Electronic Mail. DNS. P2P file sharing

Июль 25, 2022

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Electronic Mail. DNS. P2P file sharing

Содержание

2. Overview P2P file sharing (cont.) Socket programming with TCP Socket programming with UDP
3. P2P file sharing Example Alice runs P2P client application on her notebook computer Intermittently connects to
4. P2P: centralized directory original “Napster” design 1) when peer connects, it informs central server: IP address
5. P2P: problems with centralized directory Single point of failure if the directory server crashes, then the
6. Query flooding: Gnutella fully distributed no central server public domain protocol many Gnutella clients implementing protocol
7. Gnutella: protocol File transfer: HTTP Query message sent over existing TCP connections peers forward Query message
8. Gnutella: Peer joining Joining peer X must find some other peer in Gnutella network: use list
9. Exploiting heterogeneity: KaZaA Napster fully centralized Gnutella floods in limited area KaZaA: Each peer is either
10. KaZaA: Querying Each file has a hash and a descriptor Client sends keyword query to its
11. DoS resilience in p2p file-sharing systems P2p networks – highly replicated content not enough to protect
12. DoS resilience in p2p file-sharing systems (cont.) Modeling the propagation of polluted files in the system
13. Summary P2P file sharing (cont.) Socket programming with TCP Socket programming with UDP
14. Socket programming Socket API introduced in BSD4.1 UNIX, 1981 explicitly created, used, released by apps client/server
15. Socket-programming using TCP Socket: a door between application process and end-end-transport protocol (UDP or TCP) TCP
16. Socket programming with TCP Client must contact server server process must first be running server must
17. Stream jargon A stream is a sequence of characters that flow into or out of a
18. Socket programming with TCP Example client-server app: 1) client reads line from standard input (inFromUser stream)
19. Client/server socket interaction: TCP Server (running on hostid) Client
20. Example: Java client (TCP) import java.io.*; import java.net.*; class TCPClient { public static void main(String argv[])
21. Example: Java client (TCP), cont. BufferedReader inFromServer = new BufferedReader(new InputStreamReader(clientSocket.getInputStream())); sentence = inFromUser.readLine(); outToServer.writeBytes(sentence +
22. Example: Java server (TCP) import java.io.*; import java.net.*; class TCPServer { public static void main(String argv[])
23. Example: Java server (TCP), cont DataOutputStream outToClient = new DataOutputStream(connectionSocket.getOutputStream()); clientSentence = inFromClient.readLine(); capitalizedSentence = clientSentence.toUpperCase()
24. Outline P2P file sharing (cont.) Socket programming with TCP Socket programming with UDP
25. Socket programming with UDP UDP: no “connection” between client and server no handshaking sender explicitly attaches
26. Client/server socket interaction: UDP Server (running on hostid)
27. Example: Java client (UDP) Output: sends packet (TCP sent “byte stream”) Input: receives packet (TCP received
28. Example: Java client (UDP) import java.io.*; import java.net.*; class UDPClient { public static void main(String args[])
29. Example: Java client (UDP), cont. DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, 9876); clientSocket.send(sendPacket); DatagramPacket receivePacket
30. Example: Java server (UDP) import java.io.*; import java.net.*; class UDPServer { public static void main(String args[])
31. Example: Java server (UDP), cont String sentence = new String(receivePacket.getData()); InetAddress IPAddress = receivePacket.getAddress(); int port
32. Summary P2P file sharing (cont.) Socket programming with TCP Socket programming with UDP
33. Application Layer: Summary Application architectures client-server P2P hybrid application service requirements: reliability, bandwidth, delay Internet transport
34. Application Layer: Summary typical request/reply message exchange: client requests info or service server responds with data,
35. Quiz (Application Layer) Q1. List four Internet apps and the application layer protocols
36. Quiz Q2. What is the difference between network architecture and application architecture?
37. Quiz Q3. In what way is instant messaging a hybrid of client-server and P2P architectures?
38. Quiz Q4. For a communication session between a pair of processes, which process is the client
39. Quiz Q5. Do you agree with the statement: “In P2p file sharing, there is no notion
40. Quiz Q6. What information is used by a process running on one host to identify a
41. Quiz Q9. What is meant by a handshaking protocol?
42. Quiz Q10. Why HTTP, FTP, SMTP, POP3, and IMAP run on top of TCP rather than
43. Quiz Q12. What is the difference between persistent HTTP with pipelining and persistent HTTP without pipelining?
44. Quiz Q15. Why is it said that FTP sends control information “out-of-band”?
45. Quiz Q19. Is it possible for an organization’s Web server and mail server to have exactly
46. Quiz Q22. A UDP-based server needs only one socket, whereas the TCP server needs two sockets.
47. Quiz (Chapter 1) Q3. What is a client program? What is a server program? Does a
48. Quiz Q4. What are the two types of transport services that the Internet provides to its
49. Quiz Q5. What is the difference between flow and congestion control?
50. Quiz Q7. What advantage does a circuit-switched network has over a packet-switched network?
51. Quiz Q8. Why is it said that packet switching employs statistical multiplexing?
52. Quiz Q12. List five Internet access technologies. Classify each one as residential, company access, or mobile
53. Quiz Q15. Is cable-modem transmission rate dedicated or shared among users? Are collisions possible in the
54. Quiz Q19. Consider sending packet from a sending host to a receiving host over a fixed
55. Quiz Q21. What are the five layers in the Internet protocol stack?
57. Скачать презентацию

Слайд 2

Overview
P2P file sharing (cont.)
Socket programming with TCP
Socket programming with UDP

Слайд 3

P2P file sharing
Example
Alice runs P2P client application on her notebook computer
Intermittently

connects to Internet; gets new IP address for each connection
Asks for “Hey Jude”
Application displays other peers that have copy of Hey Jude.

Alice chooses one of the peers, Bob.
File is copied from Bob’s PC to Alice’s notebook: HTTP
While Alice downloads, other users uploading from Alice.
Alice’s peer is both a Web client and a transient Web server.
All peers are servers = highly scalable!

Слайд 4

P2P: centralized directory
original “Napster” design
1) when peer connects, it informs central

server:
IP address
content
2) Alice queries for “Hey Jude”
3) Alice requests file from Bob

Слайд 5

P2P: problems with centralized directory
Single point of failure
if the directory server

crashes, then the entire p2p application crashes
Performance bottleneck
a centralized server must maintain a huge database
Copyright infringement
Easy to shut down the directory servers by legal actions

file transfer is decentralized, but locating content is highly centralized

Слайд 6

Query flooding: Gnutella
fully distributed
no central server
public domain protocol
many Gnutella clients implementing

protocol

overlay network: graph
edge between peer X and Y if there’s a TCP connection
all active peers and edges is overlay net
Edge is not a physical link
Given peer will typically be connected with < 10 overlay neighbors

Слайд 7

Gnutella: protocol
File transfer:
HTTP
Query message sent over existing TCP connections
peers forward Query message

QueryHit sent over reverse path

Scalability:
limited scope flooding

Слайд 8

Gnutella: Peer joining
Joining peer X must find some other peer in

Gnutella network: use list of candidate peers
X sequentially attempts to make TCP with peers on list until connection setup with Y
X sends Ping message to Y; Y forwards Ping message.
All peers receiving Ping message respond with Pong message
X receives many Pong messages. It can then setup additional TCP connections

Слайд 9

Exploiting heterogeneity: KaZaA
Napster fully centralized
Gnutella floods in limited area
KaZaA:
Each peer is

either a group leader or assigned to a group leader.
TCP connection between peer and its group leader.
TCP connections between some pairs of group leaders.
Group leader tracks the content in all its children.

Слайд 10

KaZaA: Querying
Each file has a hash and a descriptor
Client sends keyword

query to its group leader
Group leader responds with matches:
For each match: filename, hash, IP address
If group leader forwards query to other group leaders, they respond with matches
Client then selects files for downloading
HTTP requests using hash as identifier sent to peers holding desired file

Слайд 11

DoS resilience in p2p file-sharing systems
P2p networks – highly replicated content
not

enough to protect against DoS attacks
Music industry places false content on p2p networks (e.g., KaZaA)
companies such as “Overpeer” and “Ratsnap” publicly publicly offer their pollution-based services
My dilemma…

Слайд 12

DoS resilience in p2p file-sharing systems (cont.)
Modeling the propagation of polluted

files in the system
User-behavior factors
Willingness to share files
Persistence in downloading files
Negligence in cleansing the infected hosts
Designed and evaluated attacks against p2p networks
% of nodes needed to collapse the system
Hierarchical vs. structured p2p networks
Counter-measures
Reputations systems, randomization

Слайд 13

Summary
P2P file sharing (cont.)
Socket programming with TCP
Socket programming with UDP

Слайд 14

Socket programming
Socket API
introduced in BSD4.1 UNIX, 1981
explicitly created, used, released by

apps
client/server paradigm
two types of transport service via socket API:
unreliable datagram
reliable, byte stream-oriented

Goal: learn how to build client/server application that communicate using sockets

Слайд 15

Socket-programming using TCP
Socket: a door between application process and end-end-transport protocol

(UDP or TCP)
TCP service: reliable transfer of bytes from one process to another

controlled by
application
developer

controlled by
operating
system

host or
server

controlled by
application
developer

controlled by
operating
system

host or
server

internet

Слайд 16

Socket programming with TCP
Client must contact server
server process must first be

running
server must have created socket (door) that welcomes client’s contact
Client contacts server by:
creating client-local TCP socket
specifying IP address, port number of server process
When client creates socket: client TCP establishes connection to server TCP

When contacted by client, server TCP creates new socket for server process to communicate with client
allows server to talk with multiple clients
source port numbers used to distinguish clients (more in Chap 3)

Слайд 17

Stream jargon
A stream is a sequence of characters that flow into

or out of a process.
An input stream is attached to some input source for the process, eg, keyboard or socket.
An output stream is attached to an output source, eg, monitor or socket.

Слайд 18

Socket programming with TCP
Example client-server app:
1) client reads line from standard

input (inFromUser stream) , sends to server via socket (outToServer stream)
2) server reads line from socket
3) server converts line to uppercase, sends back to client
4) client reads, prints modified line from socket (inFromServer stream)

Client
process

client TCP socket

Слайд 19

Client/server socket interaction: TCP
Server (running on hostid)
Client

Слайд 20

Example: Java client (TCP)
import java.io.;
import java.net.;
class TCPClient {

public static void main(String argv[]) throws Exception
{
String sentence;
String modifiedSentence;
BufferedReader inFromUser =
new BufferedReader(new InputStreamReader(System.in));
Socket clientSocket = new Socket("hostname", 6789);
DataOutputStream outToServer =
new DataOutputStream(clientSocket.getOutputStream());

Create
input stream

Create
client socket,
connect to server

Create
output stream
attached to socket

Слайд 21

Example: Java client (TCP), cont.
BufferedReader inFromServer =
new BufferedReader(new

InputStreamReader(clientSocket.getInputStream()));
sentence = inFromUser.readLine();
outToServer.writeBytes(sentence + '\n');
modifiedSentence = inFromServer.readLine();
System.out.println("FROM SERVER: " + modifiedSentence);
clientSocket.close();
}
}

Create
input stream
attached to socket

Send line
to server

Read line
from server

Слайд 22

Example: Java server (TCP)
import java.io.;
import java.net.;
class TCPServer {

public static void main(String argv[]) throws Exception
{
String clientSentence;
String capitalizedSentence;
ServerSocket welcomeSocket = new ServerSocket(6789);
while(true) {
Socket connectionSocket = welcomeSocket.accept();
BufferedReader inFromClient =
new BufferedReader(new
InputStreamReader(connectionSocket.getInputStream()));

Create
welcoming socket
at port 6789

Wait, on welcoming
socket for contact
by client

Create input
stream, attached
to socket

Слайд 23

Example: Java server (TCP), cont
DataOutputStream outToClient =
new DataOutputStream(connectionSocket.getOutputStream());

clientSentence = inFromClient.readLine();
capitalizedSentence = clientSentence.toUpperCase() + '\n';
outToClient.writeBytes(capitalizedSentence);
}
}
}

Read in line
from socket

Create output
stream, attached
to socket

Write out line
to socket

End of while loop,
loop back and wait for
another client connection

Слайд 24

Outline
P2P file sharing (cont.)
Socket programming with TCP
Socket programming with UDP

Слайд 25

Socket programming with UDP
UDP: no “connection” between client and server
no handshaking
sender

explicitly attaches IP address and port of destination to each packet
server must extract IP address, port of sender from received packet
UDP: transmitted data may be received out of order, or lost

Слайд 26

Client/server socket interaction: UDP
Server (running on hostid)

Слайд 27

Example: Java client (UDP)
Output: sends packet (TCP sent “byte stream”)
Input: receives

packet (TCP received “byte stream”)

Client
process

client UDP socket

Слайд 28

Example: Java client (UDP)
import java.io.;
import java.net.;
class UDPClient {

public static void main(String args[]) throws Exception
{
BufferedReader inFromUser =
new BufferedReader(new InputStreamReader(System.in));
DatagramSocket clientSocket = new DatagramSocket();
InetAddress IPAddress = InetAddress.getByName("hostname");
byte[] sendData = new byte[1024];
byte[] receiveData = new byte[1024];
String sentence = inFromUser.readLine();
sendData = sentence.getBytes();

Create
input stream

Create
client socket

Translate
hostname to IP
address using DNS

Слайд 29

Example: Java client (UDP), cont.
DatagramPacket sendPacket =
new DatagramPacket(sendData,

sendData.length, IPAddress, 9876);
clientSocket.send(sendPacket);
DatagramPacket receivePacket =
new DatagramPacket(receiveData, receiveData.length);
clientSocket.receive(receivePacket);
String modifiedSentence =
new String(receivePacket.getData());
System.out.println("FROM SERVER:" + modifiedSentence);
clientSocket.close();
}
}

Create datagram with data-to-send,
length, IP addr, port

Send datagram
to server

Read datagram
from server

Слайд 30

Example: Java server (UDP)
import java.io.;
import java.net.;
class UDPServer {

public static void main(String args[]) throws Exception
{
DatagramSocket serverSocket = new DatagramSocket(9876);
byte[] receiveData = new byte[1024];
byte[] sendData = new byte[1024];
while(true)
{
DatagramPacket receivePacket =
new DatagramPacket(receiveData, receiveData.length);
serverSocket.receive(receivePacket);

Create
datagram socket
at port 9876

Create space for
received datagram

Receive
datagram

Слайд 31

Example: Java server (UDP), cont
String sentence = new String(receivePacket.getData());
InetAddress

IPAddress = receivePacket.getAddress();
int port = receivePacket.getPort();
String capitalizedSentence = sentence.toUpperCase();
sendData = capitalizedSentence.getBytes();
DatagramPacket sendPacket =
new DatagramPacket(sendData, sendData.length, IPAddress,
port);
serverSocket.send(sendPacket);
}
}
}

Get IP addr
port #, of
sender

Write out
datagram
to socket

End of while loop,
loop back and wait for
another datagram

Create datagram
to send to client

Слайд 32

Summary
P2P file sharing (cont.)
Socket programming with TCP
Socket programming with UDP

Слайд 33

Application Layer: Summary
Application architectures
client-server
P2P
hybrid
application service requirements:
reliability, bandwidth, delay
Internet transport service

model
connection-oriented, reliable: TCP
unreliable, datagrams: UDP

Our study of network apps now complete!

specific protocols:
HTTP
FTP
SMTP, POP, IMAP
DNS
socket programming

Слайд 34

Application Layer: Summary
typical request/reply message exchange:
client requests info or service
server responds

with data, status code
message formats:
headers: fields giving info about data
data: info being communicated

Most importantly: learned about protocols

control vs. data msgs
in-band, out-of-band
centralized vs. decentralized
stateless vs. stateful
reliable vs. unreliable msg transfer
“complexity at network edge”

Слайд 35

Quiz (Application Layer)
Q1. List four Internet apps and the application layer

protocols

Слайд 36

Quiz
Q2. What is the difference between network architecture and application architecture?

Слайд 37

Quiz
Q3. In what way is instant messaging a hybrid of client-server

and P2P architectures?

Слайд 38

Quiz
Q4. For a communication session between a pair of processes, which

process is the client and which is the server?

Слайд 39

Quiz
Q5. Do you agree with the statement: “In P2p file sharing,

there is no notion of client and server sides of a communication session”?
Why or why not?

Слайд 40

Quiz
Q6. What information is used by a process running on one

host to identify a process running on another host?

Слайд 41

Quiz
Q9. What is meant by a handshaking protocol?

Слайд 42

Quiz
Q10. Why HTTP, FTP, SMTP, POP3, and IMAP run on top

of TCP rather than UDP?

Слайд 43

Quiz
Q12. What is the difference between persistent HTTP with pipelining and

persistent HTTP without pipelining?
Which of the two is used by HTTP/1.1?

Слайд 44

Quiz
Q15. Why is it said that FTP sends control information “out-of-band”?

Слайд 45

Quiz
Q19. Is it possible for an organization’s Web server and mail

server to have exactly the same alias for a hostname?
What would be the type for the RR that contains the hostname of the mail server?

Слайд 46

Quiz
Q22. A UDP-based server needs only one socket, whereas the TCP

server needs two sockets. Why?
If the TCP server were to support n simultaneous connections, each from a different client host, how many sockets would the TCP server need?

Слайд 47

Quiz (Chapter 1)
Q3. What is a client program?
What is a

server program?
Does a server program request and receive services from a client program?

Слайд 48

Quiz
Q4. What are the two types of transport services that the

Internet provides to its applications?

Слайд 49

Quiz
Q5. What is the difference between flow and congestion control?

Слайд 50

Quiz
Q7. What advantage does a circuit-switched network has over a packet-switched

network?

Слайд 51

Quiz
Q8. Why is it said that packet switching employs statistical multiplexing?

Слайд 52

Quiz
Q12. List five Internet access technologies.
Classify each one as residential,

company access, or mobile access.

Слайд 53

Quiz
Q15. Is cable-modem transmission rate dedicated or shared among users?
Are collisions

possible in the downstream channel?
Why or why not?

Слайд 54

Quiz
Q19. Consider sending packet from a sending host to a receiving

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?

Слайд 55

Electronic Mail. DNS. P2P file sharing

Содержание

OverviewP2P file sharing (cont.)Socket programming with TCPSocket programming with UDP

P2P file sharingExampleAlice runs P2P client application on her notebook computerIntermittently

P2P: centralized directoryoriginal “Napster” design1) when peer connects, it informs central

P2P: problems with centralized directorySingle point of failureif the directory server

Query flooding: Gnutellafully distributedno central serverpublic domain protocolmany Gnutella clients implementing

Gnutella: protocolFile transfer:HTTP Query message sent over existing TCP connections peers forward Query message

Gnutella: Peer joiningJoining peer X must find some other peer in

Exploiting heterogeneity: KaZaANapster fully centralizedGnutella floods in limited areaKaZaA:Each peer is

KaZaA: QueryingEach file has a hash and a descriptorClient sends keyword

DoS resilience in p2p file-sharing systemsP2p networks – highly replicated contentnot

DoS resilience in p2p file-sharing systems (cont.)Modeling the propagation of polluted

SummaryP2P file sharing (cont.)Socket programming with TCPSocket programming with UDP

Socket programmingSocket APIintroduced in BSD4.1 UNIX, 1981explicitly created, used, released by

Socket-programming using TCPSocket: a door between application process and end-end-transport protocol

Socket programming with TCPClient must contact serverserver process must first be

Stream jargonA stream is a sequence of characters that flow into

Socket programming with TCPExample client-server app:1) client reads line from standard

Client/server socket interaction: TCPServer (running on hostid)Client

Example: Java client (TCP)import java.io.*; import java.net.*; class TCPClient {

Example: Java client (TCP), cont. BufferedReader inFromServer = new BufferedReader(new

Example: Java server (TCP)import java.io.*; import java.net.*; class TCPServer {

Example: Java server (TCP), cont DataOutputStream outToClient = new DataOutputStream(connectionSocket.getOutputStream());

OutlineP2P file sharing (cont.)Socket programming with TCPSocket programming with UDP

Socket programming with UDPUDP: no “connection” between client and serverno handshakingsender

Client/server socket interaction: UDPServer (running on hostid)

Example: Java client (UDP)Output: sends packet (TCP sent “byte stream”)Input: receives

Example: Java client (UDP)import java.io.*; import java.net.*; class UDPClient {

Example: Java client (UDP), cont. DatagramPacket sendPacket = new DatagramPacket(sendData,

Example: Java server (UDP)import java.io.*; import java.net.*; class UDPServer {

Example: Java server (UDP), cont String sentence = new String(receivePacket.getData()); InetAddress

SummaryP2P file sharing (cont.)Socket programming with TCPSocket programming with UDP

Application Layer: SummaryApplication architecturesclient-serverP2Phybridapplication service requirements: reliability, bandwidth, delayInternet transport service

Application Layer: Summarytypical request/reply message exchange:client requests info or serviceserver responds

Quiz (Application Layer)Q1. List four Internet apps and the application layer

QuizQ2. What is the difference between network architecture and application architecture?

QuizQ3. In what way is instant messaging a hybrid of client-server

QuizQ4. For a communication session between a pair of processes, which

QuizQ5. Do you agree with the statement: “In P2p file sharing,

QuizQ6. What information is used by a process running on one

QuizQ9. What is meant by a handshaking protocol?

QuizQ10. Why HTTP, FTP, SMTP, POP3, and IMAP run on top

QuizQ12. What is the difference between persistent HTTP with pipelining and

QuizQ15. Why is it said that FTP sends control information “out-of-band”?

QuizQ19. Is it possible for an organization’s Web server and mail

QuizQ22. A UDP-based server needs only one socket, whereas the TCP

Quiz (Chapter 1) Q3. What is a client program?What is a

QuizQ4. What are the two types of transport services that the

QuizQ5. What is the difference between flow and congestion control?

QuizQ7. What advantage does a circuit-switched network has over a packet-switched

QuizQ8. Why is it said that packet switching employs statistical multiplexing?

QuizQ12. List five Internet access technologies. Classify each one as residential,

QuizQ15. Is cable-modem transmission rate dedicated or shared among users?Are collisions

QuizQ19. Consider sending packet from a sending host to a receiving

QuizQ21. What are the five layers in the Internet protocol stack?

Похожие презентации

Overview
P2P file sharing (cont.)
Socket programming with TCP
Socket programming with UDP

P2P file sharing
Example
Alice runs P2P client application on her notebook computer
Intermittently

P2P: centralized directory
original “Napster” design
1) when peer connects, it informs central

P2P: problems with centralized directory
Single point of failure
if the directory server

Query flooding: Gnutella
fully distributed
no central server
public domain protocol
many Gnutella clients implementing

Gnutella: protocol
File transfer:
HTTP
Query message sent over existing TCP connections
peers forward Query message

Gnutella: Peer joining
Joining peer X must find some other peer in

Exploiting heterogeneity: KaZaA
Napster fully centralized
Gnutella floods in limited area
KaZaA:
Each peer is

KaZaA: Querying
Each file has a hash and a descriptor
Client sends keyword

DoS resilience in p2p file-sharing systems
P2p networks – highly replicated content
not

DoS resilience in p2p file-sharing systems (cont.)
Modeling the propagation of polluted

Summary
P2P file sharing (cont.)
Socket programming with TCP
Socket programming with UDP

Socket programming
Socket API
introduced in BSD4.1 UNIX, 1981
explicitly created, used, released by

Socket-programming using TCP
Socket: a door between application process and end-end-transport protocol

Socket programming with TCP
Client must contact server
server process must first be

Stream jargon
A stream is a sequence of characters that flow into

Socket programming with TCP
Example client-server app:
1) client reads line from standard

Client/server socket interaction: TCP
Server (running on hostid)
Client

Example: Java client (TCP)
import java.io.;
import java.net.;
class TCPClient {

Example: Java client (TCP), cont.
BufferedReader inFromServer =
new BufferedReader(new

Example: Java server (TCP)
import java.io.;
import java.net.;
class TCPServer {

Example: Java server (TCP), cont
DataOutputStream outToClient =
new DataOutputStream(connectionSocket.getOutputStream());

Outline
P2P file sharing (cont.)
Socket programming with TCP
Socket programming with UDP

Socket programming with UDP
UDP: no “connection” between client and server
no handshaking
sender

Client/server socket interaction: UDP
Server (running on hostid)

Example: Java client (UDP)
Output: sends packet (TCP sent “byte stream”)
Input: receives

Example: Java client (UDP)
import java.io.;
import java.net.;
class UDPClient {

Example: Java client (UDP), cont.
DatagramPacket sendPacket =
new DatagramPacket(sendData,

Example: Java server (UDP)
import java.io.;
import java.net.;
class UDPServer {

Example: Java server (UDP), cont
String sentence = new String(receivePacket.getData());
InetAddress

Summary
P2P file sharing (cont.)
Socket programming with TCP
Socket programming with UDP

Application Layer: Summary
Application architectures
client-server
P2P
hybrid
application service requirements:
reliability, bandwidth, delay
Internet transport service

Application Layer: Summary
typical request/reply message exchange:
client requests info or service
server responds

Quiz (Application Layer)
Q1. List four Internet apps and the application layer

Quiz
Q2. What is the difference between network architecture and application architecture?

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Q3. In what way is instant messaging a hybrid of client-server

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Q5. Do you agree with the statement: “In P2p file sharing,

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Quiz
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Classify each one as residential,

Quiz
Q15. Is cable-modem transmission rate dedicated or shared among users?
Are collisions

Quiz
Q19. Consider sending packet from a sending host to a receiving

Quiz
Q21. What are the five layers in the Internet protocol stack?