Intro to Networks Final

5) The entries in a switch table need to be configured by the network administrator True or False

False, they are self learning

D) HTTP request and response messages are not humanly readable True or False

False, they're readable

what is DHCP's job

to give computers and other devices IP addresses

When circuit switching is used, how many users can be supported?

two

what is DNS and what is its role?

domain name server, provides IP addresses

what is DHCP

dynamic host configuration protocol

1) All link layer protocols that supports IP have the same frame structure (i.e length of frame, number and length of header fields) True or False

False

2) CRC error detection, as used in Ethernet, is always able to detect whether there is an error in a frame True or False

False, nothing is perfect

What is protocol?

Set of rules on how to communicate between network edge devices

A) Suppose a client sends an HTTP request message with the If-modified-since: header. Suppose the object in the server has not changed since the last time that client retrieved the object. Then the server will send a response message with the status code: 304 Not Modified 404 Not Found 200 OK 403 Permission Denied None of the above

304 Not modified

9) An ARP query packet is encapsulated in . . . An IP datagram A link layer broadcast frame A link layer frame addressed to a specific adapter None of the above

A link layer broadcast frame, router BROADCASTS the ARP query

How do routing tables work?

A to B: no one knows anything After packet reaches switch, switch knows where A is and broadcasts packet Packet reaches B B to A: packet travels to switch Forwards the packet to A

What is encapsulation?

A way to address data to cross over any type of network link

How long does it take a packet of length 1,000 bytes to propagate over a link of distance 2,500km, propagation speed 2.5*10^8m/s, and transmission rate 2Mbps. A) More generally, how long does it take a packet of length L to propagate over a link of distance d, propagation speed s, and transmission rate R bps? B) Does this delay depend on packet length? Does this delay depend on transmission rate?

A) Dp = d/s = (2500 km)/(2.5 x 10^8) = 0.01 sec Dt = L/R = (1000 bytes)/(2 Mbps) = (8000 bits)/(2,000,000 bps) = 0.004 sec Dp + Ds = 0.01 + 0.004 = 0.014 secs B) Yes and yes

11) Ethernet provides which of the following services to the network layer Reliable data transfer Flow control Error detection All of the above

All of the above

7) Header of a frame generally contains . . . Synchronization bytes Source link layer address Destination link layer address All of the above

All of the above, think of a letter in the mail

8) A channel partitioning protocol has which of the following characteristics: It does not generate collisions All transmitting nodes get the same amount of bandwidth There is no master node All of the above

All, channel partitioning's goal is to fairly distribute the network

E) Which of the following is an application layer service? Virtual terminal File transfer, access, and management Mail Service All of the mentioned

All, they're all applications

What are the five layers in the internet protocol stack? What are the principle responsibilities of each of these layer?

Application -- Message -- HTTP, FTP Transport -- Segment -- TCP, UDP Network -- Datagram -- IP Data Link -- Frame -- Ethernet Physical -- Bit --

15) As part of hierarchical routing, hot-potato routing does the following: Labels suspicious packets as "hot" Provides information to a router about the existence of external networks Determines the number of ASs in the shortest AS path from router to destination Chooses the gateway that has the smallest cost

Chooses the gateway that has the smallest cost OSPF -- open shortest path first

what is the CIA triangle?

Confidentiality, Integrity, Availability

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?

Constant: propagation and transmission Variable: processing and queuing

10) CRC stands for Cyclic redundancy check Code repeat check Code redundancy check Cyclic repeat check

Cyclic redundancy check

What are network edge devices?

Devices connected to the network core such as laptops, phones

What is Djikstra's algorithm?

Dijkstra's algorithm → finding shortest path between any two nodes

What is Distance Vector Routing?

Distance vector routing → protocol for finding best path based on distance

What are: FDM TDM

FDM is frequency division multiplexing TDM is time division multiplexing

Why do HTTP, FTP, SMTP, and POP3 run on top of TCP rather than on UDP?

HTTP FTP --- file sharing SMTP, POP3 --- mail clients Simply put, the features TCP has allows for more reliable data transfer and higher quality of service

what is HTTP?

Hypertext Transfer Protocol, backbone of getting web pages

What info is used by a process running on one host to identify a process running on another host?

IP address - gotta find the device Port number - gotta find the location of the process

What layer do the following belong to: MAC addresses IP addresses

MAC addresses -- Link Layer IP addresses -- transport layer

6) The data link layer takes packets from ____ and encapsulates them into frames for transmission. Network layer Physical layer Transport layer Application layer

Network Layer, remember IP stack

What is the network core? Devices?

Network core is the network itself and consists of devices like routers which facilitate connectivity

13) When a switch transmits an Ethernet frame, the Ethernet frame has: The broadcast address for the its source address The switch's LAN address for its destination address The switch's LAN address for its source address None of the above

None of the above

14) In routing among ASs, which one of the following issues dominates: Number of ASs traversed Geographical distance between ASs Current congestion levels ********** Policy

Policy, everyone has one

How do you find the following delays: Propagation Transmission

Propagation -- d/s Transmission -- L/R

What are the tasks of: router switch

Router -- route based on IP address -- transport layer Switch -- route/forward based on MAC addresses -- link layer -- switch does not have own MAC address -- can only send things inside its own network

C) Which of the following is not a field on a UDP segment? Length Source Port Number Destination Port Number Sequence Number None of the above

Sequence number, remember UDP is throwing markers

What is slotted ALOHA

Slotted ALOHA: Frame Transmission -- the user has to wait until next slot start time to transmit frame Time -- time is discrete Successful transmission -- S = G*e^-G Sync -- Time is globally synced Throughput -- Max throughput occurs at G=1, 37%

TCP process

TCP -- handshake, slow down then speed up then slow down again, sequence numbers for acks

12) In the Ethernet CSMA/CD protocol, suppose a node constructs a frame and then senses the channel as busy. Then . . . The adapter begins to transmit the frame The adapter enters exponential backoff → Backoff only if there is a collison The adapter waits until it senses the channel idle and then begins to transmit the frame None of the above

The adapter waits until it senses the channel idle and then begins to transmit frame Logic: channel is busy, wait for channel, then send

B) SMTP is a PUSH protocol. An email is "pushed" from the sender's email client to the receiver's inbox. True or False

True

3) Consider a router with multiple ARP tables, one for each of its interfaces. No two of these ARP tables can contain the same LAN address. True or False

True, no point for repeat LAN addresses

4) HTTP request and response messages are humanly readable True or False

True, they ARE readable

Suppose you wanted to do a transaction from a remote client to a server as fast as possible. Would you use UDP or TCP? Why?

UDP, simply put, has less overhead by nature and no handshake

What does DHCP use

Uses UDP

What is IP spoofing

any time you have changed your IP address to fake another

What layer does DHCP belong to?

application layer

Features of software defined networks

flow control, switching, firewall

Suppose users share a 2Mbps link. Also suppose each user transmits continuously at 1Mbps when transmitting, but each user transmits only 20 percent of the time. Should you use packet switching or circuit switching?

packet switching

What are the two routing types, how do they differ?

packet switching -- breaks streams of data into smaller blocks circuit switching -- basis of traditional phone network