What is a keep alive packet?
What is a keep alive packet?
In TCP, the keepalive is the administrative packet sent to detect stale connection. In HTTP, keepalive means the persistent connection state. This is from TCP specification, Keep-alive packets MUST only be sent when no data or acknowledgement packets have been received for the connection within an interval.
How long is TCP keep alive?
The TCP Keep-Alives, not to be confused with the HTTP Keep-Alive header, is a defined, optional TCP implementation in Request for Comments (RFC) 1122. The default is 1800 seconds. Note: For more information about TCP keep alive, refer to the Internet Engineering Task Force (RFC 1122).
How do you keep a TCP socket alive?
The SO_KEEPALIVE option for a socket is disabled (set to FALSE) by default. When this socket option is enabled, the TCP stack sends keep-alive packets when no data or acknowledgement packets have been received for the connection within an interval. For more information on the keep-alive option, see section 4.2.
What does keep alive mean in Wireshark?
They are used for window size updates detection. Wireshark treats them as keep-alive packets just because these packets look like keep-alive packet. A TCP keep-alive packet is simply an ACK with the sequence number set to one less than the current sequence number for the connection.
How does keep alive work?
Keep-Alive, also known as a persistent connection, is a communication pattern between a server and a client to reduce the HTTP request amount and speed up a web page. When Keep-Alive is turned on, the client and the server agree to keep the connection for subsequent requests or responses open.
How do you check keep alive in Wireshark?
The Wireshark TCP expert marks them as keep-alives though because it keeps track of the TCP session. You can filter for them by using the display filter, “tcp. analysis. keep_alive”.
Why keep alive is needed?
The Benefits of Connection Keep Alive The HTTP keep-alive header maintains a connection between a client and your server, reducing the time needed to serve files. A persistent connection also reduces the number of TCP and SSL/TLS connection requests, leading to a drop in round trip time (RTT).
What is keep-alive mechanism?
HTTP keep-alive, a.k.a., HTTP persistent connection, is an instruction that allows a single TCP connection to remain open for multiple HTTP requests/responses. By default, HTTP connections close after each request.
How do you keep-alive connection?
The Keep-Alive general header allows the sender to hint about how the connection may be used to set a timeout and a maximum amount of requests. Note: Set the Connection header to “keep-alive” for this header to have any effect.
How does keep-alive work?
The KeepAlive mechanism does this by sending low-level probe messages to see if the other side responds. If it does not respond to a certain number of probes within a certain amount of time, then it assumes the connection is dead and the process using the socket will then detect this through an error indication.
How long does keep alive last?
Keepalive time is the duration between two keepalive transmissions in idle condition. TCP keepalive period is required to be configurable and by default is set to no less than 2 hours.
Where do you put keep alive?
To enable Keep-Alive, you need to explicitly request it via the HTTP header by accessing . htaccess or the main configuration file of your web server. If you turn on Keep-Alive, the HTTP response header will show Connection: keep-alive.
How do I check my keep-alive status?
In order to check if your pages are delivered with a Keep-Alive header, you can use the HTTP Header Checker tool. This will display the Connection: Keep-Alive field if the HTTP Keep-Alive header is enabled.
How long does keep-alive last?
Where do you put keep-alive?
Why do we use keepalive?
Enabling the keep-alive header allows you to serve all web page resources over a single connection. Keep-alive also reduces both CPU and memory usage on your server.
How do I check my keep alive status?
How do you use keep alive?
How to enable keep-alive connections
- Edit or create an . htaccess file in your site’s document root directory.
- Copy the following lines and paste them into the .htaccess file: Header set Connection keep-alive
- Save your changes to the . htaccess file.
