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What is keep-alive request?

What is keep-alive request?

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.

What is a TCP keep-alive?

The TCP Keepalive Timer feature provides a mechanism to identify dead connections. When a TCP connection on a routing device is idle for too long, the device sends a TCP keepalive packet to the peer with only the Acknowledgment (ACK) flag turned on.

What is keep-alive in Apache?

Keep-Alive (also known as HTTP Keep-Alive or persistent connection) is a bit of communication (message) between the client and server that says: “You may grab many files.” These are extremely small messages that consume very little bandwidth. The following method assumes Apache web server.

How do you use keep-alive?

How to enable keep-alive connections

  1. Edit or create an . htaccess file in your site’s document root directory.
  2. Copy the following lines and paste them into the .htaccess file: Header set Connection keep-alive
  3. Save your changes to the . htaccess file.

How do you use 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.

What is persistent timer?

Persistent Timer – To deal with a zero-window-size deadlock situation, TCP uses a persistence timer. When the sending TCP receives an acknowledgment with a window size of zero, it starts a persistence timer. When the persistence timer goes off, the sending TCP sends a special segment called a probe.

Where do you put keep alive?

HTTP Keep-Alive settings It is recommended to set this number to 100 as that is satisfactory in most scenarios. In the case that the server needs to deliver more files, you will want to increase this setting. For an unlimited amount of request during a single connecting, set this to 0 .

What is TCP RTO?

An RTO occurs when the sender is missing too many acknowledgments and decides to take a time out and stop sending altogether. After some amount of time, usually at least one second, the sender cautiously starts sending again, testing the waters with just one packet at first, then two packets, and so on.

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.

What is tcp_retries1?

tcp_retries1 variable just controls the number of retries before the system signals a lower level to try verifying that networking is available.

What is TCP timer?

TCP Timers are used to avoid excessive delays during communication. TCP Timers are- Time Out Timer, Time Wait Timer, Keep Alive Timer, Persistent Timer. Time out timer is used for retransmission. Time Wait Timer is used during connection termination.

What is Max SYN retransmissions?

The Maximum Syn Retransmissions setting specifies the maximum number of times that the system resends a SYN when it does not receive a corresponding SYN-ACK. In BIG-IP version 10. x, the TCP profile supports values of more than 12 for either setting.

What is Tcp_max_syn_backlog?

tcp_max_syn_backlog represents the maximal number of connections in SYN_RECV queue. I.e. when your server received SYN, sent SYN-ACK and haven’t received ACK yet. This is a separate queue of so-called “request sockets” – reqsk in code (i.e. not fully-fledged sockets, “request sockets” occupy less memory.

What is Sol_socket?

SOL_SOCKET is the socket layer itself. It is used for options that are protocol independent.

What is socket address?

A socket address is defined by the IP address of the socket and the port number allocated to the socket.

How do you modify the TCP IP Max retransmission timeout?

From the Edit menu select New – DWORD value. Enter a name of InitialRtt and press Enter. Double click the new value and set to the number of milliseconds for the timeout, e.g. 5000 for 5 seconds (the old default was 3 seconds). Click OK.

What is Tcp_fin_timeout?

tcp_fin_timeout. This parameter determines the length of time an orphaned (unreferenced) connection will wait before it is aborted at the local end. This parameter is especially helpful for when something happens to the remote peer which prevents or excessively delays a response.

What is Somaxconn?

SOMAXCONN defines the maximum number you’re allowed to pass to listen() which is 128 on my system.

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