# Recent questions tagged network-layer

1
Which layer connects the network support layers and user support layers ? transport layer network layer data link layer session layer
2
Which of the following is not a transceiver function? Transmission and receipt of data Checking of line voltages Addition and subtraction of headers Collision detection
3
Suppose two hosts, A and B, are separated by 20,000 kilometers and are connected by a direct link of R = 1Gbps. Suppose the propagation speed over the link is $2.5 10^8$ meters/sec Calculate the bandwidth-delay product, $R \times d _{prop}$. Consider sending a file of ... the maximum number of bits that will be in the link at any given time? What is the width (in meters) of a bit in the link?
4
Suppose two hosts, A and B, are separated by 20,000 kilometers and are connected by a direct link of R = 2 Mbps. Suppose the propagation speed over the link is 2.5×1082.5×108 meters/sec. suppose we can modify R. For what value of R is the width of a bit as long as the length of the link?
5
.Suppose two hosts, A and B, are separated by 20,000 kilometers and are connected by a direct link of R = 2 Mbps. Suppose the propagation speed over the link is $2.5 \times 10^8$ meters/sec. Calculate the bandwidth-delay product, $R \times d _{prop}$. Consider ... a general expression for the width of a bit in terms of the propagation speed s, the transmission rate R, and the length of the link m.
6
Suppose N packets arrive simultaneously to a link at which no packets are currently being transmitted or queued. Each packet is of length L and the link has transmission rate R. What is the average queuing delay for the N packets? Now suppose that N such packets arrive to the link every LN/R seconds. What is the average queuing delay of a packet?
7
A packet switch receives a packet and determines the outbound link to which the packet should be forwarded. When the packet arrives, one other packet is halfway done being transmitted on this outbound link and four other packets are waiting to be transmitted. Packets are ... rate is R, x bits of the currently-being-transmitted packet have been transmitted, and n packets are already in the queue?
8
(Common data question P10, P11) P10. Consider a packet of length L which begins at end system A and travels over three links to a destination end system. These three links are connected by two packet switches. Let $d _i, s _i, and R _i$ denote the ... forward packets but instead immediately transmits each bit it receives before waiting for the entire packet to arrive. What is the end-to-end delay?
9
Suppose users share a 3 Mbps link. Also, suppose each user requires 150 kbps when transmitting, but each user transmits only 10 percent of the time. When circuit switching is used, how many users can be supported? For the remainder of this ... are transmitting simultaneously. (Hint: Use the binomial distribution.) Find the probability that there are 21 or more users transmitting simultaneously.
10
Consider an application that transmits data at a steady rate (for example, the sender generates an N-bit unit of data every k time units, where k is small and fixed). Also, when such an application starts, it will continue running for a relatively long period of ... sum of the application data rates is less than the capacities of each and every link. Is some form of congestion control needed? Why?
11
Give a formula for the end-to-end delay of sending one packet of length L over N links of transmission rate R. Generalize this formula for sending P such packets back-to-back over the N links.
12
Visit the Queuing and Loss applet at the companion Web site. What is the maximum emission rate and the minimum transmission rate? With those rates, what is the traffic intensity? Run the applet with these rates and determine how long it takes for packet loss to occur. ... a second time and determine again how long it takes for packet loss to occur. Are the values different? Why or why not?
13
Suppose end system A wants to send a large file to end system B. At a very high level, describe how end system A creates packets from the file. When one of these packets arrives at a packet switch, what information in the packet does the switch use to ... packet is forwarded? Why is packet switching on the Internet analogous to driving from one city to another and asking directions along the way?
14
Suppose Host A wants to send a large file to Host B. The path from Host A to Host B has three links, of rates R1 = 500 kbps, R2 = 2 Mbps, and R3 = 1 Mbps. Assuming no other traffic in the network, what is the throughput for the file transfer? Suppose the file is ... throughput, roughly how long will it take to transfer the file to Host B? Repeat (a) and (b), but now with R2 reduced to 100 kbps.
15
How long does it take a packet of length 1,000 bytes to propagate over a link of distance 2,500 km, propagation speed 2.5 · 108 m/s, and transmission rate 2 Mbps? More generally, how long does it take a packet of length L to propagate over a link ... d, propagation speed s, and transmission rate R bps? Does this delay depend on packet length? Does this delay depend on the transmission rate?
16
Visit the Transmission Versus Propagation Delay applet at the companion Web site. Among the rates, propagation delay, and packet sizes available find a combination for which the sender finishes transmitting before the first bit of the packet reaches the receiver. Find another combination for which the first bit of the packet reaches the receiver before the sender finishes transmitting.
17
Consider sending a packet from a source host to a destination host over a fixed route. List the delay components in the end-to-end delay. Which of these delays are constant and which are variable?
18
Some content providers have created their own networks. Describe Google’s network. What motivates content providers to create these networks?
19
Why will two ISPs at the same level of the hierarchy often peer with each other? How does an IXP earn money?
20
Suppose users share a 2 Mbps link. Also, suppose each user transmits continuously at 1 Mbps when transmitting, but each user transmits only 20 percent of the time. When circuit switching is used, how many users can be supported? For the remainder of this ... probability that at any given time, all three users are transmitting simultaneously. Find the fraction of time during which the queue grows.
21
What advantage does a circuit-switched network have over a packet-switched network? What advantages does TDM have over FDM in a circuit-switched network?
22
Suppose there is exactly one packet switch between a sending host and a receiving host. The transmission rates between the sending host and the switch and between the switch and the receiving host are R1 and R2, respectively. Assuming that the switch uses store-and-forward ... is the total end-to-end delay to send a packet of length L? (Ignore queuing, propagation delay, and processing delay.)
23
What is the importance of having the field LABEL in the datagram as well as the router if we already know the outgoing port number?? Is’nt it an overhead in virtual circuits?
24
An IPv4 packet has arrived with the first few hexadecimal digits as shown. Ox45000028000100000102 ... How many hops can this packet travel before being dropped? The data belong to what upper-layer protocol? Solution To find the time-to-live field, we skip 8 bytes (16 ... field is the next byte (02), which means that the upper-layer protocol is IGMP Why to skip 8 bytes????Please Explain
25
A $64000$-byte message is to be transmitted over a $2$-hop path in a store-and-forward packet-switching network. The network limits packets toa maximum size of $2032$ bytes including a $32$-byte header. The trans-mission lines in the network are error free and have a speed of $50$ Mbps. ... getting answer as $1*3*(T_t+T_p) + \;31*T_t$ where $T_t=0.325\; ms$ and $T_p=3.333\; ms$. Please Confirm.
26
Use the traceroute (UNIX) or tracert (Windows) programs to trace the route from your computer to various universities on other continents. Make a list of transoceanic links you have discovered. Some sites to try are www.berkeley.edu (California) www.mit.edu (Massachusetts) www.vu.nl (Amsterdam) www.ucl.ac.uk (London) www.usyd.edu.au (Sydney) www.u-tokyo.ac.jp (Tokyo) www.uct.ac.za (Cape Town)
27
Write a function to do forwarding in an IP router. The procedure has one parameter, an IP address. It also has access to a global table consisting of an array of triples. Each triple contains three integers: an IP address, a subnet mask, and the outline line to use. The function looks up the IP address in the table using CIDR and returns the line to use as its value.
28
Write a program that simulates a computer network using discrete time. The first packet on each router queue makes one hop per time interval. Each router has only a finite number of buffers. If a packet arrives and there is no room for it, it is discarded and ... the source router. Plot the throughput of the network as a function of the end-to-end timeout interval, parameterized by error rate.
29
Write a program to simulate routing using flooding. Each packet should contain a counter that is decremented on each hop. When the counter gets to zero, the packet is discarded. Time is discrete, with each line handling one packet per time interval. Make three versions ... best k lines are flooded. Compare flooding with deterministic routing (k = 1) in terms of both delay and the bandwidth used.