Idle timeout
The transport implementation considers the connection lost if it doesn't receive any data within the period defined by the idle timeout. The idle timeout is specified with the IdleTimeout parameter. Each side of the connection advertises its idle timeout and agree to use the minimum value during connection establishment.
The default idle timeout is 30 seconds.
Each side of a connection maintains an idle timer that it restarts when it receives data. If this idle timer ever expires, the expired side of the connection considers the connection dead and disposes of this connection immediately.
This idle timeout is comparable (but not identical) to QUIC's idle timeout.
Keeping a connection alive
Slic is responsible for preventing the connection's idle timers from expiring when the application (the upper protocol) doesn't write anything to this connection.
Slic keeps connections alive by sending Ping frames. A Slic client connection sends Ping frames to the server; a Slic server connection never sends Ping frames to the client. When the server receives a Ping frame, it restarts its idle timer and sends back a Pong frame. The reception of the Pong frame in turn restarts the idle timer of the client.