IBM Support

Information regarding avoiding SYN attack for TCP/IP Stack

Troubleshooting


Problem

Explanation of how TCP protocol on iSeries avoids a SYN attack.

Resolving The Problem

iSeries TCP protocol uses something called 'Random Event Deletion' to avoid a SYN attack. Random Event Deletion is done when the max backlog for a listener has been maxed out. TCP will then randomly delete a connection that has not been accepted by the application. Thus allowing another connection in.
When the connection is randomly deleted, the IBM i will generate and send a TCP RST to the remote system.

This is our mechanism for Denial of Service attacks for the TCP protocol.

Other applications like HTTP have a way to avoid locking up their servers when a denial of service attack occurs. This is done using the HTTP directive 'Denial of Service'.

[{"Type":"MASTER","Line of Business":{"code":"LOB57","label":"Power"},"Business Unit":{"code":"BU058","label":"IBM Infrastructure w\/TPS"},"Product":{"code":"SWG60","label":"IBM i"},"Platform":[{"code":"PF012","label":"IBM i"}],"Version":"7.1.0"}]

Historical Number

331386946

Document Information

More support for:
IBM i

Software version:
7.1.0

Operating system(s):
IBM i

Document number:
639269

Modified date:
11 December 2020

UID

nas8N1016182

Manage My Notification Subscriptions