Slowloris is an HTTP Denial of Service (DoS) tool written in PERL that is used to perform denial of service attacks against Apache-based servers (as well as other web services). Slowloris exhausts all available server connections by repeatedly initiating several hundred valid HTTP requests to the server and keeping these connections open using a minimal amount of TCP traffic to consume server resources. Once server resources are exhausted, the server is no longer able to respond to legitimate traffic.
Per CSCtu08459, you are now able to configure the ACE to mitigate a Slowloris HTTP DOS attack by including an HTTP parse timeout in your HTTP parameter map. With software version A5(1.2), the new set max-parse-time command has been added as protection from Slowloris DoS attacks. The default HTTP parsing timeout is set to 255 seconds, and if the ACE does not receive a GET request from the connection within 255 seconds, the HTTP parse timeout initiates and the ACE drops the connection and sends a reset to the client. You can increase this timeout maximum through the set max-parse-time command.
The syntax of this parameter map HTTP configuration mode command is as follows:
The time argument is the time in seconds for the maximum length of the HTTP parsing timeout. Valid entries are 1 to 65535 seconds.
For example, to enter an HTTP parsing timeout of 200 seconds, enter the following:
host1/Admin(config)# parameter-map type http HTTP_MAP
host1/Admin(config-parammap-http)# set max-parse-time 200
In the link that you provided it shows and example CSS configuration with the following explanation.
"Delayed binding typically causes the load balancer to perform an HTTP Request header completeness check, which means that the HTTP Request will not be sent to the appropriate Web server until the final two carriage return and line feeds are sent by the HTTP client. This is the key bit of information. Basically, delayed binding ensures that your Web server or proxy will never see any of the incomplete requests being sent out by Slowloris."
How does the parsing timeout accomplish this? Does the timeout do the HTTP request header completeness check prior to timing out the connection?
Looks like I need to upgrade the code on the load balancers in order to get this feature.
Yes, as was discribed in the previous message, the command does the HTTP request completeness check and if the request is not complete the ACE will drop it without passing to the real server.
The default HTTP parsing timeout is set to 255 seconds, and if the ACE does not receive a GET request from the connection within 255 seconds, the HTTP parse timeout initiates and the ACE drops the connection and sends a reset to the client.
As this command has been available since version A5(1.2), then you would need to upgrade the code to one of the latest versions to get this feature.
Introduction This article will help you understand the steps on how to
download the UCS licenses from the Cisco Systems website and then
installing it on the UCS. The redacted (blue lines) just covers up
certain numbers for privacy please do not take them...
Introduction This article will help you understand and educate the
customer on how to clear their "expired licenses"
(license-graceperiod-expired) from their UCS-M. If a customer just
purchased a license and needs a step by step guide on how to download
==================== VIC FNIC driver does not support Virtual Volumes (
second level LUN ID ) An enhancement request has been created to track
this feature - CSCux64473 UPDATE - 12-14-2016 We made some traction on
the enhancement request - The Fix is in t...