Congratulations! You have just been hired as a Network Engineer at CNN$,$ a prestigious news organization renowned for its global reach and breaking news coverage. Your expertise in networking and your ability to explain complex processes to non$-$technical individuals have earned you a spot on the team.

On your first day, you're met with anticipation and excitement as you step into the modern CNN headquarters. As you settle into your office, you're informed that the Chief Technology Officer $($CTO$)$ has scheduled a meeting to welcome you and discuss a crucial case study. With a deep breath, you head to the CTO's office.

Inside the spacious office, the CTO, a seasoned tech professional, warmly greets you and gestures for you to sit. He explain, "Welcome to CNN$!$ We're glad to have you on board. We're facing an interesting network challenge, and I$\text{'}$d like you to address it$."$

The CTO presents the case study on a large screen:

Case Study: CNN Network Optimization

As CNN$\text{'}$s network engineer, your task is to ensure seamless and efficient access to our website, $"$www$.$cnn$.$com," for users around the world. In this scenario, we're focusing on a user who is accessing our website through their web browser.

Steps of the Scenario:

$1.$ Application Layer:

Imagine a user, let's call her Sarah, who is sitting at her computer. She enters $"$www$.$cnn$.$com" into her web browser's address bar, eager to catch up on the latest news.

$2.$ DNS Resolution:

Once Sarah submits the URL, her web browser initiates DNS resolution. The browser seeks the IP address of $"$www$.$cnn$.$com" and receives $"72\mathrm{.}21\mathrm{.}91\mathrm{.}19"$ as the response.

$3.$ Transport Layer:

With the IP address in hand, Sarah's browser establishes a connection with CNN$\text{'}$s server on port $80.$ A TCP SYN packet is generated to set up the connection.

$4.$ Network Layer:

The TCP SYN packet is enclosed within an IP datagram. It carries Sarah's computer's source IP address and CNN$\text{'}$s server's destination IP address. Sarah's computer consults its routing table and identifies the default router's IP address as $"192\mathrm{.}168\mathrm{.}1\mathrm{.}1."$

$5.$ ARP and Link Layer:

Sarah's computer needs the default router's MAC address. It broadcasts an ARP request, asking for the MAC address associated with $"192\mathrm{.}168\mathrm{.}1\mathrm{.}1."$ The router responds with an ARP reply, sharing its MAC address.

$6.$ Physical Layer:

With the router's MAC address, Sarah's computer encapsulates the IP datagram in a MAC frame. The frame's source MAC address is her computer's MAC address, and the destination MAC address is the router's MAC address.

Back in the CTO's office, the case study is complete. The CTO leans forward and says, "Now that you understand the scenario, let's see how well you've grasped it$.$ Here are $5$ questions $($Question $1$ to $5)$ to gauge your comprehension."

$1.$ What is the main objective of the presented case study?

To explore DNS resolution challenges

To investigate network optimization for CNN

To analyze physical layer protocols

To understand browser functionality

$2.$ As per the case study described in Question $1,$ what does Sarah enter into her web browser's address bar?

Group of answer choices

An IP address

A URL

A MAC address

A DNS server

$3.$ As per the case study described in Question $1,$ what is the purpose of the TCP SYN packet?

Group of answer choices

To carry the IP datagram

To establish an IP address

To initiate a TCP connection

To decode network traffic

$4.$ As per the case study described in Question $1,$ how does Sarah's computer discover the router's MAC address?

Group of answer choices

By sending an ICMP request

By broadcasting an ARP request

By querying a DNS server

By using the IP datagram

$5.$ As per the case study described in Question $1,$ which layer is responsible for transmitting electrical or optical signals over the physical medium?

Group of answer choices

Application Layer

Transport Layer

Network Layer

Physical Layer