icn exam Qs

Difference between UTP and STP?

UTP (Unshielded Twisted Pair) is the most common type of twisted pair used in LANs; STP (Shielded Twisted Pair) contains an extra metallic shield to provide better protection against electromagnetic noise and interference

Difference between 802.3 and 802.4 standards?

802.3 is the standard for Ethernet. 802.4 is the Token Bus standard, which uses a "token" (the right to send) that circulates at a given rate, ensuring everyone can eventually speak but often resulting in empty waiting time

What is "service" in network software?

A service is a set of basic operations (primitives) that can be called by a layer from the layer above it. It defines what operations the layer provides to its users, but not "how" those operations are implemented

What distances are typical for WAN?

The typical distance for a Wide Area Network (WAN) is 100 km (covering a country) or 1,000 km (covering a continent)

What are typical uses for networks for home?

Typical uses include accessing information (news, e-government), communication (email, IM, P2P), entertainment (Video on Demand, MMO games), e-commerce (online shopping, netbanking), e-learning, and e-health (patient monitoring)

What is flow control? What is the problem and what is a typical solution?

Flow control is a mechanism used to prevent a fast sender from overwhelming a slow receiver. The problem it addresses is the potential flooding of nodes with more data than they can process. A typical solution is the use of buffers

What is a "trustful connection"?

A trustful (reliable) connection is a service where the source and destination negotiate parameters and use acknowledgment messages to ensure data is transferred without any errors, such as in file transfers

Main differences between Iridium and Globalstar systems?

Iridium uses satellite-to-satellite switching in space to pass communication between nodes. Globalstar uses a "bent-pipe" design where the satellite reflects the signal back to ground-based hubs for switching.

What was the main aim of creating a Packet-Switched network?

The primary aim was fault tolerance; the US Department of Defense wanted a control network capable of surviving a nuclear war where nodes could be switched off without crashing the system

What is typical for broadcast networks?

Broadcast networks use a single common channel of communication where every packet is received by all machines; the intended recipient is identified by an address field in the packet

What is characteristic for multipath fading?

It occurs when radio signals reflect off different surfaces and arrive at the receiver at different times and out of phase. This effect is sensitive to moving objects

What is a typical latency for LEO satellites?

The typical latency is 1–7 ms

How many bytes are in the payload (data) of ATM cells?

An ATM cell is 53 bytes total, containing 48 bytes of user data (payload) and a 5-byte header

What are the differences between static and dynamic channel allocation?

Static allocation uses discrete, fixed time intervals, which can result in the channel remaining unused and wasted. Dynamic allocation is request-based and requires a schedule, which can be centralized (via a scheduler) or decentralized (where hosts argue over the schedule)

What is the protocol?

A protocol is a set of rules that defines how peer entities communicate within the same layer, essentially defining the "how" of communication

Why is it good to structure network software into layers?

Layering allows for separate abstraction levels with well-defined tasks, minimizes inter-layer communication, and ensures the system is not overwhelmed by mixing different task groups

What is frequency hopping spread spectrum transmission?

It is a transmission method where the frequency changes during transmission. It is hard to detect, nearly impossible to jam, and resistant to multipath fading

What is a GEO satellite?

A Geostationary (GEO) satellite orbits at an altitude of 35,800 km, matching the Earth's rotation so it appears to stay at the same point above the surface, requiring no tracking antennas

Minimum number of GEO satellites to cover Earth's surface?

The minimum required is 3 satellites

How can we put information into electromagnetic waves?

Information is placed on a carrier signal by modifying physical parameters like voltage or current through modulation techniques such as Amplitude, Frequency, or Phase shift keying

What is not an advantage of satellite systems?

Significant propagation delays (latency) and sensitivity to atmospheric conditions like rain (especially at higher frequencies) are notable disadvantages

How does the Ethernet protocol work (based on the ALOHANET)?

It uses a shared channel where computers check if the channel is busy. If it is free, it sends data. If two computers send at the same time, a collision occurs; both stop, wait a random amount of time, and try again (CSMA/CD).

What are the main considerations (objectives) at the network creation?

The primary aims are to optimize channel capacity usage, increase the robustness of communication (fault tolerance), and decrease latency.