5.3.2 Basic of Internet Architecture

  The internet architecture can be broadly classified into three layers. The very first layer consists of Internet Backbones and very high speed network lines. The National ScienceFoundation (NSF) created the first high-speed backbone in 1987 called NSFNET, it was a T1 line that connected 170 smaller networks together and operated at 1.544 Mbps (million bitsper second). IBM, MCI and Merit worked with NSF to create the backbone and developed a T3 (45Mbps) backbone the following year. Backbones are typically fiber optic trunk lines.The trunk line has multiple fiber optic cables combined together to increase the capacity. Fiber optic cables are designated OC-48 can transmit 2,488 Mbps (2.488 Gbps). The nodes are known as Network Access Point (NAPs). The second layer is usually known as Internet Service Provider (ISP). The ISPs are connected to the Backbones at NAP’s with high speed lines.

The end users which are part of third layer are connected to ISPs by dial up or leased lines and modems. The speed of communication is usually 1400 bps to 2048 kbps.


  In the real Internet, dozens of large Internet providers interconnect at NAPs ( Network Access Point) in various cities, and trillions of bytes of data flow between the individual networks at these points. The Internet is a collection of huge corporate networks interconnected with one other at the NAPs, backbones and routers to talk to each other. A message can leave one computer and travel halfway across the world through several different networks and arrive at another computer in a fraction of a second.

The routers determine where to send information from one computer to another. Routers are specialized computers that send messages to their destinations along thousands of pathways. It joins two networks, passing information from one to the other.