From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: k@vodka.home.kg Received: from mail.kotidze.in (mail.kotidze.in [91.92.66.82]) by krantz.zx2c4.com (ZX2C4 Mail Server) with ESMTP id 4b9c673d for ; Fri, 4 Nov 2016 16:01:13 +0000 (UTC) Received: from private.domain by mail.kotidze.in with [XMail 1.27 ESMTP Server] id for from ; Fri, 4 Nov 2016 19:01:46 +0300 Date: Fri, 4 Nov 2016 19:01:40 +0300 From: k@vodka.home.kg Message-ID: <1518389796.20161104190140@vodka.home.kg> To: wireguard@lists.zx2c4.com MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Subject: [WireGuard] heavy packet loss List-Id: Development discussion of WireGuard List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , I'm trying to connect 2 endpoints with wireguard. One endpoint has MTU of inet inteface 1500, another 1456. To prevent packet fragmentation on inet interface i set up mtu 1383 for both wg interfaces. Checked that no frag occurs on inet interface in wireshark. Maximum packet data size is 1383-28 = 1355. Checked with no-fragment ping, packets pass well. First I checked packet loss between inet IPs iperf -c x.x.x.x -u -b 25M -l 1400 0.0-10.3 sec 29.6 MBytes 24.2 Mbits/sec 16.073 ms 175/23090 (0.76%) packet loss always within 0.5..1%. its normal now I try to do the same with much less bandwidth between wireguard ips on packet size <=1252 packet loss rate is 0.5..1% iperf -c 192.168.254.65 -w 500000 -u -b 1M -l 1252 0.0-10.0 sec 1.18 MBytes 991 Kbits/sec 0.659 ms 9/ 1000 (0.9%) but starting from packet size 1253 packets loss greatly increases. its 6..10% iperf -c 192.168.254.65 -w 500000 -u -b 1M -l 1253 0.0-10.0 sec 1.12 MBytes 936 Kbits/sec 0.328 ms 64/ 998 (6.4%) Thats why TCP is incredibly slow. If I set up mss for TCP to not exceed packets size threshold TCP is fast.