Notes, summaries, assignments, exams, and exercises for Computer science for Other courses

1. TCP Congestion Control

Slow Start: TCP initializes congestion window (cwnd) to a small size and doubles it every Round Trip Time (RTT) until a loss occurs (exponential growth) or the slow start threshold is reached.

Congestion Avoidance: After reaching the threshold, cwnd is incremented by one segment for each RTT, growing linearly to avoid congestion.

Fast Recovery: When triple duplicate ACKs are detected, TCP halves the cwnd and reduces the slow start threshold to half of the cwnd size before the loss, then transitions to congestion avoidance.

2. TCP RTT and Timeout

Estimating RTT: Uses Smoothed Round Trip Time (SRTT) which is a weighted average of previous RTT measurements.

Timeout Calculation: Often calculated as Timeout=SRTT+4×RTT

SnapMirror (SM)

SnapMirror (SM) requires a license. It operates at the volume or qtree level, is used for disaster recovery (DR) and replication, and requires both a source and destination filer.

Synchronous SnapMirror

Synchronous SM replicates from the source to the destination nearly at the same time data is written to the source (saved to NVRAM).

Command Notes

All SnapMirror commands must be run on the destination filer, except snapmirror status, which can be run on either the source or destination.

Configuration Steps

1. Enable SM on source & destination filer

   source-filer> options snapmirror.enable
   snapmirror.enable            on
   source-filer> options snapmirror.access
   snapmirror.access            legacy
   

2. SnapMirror access

   Ensure the destination

Program Counter (PC) and Instruction Register (IR)

The Program Counter (PC) contains the address of the instruction to be read. The Instruction Register (IR) contains the last statement read.

Interrupts

Interrupts interrupt the normal execution of the processor. They appear mainly as a way to improve processing efficiency. Interrupts can be generated by software, clock, I/O, or hardware failure.

Disabled Interrupts

Disabled interrupts mean that the processor will ignore the interrupt signal. If an interruption occurs during that time, it generally will remain pending and will be checked by the processor after it enables interrupts.

Processor Actions

When the processor interprets the instruction and performs the action, the action can be classified...

Understanding the Data Link Layer

The MAC sublayer operates at the bottom of the Data Link Layer (OSI Layer 2).

MAC Sublayer: Core Functions

The Ethernet MAC sublayer has two primary responsibilities:

• Data Encapsulation
• Medium Access Control

Some key functions of the MAC sublayer include:

• Controlling access to the physical medium.
• Adding the MAC address to frames.
• Frame delimitation (determining the beginning and end of a data frame within a string of bits received by the physical layer).
• Performing transmission error detection.
• Discarding duplicate or erroneous frames.

LLC Sublayer: Data Transfer and Control

The LLC (Logical Link Control) sublayer defines how data is transferred on the physical environment, providing services to higher layers. The LLC...

1. Analyzing Exhibit Information for Network Conclusions

Refer to the exhibit. Which two statements can be concluded from the information shown in the exhibit? (Choose two.)

• All ports listed in the exhibit are access ports.
• A router connected to the switch is required to forward traffic between hosts.

2. Router Packet Forwarding on Uplink Trunk

A router is configured to connect to an uplink trunk, as shown in the exhibit. A packet is received on the FastEthernet 0/1 physical interface from VLAN 10. The packet's destination address is 192.168.1.120. What will the router do with this packet?

• The router will forward the packet to the FastEthernet 0/1.2 interface with VLAN tagging for 60.

3. BPDU Information Usage in Spanning Tree Protocol

For which two...

This document provides practical instructions and solutions for common tasks and challenges encountered when working with ArcView GIS, covering topics from database integration and map creation to geocoding and spatial analysis.

Core ArcView GIS Operations

Joining External Data in ArcView GIS

To join an external database with attributes of the current theme:

• Open the properties of the item table (theme).
• Open the external table to be joined.
• Identify the common field in both tables.
• Select the common field in the external table.
• Select the corresponding common field in the item table's properties.
• Click the Join icon.

Adding and Arranging Themes in ArcView

To add a new theme to a view and display it in the background:

• Add the theme using the Add Theme

Software Metrics Classification and Analysis

Analysis Model Metrics

• PF (Prediction Factor) Metrics: Used to predict the size of a system based on the analysis model.
• Bang Metric: Provides an independent indication of the system's implementation size.
• Quality Metrics of the Specification: Characteristics used to assess the quality of the analysis model and the Engineering Requirements Specification (ERS).

Design Model Metrics

• Object-Oriented (OO) Design Metrics: Provide indicators for OO design characteristics (e.g., inheritance, coupling, size of classes).
• Component-Level Design Metrics: Focus on cohesion, coupling, and complexity of individual software components.
• User Interface Design Metrics: Based on the appropriateness of the design as a metric

System Calls: Core OS Interaction

A system call is the mechanism used by an application program to request a service from the operating system.

How a System Call is Made

When a call is made, it involves placing a set of parameters in a specific memory location and then executing a machine language instruction for the processor.

Common POSIX System Calls

In operating systems, common POSIX system calls include: open, read, write, close, wait, exec, fork, exit, and kill.

Understanding Processes

A process is an abstraction of a running program, also referred to as a task.

Process Model Properties

1. All software executables are organized into several sequential processes.
2. A process includes the running program, the current values of the program counter, registers,

Domain Model

• Shows concepts only: classes, attributes, associations, and multiplicities.
• No methods, no UI, and no controllers are included.
• Purpose: To understand the real-world objects involved in the system.

Use Case Model (Module 6)

• Focuses on Actor ↔ System interaction.
• Uses the Verb + Noun naming convention.
• Format: Defines Actor steps versus System steps.
• Use cases serve as input for sequence diagrams, which inform class diagrams.

UML Class Diagram (Module 7)

• Class Components: Name, attributes, and methods.
• Association: Line connecting classes with multiplicity (1, 0..1, *, 1..*).
• Inheritance: Represented by an open triangle arrow symbol.
• Interface: Indicated by the «interface» stereotype.
• DCD (Design Class Diagram): Explicitly includes methods

IoT Protocols

Link Layer Protocols

• 802.3 Ethernet Standards

  A collection of wired Ethernet standards that provide data rates from 10 Mb/s to 40 gigabits per second. The shared medium in Ethernet can be a coaxial cable, twisted-pair wire, or optical fiber. This shared medium carries communication for all devices on the network.

• 802.11 Wi-Fi Standards

  A collection of wireless Local Area Network (WLAN) communication standards.

Network/Internet Layer

• Responsible for sending IP datagrams from the source network to the destination network.
• Handles host addressing and packet routing based on IPv4 or IPv6.
• Datagrams contain a source and destination address, which are used to route them from the source to the destination across multiple networks.
• IPv4 uses 32-