How the Internet Actually Works

• A. Bits
• B. Packets ✓
• C. Frames
• D. Streams

Why: Data is divided into small units called packets, each of which is sent independently across the network and reassembled at the destination. Bits are individual 0s and 1s, frames are link-layer units, and streams are a higher-level abstraction.

• A. Only the content of the message
• B. The source and destination IP addresses and sequence information
• C. The user's password and login credentials
• D. The exact physical path the packet will take

• A. To store copies of websites permanently
• B. To encrypt all data passing through it
• C. To examine a packet's destination address and forward it toward its destination
• D. To assign domain names to devices

• A. Because each packet is randomly encrypted differently
• B. Because routers independently choose the best available route based on current network conditions
• C. Because the sender manually selects a route for each packet
• D. Because packets always follow the exact same cable

• A. The message is discarded entirely
• B. The receiver uses sequence numbers to reorder them and reassemble the original data
• C. The sender must manually resend the entire message
• D. The router reorders them before they leave the network

• A. To encrypt data sent between two computers
• B. To translate human-readable domain names into IP addresses ✓
• C. To assign physical MAC addresses to network devices
• D. To route packets across the global internet backbone

Why: DNS acts like the internet's phone book, converting names such as example.com into the numeric IP addresses that computers use to locate each other.

• A. www.example.com
• B. 00:1A:2B:3C:4D:5E
• C. 192.168.1.10 ✓
• D. https://example.com/index

Why: IPv4 addresses are written as four decimal numbers (octets) separated by dots, each ranging from 0 to 255. A domain name is not an IP address, and a MAC address uses hexadecimal pairs separated by colons.

• A. A domain name to an IPv4 address ✓
• B. A domain name to an IPv6 address
• C. A domain name to a mail server
• D. An IP address to a domain name

Why: An A record maps a hostname to an IPv4 address. IPv6 uses AAAA records, mail servers use MX records, and reverse lookups use PTR records.

• A. It stores the authoritative records for a domain permanently
• B. It assigns IP addresses to devices on a local network
• C. It performs the lookup process on behalf of a client to find the answer to a DNS query ✓
• D. It blocks malicious websites at the firewall level

Why: A recursive resolver, often run by an ISP or a public service like 8.8.8.8, queries other DNS servers step by step on the client's behalf and caches the results to speed up future lookups.

• A. To permanently store every domain name ever requested
• B. To reduce latency and load on DNS servers by reusing recent answers for a set time ✓
• C. To ensure that IP addresses never change
• D. To encrypt DNS responses from eavesdroppers

Why: Caching stores answers for a period defined by the record's TTL (time to live), so repeated requests can be answered quickly without querying the full hierarchy again.

• A. Large Area Network
• B. Local Area Network ✓
• C. Linked Access Node
• D. Logical Address Network

Why: LAN stands for Local Area Network, a network that connects devices within a limited geographic area such as a home, office, or school building.

• A. Modem
• B. Switch ✓
• C. Router only
• D. Repeater

Why: A switch receives data from connected devices and forwards it to the specific device it is addressed to, allowing efficient communication within a LAN.

• A. A unique identifier assigned to a network interface card by its manufacturer ✓
• B. The public IP address given by an internet provider
• C. A password used to secure a Wi-Fi network
• D. The domain name of a website

Why: A MAC (Media Access Control) address is a hardware identifier burned into a network interface card, used to identify devices on the same local network.

• A. Coaxial cable
• B. Fiber optic cable
• C. Twisted pair cable (Ethernet cable) ✓
• D. Serial cable

Why: Twisted pair cabling, often called Ethernet cable such as Cat5e or Cat6, is the most common wired medium for connecting devices in a LAN.

• A. To store files for all devices
• B. To connect the local network to other networks, such as the internet ✓
• C. To amplify the Wi-Fi signal only
• D. To assign domain names to devices

Why: A router connects the local network to external networks like the internet and directs traffic between them, often also assigning local IP addresses via DHCP.

• A. To manufacture the cables that carry data across oceans
• B. To provide customers with access to the internet and route their traffic onto the broader network ✓
• C. To write the protocols that govern how data is transmitted
• D. To store copies of all websites on the internet

Why: ISPs connect end users such as homes and businesses to the internet and carry their traffic to and from the wider network. They do not manufacture cables, define protocols, or host every website.

• A. A store where customers buy internet subscriptions
• B. A physical location where multiple networks connect directly to exchange traffic with each other ✓
• C. A government agency that regulates internet pricing
• D. A type of home router that manages multiple devices

Why: An IXP is a physical facility where networks such as ISPs, content providers, and CDNs interconnect to exchange traffic directly. This often keeps data local and reduces latency and transit costs.

• A. Central hubs are illegal under international law
• B. Direct interconnection is faster and cheaper because traffic can take shorter paths between networks ✓
• C. IXPs are required to store backup copies of user data
• D. Central hubs cannot handle IP addresses

Why: Direct peering at IXPs lets networks exchange traffic over shorter paths, reducing latency and the cost of paying upstream transit providers. The internet is designed as a network of networks, not a single central hub.

• A. Tier 1 ISPs are government-owned while Tier 3 ISPs are private
• B. Tier 1 ISPs can reach the entire internet through peering without paying for transit, while Tier 3 ISPs buy transit from others ✓
• C. Tier 1 ISPs only serve mobile devices while Tier 3 ISPs serve desktops
• D. Tier 3 ISPs are faster because they have fewer customers

Why: Tier 1 ISPs have global reach through settlement-free peering with other Tier 1 networks and do not pay for upstream transit. Lower-tier ISPs must pay higher-tier providers for access to parts of the internet they cannot reach directly.

• A. Local websites are stored on the user's own device
• B. The traffic may be exchanged locally at a nearby IXP, avoiding a long-distance route ✓
• C. Local traffic is encrypted so it bypasses routers
• D. Internet protocols forbid data from traveling more than 50 miles

Why: If the user's ISP and the website's host both connect to the same local IXP, the traffic can be exchanged there without traveling to distant networks. This shortens the path, reducing delay and load on long-haul links.

• A. To compress data so it transfers faster between browser and server
• B. To encrypt data in transit and verify the identity of the server ✓
• C. To assign unique IP addresses to each client on a network
• D. To translate domain names into numeric IP addresses

Why: TLS (Transport Layer Security) provides confidentiality by encrypting data in transit and authentication by using certificates to verify that the server is who it claims to be. Compression, IP assignment, and DNS resolution are handled by other mechanisms.

• A. A faster connection speed due to protocol optimizations
• B. A layer of TLS encryption beneath the HTTP protocol ✓
• C. Automatic caching of all web pages on the client device
• D. A replacement for TCP with a connectionless transport

Why: HTTPS is simply HTTP carried over a TLS-encrypted connection. The HTTP messages stay the same, but they are wrapped in encryption so eavesdroppers cannot read them. It does not inherently speed things up or change the transport layer.

• A. Asymmetric operations are much slower than symmetric ones, so they are used to establish a shared session key that is then used for bulk encryption ✓
• B. Asymmetric keys can only encrypt a single byte at a time
• C. Symmetric keys are not supported by modern browsers
• D. The TLS standard forbids asymmetric encryption after the first message

Why: Public-key (asymmetric) cryptography is computationally expensive. TLS uses it during the handshake to securely agree on a shared symmetric session key, and then uses that faster symmetric key to encrypt the actual data exchanged.

• A. It stores the user's password securely on the server
• B. It binds a public key to an identity, allowing the client to verify the server's authenticity ✓
• C. It speeds up DNS lookups by caching IP addresses
• D. It compresses the encrypted payload before transmission

Why: A certificate, issued by a trusted Certificate Authority, ties a server's public key to its domain name. The client checks the certificate's signature chain and hostname to confirm it is talking to the legitimate server rather than an impostor.

• A. Forward secrecy, so compromise of a long-term key does not expose past sessions ✓
• B. Non-repudiation of messages sent by either party
• C. Guaranteed delivery of every packet in order
• D. Protection against all denial-of-service attacks

Why: With ephemeral key exchange such as (EC)DHE, each session uses fresh keys that are discarded afterward. Even if the server's long-term private key is later stolen, previously recorded sessions cannot be decrypted, which is called forward secrecy.

• A. The web server
• B. The client, such as a web browser ✓
• C. The DNS root server
• D. The router at the internet service provider

Why: In the client-server model, the client (for example, a web browser on your laptop or phone) initiates requests, and the server responds to them. The web server waits for incoming requests and sends back the requested content.

• A. Sends data to the server to create a new resource
• B. Deletes a resource from the server
• C. Requests a resource from the server without changing it ✓
• D. Updates part of an existing resource on the server

Why: GET is the most common HTTP method and is used to retrieve a resource, such as a web page or image, from the server. It is considered safe because it should not change anything on the server.

• A. 404
• B. 500
• C. 301
• D. 200 ✓

Why: Status code 200 OK indicates the request succeeded and the response contains the requested content. 404 means Not Found, 500 means Internal Server Error, and 301 means the resource has been permanently moved.

• A. It contains the body of the web page being requested
• B. It tells the server which DNS server to use
• C. It identifies the client software making the request ✓
• D. It encrypts the connection between client and server

Why: The User-Agent header tells the server what kind of client is making the request, such as a particular browser or operating system. Servers may use this to tailor responses. It does not carry page content, handle DNS, or perform encryption.

• A. Faster page loading through compression
• B. Support for additional HTTP methods
• C. Encryption of data between client and server using TLS ✓
• D. Automatic translation of web pages into other languages

Why: HTTPS is HTTP layered over TLS (Transport Layer Security), which encrypts the data exchanged between client and server and helps verify the server's identity. It does not change the request methods or speed up pages on its own.

• A. A failure of a router's power supply
• B. When the demand for network capacity exceeds what links and devices can handle, causing queuing and packet loss ✓
• C. A deliberate block placed by an internet service provider on certain websites
• D. The process of assigning IP addresses to new devices on a local network

Why: Congestion occurs when more traffic arrives at a link or router than it can forward, so packets wait in queues and may be dropped once buffers fill up.

• A. Bandwidth
• B. Throughput
• C. Latency ✓
• D. Jitter

Why: Latency is the delay a packet experiences in traveling across the network. Bandwidth describes capacity, and throughput describes the amount of data actually delivered per unit time.

• A. Ensuring that all data is encrypted before transmission
• B. The ability of a network to keep operating correctly even when some components fail ✓
• C. Guaranteeing that every packet arrives in the same order it was sent
• D. Limiting the number of users connected to a single server

Why: Fault tolerance is the network's ability to continue functioning despite failures of links or routers, largely achieved through redundancy and dynamic rerouting.

• A. Fixed paths cannot carry video traffic
• B. Dynamic routing lets routers find new paths automatically when links fail or become congested ✓
• C. Dynamic routing eliminates the need for IP addresses
• D. Fixed paths are only allowed for government networks

Why: Dynamic routing protocols such as OSPF and BGP allow routers to share topology information and adapt to failures or congestion by choosing alternative routes.

• A. TCP ignores lost packets and relies on the application to recover them
• B. TCP detects missing acknowledgments and retransmits lost packets while reducing its sending rate ✓
• C. TCP permanently closes the connection after the first lost packet
• D. TCP sends each packet along multiple paths at once to prevent loss

Why: TCP uses acknowledgments and timeouts to detect loss, retransmits the missing data, and applies congestion control to slow its sending rate, easing pressure on the network.