Is there an sample to test L4S feature? I have enabled L4S in the developer menu.
I test L4S with iperf3 using a L4S tcp congestion algorithm on linux like: iperf3 -c x.x.x.x -C prague
As I know, IOS is using cubic as default TCP algorithm, is there any TCP algorithm support L4S in IOS 16?
Is there an sample to test L4S feature?
There is not a specific Xcode project sample to test out L4S, but as you have mentioned on iOS there is a Developer setting for this feature in HTTP/3 and QUIC. On macOS there is a defaults write that can enable L4S:
% default write -g network_enable_l4s -bool true
% default read network_enable_l4s
There is also tools, guides, and a test server setup on the WWDC video page for Reduce networking delays for a more responsive app.
One thing that is important about L4S testing is that you will need to have L4S compatible hardward to ensure that when a network is congested that the hardware can signal that there is congestion present on the network instead of dropping the packets. From there, both the sending and receiving side should adjust the way packets are sent to accomodate for this network congestion until the bottleneck is resolved.
is there any TCP algorithm support L4S in IOS 16?
To my knowledge, no. It is only supported for QUIC.
When I turned L4S enabled in the developer menu, do I still need to specify any congestion control algorithm in quic to co-work with L4S? Is the default QUIC support L4S? In linux I explicitly use TCP Prague or BBR v2 to work with L4S.