cs 447 networks and data communication packet encapsulation concept and application department of...
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CS 447 Networks and Data Communication
Packet EncapsulationConcept and Application
Department of Computer ScienceSouthern Illinois University Edwardsville
Fall, 2015
Dr. Hiroshi FujinokiE-mail: [email protected]
Packet_Encapsulation/001
Concept of packets
User Data User DataComputer Network
Internet
Request
ResponseRequest (1)
Response with tag (2)
Request (3)Response (4)
Internet
Request
Response
Without Packets
Computer NetworkUser Data User Data
Internet
Request
ResponseRequest (1)
Response with tag (2)
Request (3)Response (4)
Internet
Request
Response
With Packets Packet
Packet Header (e.g. packet sequence #)(e.g. destination address)
CS 447 Networks and Data Communication
Packet_Encapsulation/002
Concept of packet encapsulation: Layered Protocol Architecture
User Data
OSI 7-Layer Model TCP/IP Model
7 layers
Network Cable
User Data
4 layers
Network Cable
Host ComputerHost Computer
CS 447 Networks and Data Communication
Packet_Encapsulation/003
User Data (User Data Packet)
Header = Information specific to each protocol layer
Header
TCP Packet
IP Packet
Packet Encapsulation Visualized (1):
TCP Layer
IP Layer
Network Layer FrameDatalink Layer
Physical Layer FramePhysical Layer
Protocol Data Unit (PDU)
A packet = Header + PDU
CS 447 Networks and Data Communication
Packet_Encapsulation/004
User Data (User Data Packet)Header
TCP Packet
IP Packet
Packet Encapsulation Visualized (2):
TCP Layer
IP Layer
Network Layer FrameDatalink Layer
Physical Layer FramePhysical Layer
Protocol Data Unit (PDU)
Packet Encapsulation
CS 447 Networks and Data Communication
Packet_Encapsulation/005
Packet Encapsulation Visualized (3):A packet in TCP layer
PDU in IP layer
A packet (header + PDU) in an upper protocol layer=
PDU in the next protocol layer
IP Layer IP Packet
TCP Layer TCP Packet
User Data
CS 447 Networks and Data Communication
Packet_Encapsulation/006
Packet Encapsulation Visualized (3):
A packet in TCP layer
IP Layer
PDU in IP layer
IP Packet
At IP protocol layer, information in TCP headerwill be handled as if it were a part of user data
Any change in TCP will notaffect internal design of IP
PacketEncapsulation
TCP Layer TCP Packet
CS 447 Networks and Data Communication
Packet_Encapsulation/007
User Data User Data
What is possible if we have packet encapsulation?
Corresponding protocol layer can communicate
Internet
Request
ResponseRequest (1)
Response with tag (2)
Request (3)Response (4)
Internet
Request
Response
NW
Communicate using the
information in the packet header 4
3
2
1
4
3
2
1
CS 447 Networks and Data Communication
Packet_Encapsulation/008
Definition of Packet Encapsulation:
• A protocol layer can handle packets from the lower layer without knowing anything about the layer
This property guarantees the independence of each protocol layer in a protocol stack
• The entire packet in a lower protocol layer becomes the PDU for the next upper protocol layer
• Without packet encapsulation, most of the advantages in the layered structure will not be utilized
• Without packet encapsulation, each protocol layer has to know the rules in any lower layers
CS 447 Networks and Data Communication
Ext_Int/001
Protocol layers
Sender ReceiverExternal Operation
The top fourlayers in OSI7-layer model
Transport Layer
Application Layer
Presentation Layer
Session Layer
Underlying Network
Internal Operation
The bottom threelayers in OSI7-layer model
Network Layer
DataLink Layer
Physical Layer
Transport Layer
Application Layer
Presentation Layer
Session Layer
Network Layer
DataLink Layer
Physical Layer
External and Internal Operations
CS 447 Networks and Data Communication
InternalOperation
External Operation
Virtual Circuit
Virtual Circuit
Datagram
Datagram
A
B C
D
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Ext_Int/002
Example: External Virtual Circuit and Internal Datagram
External Operation(Virtual Circuit)
Internal Operation(Datagram)
External Operation(Virtual Circuit)
Internal Operation(Datagram)
3
2
1
3
2
1
3
2
1
3
2
1
Protocol layers Datagram Network
12
3
Sender Receiver
TCP
IP
TCP
IP
Packets will bere-ordered
CS 447 Networks and Data Communication
Ext_Int/003
Example: External Datagram and Internal Datagram
External Operation(Datagram)
Internal Operation(Datagram)
External Operation(Datagram)
Internal Operation(Datagram)
3
2
1
3
2
1
3
2
1
3
2
1
Protocol layers Datagram Network
12
3
Sender Receiver
UDP
IP
UDP
IP
Packets will not bere-ordered
CS 447 Networks and Data Communication
Ext_Int/004
Example: External Virtual Circuit and Internal Virtual Circuit
External Operation(Virtual Circuit)
Internal Operation(Virtual Circuit)
External Operation(Virtual Circuit)
Internal Operation(Virtual Circuit)
3
2
1
Protocol layers Virtual Circuit Network
123
Sender Receiver
2
1
3
ISDN Telephone Network
3
2
1
2
1
3
CS 447 Networks and Data Communication
Ext_Int/005
Example: External Datagram and Internal Virtual Circuit
External Operation(Datagram)
Internal Operation(Virtual Circuit)
External Operation(Datagram)
Internal Operation(Virtual Circuit)
Protocol layers Virtual Circuit Network
123
Sender Receiver
Ext_Int/006
CS 447 Networks and Data Communication
InternalOperation
External Operation
Virtual Circuit
Virtual Circuit
Datagram
Datagram TCP/IP (Internet) UDP/IP (Internet)
ISDN Telephone(Digital Telephone Network)
Analog Public Telephone
CS 447 Networks and Data Communication
Ext_Int/007