Cs 456

Front 1

Name 3 characterisitics of a server

Back 1

* always-on host
* permanent IP address
* data centers for scaling

Front 2

What are 5 P2P charactersitics?

Back 2

* no always-on server :arbitrary end systems

directly communicate
* peers request service from
other peers, provide service
in return to other peers

* self scalability – new
peers bring new service
capacity, as well as new
service demands
* peers are intermittently
connected and change IP
addresses

Front 3

within same host, two processes communicate
using___________ (defined by
OS)

Back 3

inter-process communication

Front 4

client process: process that ________

Back 4

initiates communication

Front 5

server process: process that ____________

Back 5

waits to be contacted

Front 6

"Sockets" are between two layers, which two layers are they?

Back 6

Application (process) and Transport

Front 7

A socket is a ____ between application layer and transport layer.

Back 7

API

Front 8

In addition to knowing the address of the host to which a message is destined, the sending process must also identify the receiving process. ______ serves this purpose.

Back 8

Destination port number

Front 9

Applications that have throughput
requirements are said to be ______.

Back 9

bandwidth-sensitive applications.

Front 10

_______________ can make use of as much, or as little, throughput
as happens to be available

Back 10

elastic applications

Front 11

What are 5 features of TCP?

Back 11

* reliable transport between
sending and receiving
process
* flow control: sender wont overwhelm receiver
* congestion control: throttle sender when network overloaded
* does not provide: timing,
minimum throughput
guarantee, security

* connection-oriented: setup
required between client and
server processes

Front 12

______ control is controlled by the receiving side. It ensures that the sender only sends what the receiver can handle.

Back 12

flow

Front 13

In _____ control Sender will reduce the amount of sent packets to avoid overflowing the router's buffer(Queue).

Back 13

Congestion Control

Front 14

In ______ control : Sender will send enough data that can be accommodated at the receiver end.

Back 14

Flow Control

Front 15

What are two characteristics of UDP?

Back 15

* unreliable data transfer
between sending and
receiving process

* does not provide:
reliability, flow control,
congestion control,
timing, throughput
guarantee, security,
or connection setup,

Front 16

web page consists of_____ which
includes several _________

Back 16

base HTML-file

referenced objects

Front 17

HTTP is stateless, what does this mean?

Back 17

server maintains no
information about
past client requests

Front 18

What is persistent http?

Back 18

multiple objects can
be sent over single
TCP connection
between client, server

Front 19

What is non persistent http?

Back 19

at most one object
sent over TCP
connection
* connection then
closed
* downloading multiple
objects required
multiple connections

Front 20

non-persistent HTTP requires____ RTTs per object

Back 20

2

Front 21

persistent HTTP requires____ RTTs for n objects

Back 21

near 1 RTT

Front 22

in non-persistent HTTP, there are roughly ____ RTTs in total

Back 22

Thus, roughly,
the total response time is two RTTs plus the transmission time at the server of the
HTML file ( 1 RTT for each object)

Front 23

What are methods used in HTTP1.0?

Back 23

 GET
 POST
 HEAD

Front 24

What does HEAD request do?

Back 24

asks server to leave
requested object out
of response (used for debugging)

Front 25

What methods does http 1.1 have?

Back 25

GET, POST, HEAD
 PUT
 uploads file in entity
body to path specified
in URL field
 DELETE

Front 26

What does 200 response mean?

Back 26

200 OK
 request succeeded, requested object later in this msg

Front 27

What does 301 response mean?

Back 27

301 Moved Permanently
 requested object moved, new location specified later in this msg
(Location:)

Front 28

What does 400 response mean?

Back 28

400 Bad Request
 request msg not understood by server

Front 29

What does 404 response mean?

Back 29

404 Not Found
 requested document not found on this server

Front 30

What does 505 response mean?

Back 30

505 HTTP Version Not Supported

Front 31

typically cache is
installed by ______

Back 31

ISP
(university, company,
residential ISP)

Front 32

web cache acts as client or server?

Back 32

both

Front 33

When does 304 response happen?

Back 33

When we request with If-modified-since: <date>

in header and the object has not been modified

Front 34

The most striking difference between HTTP and FTP is that FTP _______

Back 34

uses two parallel TCP connections to transfer a file, a control connection and a data
connection

Front 35

In FTP a control connection is used to

Back 35

The control connection is used for sending control information between
the two hosts—information such as user identification, password, commands to
change remote directory, and commands to “put” and “get” files

Front 36

In FTP: TCP control connection, server port ____

Back 36

21

Front 37

In FTP: TCP data connection, server port ____

Back 37

20

Front 38

Give an example of out-of-band

Back 38

Because FTP uses a separate control connection, FTP is
said to send its control information o

Front 39

Give an example of in-band

Back 39

HTTP, SMTP

Front 40

In FTP, are data connections persistent or non-persistent?

Back 40

data connections are non-persistent

Front 41

with FTP, the______ connection
remains open throughout the duration of the user session, but a new ________ connection is created for each file transferred within a session

Back 41

control

data

Front 42

Is FTP stateless or maintain state?

Back 42

It maintains state

Front 43

What are 5 basic FTP commands?

Back 43

USER username
PASS password
LIST return list of file in
current directory
RETR filename
STOR filename

Front 44

What are equivalents of get and put in FTP?

Back 44

RETR and STOR

Front 45

What is 331 response in FTP?

Back 45

331 Username OK, password required

Front 46

What is response 125 in FTP?

Back 46

• 125 Data connection already open; transfer starting

Front 47

What is response 425 in FTP?

Back 47

425 Can’t open data connection

Front 48

What is response 452 in FTP?

Back 48

• 452 Error writing file

Front 49

mailbox contains_____

Back 49

incoming
messages for user

Front 50

message queue contains

Back 50

outgoing
(to be sent) mail messages

Front 51

What are three major components of email?

Back 51

user agents, mail servers, and SMTP

Front 52

SMTP uses ____ to reliably transfer email message from

Back 52

TCP

Front 53

SMTP uses port __

Back 53

25

Front 54

SMTP restricts the body (not just the headers) of all mail messages to ____

Back 54

simple 7-bit ASCII

Front 55

Three phases of SMTP email transfer are :

Back 55

three phases of transfer
 handshaking (greeting)
 transfer of messages
 closure

Front 56

What are 6 stages of sending a message from Alice to Bob?

Back 56

1) Alice uses UA to compose
message

to
[e-mail]
2) Alices UA sends message to
her mail server; message
placed in message queue
3) client side of SMTP opens
TCP connection with Bob's mail server
4) SMTP client sends Alice's message over the TCP connection
5) Bobs mail server places the
message in Bobs mailbox
6) Bob invokes his user agent
to read message

Front 57

What are 5 SMTP commands?

Back 57

HELO, MAIL FROM, RCPT TO, DATA, QUIT

Front 58

HTTP is mainly a push/pull protocol?

Back 58

pull

Front 59

SMTP is mainly a push/pull protocol?

Back 59

push

Front 60

each object encapsulated in its own response msg: HTTP or SMTP?

Back 60

HTTP

Front 61

multiple objects sent in multipart msg, HTTP or SMTP?

Back 61

SMTP

Front 62

SMTP uses persistent/non-persistent
connections?

Back 62

persistent

Front 63

SMTP server uses _______ to determine end of message

Back 63

CRLF.CRLF

Front 64

3 differences between HTML and SMTP

Back 64

HTML :

pull

ASCII

each object
encapsulated in its own
response msg

SMTP:

push

7 bit ASCII

multiple objects
sent in multipart msg

Front 65

Does pop3 maintain state or is it stateless?

Back 65

stateless

Front 66

What are two modes of POP3?

Back 66

download and delete

download and keep

Front 67

Which mail access method allows for creating folders?

Back 67

IMAP

Front 68

Which mail access method keeps user state across sessions?

Back 68

IMAP

Front 69

DNS is a _____ database

Back 69

distributed

Front 70

DNS is a distributed database implemented in _____

Back 70

hierarchy of many name servers

Front 71

DNS is a _____ level protocol

Back 71

application

Front 72

DNS is an application-layer protocol that allows ______

Back 72

hosts to query the distributed database

Front 73

DNS runs on UDP/TCP?

Back 73

UDP

Front 74

relay1.west-coast.enterprise.com could have, say, two aliases such as enterprise.com and
www.enterprise.com. In this case, the hostname relay1.westcoast.enterprise.com is said to be a __________

Back 74

canonical hostname.

Front 75

_________ is responsible for responsible for com, org, net, edu, aero, jobs, museums, and
all top-level country domains, e.g.: uk, fr, ca, jp

Back 75

top-level domain (TLD) servers:

Front 76

If Type=A, then Name is a______ and Value is the_____ address

Back 76

hostname, IP

Front 77

Type=NS, then Name is a _____ (such as foo.com) and Value is the ____

Back 77

domain

host name of an authoritative DNS server that knows how to obtain the IP addresses
for hosts in the domain

Front 78

If Type=CNAME, then Value is a_____ for the_____ Name.
.

Back 78

canonical hostname

alias hostname

Front 79

If Type=MX, then Value is the_____ of a mail server that has an______ Name

Back 79

canonical name

alias hostname

Front 80

What is DNS poisoning?

Back 80

 Send bogus relies to
DNS server, which
caches

Front 81

In bittorent, which chunks are requested first?

Back 81

rarest

Front 82

In bittorent Alice sends chunks to those _______

Back 82

four peers currently sending her
chunks at highest rate

Front 83

In bittorent, top 4 peers are evaluated every _____

Back 83

10 seconds

Front 84

How often does a peer randomly send chunks to another peer to unchoke them?

Back 84

every 30 secs: randomly select
another peer, starts sending
chunks

Front 85

Layers of internet

Back 85

Application

Transport

Network

Data Link

Physical

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