1. The document introduces the TCP/IP protocol stack and compares it to the OSI model. It describes the layers of each from the physical layer to the application layer. 2. Packet encapsulation is explained where each layer adds a header to the data as it travels down the stack. 3. Common protocols like IP, TCP, UDP, ICMP, ARP and HTTP are described along with their functions and how they relate to each other in the TCP/IP stack.

1. 1
Introduction to TCP/IP

2. 2
OSI and Protocol Stack OSI: Open Systems Interconnect
OSI Model TCP/IP Hierarchy Protocols
7th
Application Layer
6th
Presentation Layer Application Layer
5th
Session Layer
4th
Transport Layer
Transport Layer
3rd
Network Layer
Network Layer
2nd
Link Layer
Link Layer
1st
Physical Layer
Link Layer : includes device driver and network interface card
Network Layer : handles the movement of packets, i.e. Routing
Transport Layer : provides a reliable flow of data between two hosts
Application Layer : handles the details of the particular application

3. 3
Packet Encapsulation
 The data is sent down the protocol stack
 Each layer adds to the data by prepending headers
22Bytes 20Bytes 20Bytes 4Bytes
64 to 1500 Bytes

4. 4
Ethernet
 Computer <-> Computer communication on
same network
 Each device has unique MAC address (48-bit)
example: 00-C0-4F-48-47-93
Ethernet Packet:
Preamble Dest. Source Type Data CRC
address address
8bytes 6bytes 6bytes 2bytes 64 - 1500bytes 4bytes
MAC: Media Access Control

5. 5
ARP : Address Resolution Protocol
 ARP provides mapping
32bit IP address <-> 48bit MAC address
128.97.89.153 <-> 00-C0-4F-48-47-93
 ARP cache
maintains the recent mappings from IP addresses to MAC addresses
Protocol
4. ARP request broadcast on Ethernet
5. Destination host ARP layer responds

6. 6
IP: Internet Protocol
 Unreliable … connectionless datagram delivery service
 Responsible for routing of data through intermediate
networks and computers
11 1111 1111 2222 2222 2233
IP header: 0123 4567 8901 2345 6789 0123 4567 8901
1 :ICMP
6 :TCP
17 :UDP

7. 7
IP Routing
Source Destination
Application Application
Transport Router Transport
Network Network Network
Link Link Link
 Routing Table
Destination IP address
IP address of a next-hop router
Flags
Network interface specification

8. 8
ICMP : Internet Control Message Protocol
 Used to report problems with delivery of IP Datagrams
within an IP network
 Used by Ping, Tracerout commands
ICMP Message
20bytes 4bytes
IP ICMP ICMP
Header Header Data
Types and Codes
 Echo Request (type=8, code=0) Type Code Checksum
 Echo Reply(type=0, code=0) 1byte 1byte 2bytes
 Destination Unreachable(type=3, code=0)
 Time Exceeded(type=11, code=0) : Time-to-Live =0

9. 9
TCP : Transmission Control Protocol
 Connection-Oriented, Reliable, Byte Stream Service
Protocol
3. Set up connection
4. Transfer data
5. Close connection
TCP Header Format
0 1 2 3 4 5 6 7 8 9 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
Source Port Destination Port
Sequence Number
Acknowledgement Number
- - - -
Data Window
Offset
Checksum
Urgent Pointer
Options (0
to
10
Words of 32 Bits)
TCP Payload

10. 10
TCP : State Diagram

11. 11
TCP : Connection
Client Host Client Host
Send SYN seq=x Send FIN seq=x
Receive SYN segment Receive FIN segment
Send SYN seq=y, Send ACK x+1
Receive ACK segment
Receive SYN ACK x+1
+ACK segment Send FIN seq=y,
Receive FIN ACK x+1
+ ACK segment
Send ACK y+1
Send ACK y+1
Receive ACK segment Receive ACK segment
Establishing a TCP Connection Closing a TCP Connection

12. 12
TCP : Data transfer
Client Host
Send Packet 1
Start Timer Packet Lost Packet should arrive
Timer ACK should be sent
ACK would normally
Arrive at this time
Time Expires
Retransmit Packet1
Timer Start Timer Receive Packet 1
Send AXK 1
Receive ACK 1
Cancel Timer

13. 13
HTTP : Hyper Text Transfer Protocol
 Stateless Transaction Protocol
Each transaction creates a new connection
Steps in Transaction
4. Establish connection
5. Request
Method <URL> <CR>
7. Response
Response Code <Data> <CR>
9. Close connection

14. 14
HTTP
 Common Request Methods
GET, PUT, POST
 Response Categories
Informational :100
Successful :200
Redirection :300
Client Error :400 (eg. 404 Not found)
Server Error :500

15. 15
Example: Access www.ee.ucla.edu
Client Server
Http request
Appl GET “http://www.ee.ucla.edu”<CR> Appl
Http response
HTTP 200 “” <CR> <html file in MIME format> HTTP
Transp Initiate connection (hdshk) Transp
Package data (add TCP header)
send http request packet
TCP Assemble response TCP
(break into several packets)
Send http response packets
Close connection (hdshk)
send data to next hop
Net Net Net
Relay data
IP ARP to provide IP IP
IP/MAC translation
Link Link Link
ethernet ethernet ethernet
Router(s)

16. 16
References
 “TCP/IP Illustrated, Volume 1 The Protocols “
by W. Richard Stevens (http://yenigul.net/tcpip)
 “Internet Working with TCP/IP Volume 1”
by Douglas E. Comer
 “Sams Teach Yourself TCP/IP in 24 Hours”
by Joe Casad. Published by Sams. (
http://www.informit.com)