List and define the five layers of the Internet Model in order from top to bottom.

Describe the core responsibility of each layer.

Match the name of the data unit: message, segment, datagram, and frame, to its layer.

Define what a protocol is.

Explain the advantages and disadvantages of protocol layering.

Illustrate the process of encapsulation.

Explain why every device on the Internet must implement the IP protocol, while transport and application protocols run only on end hosts.

Design a simple protocol for a new application (example: a basic chat service), defining the message format (headers and payload) and the rules for message exchange.

Trace the high-level steps of a web request, from a user click to receiving data.

Identify the host name and the path name in a URL.

Define the role of HTTP, web browser and web servers in Web browsing.

Explain why web servers are always on at well-known addresses.

Deconstruct a basic HTTP GET request, identifying the request line, headers (including Host header) and the terminating blank line.

Explain why an HTTP request needs a Host header and why header lines end in CRLF.

Deconstruct a basic HTTP response, identifying the status line, headers (example: Content-Type, Content-Length, Date, Last-Modified), and the message body containing the requested object.

Interpret common status codes (200, 404) in terms of what happened at the server.

Explain why HTTP is considered a stateless protocol and what that means for server design.

Explain the purpose of cookies and trace an HTTP request and response that includes cookies.

Calculate the time to load a page of N objects under non-persistent HTTP and persistent HTTP.

Explain how HTTP/1.1 improved the latency performance of HTTP/1.0.

Explain head-of-line blocking, why parallel TCP connections are an incomplete fix, and how HTTP/2 improved the performance of HTTP/1.1.

Explain how browser caching and conditional GET (304 Not Modified) reduce response time and load on the origin server.

Given the number and relative sizes of the objects on a web page, evaluate which HTTP performance technique helps most.

Define what a socket is and what socket() returns.

List, in order, the socket calls a TCP client and a TCP server make, and state what each call does.

Given a sequence of send() or recv() calls and the state of the socket buffer before each, determine what each call does and returns, on a blocking socket and on a non-blocking socket.

Given client or server socket code, check whether it uses the socket calls correctly, including send() and recv(), explain what goes wrong when it runs, and describe the correct usage.

Given a server’s connections, determine how many sockets it has open and the role of each.

Given a timeline of client actions, trace when a server with no concurrency serves each client.

Explain how processes, threads, and select() each let a server handle multiple clients, and compare their overhead.

Given a server loop that uses non-blocking sockets, determine where the loop spends its time and whether it serves every client.

Explain partial failure in a distributed system. Given a scenario, describe what each component can observe when another component fails.

Define the three properties of the CAP theorem. Given how a system behaves during a network partition, determine whether it chose consistency or availability.

Identify the key services provided by DNS.

Given a hostname, identify the root, TLD, and authoritative DNS servers involved in resolving it and the role of each.

Given a proposed DNS design, such as a centralized one, identify its advantages and disadvantages compared to the current hierarchical design.

Trace the sequence of DNS messages that must occur before a browser can send an HTTP request, given what the local DNS server has cached. Identify each query as iterative or recursive and compute how long the lookup takes.

Given a set of DNS resource records (A / AAAA, NS, CNAME, MX), determine the answer to a DNS query.

Interpret the output of the dig command, identifying what each section of the DNS message (header, QUESTION, ANSWER, AUTHORITY, ADDITIONAL) contains.

From a dig response with no answer, determine the next server to query in an iterative lookup.

Explain which transport protocol DNS uses and why.

Define Time-to-Live (TTL) for a DNS record. Given a timeline of queries, determine which ones the local DNS server answers from its cache.

Given a scenario, choose between a short and a long TTL and justify the trade-off.

Identify the four components of nodal delay and name what each depends on (packet size, link rate, link length, traffic, or none of these).

Given link and packet parameters, calculate transmission and propagation delay, and predict how each changes when one parameter changes.

Given a packet’s delays on a path of store-and-forward links, determine where its bits are at a given instant and when the last bit reaches the destination.

Given a new domain, determine which resource records must be created, and at which server (registrar/TLD vs. authoritative), for the domain’s web and mail servers to be reachable.

Explain how DNS can be used to implement load balancing.

Given a description of an attack on DNS, classify it as DDoS, man-in-the-middle, or cache poisoning, identify which part of the resolution process it exploits, and determine whether DNSSEC prevents it and why or why not.

Identify the components of the Internet mail system and the role of each in delivering a message.

Trace the path of an email message from the sender’s user agent to the recipient’s user agent, identifying the protocol used at each step and which components must be reachable at that moment.

Given a proposed mail architecture (for example, user agents sending directly to the recipient’s mail server), identify what fails and when.

Given a step in mail delivery, determine whether it is push or pull and which protocol carries it.

Given an SMTP transcript and the delivered message’s headers, identify which addresses come from the envelope and which from the header, which the receiving server uses for delivery, and what the recipient can and cannot trust about the sender.

Trace the sequence of a simple SMTP client-server interaction, identifying the purpose of the HELO, MAIL FROM, RCPT TO, DATA, and QUIT commands.

Given file size, link rates, the number of clients sharing a link, and propagation delays, compute the time to transfer a file and identify the bottleneck link.

Given packet arrival rate, packet length, and the outgoing link rate, compute traffic intensity, and predict how average queuing delay changes with traffic intensity and with burstiness.

Explain when and why a router drops packets.

Define video bitrate, constant bitrate, and variable bitrate, and explain how resolution, motion, and encoding affect a video’s bitrate.

Given fill rate, playout rate, and buffer level, determine whether playback stalls, and explain what the client-side buffer is for.

Explain the advantages of adaptive bitrate streaming over streaming a single fixed bitrate.

Given a client’s buffer level and recent throughput measurements, decide what a throughput-based player and a buffer-based player would each request next, and judge which choice is better and why.

Describe the components of DASH and the role of each: manifest, video segments at multiple bitrates, the client, and the server.

Explain the advantages of delivering content through a CDN rather than from a single server.