1. Layer Architecture of Network Protocols
Chapter 2 of Leon-Garcia

2. Outline 2.1 Examples of Layering
2.2 OSI Reference Model (Continued from last time)
2.3. TCP/IP Architecture
2.4 Berkeley API (Skip)
2.5 Application Protocols and TCP/IP Utilities

3. Problems for Chapter 2
2.6
2.10
2.13
2.19
2.20
2.27
2.37
2.41
2.46
Find, install, test an Internet tool. Write a paragraph on who, what, when, where -- on it.

4. Overall ISO Model 7-layer cake model discussed last time
At end of class, I have some terms for you to define, including what each of these layers do, so think about it
Specific network architectures don’t fit this model exactly; they are divided into modules that may perform part of the functions of two or more ISO layers

5. Application A Application B Application Layer Application Layer
Presentation
Layer
Presentation
Layer
Session
Layer
Session
Layer
Transport
Layer
Transport
Layer
Communication Network
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
Figure 2.6

6. The big picture for accessing Web page
The Internet is a true distributed (democratic) system in that every host is equal
However, in discussing dialog between two hosts, it is usually helpful to think of one as client, the other as server.
In accessing a Web page, actually two servers are often used. (What are they?)

7. Request
HTTP
server
HTTP
client
Response
Figure 2.1

8. Figure 1.4 - Introduces topic
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. 2. 3.
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. 4.
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. 5.
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. 6.
The TCP connection is then closed and the user may view the document.
Figure Introduces topic

9. HTTP HTTP server client Ephemeral Port # Port 80 TCP TCP GET 80, #
#, STATUS
Figure 2.2

10. n-PDUs n
entity n
entity
Figure 2.3

11. n+1 n+1 entity entity n entity n entity n-SDU n-SDU n-SAP n-SAP n-SDUH
n entity
n entity H
n-SDU
n-PDU
Figure 2.4

12. Segmentation Reassembly n-SDU n-SDU n-PDU n-PDU n-PDU n-PDU n-PDU
Blocking
Unblocking
n-SDU
n-SDU
n-SDU
n-SDU
n-SDU
n-SDU
n-PDU
n-PDU
Figure 2.5

13. C
PS = packet switch
C = computer PS C PS PS PS C C C
Figure 2.7

14. net 3 G net 1 G G G net 5 net 2 net 4 G G G = gateway/router
Figure 2.8

15. ISO Model, including PDUs at Each Level
All computer systems consist of hardware, programs, and data.
The information data structures used in network protocols consist of PDU exchanged at each layer
A PDU generally consists of the information bits from the next higher layer (the SDU) plus a header that contains the necessary additional info for that layer (+ trailer sometimes)
What are the PDUs called at each layer on the next slide?

16. Application A Application B data data ah data ph data sh data th data
Layer
Application
Layer
data ah
Presentation
Layer
Presentation
Layer
data ph
Session
Layer
Session
Layer
data sh
Transport
Layer
Transport
Layer
data th
Network
Layer
Network
Layer
data nh
Data Link
Layer
Data Link
Layer dt
data dh
Physical
Layer
Physical
Layer
bits
Figure 2.9

17. TCP/IP Architecure (5 layers counting physical layer)
Application
Layer
Application
Layer
Transport
Layer
Transport
Layer
Internet
Layer
Internet
Layer
Network
Interface
Network
Interface
(a)
(b)
Figure 2.10

18. TCP/IP in Use Machine B Machine A Application Application Transport
Internet
Network Interface
Transport
Router/Gateway
Internet
Internet
Network Interface
Network Interface
Network 1
Network 2
Figure 2.11

19. TCP/IP Protocol Graph (There’s More, too)
HTTP
SMTP
DNS
RTP
TCP
UDP IP
Network
Interface 1
Network
Interface 2
Network
Interface 3
Figure 2.12

20. (1,1) (a) (2,1) (2,2) s PPP (1,3) r w Ethernet (1,2) (b) router Server
HTTP PC
HTTP
TCP
Router
TCP IP IP IP
Net Interface
Net Interface
Net Interface
Ethernet
PPP
Figure 2.13

21. source and destination physical addresses; network protocol typeIP
Header
Header contains
source and destination physical addresses; network protocol type
Frame Check Sequence
Ethernet Header
Figure 2.14

22. HTTP Request TCP Header IP Header Ethernet Header Frame Check Sequence
Header contains source and destination port numbers
TCP Header
Header contains source and destination IP addresses; transport protocol type
IP Header
Header contains source and destination physical addresses; network protocol type
Frame Check Sequence
Ethernet Header
Figure 2.15

23. Underlying communication Protocols Underlying communication Protocols
socket interface
socket interface
Application 1
Application 2
user
user
kernel
kernel
Socket
Socket
Underlying communication Protocols
Underlying communication Protocols
Communications network
Figure 2.16

24. Control Connection Data Connection
User Interface
Control
Connection
Server PI
User PI
Server DTP
Data
Connection
User DTP
Server FTP
User FTP
PI = Protocol interpreter
DTP = Data transfer process
Figure 2.19

25. C:\WINDOWS>ping nal.toronto.edu
Pinging nal.toronto.edu [ ] with 32 bytes of data:
Reply from : bytes=32 time=118ms TTL=243
C:\WINDOWS>
Figure 2.20

26. Can you define? Application layer Client/server Confirmed service
Connectionless service
Daemon
Data Link layer
Physical Layer
Encapulation
PPP
Frame
Port
Header
PDU
HTTP
Segment
ISO
SDU
Internet layer
Internetworking
SMTP
Layer
Socket
TCP/IP Architecture
Transport Layer
Network Architecture
UDP
Traceroute
Telnet
FTP
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