Re: IPQoS values in sshd
On 2018-08-08, Mik J wrote: > Hello Daren, > Thank you for your answer, I didn't see it earlier today. > This change in current makes sense to me. > Regards > > > Le mercredi 8 août 2018 à 06:07:10 UTC+2, Darren Tucker > a écrit : > > On 8 August 2018 at 05:29, Mik J wrote: >> Does anyone knows what means lowdelay and thoughput for IPQoS parameter ? >> To what DSCP correspond these words > > From https://www.openssh.com/specs.html, which documents the most > recent release: they're the values specified in RFC1349, the first of > the dozen or so attempts to specify the meaning of those few bits > (RFCs 2474, 2597, 2598, 3168, 3246, 3260, 3662, 4301, 4594, 5865 and > 8325). > >> I did a capture when writing ls in my terminal and I see DSCP=cs0. >> I would have expected something else. > > The default values have been changed in -current but that change has > not yet made it to a release. From > https://man.openbsd.org/ssh_config.5: "The default is af21 > (Low-Latency Data) for interactive sessions and cs1 (Lower Effort) for > non-interactive sessions." > The old implementation using TOS pre-dates common use of DSCP and held on for quite some time, I think there may have been earlier concerns about network equipment not passing DSCP-marked packets properly. People using PF queues might like to note that "set queue" used with 2 queue names (e.g. "set queue (bulk, interactive)") only prioritises TOS=lowdelay, not DSCP. So people using this for prioritisation of interactive SSH traffic might want to consider either replacing the queues with "flow queues" (interactive packets are usually smaller and likely to below the "quantum" size and so have priority), or using "IPQoS lowdelay throughput" in ssh config.
Re: IPQoS values in sshd
Hello Daren, Thank you for your answer, I didn't see it earlier today. This change in current makes sense to me. Regards Le mercredi 8 août 2018 à 06:07:10 UTC+2, Darren Tucker a écrit : On 8 August 2018 at 05:29, Mik J wrote: > Does anyone knows what means lowdelay and thoughput for IPQoS parameter ? > To what DSCP correspond these words >From https://www.openssh.com/specs.html, which documents the most recent release: they're the values specified in RFC1349, the first of the dozen or so attempts to specify the meaning of those few bits (RFCs 2474, 2597, 2598, 3168, 3246, 3260, 3662, 4301, 4594, 5865 and 8325). > I did a capture when writing ls in my terminal and I see DSCP=cs0. > I would have expected something else. The default values have been changed in -current but that change has not yet made it to a release. From https://man.openbsd.org/ssh_config.5: "The default is af21 (Low-Latency Data) for interactive sessions and cs1 (Lower Effort) for non-interactive sessions." -- Darren Tucker (dtucker at dtucker.net) GPG key 11EAA6FA / A86E 3E07 5B19 5880 E860 37F4 9357 ECEF 11EA A6FA (new) Good judgement comes with experience. Unfortunately, the experience usually comes from bad judgement.
Re: IPQoS values in sshd
Hello David, Thank you for your answer. Indeed, I have (in this case) an agreement with the ISP to I can play with QoS fields. => I don't understand why in the documentation they refer to old ToS field and not DSCP field that everyone use. That would be more logic. I did captures and found ToS 0x10 or 0x8 (transfert) IP (tos 0x10, ttl 64, id 6849, offset 0, flags [DF], proto TCP (6), length 52) According to what I read tos 0x10 = DSCP 2 and tos 0x8 = DSCP 2 ? ToS 0x10 in binary 1010 = dscp 10 => 2 and ToS binary 8 in binary 1000 = dscp 10 => 2 Low delay should be 0x1000 and throughput should be 0x100 https://tools.ietf.org/html/rfc1349 4. Specification of the TOS Field I tried with openbsd 6.3 Also why these values were chosen by default in Openbsd, according to QoS models I would have chosen other values and also used dscp instead of ToS Regards Le mercredi 8 août 2018 à 11:31:39 UTC+2, Dahlberg, David a écrit : Am Dienstag, den 07.08.2018, 19:29 + schrieb Mik J: > Does anyone knows what means lowdelay and thoughput for IPQoS > parameter ? Bits 3 and 4 of old IP TOS field. > To what DSCP correspond these words You have to calculate it yourself. The lowest bit of the 6-bit DSCP is "private". The second and third lowest once have been T and D. I did indeed write a script which translates me a given value from one interpretation into the gazillion other possible interpretations. Maybe I push it to Githup soonish. "T" is e.g. AFx1 and AFx3 equivalents. "L" is e.g. AFx2 and AFx3. > I did a capture when writing ls in my terminal and I see DSCP=cs0. > I would have expected something else. CSx in DSCP directly equates to IP precedence in old TOS interpretation with all the special bits (DTRC0) set to zero. CS0 = DF (default forwarding) is all zero. But honestly, what do you want to set those values for? They have only local meaning -> So you can do something with them in your local network. If you're sending them across a administrative border, they lose meaning (unless something special has been negotiated between you and your ISP) and it is quite possible they are set to zero anyways. With regular internet access, all you can do is set the DSCP to a "well- known" value and hope that there is somebody out there who (a) does process it, (b) interprets the same way as you and (c) he did receive your value unchanged (which is not guaranteed). An example for such well-known values which "may" have "some" effect "somewhere" is mostly EF for VoIP. Cheers David
Re: IPQoS values in sshd
On 8 August 2018 at 05:29, Mik J wrote: > Does anyone knows what means lowdelay and thoughput for IPQoS parameter ? > To what DSCP correspond these words >From https://www.openssh.com/specs.html, which documents the most recent release: they're the values specified in RFC1349, the first of the dozen or so attempts to specify the meaning of those few bits (RFCs 2474, 2597, 2598, 3168, 3246, 3260, 3662, 4301, 4594, 5865 and 8325). > I did a capture when writing ls in my terminal and I see DSCP=cs0. > I would have expected something else. The default values have been changed in -current but that change has not yet made it to a release. From https://man.openbsd.org/ssh_config.5: "The default is af21 (Low-Latency Data) for interactive sessions and cs1 (Lower Effort) for non-interactive sessions." -- Darren Tucker (dtucker at dtucker.net) GPG key 11EAA6FA / A86E 3E07 5B19 5880 E860 37F4 9357 ECEF 11EA A6FA (new) Good judgement comes with experience. Unfortunately, the experience usually comes from bad judgement.
IPQoS values in sshd
Hello, Does anyone knows what means lowdelay and thoughput for IPQoS parameter ? To what DSCP correspond these words I did a capture when writing ls in my terminal and I see DSCP=cs0. I would have expected something else. Regards
