Date: Mon, 12 Jul 2010 08:01:47 -0700 From: "Kevin Oberman" <oberman@es.net> To: Andrei Kolu <antik@bsd.ee> Cc: freebsd-stable@freebsd.org Subject: Re: bogus DSCP value for ssh Message-ID: <20100712150147.542BE1CC0D@ptavv.es.net> In-Reply-To: Your message of "Mon, 12 Jul 2010 15:31:58 %2B0300." <AANLkTimR7B6SDkD_fbI5O_ggW5UQ8z7SLfgMlNbZF8p2@mail.gmail.com>
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> From: Andrei Kolu <antik@bsd.ee> > Date: Mon, 12 Jul 2010 15:31:58 +0300 > Sender: owner-freebsd-stable@freebsd.org > > Hi! > > I am testing FreeBSD 8.1-RC2 amd64 networking stuff and notice one > strange DSCP message with wireshark: > ------------------------------------ > Internet Protocol, Src: 192.168.1.111 (192.168.1.111), Dst: > 192.168.1.101 (192.168.1.101) > Differentiated Services Field: 0x10 (DSCP 0x04: Unknown DSCP; ECN: 0x00) > 0001 00.. = Differentiated Services Codepoint: Unknown (0x04) > .... ..0. = ECN-Capable Transport (ECT): 0 > .... ...0 = ECN-CE: 0 > > Transmission Control Protocol, Src Port: ssh (22), Dst Port: > attachmate-s2s (2419), Seq: 2902917, Ack: 29842, Len: 132 > ------------------------------------ > > There is no firewall enabled. Only thing I changed (should have no > effect) was: "net.inet.tcp.ecn.enable: 1" > _______________________________________________ I don't know why Wireshark does not understand this, but it is defined in RFC2474 as Class Selector 2 or simply IP precedence of 2 (of 7). If you add the ECN bit, you have Assured Forwarding at IP priority 2. Whether you pass or respond to the DSCP bits is, of course, a personal choice, but there is nothing unusual with this and ssh has bee setting the bit for a long time. -- R. Kevin Oberman, Network Engineer Energy Sciences Network (ESnet) Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab) E-mail: oberman@es.net Phone: +1 510 486-8634 Key fingerprint:059B 2DDF 031C 9BA3 14A4 EADA 927D EBB3 987B 3751
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