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1.
2.
3.
4.
5.
6.
Copyright ©2000 The McGraw Hill Companies
The user clicks on a link to indicate which document is to be
retrieved.
The browser must determine the address that contains the
document. It does this by sending a query to its local name
server.
Once the address is known the browser establishes a connection to the
specified machine, usually a TCP connection. In order for the
connection to be successful, the specified machine must be ready to
accept TCP connections.
The browser runs a client version of HTTP, which issues a request
specifying both the name of the document and the possible document
formats it can handle.
The machine that contains the requested document runs a server
version of HTTP. It reacts to the HTTP request by sending an
HTTP response which contains the desired document in the
appropriate format.
The TCP connection is then closed and the user may view
the document.
Leon-Garcia & Widjaja: Communication Networks
Figure 1.4 - Introduces topic
Request
HTTP
client
Copyright ©2000 The McGraw Hill Companies
HTTP
server
Response
Leon-Garcia & Widjaja: Communication Networks
Figure 2.1
HTTP
server
HTTP
client
Ephemeral
Port 80
Port #
GET
80, #
TCP
TCP
#, 80
Copyright ©2000 The McGraw Hill Companies
STATUS
Leon-Garcia & Widjaja: Communication Networks
Figure 2.2
n-PDUs
n
n
entity
entity
Copyright ©2000 The McGraw Hill Companies
Leon-Garcia & Widjaja: Communication Networks
Figure 2.3
n+1
entity
n+1
entity
n-SDU
n-SDU
n-SAP
n-SAP
n-SDU
H
n entity
n entity
H
n-SDU
n-PDU
Copyright ©2000 The McGraw Hill Companies
Leon-Garcia & Widjaja: Communication Networks
Figure 2.4
(a)
n-PDU
(b)
Segmentation
Reassembly
n-SDU
n-SDU
n-PDU
n-PDU
n-PDU
Blocking
n-SDU
n-SDU
n-PDU
Copyright ©2000 The McGraw Hill Companies
n-PDU
n-PDU
Unblocking
n-SDU
n-SDU
n-SDU
n-SDU
n-PDU
Leon-Garcia & Widjaja: Communication Networks
Figure 2.5
Application A
Application B
Application
Layer
Application
Layer
Presentation
Layer
Presentation
Layer
Session
Layer
Session
Layer
Transport
Layer
Communication Network
Transport
Layer
Network
Layer
Network
Layer
Network
Layer
Network
Layer
Data Link
Layer
Data Link
Layer
Data Link
Layer
Data Link
Layer
Physical
Layer
Physical
Layer
Physical
Layer
Physical
Layer
Electrical and/or Optical Signals
Copyright ©2000 The McGraw Hill Companies
Leon-Garcia & Widjaja: Communication Networks
Figure 2.6
PS = packet switch
C
PS
C
C = computer
PS
PS
PS
C
C
Copyright ©2000 The McGraw Hill Companies
C
Leon-Garcia & Widjaja: Communication Networks
Figure 2.7
net 3
G
net 1
G
G
G
net 2
net 5
G
net 4
G
G = gateway/router
Copyright ©2000 The McGraw Hill Companies
Leon-Garcia & Widjaja: Communication Networks
Figure 2.8
Application A
data
Application
Layer
data
Transport
Layer
data
Network
Layer
data
dt
Physical
Layer
Copyright ©2000 The McGraw Hill Companies
Presentation
Layer
ph
data
Session
Layer
Application
Layer
ah
data
Presentation
Layer
Data Link
Layer
Application B
data
sh
Session
Layer
th
Transport
Layer
Network
Layer
nh
dh
bits
Leon-Garcia & Widjaja: Communication Networks
Data Link
Layer
Physical
Layer
Figure 2.9
Application
Layer
Transport
Layer
Internet
Layer
Network
Interface
(a)
Copyright ©2000 The McGraw Hill Companies
Application
Layer
Transport
Layer
Internet
Layer
Network
Interface
(b)
Leon-Garcia & Widjaja: Communication Networks
Figure 2.10
Machine B
Machine A
Application
Application
Transport
Router/Gateway
Transport
Internet
Internet
Internet
Network Interface
Network Interface
Network 1
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Network Interface
Network 2
Leon-Garcia & Widjaja: Communication Networks
Figure 2.11
SMTP
HTTP
RTP
DNS
TCP
UDP
IP
Network
Network
Network
Interface 1
Interface 2
Interface 3
Copyright ©2000 The McGraw Hill Companies
Leon-Garcia & Widjaja: Communication Networks
Figure 2.12
(a)
(1,1)
(2,1)
(2,2)
router
s
Ethernet
PPP
(1,3) r
w
(1,2)
(b)
Server
HTTP
HTTP
TCP
Router
IP
IP
IP
Net Interface
Net Interface
Net Interface
Ethernet
Copyright ©2000 The McGraw Hill Companies
TCP
PPP
Leon-Garcia & Widjaja: Communication Networks
Figure 2.13
PC
IP
Header
Header contains
source and destination
physical addresses;
network protocol type
Frame
Check
Sequence
Ethernet
Header
Copyright ©2000 The McGraw Hill Companies
Leon-Garcia & Widjaja: Communication Networks
Figure 2.14
HTTP Request
Header contains source and
destination port numbers
Header contains source and
destination IP addresses;
transport protocol type
Header contains source
and destination physical
addresses; network
protocol type
TCP
Header
IP
Header
Frame
Check
Sequence
Ethernet
Header
Copyright ©2000 The McGraw Hill Companies
Leon-Garcia & Widjaja: Communication Networks
Figure 2.15
socket
interface
Application 1
Application 2
user
user
kernel
kernel
Socket
socket
interface
Socket
Underlying
communication
Protocols
Underlying
communication
Protocols
Communications
network
Copyright ©2000 The McGraw Hill Companies
Leon-Garcia & Widjaja: Communication Networks
Figure 2.16
Server
socket()
bind()
listen()
Client
accept()
socket()
blocks until server receives
a connect request from client
read()
write()
connect negotiation
connect()
data
write()
data
read()
close()
Copyright ©2000 The McGraw Hill Companies
close()
Leon-Garcia & Widjaja: Communication Networks
Figure 2.17
Server
socket()
Client
socket()
bind()
bind()
recvfrom()
blocks until server
receives data from client
data
sendto()
data
sendto()
recvfrom()
close()
close()
Copyright ©2000 The McGraw Hill Companies
Leon-Garcia & Widjaja: Communication Networks
Figure 2.18
User
Interface
Control
Server PI
Server
DTP
Server FTP
Connection
Data
User PI
User DTP
Connection
User FTP
PI = Protocol interpreter
DTP = Data transfer process
Copyright ©2000 The McGraw Hill Companies
Leon-Garcia & Widjaja: Communication Networks
Figure 2.19
C:\WINDOWS>ping nal.toronto.edu
Pinging nal.toronto.edu [128.100.244.3] with 32 bytes of data:
Reply
Reply
Reply
Reply
from
from
from
from
128.100.244.3:
128.100.244.3:
128.100.244.3:
128.100.244.3:
bytes=32
bytes=32
bytes=32
bytes=32
time=118ms
time=118ms
time=118ms
time=118ms
TTL=243
TTL=243
TTL=243
TTL=243
C:\WINDOWS>
Copyright ©2000 The McGraw Hill Companies
Leon-Garcia & Widjaja: Communication Networks
Figure 2.20