Table of Contents for
Packet Analysis with Wireshark

Version ebook / Retour

Cover image for bash Cookbook, 2nd Edition Packet Analysis with Wireshark by Anish Nath Published by Packt Publishing, 2015
  1. Cover
  2. Table of Contents
  3. Packet Analysis with Wireshark
  4. Packet Analysis with Wireshark
  5. Credits
  6. About the Author
  7. About the Reviewers
  8. www.PacktPub.com
  9. Preface
  10. What you need for this book
  11. Who this book is for
  12. Conventions
  13. Reader feedback
  14. Customer support
  15. 1. Packet Analyzers
  16. Introducing Wireshark
  17. Other packet analyzer tools
  18. Summary
  19. 2. Capturing Packets
  20. Troubleshooting
  21. Wireshark user interface
  22. Wireshark features
  23. Tcpdump and snoop
  24. References
  25. Summary
  26. 3. Analyzing the TCP Network
  27. TCP connection establishment and clearing
  28. TCP data communication
  29. TCP close sequence
  30. Lab exercise
  31. TCP troubleshooting
  32. TCP latency issues
  33. Wireshark TCP sequence analysis
  34. References
  35. Summary
  36. 4. Analyzing SSL/TLS
  37. The SSL/TLS handshake
  38. Key exchange
  39. Decrypting SSL/TLS
  40. Debugging issues
  41. Summary
  42. 5. Analyzing Application Layer Protocols
  43. BOOTP/DHCP
  44. DNS
  45. HTTP
  46. References
  47. Summary
  48. 6. WLAN Capturing
  49. Analyzing the Wi-Fi networks
  50. Wi-Fi sniffing products
  51. Summary
  52. 7. Security Analysis
  53. The DOS attack
  54. Scanning
  55. ARP duplicate IP detection
  56. DrDoS
  57. BitTorrent
  58. Wireshark protocol hierarchy
  59. Summary
  60. Index

TCP data communication

Once the three-way connection is established, the data is communicated by exchanging the segments and the PUSH flag is set to indicate that the data flows on a connection as a stream of octets, as shown in the following figure:

TCP data communication

Select packet#4 from the normal-connection.pcap file as shown in the following screenshot; expand the TCP section in the Packet Details pane:

TCP data communication

As you can see in the preceding screenshot:

  1. The server is sending data to the client as shown in the packet.
  2. The server sets tcp.flags.push = 1.
  3. The server sets tcp.flags.ack =1.
  4. The server data is (29 bytes) and the data value is: 414e495348204e415448204e4f524d414c20434f4e4e4543....
  5. The server sets (tcp.flags.ack == 1) && (tcp.flags.push == 1); that is, the [PSH,ACK] flag indicates that the host is acknowledging receipt of some previous data and also transmitting some more data.

The useful Wireshark display filters are:

  • data: Displays the packet that contains the data information, for all IPs:
    TCP data communication
  • data && ip.addr==10.0.0.221: Displays a list of packets that have data and are exchanged with the given IP address
  • tcp.flags.push == 1: Displays all PUSH packets
  • tcp.flags.push == 1 && ip.addr==10.0.0.221: Displays PUSH packets between hosts
  • tcp.flags == 0x0018: Display all PSH, ACK packets
  • tcp.flags == 0x0011: Displays all FIN, ACK packets
  • tcp.flags == 0x0010: Displays all ACK packets