DATA COMMUNICATION AND COMPUTER NETWORKS
HOMEWORK – 2
Chapter 2
Problem-10:
Consider a short, 10-meter link, over which a sender can transmit at a rate of 150 bits/sec in both directions. Suppose that packets containing data are 100,000 bits long, and packets containing only control (e.g., ACK or handshaking) are 200 bits long. Assume that N parallel connections each get 1/N of the link bandwidth. Now consider the HTTP protocol, and suppose that each downloaded object is 100 Kbits long, and that the initial downloaded object contains 10 referenced objects from the same sender. Would parallel downloads via parallel instances of non-persistent HTTP make sense in this case? Now consider persistent HTTP. Do you expect significant gains over the
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Also, 150 bits/second can be transmitted to and fro.
This is the case where each downloaded object can be completely put into one data packet.
Let P denote the one-way propagation delay between two communication party’s sender and receiver.
In the first case,
This is the case of Parallel downloads via non-persistent connections.
Parallel download would allow 10 connections share the 150 bits/sec bandwidth.
Therefore, each gets just 15 bits/sec.
Thus, the total time needed to receive all objects is given by:
(200/150+P + 200/150 +P + 200/150+P + 100,000/150+ P) + (200/ (150/10) +P + 200/ (150/10) + P + 200/ (150/10) +P + 100,000/ (150/10) +P)
= 7377 + 8*P (seconds)
In the second case,
This is the case of persistent HTTP connection case. The total time needed is given by:
(200/150+P + 200/150 +P + 200/150+P + 100,000/150+ P)+ 10*(200/150+P + 100,000/150+ P)
=7351 + 24*P (seconds)
We have speed of light = 3*106^8m/sec,
So, P = 10/ (3*10^8) = 0.03 microsecond.
But P is negligible compared with transmission delay T. Therefore, with parallel downloads, we can observe that the persistent HTTP does not have significant gain (less than 1 percent) over the non-persistent case.
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Use nslookup to find a Web server that has multiple IP addresses. Does the Web server of your institution (school or company) have multiple IP addresses?
Sol:
From the above part (b), Yahoo.com and google.com are the web servers that have multiple IP addresses Also, the web server of my school has multiple IP Addresses (two addresses) as shown below,
e. Use the ARIN whois database to determine the IP address range used by your university.
Sol:
The address range used by our university IUPUI is,
1. IUPUI Net: 134.68.0.0-134.68.255.255
2. IUPUI Net2: 149.166.0.0-149.166.255.255
f. Describe how an attacker can use whois databases and the nslookup tool to perform reconnaissance on an institution before launching an attack.
Sol:
An attacker using whois database and nslookup can find out each and every IP Address and also the target IP Addresses the company is using by port mapping during or before his attack with their associated DNS servers.
G. Discuss why whois databases should be publicly available.
Based on information provided by the SANS Institute, obtaining as much information as possible, regarding the company’s network infrastructure, network topology, and even previously discovered vulnerabilities is important, in order to better-plan for executing various penetration tests (source). Also, with Alexander Rocco Corporation based in Hawaii, a legal analysis should be conducted, accounting for the following state laws regarding penetration testing and/or cybercrimes:
Enclosed is a rough high-level conceptual view of the communication channels. This is very preliminary as we don't what suitable devices we can use for multiplexers, demux, and converters. The idea is to design a full-duplex serial com link between point A and B. The bandwidth is limited in the copper wiring (telephone line) probably would not go any higher than 115 kbps using a modem a constraint distance of 5 miles.
I am a plate that is made of clay that was taken from the Earth of Japan. But before I was made into a plate I was up to the mountains near a big forest that had a Jinja on top a beautiful waterfall where water fell from the top to the bottom and sometimes flowing to rivers. But when winter comes the waterfall would freeze into shards and when the winter goes the shards and snow turn into water filling up the waterfall making a waterfall from the top to the bottom flowing with an immense amount of water to rivers and ponds that would sometimes connect with the waterfall. My maker crafted me to be used as art depicting many natural objects or buildings even sometimes people in the drawing. I am also used to hold a meal for a person who would eat the nourishment from top to bottom. Most of the time I would have fish from the ocean or rice that was farmed in flatlands on top of me.
Overview dashboards for all report sets. For navigation consistency, it is required that a chart from each report set to be displayed on this dashboard
date with the latest software and security patches. Reputable antivirus programs such as Norton Security, McAfee Antivirus, and Bitdefender Antivirus and firewall programs should be installed and kept up to date for maximum protection.
eMILPO uses webservers and application servers as part of the hardware to run this system. The system uses Dell servers running Microsoft Windows 2000 Advanced Server or Microsoft Windows Enterprise Server. The software that the eMILPO System uses to run their web application and the servers that are u...
you can play the song instantly–as many times as you want--regardless of your modem speed!
The Aim Higher College’s system administrators and network engineers have described seeing some strange behaviors such as high levels of traffic from many hosts that are causing system outages. The web servers of the college have been shutting down frequently by this traffic, it must be from a hacker group trying to attack the school with malicious software. I will review the network traffic from the college’s intrusion detection system and use an intrusion prevention system to block off these threats from the hackers.
Sending data through the internet efficiently has always posed many problems. The two major technologies used, Ethernet and Asynchronous Transfer Mode (ATM), have done an admirable job of porting data, voice and video from one point to another. However, they both fall short in differing areas; neither has been able to present the "complete" package to become the single, dominant player in the internet market. They both have dominant areas they cover. Ethernet has dominated the LAN side, while ATM covers the WAN (backbone). This paper will compare the two technologies and determine which has a hand-up in the data trafficking world.
Akamai provides services to their customers, it delivers the content to user by just browsing through web browser and downloading the contents from the server. “ Akamai does this task simultaneously mirroring contents, sometimes all site content including HTML, CSS and all software downloads and sometime just media objects, audio, graphics, animation, video or hyper texts ”, than Customer makes up an request and domain name is same and the Internet protocol address points to the one of the Akamai server or to some different machine, after the client request the servers from Akamai picked up automatically which depends on the current location of the user or the contents required by the user.
Enikeev, Ruslan. "The Internet Map.". Ruslan Enikeev, 11th February 2013 Web. 17th March 2014. < http://internet-map.net/#8-175.21049171691348-75.2675525371512>.
IP address is you Internet identity when you are connected to the web. It is synonymous to a postal address.
Thanks to the HTTP, a web server running some simple software programs can acquire our IP address and then gather information about us from our own computer. This information can be anywhere from what kind of software the computer is running to gaining access to all our email contacts. Sometimes less desirabl...
In a client-server network, the capability of the server will decline as the amount of clients asking for services from the server increment. In spite of that, in P2P systems overall network performance really enhances as an increasing number of nodes are added to the system. These companions can arrange themselves into a specific purpose groups(ad hoc) as they impart, work together and offer data transfer capacity with another to finish the current workload (sharing of files). Each companion can transfer and download at the meantime, and in a procedure like this, new companions can join the group while old companions leave at whatever time. This active re-association of group peer members is not opaque to ultimate consumer.
Many schools have made the decision to go high-tech and create their own web pages via the World Wide Web. This allows them to advertise themselves to the virtual community. There has, also, been a change in how the Internet is being accessed by the various school systems. Dial-up Internet access has often been replaced by the high speed or cable Internet.