From: xnor <xnoreq@gmail.com>
To: cake@lists.bufferbloat.net
Subject: [Cake] ECN not working?
Date: Tue, 22 Dec 2020 21:06:32 +0100 [thread overview]
Message-ID: <421ffd89-0c2c-1187-380c-03a0968f4095@gmail.com> (raw)
Hello,
after observing mostly drops in cake (instead of marks) I did a little test:
Client is a Linux 5.9.13, server is the same.
Kernel ECN parameters are set identically for both client and server to:
net.ipv4.tcp_ecn = 1
net.ipv4.tcp_ecn_fallback = 1
Using tcpdump on the server I see the following:
The client initiates the IPv4 TCP connection with:
IP Differentiated Services Field: 0x02 (DSCP: CS0, ECN: ECT(0))
TCP Flags: 0x0c2 (SYN, ECN, CWR)
Seq=0 Win=64240 Len=0 MSS=1460 WS=256 SACK_PERM=1
The server responds:
Differentiated Services Field: 0x00 (DSCP: CS0, ECN: Not-ECT)
Flags: 0x012 (SYN, ACK)
Seq=0 Ack=1 Win=64240 Len=0 MSS=1460 SACK_PERM=1 WS=128
Shouldn't the server respond with ECT set in the SYN ACK packet
and possibly also have ECN-related flags set in the TCP header?
next reply other threads:[~2020-12-22 20:07 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-22 20:06 xnor [this message]
2020-12-22 20:15 ` Jonathan Morton
2020-12-22 21:44 ` xnor
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