1. Review of Important Networking Concepts
Introductory material.
This module uses the example from the previous module to review important networking concepts: protocol architecture, protocol layers, encapsulation, demultiplexing, network abstractions.

2. Sending a packet from Argon to Neon

3. Sending a packet from Argon to Neon
is not on my local network.
Therefore, I need to send the packet to my
default gateway with address
is on my local network.
Therefore, I can send the packet directly.
DNS: What is the IP address of “neon.tcpip-lab.edu”?
DNS: The IP address of “neon.tcpip-lab.edu” is
ARP: What is the MAC address of ?
ARP: The MAC address of is 00:e0:f9:23:a8:20
ARP: What is the MAC address of ?
ARP: The MAC address of is 00:20:af:03:98:28
frame
frame

4. TCP/IP Protocol Architecture
The TCP/IP protocol architecture is the protocol architecture of the Internet
The TCP/IP suite has four layers: Application, Transport, Network, and Data Link Layer
End systems (hosts) implement all four layers. Gateways (Routers) only have the bottom two layers.

5. TCP/IP Suite and OSI Reference Model
The TCP/IP protocol stack does not define the lower layers of a complete protocol stack

6. Assignment of Protocols to Layers

7. Layered Communications
An entity of a particular layer can only communicate with:
1. a remote entity a the same layer using a common protocol
2. adjacent entities at the local system via service interfaces

8. Layers in the Example

9. Layers in the Example Send the datagram to 128.143.7.21
Send HTTP Request to neon
Establish a connection to at port 80
Open TCP connection to port 80
IP datagram is a TCP segment for port 80
Send a datagram (which contains a connection request) to
Send IP data-gram to
Send IP datagram to
Frame is an IP datagram
Frame is an IP datagram
Send the datagram to
Send the datagram to
Send Ethernet frame to 00:e0:f9:23:a8:20
Send Ethernet frame to 00:20:af:03:98:28

10. Encapsulation and Demultiplexing
As data is moving down the protocol stack, each protocol adds layer-specific control information

11. Encapsulation and Demultiplexing in our Example
Let us look in detail at the Ethernet frame between Argon and the Router, which contains the TCP connection request to Neon.
This is the frame in hexadecimal notation.
00e0 f923 a820 00a e c 9d bff 808f f b b e b4

12. Parsing the information in the frame

13. Encapsulation and Demultiplexing

14. Encapsulation and Demultiplexing: Ethernet Header

15. Encapsulation and Demultiplexing: IP Header

16. Encapsulation and Demultiplexing: IP Header

17. Encapsulation and Demultiplexing: TCP Header
Option: maximum segment size

18. Encapsulation and Demultiplexing: TCP Header

19. Encapsulation and Demultiplexing: TCP Header

20. Encapsulation and Demultiplexing: Application data
No Application Data
in this frame

21. Different Views of Networking
Different Layers of the protocol stack have a different view of the network. This is HTTP’s and TCP’s view of the network.

22. Network View of IP Protocol

23. Network View of Ethernet
Ethernet’s view of the network