For securing the data, the TLS session is created with the TLS handshake.The TCP connection is established with the TCP 3-way handshaking.The data transfer follows the steps below: The screenshot below shows a typical data transfer over a TLS connection. Unless some other fatal alert has been transmitted, each party is required to send this alert (close notify) before closing the write side of the connection. Any data received after a closure alert is ignored. Either party may initiate a close by sending this alert.
For troubleshooting, we will analyze messages in two groups: Closure and Error Alerts.Įvery TLS connection ends with this alert message, which notifies the recipient that the sender will not send any more messages on this connection. Like other messages, alert messages are encrypted and compressed, as specified by the current connection state. Alert messages with a level of fatal result in the immediate termination of the connection.
Requires immediate termination of the connection.Īlert messages convey the severity of the message (warning or fatal) and a description of the alert. It is a warning, which does not cause a connection termination. In this article, we will focus on the Alert Protocol to troubleshoot TLS issues.ĪLSO READ: How to create or configure NIC Teaming using nmcli (CentOS / RHEL 7/8) Alert Level
The Alert Protocol, which sends important messages about the state of the SSL/TLS connection from one side to the other.The ChangeCipherSpec Protocol, which changes the encryption system currently in use.The Handshake Protocol, which performs the initial key negotiation.TLS handshaking employs three subprotocols that are used to allow peers to agree upon security parameters for the record layer, to authenticate themselves, to instantiate negotiated security parameters, and to report error conditions to each other. In one of the previous articles Analyze TLS and mTLS Authentication with Wireshark, we explored how SSL/TLS handshake works and analyzed SSL/TLS record types in Wireshark.
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