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Description
Flashcards by Tobias Aspegårdh, updated more than 1 year ago
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Created by Tobias Aspegårdh
over 4 years ago
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| Question | Answer |
| What transport services does an app need? | Data Integrity Timing Throughput Security |
| What layers does the OSI-model consist of? | Application Presentation Session Transport Network Data Link Physical |
| What layers does the TCP/IP-model consist of? | Network Internet Transport Application |
| What does the protocol for the application layer define? | Type of messages exchanged. Message syntax. Rules for how and when processes send and recieve msgs. |
| What does DoS stand for and how is it utilized? | Denial of service: Attackers overwhelm the target with data |
| When does packet loss occur? | When the buffer/queue is full |
| What factors affect queueing delay? | Time waiting at output link for transmission Congestion level at router |
| What factors affect transmission delay and what formula is used to calculate it? | Packet Size (bits) - L Link Capacity (bits/s) - B d(trans) = L / B |
| What is the difference between packet- and circuit switching? | Packet Switching - Msgs are broken up into packet at the application layers and sent over multiple links to reciever. Circuit Switching - One link is set up to reciever and used to its full capacity. |
| What is the pros/cons of packet switching? | Pros - Better utilization of network, connectionless. Cons - Higher chance of delay and loss. |
| What does "store and forward" mean? | That the entire message must arrive at a router before it can be transmitted to the next link. |
| Name three types of guided physical media? | Coxial cable Twisted Pair Fiber |
| What is the difference between guided/unguided media and give an example of each? | Unguided - Doesn´t use a physical direct link between sender/reciever. ex. Wifi Guided - Uses a physical link between sender/reciever. ex Fiber |
| What are the differences between the Client/Server model and P2P (Peer-Peer) model and give an example of how these are used? | Client/Server - Uses server between sender and reciever to store data. ex. Email via server. P2P - Direct communication between two hosts. ex. Skype |
| What factors affect propagation delay and what is the formula used to calculate it? | Distance between sender and reciever, distance of used link (m) - D Propagation speed of wave signal (b/s) - S d(prop) = D / S |
| What formula is used to calculate the nodal delay? a) dnodal = dproc – dqueue + dtrans + dprop b) dnodal = dproc + dtrans – dqueue c) dnodal = dproc + dqueue + dtrans + dprop d) dnodal = dproc + dqueue – dtrans – dprop | c) dnodal = dproc + dqueue + dtrans + dprop |
| What service is provided by the Internet Protocol (IP)? | Adresssing, providing nodes with unique IP-adresses used for routing and forwarding. |
| What is the key difference between Collision Avoidance (CA) and with Collision Detection (CD), and where are they used in? | CA - Avoids any error that might occur. Can send Reguest to Send in order to accomplish this. CD - Dectects error on a link that is being used an corrects it. |
| What is the purpose of ARP | Adress Resolution Protocol It connects the IP and MAC adress. |
| What is the service provided by DNS? | Domain Name System It connects domain name of (for example) a website and the IP-adress. |
| What is the difference between routing and forwarding? | Routing - Sets a table of routes for packets heading to different destinations. Forwarding - Sends a data packet to the right interface in a router. This makes sure the packet is sent to the correct next hop. |
| True or false? HTTP response messages cannot have an empty message body. | False |
| True or false? The size of the TCP rwnd can change throughout the duration of the connection. | True |
| Which cause of delay typically dominates in highly utilized multi-hop networks and why? | Queueing delay |
| Transmission delay does not depend on a) Packet length b) Distance between the routers c) Transmission rate d) None of the above | b) Distance between the routers |
| Propagation delay depends on a) Packet length b) Transmission rate c) Distance between the routers d) None of the mentioned | b) Transmission rate c) Distance between the routers |
| In the transfer of file between server and client, if the transmission rates along the path is 10Mbps, 20Mbps, 30Mbps, 40Mbps. The throughput is usually a) 10Mbps b) 20Mbps c) 40Mbps d) 50Mbps | a) 10 Mbps |
| What is the difference between IP and MAC-adresses? | IP-adresses are attached to network devices via software. MAC adresses are unique within a network (local network) and attached to hardware. |
| How big is the MAC address space? The IPv4 adress space? IPv6? | MAC: 2^48 IPv4: 2^32 IPv6: 2^128 |
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Assume a TCP sender transmits 4 TCP segments with respective sequence numbers 1200, 2400, 3600, 4800.
The sender receives four acknowledgements with the following sequence numbers, 2400, 2400, 2400, 6000. Complete Figure 6 to show what TCP segments are exchanged between sender and receiver.
Image:
Fig6 (binary/octet-stream)
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Seq #2400 doesn´t arrive but the sender sends the rest and the reciever acknowledges them but keeps asking for #2400 |
| What is always done in the beginning and ending of a communication between two hosts using a TCP-connection? | An Handshake |
| What are the two types connections for HTTP? And what are their differences? | Non-Persistent: The connection is closed after the server sends the requested object to the client. Persistent: The connection only closes after a certain amount of time of no information shared. |
| What is the main difference between s TCP and a UDP - connection? | TCP - Requires handshake before sending data between sender/reciever. UDP - No handshake, each packet has the destination IP and port attached to it. |
| What is the pros and cons of a UDP connection? | Pros - Faster, especially when sending heavy amount of data. Cons - Risk of loss, out of order. |
| What is the main service of the transport layer? | Providing a logical connection between applications running on different networks. |
| What does rdt stand for and what is the main problem with rdt2.0? | Reliable Data Transfer If a ACK or NACK is corrupted, the sender doesn´t know what to do. (one cannot simply send again...) |
| What is the main difference between rdt2.0 and rdt2.2? | rdt2.2 is a NAK-free protocol. |
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