What are common examiner traps in DNS and HTTP?

Confusing transport-layer state with application-layer state: marking TCP as a stateful application layer protocol (GATE 2016 Set 1). Believing cookies are executable security threats/code rather than static header data stored on the host (GATE 2015 Set 2). Forgetting the initial 1 TCP connection / 2 RTTs required for the base HTML page before embedded objects can even be discovered and fetched (GATE 2020, 2023). Assuming persistent HTTP 1.1 can multiplex requests across distinct physical servers in the same TCP connection (a TCP socket is strictly bound to one server IP:port) (GATE 2026 Set 1). Counting only top-level domains and forgetting the root server or multi-level domains (e.g. counting '.org.in' as 1 instead of '.in' then 'org.in') in iterative DNS resolution (GATE 2022). Mistaking DHCP for an address resolution protocol (it is host configuration/allocation, whereas DNS/ARP/RARP map identifiers) (GATE 2016 Set 1). Assuming all application layer protocols operate strictly over point-to-point unicast TCP connections. Overlooking that a host does not yet have an assigned IP address during initial DHCP discovery, mandating broadcast delivery.

DNS and HTTP

18 Qs · since 2011 · 20 marks · 0.8 marks/paperStandard yield

Take topic test

In GATE CS, the 'DNS and HTTP' topic is tested predominantly through conceptual protocol interaction, chronological packet sequencing, connection lifecycle mechanics, and timing ca… Guide

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GATE CSE 2026 Set 1Q19MSQ1 markMediumWhich of the following statements is/are true with respect to the interaction of a web browser with a web server using HTTP 1.1?
GATE CSE 2026 Set 2Q22MCQ1 markEasyWhich one of the following protocols may need to broadcast some of its messages?
GATE CSE 2024 Set 1Q16MCQ1 markEasyA user starts browsing a webpage hosted at a remote server. The browser opens a single TCP connection to fetch the entire webpage from the server. The webpage consists of a top-level index page with multiple embedded image objects. Assume that all caches (e.g., DNS cache, browser cache) are all initially empty. The…
GATE CSE 2023Q52MSQ2 marksMediumSuppose in a web browser, you click on the www.gate-2023.in URL. The browser cache is empty. The IP address for this URL is not cached in your local host, so a DNS lookup is triggered (by the local DNS server deployed on your local host) over the 3-tier DNS hierarchy in an iterative mode. No resource…
GATE CSE 2022Q35NAT1 markMediumConsider the resolution of the domain name www.gate.org.in by a DNS resolver. Assume that no resource records are cached anywhere across the DNS servers and that iterative query mechanism is used in the resolution. The number of DNS query-response pairs involved in completely resolving the domain name is…
GATE CSE 2020Q25NAT1 markEasyAssume that you have made a request for a web page through your web browser to a web server. Initially the browser cache is empty. Further, the browser is configured to send HTTP requests in non-persistent mode. The web page contains text and five very small images. The minimum number of TCP connections required to…
GATE CSE 2019Q16MCQ1 markEasyWhich of the following protocol pairs can be used to send and retrieve e-mails (in that order)?
GATE CSE 2016 Set 1Q24MCQ1 markEasyWhich one of the following protocols is NOT used to resolve one form of address to another one?
GATE CSE 2016 Set 1Q25MCQ1 markMediumWhich of the following is/are example(s) of stateful application layer protocols? (i) HTTP (ii) FTP (iii) TCP (iv) POP3
GATE CSE 2016 Set 2Q25MCQ1 markEasyIdentify the correct sequence in which the following packets are transmitted on the network by a host when a browser requests a webpage from a remote server, assuming that the host has just been restarted.
GATE CSE 2015 Set 1Q15MCQ1 markEasyWhich of the following statements is/are FALSE? I. XML overcomes the limitations in HTML to support a structured way of organizing content. II. XML specification is not case sensitive while HTML specification is case sensitive. III. XML supports user defined tags while HTML uses pre-defined tags. IV. XML tags need not…
GATE CSE 2015 Set 1Q17MCQ1 markEasyIn one of the pairs of protocols given below, both the protocols can use multiple TCP connections between the same client and the server. Which one is that?
GATE CSE 2015 Set 2Q13MCQ1 markEasyWhich one of the following statements is NOT correct about HTTP cookies?
GATE CSE 2015 Set 3Q8MCQ1 markMediumIn a web server, ten WebPages are stored with the URLs of the form http://www.yourname.com/ $var$ .html; where, $var$ is a different number from 1 to 10 for each Webpage. Suppose, the client stores the Webpage with $var = 1$ (say W1) in local machine, edits and then tests. Rest of the WebPages remains on the web…
GATE CSE 2014 Set 1Q25MCQ1 markEasyIdentify the correct order in which the following actions take place in an interaction between a web browser and a web server. 1. The web browser requests a webpage using HTTP. 2. The web browser establishes a TCP connection with the web server. 3. The web server sends the requested webpage using HTTP. 4. The web…
GATE CSE 2014 Set 2Q28MCQ2 marksMediumA graphical HTML browser resident at a network client machine $Q$ accesses a static HTML webpage from a HTTP server $S$ . The static HTML page has exactly one static embedded image which is also at $S$ . Assuming no caching, which one of the following is correct about the HTML webpage loading (including the…
GATE CSE 2011Q4MCQ1 markEasyConsider different activities related to email. m1: Send an email from a mail client to a mail server m2: Download an email from mailbox server to a mail client m3: Checking email in a web browser Which is the application level protocol used in each activity?
GATE CSE 2011Q9MCQ1 markEasyHTML (HyperText Markup Language) has language elements which permit certain actions other than describing the structure of the web document. Which one of the following actions is NOT supported by pure HTML (without any server or client side scripting) pages?

Topic guide

What does GATE test in DNS and HTTP?

In GATE CS, the 'DNS and HTTP' topic is tested predominantly through conceptual protocol interaction, chronological packet sequencing, connection lifecycle mechanics, and timing calculations. Early exams focused on basic protocol roles (SMTP, POP3, HTTP), statefulness, and HTML/XML properties, whereas recent exams (2020–2026) strongly emphasize quantitative analysis of iterative DNS hierarchies, persistent vs. non-persistent HTTP, pipelining, and total round-trip time (RTT) latency.

Core concepts

DNS resolution mechanism (iterative vs. recursive, root, TLD, SLD, authoritative servers)
HTTP 1.0 non-persistent vs. HTTP 1.1 persistent connections
HTTP request pipelining and head-of-line considerations across a single TCP stream
Dependency ordering: DNS lookup -> TCP 3-way handshake (SYN) -> HTTP request -> HTTP response
Embedded web objects and parallel TCP connections
HTTP Cookies (text key-value pairs stored at client, Set-Cookie headers, expiration, statelessness mitigation)
Stateful vs. stateless protocols (HTTP is stateless; FTP and POP3 maintain state; TCP is stateful at transport layer)
Application-level email protocols (SMTP push vs. POP3/IMAP pull vs. HTTP webmail)
Dynamic Host Configuration Protocol (DHCP) bootstrapping and DORA process
Application-layer broadcasting mechanisms (e.g., DHCPDISCOVER using 255.255.255.255)
Unicast TCP-based protocols (HTTP, SMTP, FTP) vs. UDP/broadcast-capable protocols
Transport layer dependencies of application protocols (TCP vs. UDP)

Recurring question patterns

Chronological Sequence of Browser/Web Request Events
common · MCQ · 1 marks · 2024, 2016, 2014
Determining the exact sequential order of protocol actions or packet transmissions when a client resolves an address, opens a transport connection, and requests web assets (DNS query -> TCP SYN/Handshake -> HTTP GET base page -> HTTP GET embedded resources).
Total RTT and Latency Calculation for Webpage Fetching
occasional · mixed · 2 marks · 2023, 2020
Calculating the total elapsed time in multiples of RTT required to resolve domain names via iterative DNS servers, establish TCP connections, and fetch a base HTML document plus multiple embedded objects under varying modes (non-persistent parallel connections vs. persistent pipelined HTTP).
Iterative vs. Recursive DNS Query Hierarchy Counting
occasional · NAT · 1 marks · 2023, 2022
Counting the exact number of query-response pairs or DNS server traversals needed to resolve a fully qualified domain name (FQDN) across root, TLD, and authoritative nameservers assuming cold caches.
HTTP Mechanics: Persistence, Pipelining, and Cookies
common · mixed · 1 marks · 2026, 2015, 2014
Evaluating conceptual assertions regarding HTTP 1.0 vs. HTTP 1.1 features (persistent TCP connections, single vs multi-server socket constraints, pipelining) and session tracking via HTTP cookies.
Application Layer Protocol Characteristics and Role Mapping
common · MCQ · 1 marks · 2019, 2016, 2015, 2011
Categorizing application-layer protocols based on statefulness (FTP, POP3 vs. stateless HTTP), address resolution nature (DNS, ARP, RARP vs. DHCP configuration), or specific application tasks (SMTP push vs. POP3/IMAP pull).
Protocol Transmission and Operational Behavior Identification
rare · MCQ · 1 marks · 2026
Questions that present a specific communication characteristic (e.g., broadcasting messages, transport layer protocol dependency, statefulness) and ask the candidate to identify which application-layer protocol exhibits that behavior.

Formulas GATE uses

Non-Persistent HTTP Connection Count

\text{TCP Connections} = 1 + N_{\text{embedded objects}}

Used to compute total TCP handshakes when fetching a base HTML page containing $N$ embedded objects in non-persistent HTTP mode.

Iterative DNS Query-Response Pairs

\text{Pairs} = L_{\text{hierarchy}} = 1 \text{ (Root)} + \sum \text{intermediate domain levels} + 1 \text{ (Authoritative)}

Used when calculating the number of DNS query-response round trips needed without caching across an iterative DNS resolution tree.

Webpage Retrieval Delay (Non-persistent with $k$ parallel TCP connections)

\text{Time} = \text{Time}_{\text{DNS}} + 2\text{ RTT}_{\text{base}} + 2 \left\lceil \frac{N}{k} \right\rceil \text{RTT}

Used to calculate elapsed RTTs when downloading base HTML followed by $N$ objects over at most $k$ concurrent non-persistent TCP connections.

Webpage Retrieval Delay (Persistent HTTP with Pipelining)

\text{Time} = \text{Time}_{\text{DNS}} + 2\text{ RTT}_{\text{base}} + 1\text{ RTT}_{\text{pipelined objects}}

Used to calculate total RTTs when all embedded objects on the same server are requested in a single pipelined burst over the existing persistent connection.

Examiner traps in DNS and HTTP

Confusing transport-layer state with application-layer state: marking TCP as a stateful application layer protocol (GATE 2016 Set 1).
Believing cookies are executable security threats/code rather than static header data stored on the host (GATE 2015 Set 2).
Forgetting the initial 1 TCP connection / 2 RTTs required for the base HTML page before embedded objects can even be discovered and fetched (GATE 2020, 2023).
Assuming persistent HTTP 1.1 can multiplex requests across distinct physical servers in the same TCP connection (a TCP socket is strictly bound to one server IP:port) (GATE 2026 Set 1).
Counting only top-level domains and forgetting the root server or multi-level domains (e.g. counting '.org.in' as 1 instead of '.in' then 'org.in') in iterative DNS resolution (GATE 2022).
Mistaking DHCP for an address resolution protocol (it is host configuration/allocation, whereas DNS/ARP/RARP map identifiers) (GATE 2016 Set 1).
Assuming all application layer protocols operate strictly over point-to-point unicast TCP connections.
Overlooking that a host does not yet have an assigned IP address during initial DHCP discovery, mandating broadcast delivery.

How questions are asked

Chronological packet/event ordering
Multi-tier iterative DNS query counting (NAT)
Total RTT calculation with parallel/pipelined HTTP (MSQ/NAT)
Multi-statement correctness regarding HTTP versions, cookies, or persistent channels (MSQ)
Protocol classification and property matching
Direct protocol identification matching an operational property (e.g., message broadcast requirement)

Paper trends

Shift from qualitative protocol identification (SMTP, POP3, basic HTML tags) to rigorous multi-RTT latency calculations and deep HTTP 1.1 connection semantics.
2026, 2023, 2020, 2014, 2011
Introduction of NAT and MSQ formats replacing simple 4-option MCQs to test multi-level iterative DNS resolution and combinatorial multi-statement evaluation.
2026, 2023, 2022, 2020
Direct conceptual 1-mark MCQs focusing on fundamental communication needs (such as broadcast during bootstrap/discovery) among standard TCP/IP application layer protocols.
2026

Difficulty notes

Easy: Single-concept protocol matching (SMTP/POP/HTTP), identification of stateless/stateful protocols, basic packet ordering, or simple non-persistent connection counting. Medium: Calculating multi-step RTT elapsed time under differing concurrency models (iterative DNS + parallel TCP vs. persistent pipelined HTTP), and rigorous evaluation of HTTP/1.1 socket boundaries and connection reuse (MSQ).

DNS and HTTP

18 Qs · since 2011 · 20 marks · 0.8 marks/paperStandard yield

Take topic test

In GATE CS, the 'DNS and HTTP' topic is tested predominantly through conceptual protocol interaction, chronological packet sequencing, connection lifecycle mechanics, and timing ca… Guide

Type

Topic guide

What does GATE test in DNS and HTTP?

Core concepts

DNS resolution mechanism (iterative vs. recursive, root, TLD, SLD, authoritative servers)
HTTP 1.0 non-persistent vs. HTTP 1.1 persistent connections
HTTP request pipelining and head-of-line considerations across a single TCP stream
Dependency ordering: DNS lookup -> TCP 3-way handshake (SYN) -> HTTP request -> HTTP response
Embedded web objects and parallel TCP connections
HTTP Cookies (text key-value pairs stored at client, Set-Cookie headers, expiration, statelessness mitigation)
Stateful vs. stateless protocols (HTTP is stateless; FTP and POP3 maintain state; TCP is stateful at transport layer)
Application-level email protocols (SMTP push vs. POP3/IMAP pull vs. HTTP webmail)
Dynamic Host Configuration Protocol (DHCP) bootstrapping and DORA process
Application-layer broadcasting mechanisms (e.g., DHCPDISCOVER using 255.255.255.255)
Unicast TCP-based protocols (HTTP, SMTP, FTP) vs. UDP/broadcast-capable protocols
Transport layer dependencies of application protocols (TCP vs. UDP)

Recurring question patterns

Chronological Sequence of Browser/Web Request Events
common · MCQ · 1 marks · 2024, 2016, 2014
Determining the exact sequential order of protocol actions or packet transmissions when a client resolves an address, opens a transport connection, and requests web assets (DNS query -> TCP SYN/Handshake -> HTTP GET base page -> HTTP GET embedded resources).
Total RTT and Latency Calculation for Webpage Fetching
occasional · mixed · 2 marks · 2023, 2020
Calculating the total elapsed time in multiples of RTT required to resolve domain names via iterative DNS servers, establish TCP connections, and fetch a base HTML document plus multiple embedded objects under varying modes (non-persistent parallel connections vs. persistent pipelined HTTP).
Iterative vs. Recursive DNS Query Hierarchy Counting
occasional · NAT · 1 marks · 2023, 2022
Counting the exact number of query-response pairs or DNS server traversals needed to resolve a fully qualified domain name (FQDN) across root, TLD, and authoritative nameservers assuming cold caches.
HTTP Mechanics: Persistence, Pipelining, and Cookies
common · mixed · 1 marks · 2026, 2015, 2014
Evaluating conceptual assertions regarding HTTP 1.0 vs. HTTP 1.1 features (persistent TCP connections, single vs multi-server socket constraints, pipelining) and session tracking via HTTP cookies.
Application Layer Protocol Characteristics and Role Mapping
common · MCQ · 1 marks · 2019, 2016, 2015, 2011
Categorizing application-layer protocols based on statefulness (FTP, POP3 vs. stateless HTTP), address resolution nature (DNS, ARP, RARP vs. DHCP configuration), or specific application tasks (SMTP push vs. POP3/IMAP pull).
Protocol Transmission and Operational Behavior Identification
rare · MCQ · 1 marks · 2026
Questions that present a specific communication characteristic (e.g., broadcasting messages, transport layer protocol dependency, statefulness) and ask the candidate to identify which application-layer protocol exhibits that behavior.

Formulas GATE uses

Non-Persistent HTTP Connection Count

\text{TCP Connections} = 1 + N_{\text{embedded objects}}

Used to compute total TCP handshakes when fetching a base HTML page containing $N$ embedded objects in non-persistent HTTP mode.

Iterative DNS Query-Response Pairs

\text{Pairs} = L_{\text{hierarchy}} = 1 \text{ (Root)} + \sum \text{intermediate domain levels} + 1 \text{ (Authoritative)}

Used when calculating the number of DNS query-response round trips needed without caching across an iterative DNS resolution tree.

Webpage Retrieval Delay (Non-persistent with $k$ parallel TCP connections)

\text{Time} = \text{Time}_{\text{DNS}} + 2\text{ RTT}_{\text{base}} + 2 \left\lceil \frac{N}{k} \right\rceil \text{RTT}

Used to calculate elapsed RTTs when downloading base HTML followed by $N$ objects over at most $k$ concurrent non-persistent TCP connections.

Webpage Retrieval Delay (Persistent HTTP with Pipelining)

\text{Time} = \text{Time}_{\text{DNS}} + 2\text{ RTT}_{\text{base}} + 1\text{ RTT}_{\text{pipelined objects}}

Used to calculate total RTTs when all embedded objects on the same server are requested in a single pipelined burst over the existing persistent connection.

Examiner traps in DNS and HTTP

Confusing transport-layer state with application-layer state: marking TCP as a stateful application layer protocol (GATE 2016 Set 1).
Believing cookies are executable security threats/code rather than static header data stored on the host (GATE 2015 Set 2).
Forgetting the initial 1 TCP connection / 2 RTTs required for the base HTML page before embedded objects can even be discovered and fetched (GATE 2020, 2023).
Assuming persistent HTTP 1.1 can multiplex requests across distinct physical servers in the same TCP connection (a TCP socket is strictly bound to one server IP:port) (GATE 2026 Set 1).
Counting only top-level domains and forgetting the root server or multi-level domains (e.g. counting '.org.in' as 1 instead of '.in' then 'org.in') in iterative DNS resolution (GATE 2022).
Mistaking DHCP for an address resolution protocol (it is host configuration/allocation, whereas DNS/ARP/RARP map identifiers) (GATE 2016 Set 1).
Assuming all application layer protocols operate strictly over point-to-point unicast TCP connections.
Overlooking that a host does not yet have an assigned IP address during initial DHCP discovery, mandating broadcast delivery.

How questions are asked

Chronological packet/event ordering
Multi-tier iterative DNS query counting (NAT)
Total RTT calculation with parallel/pipelined HTTP (MSQ/NAT)
Multi-statement correctness regarding HTTP versions, cookies, or persistent channels (MSQ)
Protocol classification and property matching
Direct protocol identification matching an operational property (e.g., message broadcast requirement)

Paper trends

Shift from qualitative protocol identification (SMTP, POP3, basic HTML tags) to rigorous multi-RTT latency calculations and deep HTTP 1.1 connection semantics.
2026, 2023, 2020, 2014, 2011
Introduction of NAT and MSQ formats replacing simple 4-option MCQs to test multi-level iterative DNS resolution and combinatorial multi-statement evaluation.
2026, 2023, 2022, 2020
Direct conceptual 1-mark MCQs focusing on fundamental communication needs (such as broadcast during bootstrap/discovery) among standard TCP/IP application layer protocols.
2026