Re: explain priority codepoints and their mapping in vlan.4
On Thu, Dec 30, 2021 at 12:34:14PM -0800, Chris Cappuccio wrote: > Christopher Zimmermann [chr...@openbsd.org] wrote: > > On Mon, Dec 20, 2021 at 04:41:07PM -0700, Theo de Raadt wrote: > > > You say it twice. But my eyes still glazed over it, not seeing what was > > > going on the first two times. > > > > > > Maybe something more like > > > > > > prio 0 and 1 are mapped out of order to PCP 1 and 0, but prio 2 to > > > 7 are mapped directly to PCP 2 to 7. > > > > > > No that still doesn't quite capture it in a visible way. How about > > > > > > prio 2 to 7 are mapped directly to PCP 2 to 7, but prio 0 and 1 > > > are mapped backwards, to PCP 1 and 0, because <...> > > > > > > Something which will draw the eye+brain to 'something is different here'. > > > The table alone doesn't do that. > > > > I agree. How about this? > > > > The 802.1Q and 802.1ad protocols include a Priority Code Point (PCP). > > By > > default, the 802.1p PCP in a transmitted packet is based on the > > priority > > of packets sent over the interface, which may be altered via > > pf.conf(5); > > see the prio option for more information. Alternatively, the > > ifconfig(4) > > txprio option can set a specific priority for transmitted packets. On > > vlan and svlan interfaces priorities 2 to 7 will be mapped directly to > > PCP 2 to 7, but priorities 0 and 1 are mapped backwards, to PCP 1 and > > 0. > > This is because 802.1p defines PCP 1 as lowest priority and PCP 0 as > > second lowest priority, which is meant to be used as default (???best > > effort???). > > > > I think the best way to get someone's attention is to mention the > conflict first, like in Theo's example. Yours seems wordy, a person > has to read several sentences before they even realize something > unusual going on here. > > Chris > hi chris. it's a fair point. but i suppose the other side is that this way all man pages would begin with a list of important points. almost like sticking CAVEATS at page top. i think the text is written in a logical order, to be honest. if all the stuff before the "watch out!" text is not needed, then i guess a CAVEATS might be better. but it reads like it;s all useful. (but to be fair, i really am not familiar with this stuff) jmc
Re: explain priority codepoints and their mapping in vlan.4
Christopher Zimmermann [chr...@openbsd.org] wrote: > On Mon, Dec 20, 2021 at 04:41:07PM -0700, Theo de Raadt wrote: > > You say it twice. But my eyes still glazed over it, not seeing what was > > going on the first two times. > > > > Maybe something more like > > > > prio 0 and 1 are mapped out of order to PCP 1 and 0, but prio 2 to > > 7 are mapped directly to PCP 2 to 7. > > > > No that still doesn't quite capture it in a visible way. How about > > > > prio 2 to 7 are mapped directly to PCP 2 to 7, but prio 0 and 1 > > are mapped backwards, to PCP 1 and 0, because <...> > > > > Something which will draw the eye+brain to 'something is different here'. > > The table alone doesn't do that. > > I agree. How about this? > > The 802.1Q and 802.1ad protocols include a Priority Code Point (PCP). By > default, the 802.1p PCP in a transmitted packet is based on the priority > of packets sent over the interface, which may be altered via pf.conf(5); > see the prio option for more information. Alternatively, the ifconfig(4) > txprio option can set a specific priority for transmitted packets. On > vlan and svlan interfaces priorities 2 to 7 will be mapped directly to > PCP 2 to 7, but priorities 0 and 1 are mapped backwards, to PCP 1 and 0. > This is because 802.1p defines PCP 1 as lowest priority and PCP 0 as > second lowest priority, which is meant to be used as default (???best > effort???). > I think the best way to get someone's attention is to mention the conflict first, like in Theo's example. Yours seems wordy, a person has to read several sentences before they even realize something unusual going on here. Chris
Re: explain priority codepoints and their mapping in vlan.4
On Thu, Dec 30, 2021 at 09:04:53PM +0100, Christopher Zimmermann wrote:
> On Mon, Dec 20, 2021 at 04:41:07PM -0700, Theo de Raadt wrote:
> >You say it twice. But my eyes still glazed over it, not seeing what
> >was going on the first two times.
> >
> >Maybe something more like
> >
> > prio 0 and 1 are mapped out of order to PCP 1 and 0, but prio 2 to
> > 7 are mapped directly to PCP 2 to 7.
> >
> >No that still doesn't quite capture it in a visible way. How about
> >
> > prio 2 to 7 are mapped directly to PCP 2 to 7, but prio 0 and 1
> > are mapped backwards, to PCP 1 and 0, because <...>
> >
> >Something which will draw the eye+brain to 'something is different here'.
> >The table alone doesn't do that.
>
> I agree. How about this?
>
> The 802.1Q and 802.1ad protocols include a Priority Code Point (PCP).
> By
> default, the 802.1p PCP in a transmitted packet is based on the priority
> of packets sent over the interface, which may be altered via pf.conf(5);
> see the prio option for more information. Alternatively, the
> ifconfig(4)
> txprio option can set a specific priority for transmitted packets. On
> vlan and svlan interfaces priorities 2 to 7 will be mapped directly to
> PCP 2 to 7, but priorities 0 and 1 are mapped backwards, to PCP 1 and 0.
> This is because 802.1p defines PCP 1 as lowest priority and PCP 0 as
> second lowest priority, which is meant to be used as default (???best
> effort???).
>
hi.
some feedback, inline.
>
> Index: vlan.4
> ===
> RCS file: /cvs/src/share/man/man4/vlan.4,v
> retrieving revision 1.51
> diff -u -p -r1.51 vlan.4
> --- vlan.44 Oct 2020 12:44:49 - 1.51
> +++ vlan.430 Dec 2021 20:00:38 -
> @@ -83,17 +83,26 @@ interfaces by their respective protocol
> identifiers, and decapsulated for reception on the associated virtual
> interfaces.
> .Pp
> -The 802.1Q and 802.1ad protocols include a priority field.
> -By default, the 802.1p priority in a transmitted packet is based on the
> +The 802.1Q and 802.1ad protocols include a Priority Code Point (PCP).
> +By default, the 802.1p PCP in a transmitted packet is based on the
> priority of packets sent over the interface, which may
> be altered via
> .Xr pf.conf 5 ;
> see the
> .Cm prio
> option for more information.
> -Alternatively,
> +Alternatively, the
> +.Xr ifconfig 4
> .Cm txprio
> -can set a specific priority for transmitted packets.
> +option can set a specific priority for transmitted packets. On
you should start new sentences on new lines
> +.Nm vlan
> +and
> +.Nm svlan
> +interfaces priorities 2 to 7 will be mapped directly to PCP 2 to 7, but
> +priorities 0 and 1 are mapped backwards, to PCP 1 and 0. This is because
ditto
also, consider s/and 0/and 0, respectively/
it is more explicit (which seems to be relevant here)
> +802.1p defines PCP 1 as lowest priority and PCP 0 as second lowest
> +priority, which is meant to be used as default
i'm having trouble with the lack of a/the here. i don;t know the subject
matter well enough to say exactly what it should be, but:
as lowest priority -> as the lowest priority
as second -> as the second
as default -> as the default
(not sure, just asking)
> +.Pq Dq best effort .
i would not mark this up i.e. use ("best effort")
jmc
> .Pp
> .Nm vlan
> and
Re: explain priority codepoints and their mapping in vlan.4
On Mon, Dec 20, 2021 at 04:41:07PM -0700, Theo de Raadt wrote: You say it twice. But my eyes still glazed over it, not seeing what was going on the first two times. Maybe something more like prio 0 and 1 are mapped out of order to PCP 1 and 0, but prio 2 to 7 are mapped directly to PCP 2 to 7. No that still doesn't quite capture it in a visible way. How about prio 2 to 7 are mapped directly to PCP 2 to 7, but prio 0 and 1 are mapped backwards, to PCP 1 and 0, because <...> Something which will draw the eye+brain to 'something is different here'. The table alone doesn't do that. I agree. How about this? The 802.1Q and 802.1ad protocols include a Priority Code Point (PCP). By default, the 802.1p PCP in a transmitted packet is based on the priority of packets sent over the interface, which may be altered via pf.conf(5); see the prio option for more information. Alternatively, the ifconfig(4) txprio option can set a specific priority for transmitted packets. On vlan and svlan interfaces priorities 2 to 7 will be mapped directly to PCP 2 to 7, but priorities 0 and 1 are mapped backwards, to PCP 1 and 0. This is because 802.1p defines PCP 1 as lowest priority and PCP 0 as second lowest priority, which is meant to be used as default (“best effort”). Index: vlan.4 === RCS file: /cvs/src/share/man/man4/vlan.4,v retrieving revision 1.51 diff -u -p -r1.51 vlan.4 --- vlan.4 4 Oct 2020 12:44:49 - 1.51 +++ vlan.4 30 Dec 2021 20:00:38 - @@ -83,17 +83,26 @@ interfaces by their respective protocol identifiers, and decapsulated for reception on the associated virtual interfaces. .Pp -The 802.1Q and 802.1ad protocols include a priority field. -By default, the 802.1p priority in a transmitted packet is based on the +The 802.1Q and 802.1ad protocols include a Priority Code Point (PCP). +By default, the 802.1p PCP in a transmitted packet is based on the priority of packets sent over the interface, which may be altered via .Xr pf.conf 5 ; see the .Cm prio option for more information. -Alternatively, +Alternatively, the +.Xr ifconfig 4 .Cm txprio -can set a specific priority for transmitted packets. +option can set a specific priority for transmitted packets. On +.Nm vlan +and +.Nm svlan +interfaces priorities 2 to 7 will be mapped directly to PCP 2 to 7, but +priorities 0 and 1 are mapped backwards, to PCP 1 and 0. This is because +802.1p defines PCP 1 as lowest priority and PCP 0 as second lowest +priority, which is meant to be used as default +.Pq Dq best effort . .Pp .Nm vlan and
Re: explain priority codepoints and their mapping in vlan.4
Christopher Zimmermann wrote: > We are not doing it different. But in my mind especially the mapping > of PCP / prio 0 / 1 is not intuitive and may be confusing (but is > correct!). That's why I think this should be documented in detail. Right. > >> The 802.1Q and 802.1ad protocols include a 3-bit priority code point > >> (PCP): > >>PCP 1 is defined as the lowest priority (“background”) > >>PCP 0 is the default (“best effort”) - second lowest priority. > >>PCPs 2-7 are increasing priority above best effort. > >> The priority may be altered via pf.conf(5); see the prio option for > >> more > >> information. > >>“prio 0” is mapped to PCP 1. > >>“prio 1” is mapped to PCP 0. > >>“prio 2-7” are mapped to PCP 2-7. > >> Alternatively, the txprio property of an interface can set a specific > >> priority for transmitted packets. You say it twice. But my eyes still glazed over it, not seeing what was going on the first two times. Maybe something more like prio 0 and 1 are mapped out of order to PCP 1 and 0, but prio 2 to 7 are mapped directly to PCP 2 to 7. No that still doesn't quite capture it in a visible way. How about prio 2 to 7 are mapped directly to PCP 2 to 7, but prio 0 and 1 are mapped backwards, to PCP 1 and 0, because <...> Something which will draw the eye+brain to 'something is different here'. The table alone doesn't do that.
Re: explain priority codepoints and their mapping in vlan.4
On Tue, Dec 21, 2021 at 07:12:31AM +1000, David Gwynne wrote: are you able to find a reference for this in any of the current specs? or in documentation from other vendors? https://en.wikipedia.org/wiki/IEEE_P802.1p i've faithfully maintained this behaviour, but the only place i've seen in with my own eyes is in our code. if we're doing it different to literally everyone else, then maybe we shouldnt? We are not doing it different. But in my mind especially the mapping of PCP / prio 0 / 1 is not intuitive and may be confusing (but is correct!). That's why I think this should be documented in detail. On 21 Dec 2021, at 00:54, Christopher Zimmermann wrote: Hi, it might be helpful for others to understand the meaning of codepoints 0 and 1 of the vlan priority field. OK? Christopher Here is the formatted content: The 802.1Q and 802.1ad protocols include a 3-bit priority code point (PCP): PCP 1 is defined as the lowest priority (“background”) PCP 0 is the default (“best effort”) - second lowest priority. PCPs 2-7 are increasing priority above best effort. The priority may be altered via pf.conf(5); see the prio option for more information. “prio 0” is mapped to PCP 1. “prio 1” is mapped to PCP 0. “prio 2-7” are mapped to PCP 2-7. Alternatively, the txprio property of an interface can set a specific priority for transmitted packets. And here's the diff: Index: vlan.4 === RCS file: /cvs/src/share/man/man4/vlan.4,v retrieving revision 1.51 diff -u -p -r1.51 vlan.4 --- vlan.4 4 Oct 2020 12:44:49 - 1.51 +++ vlan.4 20 Dec 2021 14:51:31 - @@ -83,16 +83,38 @@ interfaces by their respective protocol identifiers, and decapsulated for reception on the associated virtual interfaces. .Pp -The 802.1Q and 802.1ad protocols include a priority field. -By default, the 802.1p priority in a transmitted packet is based on the -priority of packets sent over the interface, which may -be altered via +The 802.1Q and 802.1ad protocols include a 3-bit priority code point +(PCP): +.Bl -item -compact -offset MMM +.It +PCP 1 is defined as the lowest priority +.Pq Dq background +.It +PCP 0 is the default +.Pq Dq best effort +- second lowest priority. +.It +PCPs 2-7 are increasing priority above best effort. +.El +The priority may be altered via .Xr pf.conf 5 ; see the .Cm prio option for more information. -Alternatively, +.Bl -item -compact -offset MMM +.It +.Dq prio 0 +is mapped to PCP 1. +.It +.Dq prio 1 +is mapped to PCP 0. +.It +.Dq prio 2-7 +are mapped to PCP 2-7. +.El +Alternatively, the .Cm txprio +property of an interface can set a specific priority for transmitted packets. .Pp .Nm vlan -- http://gmerlin.de OpenPGP: http://gmerlin.de/christopher.pub CB07 DA40 B0B6 571D 35E2 0DEF 87E2 92A7 13E5 DEE1
Re: explain priority codepoints and their mapping in vlan.4
are you able to find a reference for this in any of the current specs? or in documentation from other vendors? i've faithfully maintained this behaviour, but the only place i've seen in with my own eyes is in our code. if we're doing it different to literally everyone else, then maybe we shouldnt? > On 21 Dec 2021, at 00:54, Christopher Zimmermann wrote: > > Hi, > > it might be helpful for others to understand the meaning of codepoints 0 and > 1 of the vlan priority field. OK? > > Christopher > > Here is the formatted content: > > The 802.1Q and 802.1ad protocols include a 3-bit priority code point > (PCP): >PCP 1 is defined as the lowest priority (“background”) >PCP 0 is the default (“best effort”) - second lowest priority. >PCPs 2-7 are increasing priority above best effort. > The priority may be altered via pf.conf(5); see the prio option for more > information. >“prio 0” is mapped to PCP 1. >“prio 1” is mapped to PCP 0. >“prio 2-7” are mapped to PCP 2-7. > Alternatively, the txprio property of an interface can set a specific > priority for transmitted packets. > > > And here's the diff: > > Index: vlan.4 > === > RCS file: /cvs/src/share/man/man4/vlan.4,v > retrieving revision 1.51 > diff -u -p -r1.51 vlan.4 > --- vlan.44 Oct 2020 12:44:49 - 1.51 > +++ vlan.420 Dec 2021 14:51:31 - > @@ -83,16 +83,38 @@ interfaces by their respective protocol identifiers, and > decapsulated for reception on the associated virtual > interfaces. > .Pp > -The 802.1Q and 802.1ad protocols include a priority field. > -By default, the 802.1p priority in a transmitted packet is based on the > -priority of packets sent over the interface, which may > -be altered via > +The 802.1Q and 802.1ad protocols include a 3-bit priority code point > +(PCP): > +.Bl -item -compact -offset MMM > +.It > +PCP 1 is defined as the lowest priority > +.Pq Dq background > +.It > +PCP 0 is the default > +.Pq Dq best effort > +- second lowest priority. > +.It > +PCPs 2-7 are increasing priority above best effort. > +.El > +The priority may be altered via > .Xr pf.conf 5 ; > see the > .Cm prio > option for more information. > -Alternatively, > +.Bl -item -compact -offset MMM > +.It > +.Dq prio 0 > +is mapped to PCP 1. > +.It > +.Dq prio 1 > +is mapped to PCP 0. > +.It > +.Dq prio 2-7 > +are mapped to PCP 2-7. > +.El > +Alternatively, the > .Cm txprio > +property of an interface > can set a specific priority for transmitted packets. > .Pp > .Nm vlan >
explain priority codepoints and their mapping in vlan.4
Hi, it might be helpful for others to understand the meaning of codepoints 0 and 1 of the vlan priority field. OK? Christopher Here is the formatted content: The 802.1Q and 802.1ad protocols include a 3-bit priority code point (PCP): PCP 1 is defined as the lowest priority (“background”) PCP 0 is the default (“best effort”) - second lowest priority. PCPs 2-7 are increasing priority above best effort. The priority may be altered via pf.conf(5); see the prio option for more information. “prio 0” is mapped to PCP 1. “prio 1” is mapped to PCP 0. “prio 2-7” are mapped to PCP 2-7. Alternatively, the txprio property of an interface can set a specific priority for transmitted packets. And here's the diff: Index: vlan.4 === RCS file: /cvs/src/share/man/man4/vlan.4,v retrieving revision 1.51 diff -u -p -r1.51 vlan.4 --- vlan.4 4 Oct 2020 12:44:49 - 1.51 +++ vlan.4 20 Dec 2021 14:51:31 - @@ -83,16 +83,38 @@ interfaces by their respective protocol identifiers, and decapsulated for reception on the associated virtual interfaces. .Pp -The 802.1Q and 802.1ad protocols include a priority field. -By default, the 802.1p priority in a transmitted packet is based on the -priority of packets sent over the interface, which may -be altered via +The 802.1Q and 802.1ad protocols include a 3-bit priority code point +(PCP): +.Bl -item -compact -offset MMM +.It +PCP 1 is defined as the lowest priority +.Pq Dq background +.It +PCP 0 is the default +.Pq Dq best effort +- second lowest priority. +.It +PCPs 2-7 are increasing priority above best effort. +.El +The priority may be altered via .Xr pf.conf 5 ; see the .Cm prio option for more information. -Alternatively, +.Bl -item -compact -offset MMM +.It +.Dq prio 0 +is mapped to PCP 1. +.It +.Dq prio 1 +is mapped to PCP 0. +.It +.Dq prio 2-7 +are mapped to PCP 2-7. +.El +Alternatively, the .Cm txprio +property of an interface can set a specific priority for transmitted packets. .Pp .Nm vlan
