Computer networks

Chapter 1

What was the primary motivation behind the development of the ARPANET?

The U.S. Department of Defense (DoD) sought a command-and-control network capable of withstanding a nuclear attack, as the existing public telephone network was deemed vulnerable

Who conceived the initial design for a distributed, fault-tolerant network that later influenced the ARPANET?

Paul Baran, an employee at the RAND Corporation, proposed this network design, advocating for digital packet-switching technology

Why did AT&T reject Baran's proposal for a distributed network?

AT&T, the telephone monopoly at the time, dismissed Baran's ideas, believing his network was impractical.

What event prompted the creation of ARPA (Advanced Research Projects Agency)?

The Soviet Union's launch of Sputnik, the first artificial satellite, in 1957, exposed inter-service rivalry within the U.S. military over research funding. President Eisenhower established ARPA in response.

Who played a key role in the development of the ARPANET and its focus on networking?

Larry Roberts, a program manager at ARPA, recognized the potential of networking and sought expert advice, eventually leading to the ARPANET's development

What was the role of IMPs (Interface Message Processors) in the ARPANET?

IMPs acted as minicomputers within the ARPANET, responsible for packet switching and routing data between connected hosts

Describe the initial structure of the ARPANET

The ARPANET initially connected four nodes located at UCLA, UCSB, SRI, and the University of Utah, chosen due to their ARPA contracts and diverse, incompatible host computers

How did the ARPANET expand in its early years?

The ARPANET experienced rapid growth as more IMPs were installed, expanding its reach across the United States and connecting a growing number of institutions

What limitation of the ARPANET protocols led to the development of TCP/IP

The ARPANET protocols proved unsuitable for communication across different networks (internetworks). TCP/IP was designed specifically to address this issue.

How did the University of California, Berkeley, contribute to the widespread adoption of TCP/IP?

Researchers at Berkeley integrated TCP/IP into the 4.2BSD release of Berkeley UNIX, adding a user-friendly programming interface called sockets and developing network utilities. This made TCP/IP accessible and encouraged its adoption.

What prompted the National Science Foundation (NSF) to establish CSNET and later NSFNET?

Recognizing the ARPANET's impact on research but its limited access, NSF created CSNET to connect computer science departments. Later, NSFNET was established to provide a research network open to all universities

What was the initial purpose of the NSFNET backbone?

The NSFNET backbone aimed to connect NSF's six supercomputer centers, facilitating access for researchers across the country

How did the NSFNET evolve to become more commercially viable?

NSF encouraged the creation of ANS (Advanced Networks and Services), a nonprofit corporation, to manage and commercialize NSFNET, ultimately transitioning it away from government funding

What role did NAPs (Network Access Points) play in the transition to a commercialized internet infrastructure?

NAPs served as interconnection points for different network operators, fostering competition and ensuring communication between regional networks as the internet transitioned away from a single backbone structure

How has the internet's architecture transformed with the growth of content providers like Google and Netflix?

The rise of large-scale content providers has led to a flattening of the internet hierarchy. These entities now often connect directly to access ISPs, bypassing traditional transit networks.

What are IXPs (Internet eXchange Points) and why are they significant?

IXPs are physical locations where multiple ISPs connect and exchange internet traffic. They facilitate peering arrangements, allowing ISPs to directly handle traffic between their networks.

Define "peering" in the context of internet infrastructure

Peering refers to agreements between ISPs to exchange traffic directly, often at IXPs, to avoid relying solely on paid transit services.

What are Tier-1 ISPs and how do they differ from other ISPs?

Tier-1 ISPs operate extensive international backbone networks. Unlike other ISPs, they do not pay for transit and form the core of the internet, with all other networks connecting to them.

What are the common types of LAN?

LANs can be wired, using Ethernet cables, or wireless, using Wi-Fi (IEEE 802.11 standard).

Give an example of a PAN.

A common example of a PAN is a Bluetooth network connecting a smartphone to wireless headphones or a smartwatch.

What is Bluetooth technology?

Bluetooth is a wireless technology standard used for exchanging data over short distances. It uses radio waves and is commonly employed in PANs

Give an example of a MAN.

cable television network.

What are the two main components of a WAN subnet?

A WAN subnet typically comprises transmission lines, such as fiber optic cables, and switching elements, commonly known as routers

What is a VPN?

A VPN (Virtual Private Network) is a technology that creates a secure and encrypted connection over a public network, such as the internet. It allows users to access private networks remotely as if they were physically present.

How do networks connect to form an internetwork?

Networks connect to form an internetwork using special devices called gateways, which facilitate communication between networks using different protocols

What is a gateway?

A gateway is a device that connects two or more different networks, allowing them to communicate. It acts as a translator between different protocols or network architectures e.g Router

What is path diversity? How is it used to mitigate multipath fading?

Path diversity is a technique to combat multipath fading by sending information over multiple independent paths. It increases the probability of successful reception even if one path experiences fading.