GATE CS Computer Networks questions

In an IPv4 datagram, the $M$ bit is $0$, the value of $HLEN$ is $10$, the value of total length is $400$ and the fragment offset value is $300$. The position of the datagram, the sequence numbers of the first and the last bytes of the payload, respectively are:

Determine the maximum length of the cable (in km) for transmitting data at a rate of $500$ Mbps in an Ethernet LAN with frames of size $10,000$ bits. Assume the signal speed in the cable to be $2,00,000$ km/s.

Assume that source S and destination D are connected through two intermediate routers labeled R. Determine how many times each packet has to visit the network layer and the data link layer during a transmission from S to D.

Using public key cryptography, $X$ adds a digital signature σ to message $M$, encrypts $\langle M, \sigma \rangle$, and sends it to $Y$, where it is decrypted. Which one of the following sequences of keys is used for the operations?

The transport layer protocols used for real time multimedia, file transfer, $\textsf{DNS}$ and email, respectively are

Consider an instance of TCP’s Additive Increase Multiplicative Decrease (AIMD) algorithm where the window size at the start of the slow start phase is $2$ MSS and the threshold at the start of the first transmission is $8$ MSS. Assume that a timeout occurs during the fifth transmission. Find the congestion window size at the end of the tenth …

Consider a source computer $(S)$ transmitting a file of size $10^{6}$ bits to a destination computer $(D)$ over a network of two routers $(R_{1}\text{ and }R_{2})$ and three links $(L_{1},L_{2},\text{ and } L_{3})$. $L_{1}$ connects $S$ to $R_{1}$; $L_{2}$ connects $R_{1}$ to $R_{2}$; and $L_{3}$ connects $R_{2}$ to $D$. Let each …

An Internet Service Provider (ISP) has the following chunk of CIDR-based IP addresses available with it: $245.248.128.0/20$. The ISP wants to give half of this chunk of addresses to Organization $A$, and a quarter to Organization $B$, while retaining the remaining with itself. Which of the following is a valid allocation of addresses to $A$ and …

In the IPv4 addressing format, the number of networks allowed under Class $C$ addresses is:

Which of the following transport layer protocols is used to support electronic mail?

The protocol data unit (PDU) for the application layer in the Internet stack is:

Consider a network with five nodes, $N1$ to $N5$, as shown as below. The network uses a Distance Vector Routing protocol. Once the routes have been stabilized, the distance vectors at different nodes are as follows. N1: $(0, 1, 7, 8, 4)$ N2: $(1, 0, 6, 7, 3)$ N3: $(7, 6, 0, 2, 6)$ N4: $(8, 7, 2, 0, 4)$ N5: $(4, 3, 6, 4, 0)$ Each distance vector …

Consider a network with five nodes, $N1$ to $N5$, as shown as below. The network uses a Distance Vector Routing protocol. Once the routes have been stabilized, the distance vectors at different nodes are as follows. N1: $(0, 1, 7, 8, 4)$ N2: $(1, 0, 6, 7, 3)$ N3: $(7, 6, 0, 2, 6)$ N4: $(8, 7, 2, 0, 4)$ N5: $(4, 3, 6, 4, 0)$ Each distance vector …

Consider the different activities related to email. $\text{m1}:$ Send an email from mail client to mail server $\text{m2}:$ Download an email from mailbox server to a mail client $\text{m3}:$ Checking email in a web browser Which is the application level protocol used in each activity?

A layer-$4$ firewall (a device that can look at all protocol headers up to the transport layer) CANNOT

Consider a network with $6$ routers $R1$ to $R6$ connected with links having weights as shown in the following diagram. Suppose the weights of all unused links are changed to $2$ and the distance vector algorithm is used again until all routing tables stabilize. How many links will now remain unused?

Consider a network with $6$ routers $\textbf{R1}$ to $\textbf{R6}$ connected with links having weights as shown in the following diagram. All the routers use the distance vector based routing algorithm to update their routing tables. Each router starts with its routing table initialized to contain an entry for each neighbor with the weight of the …

Suppose computers $A$ and $B$ have $IP$ addresses $10.105.1.113$ and $10.105.1.91$ respectively and they both use same netmask $N$. Which of the values of $N$ given below should not be used if $A$ and $B$ should belong to the same network?

Frames of $1000\text{ bits}$ are sent over a $10^6$ bps duplex link between two hosts. The propagation time is $25ms$. Frames are to be transmitted into this link to maximally pack them in transit (within the link). Let $I$ be the minimum number of bits $(I)$ that will be required to represent the sequence numbers distinctly assuming that no time …

Frames of $\text{1000 bits}$ are sent over a $10^6$ $\text{bps}$ duplex link between two hosts. The propagation time is $\text{25 ms}$. Frames are to be transmitted into this link to maximally pack them in transit (within the link). What is the minimum number of bits $(I)$ that will be required to represent the sequence numbers distinctly? Assume …