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Re: ack delay in rx packets

Jana Iyengar <jri.ietf@gmail.com> Wed, 25 April 2018 15:53 UTC

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From: Jana Iyengar <jri.ietf@gmail.com>
Date: Wed, 25 Apr 2018 15:53:12 +0000
Message-ID: <CACpbDcd-N+KLECz9z1JQJwE_JXqq_4rNzP9i9Aq9itfRhGaPgA@mail.gmail.com>
Subject: Re: ack delay in rx packets
To: Subodh Iyengar <subodh@fb.com>
Cc: QUIC WG <quic@ietf.org>
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If the sender has seen a previous ack for the same largest received, then
it should basically ignore this new ack. If not, the ack delay will be
accurate... What concern do you see with having a large ack delay?

On Wed, Apr 25, 2018, 8:08 AM Subodh Iyengar <subodh@fb.com> wrote:

> We ran into very common cases where we might have all our data to send
> already outstanding, so when a TLP and RTO alarm fires, we have no new data
> to send, so we resend data that was in previous packets.
>
>
> In the time that the RTO fires, we might not have received any new
> packets, however want to send ACKs in this new packet as well. Since no new
> packets were received, this ACK will have the same largest acked as the
> previous packet.
>
>
> One question came up as to what the ack delay of an ACK in such a rx
> packet should be. We could technically set it to the time since receipt of
> the packet, however with the new max_ack_delay computations, adding this
> might screw up our estimate of the normal ack delay, so I don't really want
> to do that. Is there a better option here, or does max_ack_delay not cover
> this case?
>
>
> Subodh
>

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