Sunday, February 9, 2014

Brainstorming of Network Communication

Regarding TCP, UDP, IP, and routing:
What are the important fields in the TCP, UDP, and IP headers? Without these fields, the protocols would clearly not “work”. 
 TCP = ports #s, seq/ack #s, flags, checksum, and windows size
UDP = port #s and checksum

IP = addresses, checksum for header

What are the important attributes for a good routing algorithm? 
 Fast, simple, little traffic, no loops, converge to optimum 
 
What is a key difference between a distance vector and link state routing protocol? 
DV uses neighbor exchange of routing vectors, LS uses broadcast of link state 
information.


Regarding Application Layer :
We say that FTP has out-of-band control. What do we mean by that? 

 We mean that commands and data flow across different TCP connections.

How is it that sender addresses can be spoofed in an email? 
 There is no authentication of commands in SMTP. Thus anyone with access to an SMTP

server can enter any from address (i.e., spoof who they are).

What is HTTP (in about 100 words, use a drawing if it will help)? 
 The HyperText Transfer Protocol is a stateless application layer protocol. HTTP is
used to transfer web content between a browser application (client) and an HTTP server.
All web content is identified by a URL. HTTP is a request response protocol that uses
TCP for assured delivery. HTTP uses ASCII encoded headers. The HTTP GET command
retrieves HTML files and other objects. The GET header includes the URL of the object
and other optional fields such as capability, language, and so on. The response
includes a response header with a response code (code 200 is OK and 404 is page not
found). Other commands include POST and HEAD.



Regarding the basics of computer networks and the Internet. 
What are the fundamental measures of interest for a communications system? 
 Throughput, delay, loss, cost, mobility, robustness, and secrecy

What are the basic tasks or functions of a communications system? 
 Message formatting, error detection and recovery, addressing, routing, flow control,
system management, security, and QoS

Precisely define protocol and interface (as we described them in class). 
 A protocol is a complete set of rules regarding information exchange between same level
layers between sites. An interface is a complete set of rules regarding information

exchange between adjacent layers in a single site.


Regarding the Internet
What are the four causes of packet delay? 
 Processing, transmission, propagation, and queueuing. 
 
What are the possible mechanisms of packet loss? 
 Buffer overflow (e.g., due to congestion) and electrical noise corrupting a packet 
 
What is a tool that can be used to determine the number of hops to a destination and the round trip time (RTT) for each hop? 
 traceroute 

What is quality of service? 

 QoS is the requirements an application places on the network. 

Resources :

http://www.proprofs.com/quiz-school/story.php?title=networking-midterm
(http://www.proprofs.com/quiz-school/search.php?search=network)
http://courses.engr.illinois.edu/cs438/sp2012/assignments/midterm-ol-s12-sol.pdf
http://www.cram.com/flashcards/networking-midterm-2433165
http://www.cram.com/flashcards/network-midterm-exam-study-stet-2441344
http://www.csee.usf.edu/~christen/class2/oldExams/ex2_1_sol_spr06.pdf
http://www.cs.princeton.edu/courses/archive/spr11/cos461/docs/lec12-midreview.pdf
http://www.cs.uiuc.edu/class/fa06/cs438/CS438-MidtermSolutions.pdf
http://server.casa.umass.edu/~zink/ECE374/Exams/MidtermII_Exam_With_Fall_2011_SOLUTIONS.pdf
http://server.casa.umass.edu/~zink/ECE374/Exams/MidtermExam2010withsolutions.pdf
http://cs.brown.edu/courses/cs196-5/f13/handouts/midterm-s12.pdf

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