computer networks chapter1

keith ross

What does the term "hosts" or "end systems" refer to in the context of the Internet?

All connected devices like traditional computers, smartphones, and nontraditional devices.

What do packet switches, such as routers, do in a network?

They forward packets to their destinations.

What is the sequence of links and switches that a packet traverses called?

A route or path through the network.

What analogy is used to describe packet-switched networks?

Packets are compared to trucks and communication links to highways and roads.

What types of Internet Service Providers (ISPs) do end systems connect through?

Residential, corporate, university, WiFi, and cellular data ISPs.

What are Internet protocols like TCP and IP collectively known as?

TCP/IP.

Which organization develops Internet standards documented as requests for comments (RFCs)?

The Internet Engineering Task Force (IETF).

What is the primary purpose of Internet applications?

To serve various services like messaging, mapping, streaming, and social media.

Where do Internet applications run?

On end systems, not within packet switches.

What is a socket interface in the context of internet applications?

It specifies how a program on one end system asks the Internet to deliver data to a specific program on another end system.

What must be followed to create an Internet application involving data delivery?

Rules that are defined by a protocol.

What do hosts consist of at the network edge?

Computers, smartphones, and other devices.

How are hosts divided in network architectures?

Into clients and servers.

What role do servers play in network environments?

They store and distribute content.

What connectivity method does DSL typically use?

Frequency division multiplexing.

What does DSL allow to share the same line?

Data and telephone signals.

What does the cable Internet infrastructure primarily utilize?

Existing cable TV infrastructure.

What is hybrid fiber coax (HFC)?

A combination of fiber optics and coaxial cable used in cable Internet.

What role does the CMTS play in cable Internet?

It turns analog signals from cable modems into digital format.

What kind of access technology provides gigabit per second internet speeds?

Fiber to the home (FTTH).

What are the two architectures used for shared fiber networks in FTTH?

Active optical networks (AON) and passive optical networks (PON).

What technology does 5G fixed wireless utilize?

Beam forming technology for high-speed residential access.

What are the primary types of physical media used in network access technologies?

Fiber cable, coaxial cable, copper wire, and radio spectrum.

What are the two categories of physical media?

Guided media and unguided media.

What common type of guided transmission medium is used in telephone networks?

Twisted pair copper wire.

What is a characteristic feature of coaxial cable?

It consists of two concentric copper conductors.

What allows multiple end systems to connect to coaxial cable in cable Internet?

Shared medium nature.

What do optical fibers conduct as bits?

Light pulses.

Why are optical fibers preferred for long-distance transmission?

They offer high data rates, low attenuation, and resistance to interference.

What are the different categories of terrestrial radio channels?

Short range, local area, and wide area.

What are the two types of satellites involved in satellite communication?

Geostationary and low earth orbiting (LEO) satellites.

What type of delay occurs when each packet switch must receive the entire packet before forwarding it?

Store and forward transmission delay.

What happens when the arrival rate of packets exceeds a certain threshold at a router?

Congestion occurs, leading to queuing delays and possibly packet loss.

How do routers determine outbound links for packet forwarding?

Using forwarding tables based on destination addresses.

What is the primary function of a circuit-switched network?

To reserve resources for the entire duration of the communication session.

What are two types of multiplexing in circuit-switched networks?

Frequency division multiplexing (FDM) and time division multiplexing (TDM).

What is a key characteristic of packet switching compared to circuit switching?

Packet switching does not reserve resources during idle periods.

What are three types of delays that can affect packets during their journey?

Processing delay, queuing delay, and transmission delay.

What is traffic intensity in networking?

The ratio of arrival rate to transmission rate, significant for estimating queuing delay.

What tool measures end-to-end delay by tracing the route packets take?

Trace Route.

What does throughput measure in networking?

The average rate of successful data transfer over a network.

What happens in a network with multiple links?

Throughput is limited by the slowest link along the path.

How does intervening traffic affect throughput?

It can reduce throughput even if the link has a high transmission rate.

What are the five layers of the Internet protocol stack?

Physical, link, network, transport, and application layers.

What does encapsulation in networking refer to?

The process of adding header information as data moves down the protocol stack.

What can malware lead to in a network?

File deletion, data theft, and turning hosts into botnets.

What are the three types of DoS attacks?

Vulnerability attacks, bandwidth flooding, and connection flooding.

What are DDoS attacks characterized by?

Attackers controlling multiple sources to launch attacks.

What defense against packet sniffing can enhance security?

Cryptography.

What is IP spoofing in the context of network security?

Forging source addresses on packets to masquerade as someone else.

What mechanisms validate the source of messages to counteract IP spoofing?

End point authentication mechanisms.

What is the function of queuing delays in packet-switching environments?

They occur when packets wait in a queue before being transmitted on the link.

What is the formula to calculate delay in a simple source-destination network?

Delay = 2L/R.

What happens when queuing delay exceeds certain rates?

Queuing delay may approach infinity.

Which body is primarily responsible for specifying standards for network components like Ethernet and WiFi?

IEEE 802 LAN Standards Committee.

What does store and forward transmission imply for packet processing?

A packet switch must first store the entire packet before it can forward any part of it.

How do processing delays typically compare in high-speed routers?

They are usually in microseconds.

How does fiber optics compare to copper wire in terms of data transmission?

Fiber optics offer much higher data rates and lower signal loss.

What often acts as a bottleneck in today's Internet structure?

The access network.

What type of Internet access is being revolutionized by 5G technology?

Fixed wireless internet access.

What are the key benefits of protocol layering in network protocols?

Modularity and easier component updates.

In the context of Internet standards, how many RFCs are defining various protocols?

Nearly 9000 RFCs.

What role do Internet Exchange Points (IXPs) play in the ISP ecosystem?

They facilitate direct connections between ISPs, enhancing efficiency.

What is the primary difference between instantaneous throughput and average throughput?

Instantaneous throughput is measured at a specific moment, while average throughput is over the entire data transfer.

Why are twisted pair copper wires twisted together?

To reduce interference.

What is one drawback of protocol layering some critics argue about?

Potential duplication of functionality.

What impact does signal propagation delay have on satellite communications?

It introduces delays depending on satellite type and elevation.

What technology does FTTH use to achieve high speeds?

Optical fiber.

What does it mean for a cable internet to be a shared broadcast medium?

Multiple users share the same bandwidth, which can reduce individual performance during peak usage.

What challenge does satellite communication face due to the orbit of geostationary satellites?

Signal propagation delays due to their fixed position above Earth.

What characterizes active optical networks (AON)?

They use powered devices to manage data traffic.

What is a consequence of large companies creating their networks?

Better control and cost reduction.

What happens in packet-switched networks when multiple packets arrive simultaneously?

Queuing delays occur as packets wait to be processed.

Why might packet loss occur in a packet-switched environment?

When the output buffer is full due to congestion.

What is the role of a transport layer protocol in network communication?

It ensures reliable data transmission between hosts.

What does a queuing delay depend on?

The number of packets waiting to be transmitted.

How is the access network's performance often limited?

By the common bottlenecks that arise from overprovisioned core network links.

What happens to packets during a routing process?

They are examined and address information is checked for forwarding.

What defines the average throughput formula?

Average throughput is calculated as F/T bits/sec.

What feature do modem technologies share across DSL, cable, and 5G?

They connect home networks to the Internet.

Why does physical wiring installation incur high costs in network infrastructures?

Because labor costs can exceed material costs significantly.