Return-Path: X-Original-To: quic-issues@ietfa.amsl.com Delivered-To: quic-issues@ietfa.amsl.com Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 624F63A0C10 for ; Wed, 22 Jul 2020 21:05:06 -0700 (PDT) X-Virus-Scanned: amavisd-new at amsl.com X-Spam-Flag: NO X-Spam-Score: -3.1 X-Spam-Level: X-Spam-Status: No, score=-3.1 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, HTML_IMAGE_ONLY_32=0.001, HTML_MESSAGE=0.001, MAILING_LIST_MULTI=-1, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001] autolearn=ham autolearn_force=no Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (1024-bit key) header.d=github.com Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id iDoGhB3BAd03 for ; Wed, 22 Jul 2020 21:05:05 -0700 (PDT) Received: from out-24.smtp.github.com (out-24.smtp.github.com [192.30.252.207]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id D746B3A0C0F for ; Wed, 22 Jul 2020 21:05:04 -0700 (PDT) Received: from github-lowworker-1b8c660.ash1-iad.github.net (github-lowworker-1b8c660.ash1-iad.github.net [10.56.18.59]) by smtp.github.com (Postfix) with ESMTP id 72C8B6A0A56 for ; Wed, 22 Jul 2020 21:05:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=github.com; s=pf2014; t=1595477102; bh=QvfJlDLFfK6YUGBo4z4RcnCmXo7ffhceFf5mO5GVkgo=; h=Date:From:Reply-To:To:Cc:In-Reply-To:References:Subject:List-ID: List-Archive:List-Post:List-Unsubscribe:From; b=SmfpSlNSm+9UPo9MQj432z+VF+AIBTQ+wq6Kx5oI6V/1R2DipzDHNyySlkx8z4p+Y noaPuNwfXv2dcde85Q9Vd12z+fE34x2OvVJjQ1QQTtcvbKkUCj1376qvVL4zMSXCU7 EMguCqzOKHGgLKjX8k4ldkD0U9vDZxz5xAMa+Zo8= Date: Wed, 22 Jul 2020 21:05:02 -0700 From: Kazuho Oku Reply-To: quicwg/base-drafts To: quicwg/base-drafts Cc: Subscribed Message-ID: In-Reply-To: References: Subject: Re: [quicwg/base-drafts] It's unclear if persistent congestion is a per-PN-space property (#3939) Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="--==_mimepart_5f190c6e5f2b5_36f93f80bf6cd96c13417"; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: list X-GitHub-Sender: kazuho X-GitHub-Recipient: quic-issues X-GitHub-Reason: subscribed X-Auto-Response-Suppress: All X-GitHub-Recipient-Address: quic-issues@ietf.org Archived-At: X-BeenThere: quic-issues@ietf.org X-Mailman-Version: 2.1.29 List-Id: Notification list for GitHub issues related to the QUIC WG List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 23 Jul 2020 04:05:06 -0000 ----==_mimepart_5f190c6e5f2b5_36f93f80bf6cd96c13417 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit @janaiyengar Sure. The following is what was written in https://github.com/quicwg/base-drafts/pull/3889#discussion_r459160599: One trivial way of implementing `InPersistentCongestion` is as follows: * Retain the entries in sentmap (the list of packets being sent) for at least 3 PTO. * When receiving an acknowledgement, mark a hole in the sentmap for the packet being acked. * When a loss is detected in a packet number space, check if that loss spans across more than 3 PTO, by traversing the sentmap. Then, if did, check the sentmap of other packet number spaces (by traversing through those sentmaps) to see if any ACK-eliciting packet sent in that period has been acked. This approach might sound too trivial, as it is O(N) where N is the number of packets being lost (or in case there are multiple PN spaces in action, the number of inflight packets in other PN spaces). But in practice, I think this approach is sufficient in terms of performance, because N would be like 3 for the current packet number space, and because we would not be sending that many packets on Initial and Handshake packet number spaces. -- You are receiving this because you are subscribed to this thread. Reply to this email directly or view it on GitHub: https://github.com/quicwg/base-drafts/issues/3939#issuecomment-662808337 ----==_mimepart_5f190c6e5f2b5_36f93f80bf6cd96c13417 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: 7bit

@janaiyengar Sure. The following is what was written in #3889 (comment):

One trivial way of implementing InPersistentCongestion is as follows:

  • Retain the entries in sentmap (the list of packets being sent) for at least 3 PTO.
  • When receiving an acknowledgement, mark a hole in the sentmap for the packet being acked.
  • When a loss is detected in a packet number space, check if that loss spans across more than 3 PTO, by traversing the sentmap. Then, if did, check the sentmap of other packet number spaces (by traversing through those sentmaps) to see if any ACK-eliciting packet sent in that period has been acked.

This approach might sound too trivial, as it is O(N) where N is the number of packets being lost (or in case there are multiple PN spaces in action, the number of inflight packets in other PN spaces). But in practice, I think this approach is sufficient in terms of performance, because N would be like 3 for the current packet number space, and because we would not be sending that many packets on Initial and Handshake packet number spaces.

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