CS372 Computer Networking Week 1-3 review for quiz 1
Convert the following units. Your answer should be a whole number with no text in the answer field: 60.51 Kbps = _____ bits per second
60510
Al Gore invented the internet.
False
FTP is implemented over a pair of UDP connections.
False
FTP is implemented over a single TCP connection.
False
HTTP implements caching by use of a UDP check.
False
In store-and-forward transmission, a packet switch may begin transmitting the first bits of packet before it has finished receiving that the last bits of the packet.
False
In store-and-forward transmission, a packet switch may being transmitting the first bits of packet before it has finished receiving that the last bits of the packet.
False
The UDP protocol implements congestion control.
False
The UDP protocol implements flow control.
False
The following is a valid IP address: 130.154.1.256
False
The internet is a system for connecting computers using a single transmission technology.
False
There is a single, central DNS server.
False
An FTP server maintains client states.
True
FTP is implemented over a pair of TCP connections.
True
HTTP implements caching by use of a conditional GET.
True
Most packet switches use store-and-forward transmission.
True
The TCP protocol implements congestion control.
True
The TCP protocol implements flow control.
True
The TCP protocol implements reliable data transfer.
True
Viruses and spyware both infect a host computer by being (usually accidentally) downloaded. How is a computer virus different from spyware?
Viruses are designed to destroy files and cause a computer to malfunction in some way. Spyware is software that acts like a server. Once installed, a knowledgeable client can request and receive information from the infected host.
Protocol ___________ allows multiple protocols to work together.
interoperability
In the Internet protocol stack, the ________ is responsible for assembling user data to be sent.
Application Layer
In the Internet protocol stack, the _________ is responsible for finding the destination IP address.
Application Layer
In the Internet protocol stack, the______ is responsible for finding the destination IP address.
Application Layer
What are some examples of unguided media, and where are they used?
Human speech, broadcast wireless, etc... Used in cellular networks, 802.11b/g/n
What is the minimum necessary information for identifying a process on a remote host? What do we call this identifier? What do we call a pair of these identifiers (one on each end host)
IP address & Port Number (process) Together, we call this a "socket" (or endpoint) We call a paired set of two sockets a "connection".
In terms of physical media, what is multiplexing
Merging multiple communication streams onto the same medium
What devices reside in the network core?
Switches and routers
Convert the following units. Your answer should be a whole number with no text in the answer field: 13 KiB = _____ bits
106496
Convert the following units. Your answer should be a whole number with no text in the answer field: 38.61 Mbps = _____ bits per second
38.61 Mbps = 38610000 bits per second
Convert the following units. Your answer should be a whole number with no text in the answer field: 38.07 Mbps = _____ Kbps
38070
Convert the following units. Your answer should be a whole number with no text in the answer field: 48 MiB = _____ bytes
50331648
• Size in bits, Bytes is measured in binary units
- Commonly used: K = 2^10, M = 2^20, G = 2^30, etc.
• Speed (distance/time) is measured in electronic units:
- K = 10^3, M = 10^6, G = 10^9, etc. - E.G., network speed of 8 Mbps means 8,000,000 bits per second
The dotted-decimal form of 32-bit internet addresses is composed of 4 decimal numbers, separated by periods. What is range of possible values for each of the four decimal numbers?
0 - 255
Suppose there are 3 routers in sequence between Host A and Host B, all of which use store-and-forward routing. What is the total end-to-end delay for a packet originating from Host A with destination Host B, under the following conditions. Each of the link transmission rates are 7.9 Mbps The total distance from Host A to Host B along its path of transmisison is 199.9 km The speed of propagation through the transmission medium is is 2.7 x 108 m/s The packet size is 4 KiB Remember that you must also uplink from Host A to the first router. Give answer in milliseconds, rounded to 1 decimal place, without units (e.g. for 0.12345 seconds you would enter "123.5" without the quotes).
17.4 ms
How many unique 32-bit IP addresses are possible?
32 binary digits means 232 = 4,294,967,296 unique numbers. Many of these are reserved, so clearly there are not enough possible addresses for every individual host on the internet. (We will discuss this problem soon.)
A network is______
A network is a system for connecting computers using a single transmission technology
What is an access network?
A network that allows a host to connect to the internet
What is RFC
A repository for comments, and the place to find (and post) the adopted standards for networking - in addition to a major resource for students and researchers in networking.
A network is a system for connecting computers using multiple, possibly different, transmission technologies.
False
What is "packet sniffing"?
An attacker gets access to communication hardware at some point in the route from a packet's source to its destination. By intercepting a packet and deconstructing it, the attacker can find out source/destination information, and can inspect the actual data message.
Please place the following in the order of the OSI layering model. Layer 7: Layer 6: Layer 5: Layer 4: Layer 3: Layer 2: Layer 1:
Answer 1:Application Layer Answer 2:Presentation Layer Answer 3:Session Layer Answer 4:Transport Layer Answer 5:Network Layer Answer 6:Link Layer Answer 7:Physical Layer
Please place the following in the order of the Internet protocol stack. Layer 5: Layer 4: Layer 3: Layer 2: Layer 1:
Answer 1:Application Layer Answer 2:Transport Layer Answer 3:Network Layer Answer 4:Data Link Layer Answer 5:Physical Layer
What is the benefit of broadband cabling over baseband cabling?
Broadband cabling can utilize a greater range of frequencies in transferring information. This allows more data to be transferred over this type of cabling.
In the HTTP protocol, how is an object addressable?
By its Uniform Resource Locator (URL)
How does a client application communicate with a server application, after the connection has been established?
By sending data into a the socket involved in that connection
In a ________ architecture, one host is always on, and other hosts may connect and be continually serviced by this first host. Peer to peer Client server Hybrid client server P2P
Client server
What internet service uses default ("well-known") port #606? (Hint: This is quite deeply buried in RFC #1700.)
Cray Unified Resource Manager (URM)
An attack which attempts to make network resources unavailable to legitimate users by flooding a system with illegitimate traffic is called a ___ attack.
Denial of Service (DoS)
What are some responsibilities of the Application Layer?
Determine destination IP address Support network applications Decide which data which will transit the internet
If a botnet or another large group of hosts is used to execute this attack it is called a ________ attack
Distributed Denial of Service (DDoS)
Cookies are not a security or privacy concern.
False
What are some applications which would have stringent security requirements
Email, payment services, identity services, etc...
What devices reside on the network edge?
End Systems / Hosts (smartphones, computers, servers, peers, etc...)
Please select all examples of systems using guided media. Ethernet Home Networks Fiber-Optic Internet Human speech ADSL Cable television/internet 802.11 Wifi Home Networks Signal flares Global Positioning System (GPS
Ethernet Home Networks Fiber-Optic Internet ADSL Cable television/internet
What are some applications which would have stringent data integrity requirements
File transfer, email, web services...
What are some application-layer protocols, and what are they used for?
HTTP - Used often for communication of hosted information on the internet (web pages) FTP - Used often for transfer of files without a web interface (uploading, etc) SMTP/IMAP/POP3 - Email protocols DNS - Domain name resolution (from www.google.com to 173.194.33.176, etc) SCCP - used in VoIP etc..
What states does HTTP preserve?
HTTP is stateless. It does not preserve states.
What transport-layer protocol does HTTP use? What port number is reserved for this?
HTTP utilizes TCP, at port 80
If an HTTP server can send 14 objects over a single TCP connection, this is an example of _____ HTTP.
If an HTTP server can send 14 objects over a single TCP connection, this is an example of __Persistent___ HTTP.
If your computer becomes infected, you may be enrolled in a_________ and used in_________ against other hosts without your knowledge.
If your computer becomes infected, you may be enrolled in a botnet and used in DDoS attack against other hosts without your knowledge.
How is client-server architecture different from peer-to-peer (P2P) architecture?
In a client-server architecture, the server is always on and waiting for requests from clients, so when a request is received, the server can respond to the client. The client initiates communication with a server by sending a request.
What devices reside in the network core?
Interconnection devices (routers, switches, associated network cards, etc...)
Which are faster: Circuit-switched networks or Packet-switched networks?
It depends! A circuit-switched network may be faster due to the packet header overhead of packet-switched networks. However, a packet-switched network may be faster due to its more adaptive use of the transmission medium. It's even more complicated than this...
If none of the links from the HTTP client to the HTTP server are congested, will a connection be faster with or without caching enabled.
It will still likely be faster with caching, because any time you request a file a second time, the proxy server will eliminate the necessity for the packets to traverse the internet, saving time.
Who invented the internet?
No one person invented the internet, but DARPA financed initial research, and a number of universities devoted significant research personnel to developing and establishing communication protocols for interconnectivity hardware and software.
What transport-layer services are provided by the base UDP protocol? (Check all that apply) Congestion control Flow control Message security None of these services are provided by UDP Connection-oriented service Minimum bandwidth Jitter minimization
None of these services are provided by UDP
What transport-layer services are provided by the base UDP protocol? (Check all that apply) Congestion control Minimum bandwidth None of these services are provided by UDP Jitter minimization Flow control Connection-oriented service Message security
None of these services are provided by UDP
What are three important functions of a packet-switched network
Packet Construction, Transmission, and Interpretation
As discussed in the lectures, what are the primary functions of a packet-switched network?
Packet construction Packet transmission Packet interpretation
Which of the following are application-layer protocols? Post Office Protocol v3 (POP3) Transmission Control Protocol (TCP) Internet Protocol (IP) File Transfer Protocol (FTP) Secure Shell (SSH) User Datagram Protocol (UDP) Telnet Domain Name Service (DNS)
Post Office Protocol v3 (POP3) File Transfer Protocol (FTP) Secure Shell (SSH) Telnet Domain Name Service (DNS)
Describe the sources of nodal delay in packet-switched networks.
Processing delay: Time spent processing header information, checking bit errors, and deciding outport link Queueing delay: Time waiting for the transmission medium Transmisison delay: Time spent being placed on the transmission medium, limited by the transmission protocol. Propagation delay: Time spent traveling on the physical medium
The IMAP e-mail protocol is called a _______protocol.
Pull
What transport-layer services are provided by the base TCP protocol? (Choose all that apply) Reliable data transmission Congestion control Message security Minimum bandwidth Jitter minimization Flow control Connection-oriented service
Reliable data transmission Congestion control Flow control Connection-oriented service
What is "IP spoofing"?
Sending information into the network with false "Sender IP" information.
How are cokies implemented in the HTTP handshaking procedure?
Server responds to client request, and includes in this response a request to use cookies. Client either sends next message with cookies enabled (to use cookies) or disabled. Sever generates cookie number and send this back to client.
Describe statistical multiplexing
Statistical multiplexing is the adaptive sharing of the transmission medium in packet-switched networks, based on whether or not hosts have data to transmit (on-demand), preventing the medium from being wasted by hosts without any data to transmit.
Signal attenuation is less of an issue in______ media than it is in ______media.
Signal attenuation is less of an issue in guided media than it is in unguided media.
A network protocol may do the following (check all that apply): Specify actions taken upon message transmission Specify the order of messages sent and received Specify the whether or not information is sent Specify actions taken upon message receipt Specify the time between sending information. Specify the form of messages sent and received
Specify actions taken upon message transmission Specify the order of messages sent and received Specify actions taken upon message receipt Specify the form of messages sent and received
__________ is designed to act like a server, and can distribute data from an infected computer to a remote host upon request.
Spyware
Choose one: In the internet, an application-level protocol implemeting email service would most likely utilize TCP/UDP as its transport-layer protocol.
TCP
The FTP application-layer protocol utilizes the _______transport-layer protocol.
TCP
The HTTP application-layer protocol utilizes the _____transport-layer protocol.
TCP
What is the Domain Name System (DNS) application-layer protocol used for? What transport-layer protocol does it make use of?
The DNS protocol uses UDP, and is used to resolve human-friendly word-based web addresses into Network-layer IP addresses and alias web and mail servers.
Why does the HTTP request message require an extra \r\n at the end of the header section?
The HTTP header must be separated from the entity body
Consider the following: http://www.google.com/images/nav_logo195.png
The Host Name is www.google.com The Path Name is /images/nav_logo195.png The URL is http://www.google.com/images/nav_logo195.png The TLD is COM
Consider the following: http://oregonstate.edu/img/audience/future-apply.jpg The Host Name: The Path Name: The URL: The TLD:
The Host Name: oregonstate.edu The Path Name: /img/audience/future-apply.jpg The URL: http://oregonstate.edu/img/audience/future-apply.jpg The TLD: EDU
Consider the following: http://www.oregon.gov/SiteCollectionImages/branding/portal/bigfoot.png The Host Name: The Path Name: The URL: The TLD:
The Host Name: www.oregon.gov The Path Name: /SiteCollectionImages/branding/portal/bigfoot.png The URL: http://www.oregon.gov/SiteCollectionImages/branding/portal/bigfoot.png The TLD: GOV
What is the IETF
The Internet Engineering Task Force - who produces documentations which lay out standards for the Internet (without official decree).
The internet core is a __________ network. a) circuit-switched b) packet-switched
The internet core is a packet-switched network.
The internet is _______
The internet is _a network of networks
What is done with network resources in a circuit switched network to allow multiple users to utilize the network?
The network resource is divided into chunks
What is the role of physical media in access networks.
The physical media is physical link in the chain between sender/receiver pairs. Analog signals relating to bits propagate over/through the physical media
What organization manages the .org TLD?
This might require a bit of searching: The .org TLD is managed by PIR, the Public Interest Registry.
_______ is the rate at which bits are actually transferred between sender/receiver.
Throughput is the rate at which bits are actually transferred between sender/receiver.
What are some services the TCP protocol does not provide
Timing, Bandwidth, (additional answers possible)
What is the equation for end-to-end delay?
dnodal = dproc + dqueue + dtrans+ dprop
The _______ layer manages communications from process to process.
Transport
What are some applications which would have stringent timing requirements
Video games, VoIP, streaming video (any streaming service), etc...
As a packet is being constructed and passed "down" to the next layer of the internet protocol stack, a new "header" is added. This process is called ________
____encapsulation____
The payload (non-header portion) of a transport-layer segment is __________
__application data__
What units are we using for network bandwidth?
_bps
A third party intercepting a packing and downloading its information before sending it onward toward its destination is called _______________
a packet sniffer
In a circuit-switched network, if a user is allowing his available bandwidth to be idle, it is called
a silent period
At the transport layer, what is the payload?
application data
Time spent checking bit errors and deciding output link is considered a) Queueing Delay b) Processing Delay c) Transmission Delay d) Propagation Delay
b) Processing Delay
What units are used for transmission rate?
bps
When a packet is passed down to the next lower layer, it is _____________ into the lower-layer packet.
encapsulated
Protocol ________ allows multiple protocols to work together.
interoperability
Suppose there are 95 packets entering a queue at the same time. Each packet is of size 5 MiB. The link transmission rate is 1.4 Gbps. What is the queueing delay of packet number 25 (in milliseconds, rounded to one decimal place, e.g. 0.01234 seconds would be entered as "12.3")
queueing delay of packet number 25 = 719.0
If I were to send information into the internet with your IP address listed as the sender IP, I would be _____
spoofing my IP address
Given a link with a maximum transmission rate of 84 Mbps. Only two computers, X and Y, wish to transmit starting at time t = 0 seconds. Computer X sends fileX (13 MiB) and computer Y sends fileY (47 KiB), both starting at time t = 0. Computer X gets the transmission medium first, so Computer Y must wait. For the following calculations, assume maximum transmission rate during transmission. Suppose that entire files are sent as a stream (no packets, no multiplexing). At what time (t = ?) would FileY finish transmitting? Give answer in seconds, without units, and round to two decimal places (e.g. for an answer of 12.4567 seconds you would enter "12.46" without the quotes)
1.3
Suppose there are 92 packets entering a queue at the same time. Each packet is of size 4 MiB. The link transmission rate is 4.3 Gbps. What is the queueing delay of packet number 14 (in milliseconds, rounded to one decimal place, e.g. 0.01234 seconds would be entered as "12.3")
101.4
Convert the following units. Your answer should be a whole number with no text in the answer field: 10 KiB = _____ bytes
10240
Convert the following units. Your answer should be a whole number with no text in the answer field: 11.19 Mbps = _____ Kbps
11190
Convert the following units. Your answer should be a whole number with no text in the answer field: 11.74 Mbps = _____ bits per second
11740000
How many unique network interface hardware addresses are possible?
12 hex digits means 16^12 = 281,474,976,710,656 unique numbers. Even though some of these numbers are reserved, this seems adequate for the time being.
How long does it take to send a 5 MiB file from Host A to Host B over a circuit-switched network, assuming: Total link transmission rate = 33.7 Gbps. Network is TDM, with 17 permitted users, each with an equal time slot size. A link connection requires a setup time of 98.8 ms. Your answer should be in miliseconds (ms) with one decimal place, and without the unit (e.g. "140.6" without the quotes)
120
Suppose there are 86 packets entering a queue at the same time. Each packet is of size 184 KiB. The link transmission rate is 2 Gbps. What is the queueing delay of packet number 22 (in milliseconds, rounded to one decimal place, e.g. 0.01234 seconds would be entered as "12.3")
15.8
3) What is the total utilization of a circuit-switched network, accommodating 10 users with equal bandwidth, with the following users: • Four users are utilizing 100% their bandwidth • Two users are utilizing 60% of their bandwidth • Four users are inactive
4 * (1.00) * 0.10 + 2 * (0.60) * 0.10 + 4 * (0.00) * 0.10 = 0.52 = 52%
A client in a network with a proxy server requests a 6 MiB file from an internet server, fakeservername.com. The network's proxy server has a 2.97 Mbps connection to fakeservername.com. The average response time between the network's proxy server and the internet origin server (including RTT) is 2.8 seconds for a small "header-only" HTTP request/response. The file requested by the client is currently in the proxy server cache, but the proxy server relays the client's request to the internet server with "if-modified since". Assume that transmissions between the proxy and the origin servers are stream (not packets) at fullbandwidth, with negligible propagation delay. How much time is saved if the file has not been modified? (Give answer in seconds, without units, rounded to two decimal places, so for an answer of 1.4233 seconds you would enter "1.42" without the quotes.)
16.95
Given the attached image, and:h Host A converts analog to digital at a = 57 Kbps Link transmission rate R = 1.5 Mbps Host A groups data into packets of length L = 100 bytes Distance to travel d = 816.6 km Propagation speed s = 2.5 x 108 m/s Host A sends each packet to Host B as soon as it gathers a whole packet. Host B converts back from digital to analog as soon as it receives a whole packet. How much time elapses from when the first bit starts to be created until the conversion back to analog begins? Give answer in milliseconds (ms) to two decimal places, normal rounding, without units (e.g. 1.5623 ms would be entered as "1.
17.83
Suppose there are 4 routers in sequence between Host A and Host B, all of which use store-and-forward routing. What is the total end-to-end delay for a packet originating from Host A with destination Host B, under the following conditions. Each of the link transmission rates are 8 Mbps The total distance from Host A to Host B along its path of transmisison is 124 km The speed of propagation through the transmission medium is is 2.7 x 108 m/s The packet size is 4 KiB Remember that you must also uplink from Host A to the first router. Give answer in milliseconds, rounded to 1 decimal place, without units (e.g. for 0.12345 seconds you would enter "123.5" without the quotes).
21
Suppose there are 2 routers in sequence between Host A and Host B, all of which use store-and-forward routing. What is the total end-to-end delay for a packet originating from Host A with destination Host B, under the following conditions. Each of the link transmission rates are 3 Mbps The total distance from Host A to Host B along its path of transmisison is 154 km The speed of propagation through the transmission medium is is 2.7 x 108 m/s The packet size is 3 KiB Remember that you must also uplink from Host A to the first router. Give answer in milliseconds, rounded to 1 decimal place, without units (e.g. for 0.12345 seconds you would enter "123.5" without the quotes)
25.2
Given a link with a maximum transmission rate of 29.5 Mbps. Only two computers, X and Y, wish to transmit starting at time t = 0 seconds. Computer X sends fileX (11 MiB) and computer Y sends fileY (98 KiB), both starting at time t = 0. Computer X gets the transmission medium first, so Computer Y must wait. For the following calculations, assume maximum transmission rate during transmission. Suppose that entire files are sent as a stream (no packets, no multiplexing). At what time (t = ?) would FileX finish transmitting? Give answer in seconds, without units, and round to two decimal places (e.g. for an answer of 12.4567 seconds you would enter "12.46" without the quotes)
3.13
Convert the following units. Your answer should be a whole number with no text in the answer field: 41 B = _____ bits
328
What is the total utilization of a circuit-switched network, accommodating five users with equal bandwidth share, and the following properties: Two users each using 91% of their bandwidth share Two users each using 43% of their bandwidth share One user using 16% of their bandwidth share Give answer in percent, with one decimal place (normal rounding) and no percentage sign (e.g. for 49.15% you would enter "49.2" without the quotes).
56.8
A client's browser sends an HTTP request to a website. The website responds with a handshake and sets up a TCP connection. The connection setup takes 6.9 ms, including the RTT. The browser then sends the request for the website's index file. The index file references 10 additional images, which are to be requested/downloaded by the client's browser. Assuming all other conditions are equal, how much longer would non-persistent HTTP take than persistent HTTP? (Give answer in milliseconds, without units, rounded to one decimal place. For an answer of 0.01005 seconds, you would enter "10.1" without the quotes.)
69
What is the difference between the client/server model and the Peer-to-Peer (P2P) model
A client-server model has a dedicated service provider, and a dedicated service consumer. In a peer-to-peer model, there is no dedicated provider/consumer, and organization is handled amongst the hosts
How long does it take to send a 5 MiB file from Host A to Host B over a circuit-switched network, assuming: Total link transmission rate = 89.1 Gbps. Network is FDM, with 12 permitted users, each with an equal bandwidth share. A link connection requires a setup time of 93.6 ms. Your answer should be in miliseconds (ms) with one decimal place, and without the unit (e.g. "140.6" without the quotes)
99.2
A ________-switched network has a dedicated circuit through which information is sent, whereas a ________-switched network sends information in "chunks" through a network on shared media
A ____circuit____-switched network has a dedicated circuit through which information is sent, whereas a ____packet____-switched network sends information in "chunks" through a network on shared media
A client-side history of transactions between a client and server using HTTP is called a ___________.
A client-side history of transactions between a client and server using HTTP is called a _____Cookie______.
What are the major trade-offs implied by the use of cookies?
Cookies make some web browsing more convenient by saving browsing history (e.g., shopping cart, location for weather report, etc.), but also allow servers to keep personal information about its clients, which may be seen as a violation of privacy.
What are some examples of guided media, and where are they used?
Cups with a string connecting them, twisted pair copper wires, coaxial cables, waveguide cabling (fiber-optic), etc... These are used in ADSL, cable internet
How long does it take to send a 13 KiB file from Host A to Host B over a circuit-switched network, assuming Total link transmission rate = 500Mbps The network is FDM, with 250 permitted users, each with an equal bandwidth share A link connection setup requires 100ms.
File size (L) = 13KiB = 13 * 1024 Bytes = 13 * 1024 * 8 bits = 106,496 bits One link's transmission rate (R) = 500Mbps / 250 users = 2Mbps = 2,000,000 bps Time to transmit file = L/R = 106496 bits / 2,000,000 bps = 0.053248 s = 53.25 ms Total sending time = setup time + transfer time = 100ms + 53.25ms = 153.25ms
What are some reasons for the layering of network protocols?
Protocols can be tested independently of one another When maintenance is required at one level, changes do not affect other layers Can update a the inner workings of a protocol, as long as input/output remain the same The complication of dealing with the intermeshed types of hosts and data is lessened
What are some applications which would have stringent bandwidth requirements
Video games, large databases, etc...
What is the difference between TDM and FDM
TDM divides the available bandwidth into discrete blocks of time, during which only one of the users is permitted to transmit. FDM divides the available into bands of frequency (like radio stations), in which only one user is permitted to transmit.
A client in a network with a proxy server requests a 3MiB file from an internet server, x.y.z.com. The network's proxy server has a 1.54Mbps connection to x.y.z.com. The average response time between the network's proxy server and the internet origin server (including RTT) is 2 seconds for a small "header-only" HTTP request/response. The file requested by the client is currently in the proxy server cache, but the proxy server relays the client's request to the internet server with "if-modified since". Assume that transmissions between the proxy and the origin servers are stream (not packets) at full bandwidth, with negligible propagation delay. How much time is saved if the file has not been modified?
The connection and GET requests from the proxy server to the origin server, and the delivery from the proxy server to the client, are the same in either case. The only difference is in whether or not the file has been modified at the origin server, in which case the new file must be downloaded to the proxy server. As a stream download, this takes (3 x 1024 x 1024 x 8 bits) / (1,540,000 bits per second) ≈ 16.34 seconds.
In an internet name, what is the highest-priority component? The second-highest priority component? What are subsequently prioritized components used for?
The right-most (.com, .org) TLD is the highest priority. The next-leftmost ("Comcast" in www.comcast.net) is the domain name. fields to the left of this are used internally (such as "engr" in engr.oregonstate.edu) as host names.
What is the goal of caching in HTTP?
To keep information requests from having to go to the goal server. This prevents the same information from being repeatedly downloaded, which would cause additional congestion in the internet (and slow down the rate at which the internet is perceived to load at the user end.
In the Internet protocol stack, the______ is responsible for process-to-process communication.
Transport Layer
What must an application layer protocol specify?
Types of message exchanged Message Syntax (fields, structure) Message Semantics (meaning) Rules for message send & response (how, when)
In the internet, an application-level protocol implemeting streaming video would most likely utilize _______ as its transport-layer protocol.
UDP
For the following question, proper hexadecimal format is (0xYYYY) where Y will range in (0-9) or (A-F). Only proper formats will be accepted. Suppose that we send a DNS request with ID #64325 What is the little-endian representation (hexadecimal)? What is the big-endian representation (hexadecimal)? Which representation is required for network communication? (Enter "1" or "2" without quotes)
What is the little-endian representation (hexadecimal)? What is the big-endian representation (hexadecimal)? Which representation is required for network communication? (Enter "1" or "2" without quotes) Answer 1: 0x45FB Answer 2: 0xFB45 Answer 3: 2
Application layer protocols must specify transport requirement by selecting a transport protocol from the transport layer. a. Give an example of an application that uses TCP, and explain why it uses TCP. b. Give an example of an application that uses UDP, and explain why it uses UDP.
a. Give an example of an application that uses TCP, and explain why it uses TCP. (Many possible answers) Example: File downloading. TCP provides reliable transfer, so we can be confident that every bit of the file will be transferred and received in the correct order. b. Give an example of an application that uses UDP, and explain why it uses UDP. (Many possible answers) Example: Streaming video. This requires fast data transfer, because video requires large amounts of data. UDP is much faster than TCP, because it does not perform all of the validation that TCP performs. While it is possible that some data may be lost or corrupted, it usually does not produce enough "jitter" to affect the performance.
Consider two hosts (A and B) connected by a single link with transmission rate R bps. The hosts are separated physically by d meters along a cable for which the speed of propagation is s meters per second. Host A sends a packet of length L bits to host B a. Show the propagation delay dprop in terms of d and s b. Show the transmission delay dtrans in terms of L and R c. Suppose Host A begins to transmit at time t = 0. At time t = dtrans where is the last bit of the packet? d. Suppose that dprop > dtrans . At time t = dtrans , where is the first bit of the packet? Somewhere in the link between Host A and Host B e. Suppose that dprop < dtrans . At time t = dtrans , where is the first bit of the packet? f. Let s = 2.5x108 m/s, L = 120 bits, R = 56 Kbps. Find d such that dprop = dtrans.
a. Show the propagation delay dprop in terms of d and s: dprop = d/s b. Show the transmission delay dtrans in terms of L and R: dtrans = L/R c. Suppose Host A begins to transmit at time t = 0. At time t = dtrans where is the last bit of the packet? Just leaving the sending host (Host A) d. Suppose that dprop > dtrans . At time t = dtrans , where is the first bit of the packet? Somewhere in the link between Host A and Host B e. Suppose that dprop < dtrans . At time t = dtrans , where is the first bit of the packet? At the receiving host (Host B) f. Let s = 2.5x108 m/s, L = 120 bits, R = 56 Kbps. Find d such that dprop = dtrans. Set d/s = L/R 120 / 56,000 = d / 250,000,000 d = 250,000,000 * 120 / 56,000 = 535,714.28 m ≈ 535.7 km
A client's browser sends an HTTP request to a website. The website responds with a handshake and sets up a TCP connection. The connection setup takes 2 sec, including the RTT. The browser then sends the request for the website's index file. The index file references 6 additional image, which are to be requested/downloaded by the client's browser. How many requests (including the initial request) must be sent by the browser... a. With non-persistent HTTP? Show the Requests. b. With persistent HTTP? Show the Requests. c. Assuming that all other conditions are equal, which type of HTTP takes longer to complete the entire transfer? d. How much longer?
a. With non-persistent HTTP? Show the Requests. ___ 14___ b. With persistent HTTP? Show the Requests. ___ 8___ c. Assuming that all other conditions are equal, which type of HTTP takes longer to complete the entire transfer? Non-persisted HTTP takes longe d. How much longer? (14 req - 8 req) * 2 sec/req = 12 seconds. It takes 12 seconds longer
A _______ is a group of computers all controlled for a common objective, possibly by an infection in the system, used cooperatively to process and/or send information in mass amounts (DDoS, distributed computing).
botnet
If an HTTP server requires 2 TCP connections to send 2 objects, this is an example of______ HTTP.
non-persistent
We call a program that is running on a host a _______.
process
The SMTP e-mail protocol is called a_____ protocol.
push
________are designed to destroy files or cause a computer malfunction.
viruses
What are some components of the TCP protocol?
• Connection-Oriented with 3-way connection-setup handshake • Reliable, in-order data transfer • Flow control • Congestion Control
What are some components of the UDP protocol?
• Connection-less • Unreliable data transfer (Fire & Forget) • No flow or congestion control
What are some of the effects of congestion in a packet-switched network.
• Packet Delay • Packet Loss • Jitter • etc..
What does a protocol do?
• Specifies the format and order of messages sent and received among network entities. • Specifies actions taken upon the transmission and receipt of messages
What are some factors in why computer networking so complicated?
• Variety of hardware devices which must communicate with each other (legacy, modern) • Software being developed which must be interoperable • Numerous protocols and communication standards • Complicated terminology and acronyms • Wireless and Mobility challenges • etc...
Communication via guided media is complex enough by itself, but communication via unguided (wireless) media is even more complicated. What are some additional difficulties of wireless networking?
• Wireless signals are more vulnerable to interference and noise. • Wireless signals may be blocked, especially by metal. • Wireless signals may reflect and interfere with other wireless signals. • (Other answers are possible.)
Convert the following units. Your answer should be a whole number with no text in the answer field: 10 KiB = _____ bytes
10 KiB = 10240 bytes
Convert the following units. Your answer should be a whole number with no text in the answer field: 10 MiB = _____ bytes
10485760
Convert the following units. Your answer should be a whole number with no text in the answer field: 6 KiB = _____ bytes
6 KiB = 6144 bytes
Convert the following units. Your answer should be a whole number with no text in the answer field: 874 B = _____ bits
874 B = 6992 bits
A client's browser sends an HTTP request to a website. The website responds with a handshake and sets up a TCP connection. The connection setup takes 2 sec, including the RTT. The browser then sends the request for the website's index file. The index file references 5 additional images, which are to be requested/downloaded by the client's browser. How many requests (including the initial request) must be sent by the browser... 1. With non-persistent HTTP? 2. With persistent HTTP?
1. 12 requests 2. 7 requests
A client's browser sends an HTTP request to a website. The website responds with a handshake and sets up a TCP connection. The connection setup takes 5.4 ms, including the RTT. The browser then sends the request for the website's index file. The index file references 2 additional images, which are to be requested/downloaded by the client's browser. Assuming all other conditions are equal, how much longer would non-persistent HTTP take than persistent HTTP? (Give answer in milliseconds, without units, rounded to one decimal place. For an answer of 0.01005 seconds, you would enter "10.1" without the quotes.)
10.8 ms
How long does it take to send a 13 MiB file from Host A to Host B over a circuit-switched network, assuming: Total link transmission rate = 57.7 Gbps. Network is FDM, with 4 permitted users, each with an equal bandwidth share. A link connection requires a setup time of 99.8 ms. Your answer should be in miliseconds (ms) with one decimal place, and without the unit (e.g. "140.6" without the quotes)
107.4 ms
Convert the following units. Your answer should be a whole number with no text in the answer field: 15 KiB = _____ bits
15 KiB = 122880 bits
Voice over IP (VoIP) Given the attached image, and: Host A converts analog to digital at a = 57 Kbps Link transmission rate R = 4.9 Mbps Host A groups data into packets of length L = 94 bytes Distance to travel d = 696.4 km Propagation speed s = 2.5 x 108 m/s Host A sends each packet to Host B as soon as it gathers a whole packet. Host B converts back from digital to analog as soon as it receives a whole packet. How much time elapses from when the fi rst bit starts to be created until the conversion back to analog begins? Give answer in milliseconds (ms) to two decimal places, normal rounding, without units (e.g. 1.5623 ms would be entered as "1.56" without the quotes)
16.13 ms
Suppose there are 77 packets entering a queue at the same time. Each packet is of size 165 KiB. The link transmission rate is 1 Gbps. What is the queueing delay of packet number 16 (in milliseconds, rounded to one decimal place, e.g. 0.01234 seconds would be entered as "12.3")
20.3 ms
A client in a network with a proxy server requests a 7 MiB file from an internet server, fakeservername.com. The network's proxy server has a 2.73 Mbps connection to fakeservername.com. The average response time between the network's proxy server and the internet origin server (including RTT) is 1.6 seconds for a small "header-only" HTTP request/response. The file requested by the client is currently in the proxy server cache, but the proxy server relays the client's request to the internet server with "if-modified since". Assume that transmissions between the proxy and the origin servers are stream (not packets) at fullbandwidth, with negligible propagation delay. How much time is saved if the file has not been modified? (Give answer in seconds, without units, rounded to two decimal places, so for an answer of 1.4233 seconds you would enter "1.42" without the quotes.)
21.51 seconds
Voice over IP (VoIP) Given the attached image, and: Host A converts analog to digital at a = 39 Kbps Link transmission rate R = 4.1 Mbps Host A groups data into packets of length L = 110 bytes Distance to travel d = 590.2 km Propagation speed s = 2.5 x 108 m/s Host A sends each packet to Host B as soon as it gathers a whole packet. Host B converts back from digital to analog as soon as it receives a whole packet. How much time elapses from when the first bit starts to be created until the conversion back to analog begins? Give answer in milliseconds (ms) to two decimal places, normal rounding, without units (e.g. 1.5623 ms would be entered as "1.56" without the quotes)
25.14 ms
Given a link with a maximum transmission rate of 28.2 Mbps. Only two computers, X and Y, wish to transmit starting at time t = 0 seconds. Computer X sends fileX (20 MiB) and computer Y sends fileY (486 KiB), both starting at time t = 0. Statistical multiplexing is used, with details as follows Packet Payload Size = 1000 Bytes Packet Header Size = 24 Bytes (overhead) Ignore Processing and Queueing delays Assume partial packets (packets consisting of less than 1000 Bytes of data) are padded so that they are the same size as full packets. Assume continuous alternating-packet transmission. Computer X gets the transmission medium first. At what time (t = ?) would FileY finish transmitting? Give answer in milliseconds, without units, and round to one decimal places (e.g. for an answer of 0.013777 seconds you would enter "13.8" without the quotes)
289.3 ms
Convert the following units. Your answer should be a whole number with no text in the answer field: 53.01 Mbps = _____ Kbps
53010
What is the total utilization of a circuit-switched network, accommodating five users with equal bandwidth share, and the following properties: Two users each using 94% of their bandwidth share Two users each using 46% of their bandwidth share One user using 11% of their bandwidth share Give answer in percent, with one decimal place (normal rounding) and no percentage sign (e.g. for 49.15% you would enter "49.2" without the quotes).
58.2%
What is the total utilization of a circuit-switched network, accommodating five users with equal bandwidth share, and the following properties: Two users each using 95% of their bandwidth share Two users each using 56% of their bandwidth share One user using 19% of their bandwidth share Give answer in percent, with one decimal place (normal rounding) and no percentage sign (e.g. for 49.15% you would enter "49.2" without the quotes).
64.2%
How long does it take to send a 4 MiB file from Host A to Host B over a circuit-switched network, assuming: Total link transmission rate = 76.4 Gbps. Network is FDM, with 5 permitted users, each with an equal bandwidth share. A link connection requires a setup time of 67.3 ms. Your answer should be in miliseconds (ms) with one decimal place, and without the unit (e.g. "140.6" without the quotes)
69.5 ms
Convert the following units. Your answer should be a whole number with no text in the answer field: 70 B = _____ bits
70 B = 560 bits
Convert the following units. Your answer should be a whole number with no text in the answer field: 82.22 Mbps = _____ Kbps
82220
How long does it take to send a 5 MiB file from Host A to Host B over a circuit-switched network, assuming: Total link transmission rate = 36.4 Gbps. Network is TDM, with 4 permitted users, each with an equal time slot size. A link connection requires a setup time of 81.2 ms. Your answer should be in miliseconds (ms) with one decimal place, and without the unit (e.g. "140.6" without the quotes)
85.8 ms
A connection-oriented protocol in a packet-switched network guarantees a dedicated line - similar to how a circuit-switched network works.
False
A server-side piece of data which is used to keep track of transactions between a client and server is called a cookie.
False
The UDP protocol implements reliable data transfer.
False
The UDP protocol is connection-oriented.
False. It is a connectionless service.
For the following question, proper hexadecimal format is (0xYYYY) where Y will range in (0-9) or (A-F). Only proper formats will be accepted. Suppose that we send a DNS request with ID #4779. What is the little-endian representation (hexadecimal)? What is the big-endian representation (hexadecimal)? Which representation is required for network communication?
Little-endian: 0xAB12 Big-endian: 0x12AB Big-endian representation is required for network communication.
What must an application-level protocol specify? (Check all that apply) Message sending rules Message Fields & Structure Protocol versioning info Protocol authoring information Message Semantics Message response rules Types of messages exchanged
Message sending rules Message Fields & Structure Message Semantics Message response rules Types of messages exchanged
Choose from the following choices to fill in the two blanks: -Propagation delay -Transmission delay -Queuing delay -Processing delay __________ is proportional to the rate of travel of electrons through the transmission medium, whereas __________ is proportional to the rate at which the receiving node can interpret the electronic signal.
Propagation delay is proportional to the rate of travel of electrons through the transmission medium, whereas Transmission delay is proportional to the rate at which the receiving node can interpret the electronic signal.
The minimum necessary information for identifying a process on a remote host would be (check all that apply): Local Socket Info Local Port Number Local Host IP Remote Host IP Gateway Router IP Remote Port Number
Remote Host IP Remote Port Number
In the internet, an application-level protocol implemeting web browsing would most likely utilize ______as its transport-layer protocol.
TCP
The HTTP application-layer protocol utilizes the _______ transport-layer protocol. SMTP TCP HTTP UDP IP
TCP
The IMAP/POP3 application-layer protocols utilizes the ________ transport-layer protocol. IP HTTP TCP SMTP UDP
TCP
The SMTP application-layer protocol utilizes the _______ transport-layer protocol. SMTP TCP HTTP UDP IP
TCP
The SMTP application-layer protocol utilizes the ____transport-layer protocol.
TCP
Which of the following are application-layer protocols? Telnet Domain Name Service (DNS) Internet Protocol (IP) File Transfer Protocol (FTP) Post Office Protocol v3 (POP3) Transmission Control Protocol (TCP) Secure Shell (SSH) User Datagram Protocol (UDP)
Telnet Domain Name Service (DNS) File Transfer Protocol (FTP) Post Office Protocol v3 (POP3) Secure Shell (SSH)
Consider the following: http://www.oregon.gov/images/logo.png The Host Name: The Path Name: The URL: The TLD:
The Host Name: www.oregon.gov The Path Name: /images/logo.png The URL: http://www.oregon.gov/images/logo.png The TLD: GOV
A network is a system for connecting multiple computers using a single transmission technology.
True
The following is a valid IP address: 130.154.1.25
True
The internet is a network of networks.
True
The DNS application-layer protocol utilizes the _______ transport-layer protocol. SMTP TCP HTTP UDP IP
UDP
The DNS application-layer protocol utilizes the ________transport-layer protocol
UDP
For the following question, proper hexadecimal format is (0xYYYY) where Y will range in (0-9) or (A-F). Only proper formats will be accepted. Suppose that we send a DNS request with ID #47806. What is the little-endian representation (hexadecimal)? What is the big-endian representation (hexadecimal)? Which representation is required for network communication? (Enter "1" or "2" without quotes)
What is the little-endian representation (hexadecimal)? 0xBEBA What is the big-endian representation (hexadecimal)? 0xBABE Which representation is required for network communication? (Enter "1" or "2" without quotes) 2
A client's browser sends an HTTP request to a website. The website responds with a handshake and sets up a TCP connection. The connection setup takes 2 sec, including the RTT. The browser then sends the request for the website's index file. The index file references 4 additional images, which are to be requested/downloaded by the client's browser. How many requests (including the initial request) must be sent by the browser... With non-persistent HTTP? With persistent HTTP?
With non-persistent HTTP? 10 With persistent HTTP? 6
A client's browser sends an HTTP request to a website. The website responds with a handshake and sets up a TCP connection. The connection setup takes 2 sec, including the RTT. The browser then sends the request for the website's index file. The index file references 9 additional images, which are to be requested/downloaded by the client's browser. How many requests (including the initial request) must be sent by the browser... With non-persistent HTTP? With persistent HTTP?
With non-persistent HTTP? 20 With persistent HTTP? 11
Time spent being placed on the transmission medium is called a) Transmission delay b) Propagation delay c) Queueing delay d) Processing delay
a) Transmission delay
A FDM-based network is a _______ network. a) circuit-switched b) packet-switched
a) circuit-switched
A TDM-based network is a _______ network. a) circuit-switched b) packet-switched
a) circuit-switched
Time spent in transit between nodes in a network is called a) Transmission delay b) Propagation delay c) Queueing delay d) Processing delay
b) Propagation delay
Choose an answer: peer-to-peer client-server hybrid client-server/P2P In the __________ architecture, one host is always one, and the other hosts may connect and be continually serviced by this first host.
client-server
A pair of sockets is called a __________. port socket couple connection process
connection
Merging multiple communication streams into the same media is called _________?
multiplexing
In a ___________ architecture, no one host is always on, but hosts may connect amongst themselves in an on-demand fashion. Choose one: peer-to-peer client-server hybrid client-server/P2P
peer-to-peer
In_________ a architecture, no one host is always on, but hosts may connect amongst themselves in an on-demand fashion.
peer-to-peer
The reserved port for FTP data transfer is port ______.
port 20
The reserved port for FTP control is port
port 21
The reserved port for SSH is port ________.
port 22
A program running on a host is called a ___________. Choose an answer: process socket port connection
process
A program running on a host is called a ______________. connection socket port process
process
A paired IP address and port number is called a ______. connection socket process port pair
socket
Suppose there are 5 routers in sequence between Host A and Host B, all of which use store-and-forward routing. What is the total end-to-end delay for a packet originating from Host A with destination Host B, under the following conditions. Each of the link transmission rates are 4.4 Mbps The total distance from Host A to Host B along its path of transmisison is 175.6 km The speed of propagation through the transmission medium is is 2.7 x 108 m/s The packet size is 2 KiB Remember that you must also uplink from Host A to the first router. Give answer in milliseconds, rounded to 1 decimal place, without units (e.g. for 0.12345 seconds you would enter "123.5" without the quotes).
total end-to-end delay = 23.0 ms
