Tcp ip
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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.
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 ๏ฎ The data is sent down the protocol stack ๏ฎ Each layer adds to the data by prepending headers 22Bytes 20Bytes 20Bytes 4Bytes 64 to 1500 Bytes
- 4. 4 Ethernet ๏ฎ Computer <-> Computer communication on same network ๏ฎ 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 ๏ฎ ARP provides mapping 32bit IP address <-> 48bit MAC address 128.97.89.153 <-> 00-C0-4F-48-47-93 ๏ฎ 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 ๏ฎ Unreliable โฆ connectionless datagram delivery service ๏ฎ 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 ๏ฎ Routing Table Destination IP address IP address of a next-hop router Flags Network interface specification
- 8. 8 ICMP : Internet Control Message Protocol ๏ฎ Used to report problems with delivery of IP Datagrams within an IP network ๏ฎ Used by Ping, Tracerout commands ICMP Message 20bytes 4bytes IP ICMP ICMP Header Header Data Types and Codes ๏ฎ Echo Request (type=8, code=0) Type Code Checksum ๏ฎ Echo Reply(type=0, code=0) 1byte 1byte 2bytes ๏ฎ Destination Unreachable(type=3, code=0) ๏ฎ Time Exceeded(type=11, code=0) : Time-to-Live =0
- 9. 9 TCP : Transmission Control Protocol ๏ฎ 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 ย ย ย ย ย ย ย ย Checksumย ย ย ย ย ย ย ย ย ย ย ย ย ย ย ย Urgent Pointer ย ย ย ย ย ย ย ย ย ย ย ย ย ย ย ย ย ย ย ย ย ย ย ย ย Optionsย ย (0 ย ย ย ย ย ย ย ย ย toย ย ย 10ย Words of 32 Bits) TCP Payload ย
- 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 ๏ฎ 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 ๏ฎ Common Request Methods GET, PUT, POST ๏ฎ 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 โhttp://www.ee.ucla.eduโ<CR> Appl Http response HTTP 200 โโ <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 ๏ฎ โTCP/IP Illustrated, Volume 1 The Protocols โ by W. Richard Stevens (http://yenigul.net/tcpip) ๏ฎ โInternet Working with TCP/IP Volume 1โ by Douglas E. Comer ๏ฎ โSams Teach Yourself TCP/IP in 24 Hoursโ by Joe Casad. Published by Sams. ( http://www.informit.com)
Editor's Notes
- #10: Connection connection must be established before data is transferred Reliable Data guaranteed to eventually arrive with no errors