, if not, send the packet to the NSP backbones that has the largest routing tables that the packet can be directed correctly.

What if the destination IP not recognized? There are DNS (Domain Name Service) companies which keep track of computer’s name, and the corresponding IP addresses on the Internet.

 DNS servers contain the database that has the information of IP addresses and if a DNS server doesn’t have the domain name requested information, it will redirect the request to another DNS server.

I would like to also go over OSI 7-layer model as it is known among IT industry for Internet Protocol Stack and you can imagine for yourself there are other protocols involved for the communication and building the infrastructure of Internet. The following image will show you each layer and next to it some of the protocols on each layer:

 And here is a little description of each layer and its role: 

Here is the link if you like to view most of the protocols involved in each OSI layer: http://en.wikipedia.org/wiki/List_of_network_protocols

Through these seven layers you can see better how different types of services are communicate with each other and how all computers are interconnected and form the Internet Infrastructure. To sum up, Internet Infrastructure is computers as clients and some as servers running over the huge networks and communicating through protocols.