GATE CS Computer Networks questions

​​​​Suppose we are transmitting frames between two nodes using Stop-and-Wait protocol. The frame size is $3000$ bits. The transmission rate of the channel is $2000$ bps (bits/second) and the propagation delay between the two nodes is $100$ milliseconds. Assume that the processing times at the source and destination are negligible. Also, assume that the …

A 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 following packets leave the user's computer …

​$\mathrm{TCP}$ client $\mathrm{P}$ successfully establishes a connection to $\text{TCP}$ server $\mathrm{Q}$. Let $\text{N}_{P}$ denote the sequence number in the $\text{SYN}$ sent from $\mathrm{P}$ to $\mathrm{Q}$. Let $\text{N}_{Q}$ denote the acknowledgement number in the SYN ACK from $\text{Q}$ to $\text{P}$. Which of the following …

Which of the following fields is/are modified in the $\text{IP}$ header of a packet going out of a network address translation $\text{(NAT)}$ device from an internal network to an external network?

Consider a network path $\mathrm{P}-\mathrm{Q}-\mathrm{R}$ between nodes $\mathrm{P}$ and $\mathrm{R}$ via router $\mathrm{Q}$. Node $\mathrm{P}$ sends a file of size $10^6$ bytes to $\text{R}$ via this path by splitting the file into chunks of $10^3$ bytes each. Node $\text{P}$ sends these chunks one after the other without any wait time …

Consider the entries shown below in the forwarding table of an $\text{IP}$ router. Each entry consists of an $\text{IP}$ prefix and the corresponding next hop router for packets whose destination $\text{IP}$ address matches the prefix. The notation " /$\mathrm{N}$ " in a prefix indicates a subnet mask with the most significant $\mathrm{N}$ bits set …

Consider sending an $\text{IP}$ datagram of size $1420$ bytes (including $20$ bytes of $\text{IP}$ header) from a sender to a receiver over a path of two links with a router between them. The first link (sender to router) has an $\text{MTU}$ (Maximum Transmission Unit) size of $542$ bytes, while the second link (router to receiver) has an …

​Node $\text{X}$ has a $\text{TCP}$ connection open to node $\text{Y}$. The packets from $\text{X}$ to $\text{Y}$ go through an intermediate $\text{IP}$ router $\mathrm{R}$. Ethernet switch $\mathrm{S}$ is the first switch on the network path between $\mathrm{X}$ and $\mathrm{R}$. Consider a packet sent from $\mathrm{X}$ to …

​​​​​Which of the following statements about $\text{IPv4}$ fragmentation is/are TRUE?

​​​​Which of the following fields of an $\text{IP}$ header is/are always modified by any router before it forwards the $\text{IP}$ packet?

​​​​​Which one of the following $\text{CIDR}$ prefixes exactly represents the range of $\text{IP}$ addresses $10.12 .2 .0$ to $10.12 .3 .255$?

Consider a $\text{TCP}$ connection operating at a point of time with the congestion window of size $12$ $\text{MSS}$ (Maximum Segment Size), when a timeout occurs due to packet loss. Assuming that all the segments transmitted in the next two $\text{RTTs}$ (Round Trip Time) are acknowledged correctly, the congestion window size (in $MSS$) during the …

Consider an Ethernet segment with a transmission speed of $10^{8} \mathrm{bits} / \mathrm{sec}$ and a maximum segment length of $500$ meters. If the speed of propagation of the signal in the medium is $2 \times 10^{8} \mathrm{~meters} / \mathrm{sec}$, then the minimum frame size (in bits) required for collision detection is ___________.

Suppose two hosts are connected by a point-to-point link and they are configured to use $\textsf{Stop-and-Wait}$ protocol for reliable data transfer. Identify in which one of the following scenarios, the utilization of the link is the lowest.

Which of the following statements is/are $\text{INCORRECT}$ about the $\textsf{OSPF (Open Shortest Path First)}$ routing protocol used in the Internet?

Suppose you are asked to design a new reliable byte-stream transport protocol like $\text{TCP}.$ This protocol, named $\textsf{myTCP}$, runs over a $100 \mathrm{~Mbps}$ network with Round Trip Time of $150$ milliseconds and the maximum segment lifetime of $2$ minutes. Which of the following is/are valid lengths of the Sequence Number field in the …

Suppose in a web browser, you click on the $\textsf{www. gate-2023.in}\; \text{URL}$. The browser cache is empty. The $\text{IP address}$ for this $\text{URL}$ is not cached in your local host, so a $\text{DNS}$ lookup is triggered (by the local $\text{DNS}$ server deployed on your local host) over the $3$-tier $\text{DNS}$ hierarchy in an …

The forwarding table of a router is shown below. …

Consider an enterprise network with two Ethernet segments, a web server and a firewall, connected via three routers as shown below. What is the number of subnets inside the enterprise network?

Consider the resolution of the domain name $\textsf{www.gate.org.in}$ by a $\text{DNS}$ resolver. Assume that no resource records are cached anywhere across the $\text{DNS}$ servers and that iterative query mechanism is used in the resolution. The number of $\text{DNS}$ query-response pairs involved in completely resolving the domain name is …