what is the difference of persistent connection and keep alive

beer9 used Ask the Experts™
I would like to understand the difference of persistent connection and keep alive. Is it only applicable to HTTP protocol? Thanks!
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Last Knight
Distinguished Expert 2018
Hi beer9,

They both mean the same thing. Vendors may distinguish nuances or differences but in the end they are similes. HTTP persistent connection is synonymous with HTTP keep-alive, or HTTP connection reuse. It is the premise of using a single TCP connection to send/receive multiple HTTP requests/responses, as opposed to opening a new connection for every single request/response pair. The newer HTTP/2 protocol uses the same idea and takes it further to allow multiple concurrent requests/responses to be multiplexed over a single connection.

What vendor/mfg is talking about this...can you provide some context?

Here is an example by SonicWALL of the term "Keep Alive" used outside of the context you originally described...Keep Alive [in terms of VPNs] uses heartbeat messages between peers on this VPN tunnel. If one end of the tunnel fails, using Keep Alives will allow for the automatic renegotiation of the tunnel once both sides become available again without having to wait for the proposed Life Time to expire.

Does this make sense?

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