GATE CS Computer Networks questions

Consider that $B$ wants to send a message $m$ that is digitally signed to $A$. Let the pair of private and public keys for $A$ and $B$ be denoted by ${K_{x}}^-$ and ${K_{x}}^+$ for $x=A, B$, respectively. Let $K_{x}(m)$ represent the operation of encrypting $m$ with a key $K_{x}$ and $H(m)$ represent the message digest. Which one of …

Which one of the following protocols is NOT used to resolve one form of address to another one?

Which of the following is/are example(s) of stateful application layer protocol? $\textsf{HTTP}$ $\textsf{FTP}$ $\textsf{TCP}$ $\textsf{POP3}$

For the $\text{IEEE 802.11 MAC}$ protocol for wireless communication, which of the following statements is/are TRUE? At least three non-overlapping channels are available for transmissions. The RTS-CTS mechanism is used for collision detection. Unicast frames are ACKed.

A network has a data transmission bandwidth of $20 \times 10^{6}$ bits per second. It uses CSMA/CD in the MAC layer. The maximum signal propagation time from one node to another node is $40$ microseconds. The minimum size of a frame in the network is __________ bytes.

Consider a $128 \times 10^3$ bits/second satellite communication link with one way propagation delay of $150$ milliseconds. Selective retransmission (repeat) protocol is used on this link to send data with a frame size of $1$ kilobyte. Neglect the transmission time of acknowledgement. The minimum number of bits required for the sequence number field to …

Identify 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.

Anarkali digitally signs a message and sends it to Salim. Verification of the signature by Salim requires.

In an Ethernet local area network, which one of the following statements is TRUE?

Suppose that the stop-and-wait protocol is used on a link with a bit rate of $64$ $\text{kilobits}$ per second and $20$ $\text{milliseconds}$ propagation delay. Assume that the transmission time for the acknowledgment and the processing time at nodes are negligible. Then the minimum frame size in bytes to achieve a link utilization of at least $50$ …

Suppose that everyone in a group on $N$ people wants to communicate secretly with the $(\text{N - 1})$ others using symmetric Key cryptographic system. The communication between any two person should not be decodable by the others in the group. The numbers of keys required in the system as a whole to satisfy the confidentiality requirement is

Consider a LAN with four nodes $S_1, S_2, S_3,$ and $S_4$. Time is divided into fixed-size slots, and a node can begin its transmission only at the beginning of a slot. A collision is said to have occurred if more than one node transmits in the same slot. The probabilities of generation of a frame in a time slot by $S_1, S_2, S_3,$ and $S_4$ are …

Which of the following fields of an IP header is NOT modified by a typical IP router?

Suppose two hosts use a TCP connection to transfer a large file. Which of the following statements is/are FALSE with respect to the TCP connection? If the sequence number of a segment is $m,$ then the sequence number of the subsequent segment is always $m+1.$ If the estimated round trip time at any given point of time is $t$ sec, the value of the …

In one of the pairs of protocols given below , both the protocols can use multiple $\textsf{TCP}$ connections between the same client and the server. Which one is that?

$\text{Host A}$ sends a $\text{UDP}$ datagram containing $8880\text{ bytes}$ of user data to $\text{host B}$ over an $\text{Ethernet LAN}.$ Ethernet frames may carry data up to $1500\text{ bytes (i.e. MTU = 1500 bytes)}.$ Size of $\text{UDP}$ header is $8\text{ bytes}$ and size of $\text{IP}$ header is $20\text{ bytes}.$ There is no …

Consider the following routing table at an IP router: …

Assume that the bandwidth for a $\text{TCP}$ connection is $1048560$ bits/sec. Let $\alpha$ be the value of RTT in milliseconds (rounded off to the nearest integer) after which the $\text{TCP}$ window scale option is needed. Let $\beta$ be the maximum possible window size with window scale option. Then the values of $\alpha$ and $\beta$ are

Identify the correct order in which a server process must invoke the function calls accept, bind, listen, and recv according to UNIX socket API.

In the network $200.10.11.144/27$, the $\text{fourth}$ octet (in decimal) of the last $\text{IP}$ address of the network which can be assigned to a host is _______.