Inquiry regarding "maxReceiveTimestampsPerAckStored" parameter in QUIC protocol

[xs-411]

Hello,

I am currently exploring the QUIC protocol and came across the "maxReceiveTimestampsPerAckStored" parameter in an open-source project's codebase. However, I noticed that this parameter is not mentioned in the QUIC protocol specification. I am curious to understand the significance and purpose of this parameter.

Could you kindly provide insights into the following:

What is the purpose of the "maxReceiveTimestampsPerAckStored" parameter in the context of the QUIC protocol?
How does it affect the behavior or performance of the QUIC connection?
Is this parameter specific to the particular open-source project or is it a standard part of the QUIC protocol?
Are there any recommended or default values for this parameter, or is it configurable?
I appreciate any information or references you can provide to clarify the presence and usage of this parameter in the QUIC protocol.

Thank you for your attention to this inquiry. I look forward to your response.

Sincerely yy

[jbeshay]

The parameter controls the number of packet receive timestamps the transport stores in order to write them back to an ACK_RECEIVE_TIMESTAMPS if requested by the peer. This functionality is from the extension introduced by this draft: https://www.ietf.org/archive/id/draft-smith-quic-receive-ts-00.html

The comment here outlines the motivation and the code sets the default value:

mvfst/quic/state/TransportSettings.h

Lines 355 to 360 in 2c2b3ce

	// Maximum number of received packet timestamps stored per ACK. This will be
	// controlled by a MC and will be dependent on device capabilities and
	// resources. Hence, this isn't contigent on whether ACK receive timestamps
	// are enabled or not and should not a part of
	// maybeAckReceiveTimestampsConfigSentToPeer optional.
	uint64_t maxReceiveTimestampsPerAckStored{kMaxReceivedPktsTimestampsStored};

I will close this issue since it's old but feel free to re-open if you have more questions.