[Cake] diffserv based on firewall mark
ching lu
lsching17 at gmail.com
Wed Oct 12 20:08:44 EDT 2016
2016年10月12日 下午9:07，"moeller0" <moeller0 at gmx.de>寫道：
>
> Hi Ching,
>
> > On Oct 12, 2016, at 14:40 , ching lu <lsching17 at gmail.com> wrote:
> >
> > There is no need for cleansing dscp for wan ingress, I think it is
unnecessary, too
> >
> > In https://www.bufferbloat.net/projects/codel/wiki/Cake/
> >
> > There is a statement:
> >
> > “The only way we know how to “fix” bittorrent is to classify it
somewhat, somehow, as “background”."
>
> Which was true at the time. In the mean time cake grew new
“isolation” modes that will attempt to provide on a first level
per-(internal)-IP-address fairness and iside each internal IP-address
“band” also per-flow fairness. This should allow to restrict the bad effect
of bit-torrent traffic on the machine actually running the torrent client.
Which seems like a goos compromise since most torrent clients allow
configurations to alleviate the issue somewhat for that specific machine
(like bandwidth limits). These additional modes do require a bit of testing
and especially on ingress they will not be 100% robust (too many in-rushing
bit-torrent connections might cause buffers upstream of the cake-managed
link to fill and cause increased latency), but that just comes with
instantiating a shaper on the wrong end of the real bottleneck. As a
sidenote the more bandwidth difference exist between real bottleneck and
the artifical cake-managed bottleneck the better ingress shaping will work…
>
>
This is very interesting feature
> >
> > But in fact, there is no simply way to classify bittorrent INGRESS
traffic
>
> Yes, and no…
>
> >
> > DSCP -> unreliable, easily spoofed by attacker, and the value is most
likely 0x0\
>
> Well, if BT clients would mark CS1/BK that would be a decent 1st
step, except that will also tell ISPs which packets to drop first… (which
might be actually in the users interest)
>
> > firewall mark -> cake do not use firewall mark/connmark
>
> If you can firewall mark you can also re-map dscp… But I believe
the real issue is that bit-torrent was designed to have no clear
unambiguous signature so figuring out which packets belong to bit-torrent
flows is the tricky bit…
>
You may be able to detect your bittorrent client's connection by iptables
(e.g. restrict its port range, or use DSCP for outgress).
After the connmark is set, it can be reused by tc filter, for both
ingress/outgress traffic
for windows update traffic, I do not know how to classify it yet
> >
> > Finally, I guess most likely home users will use bit torrent.
>
> But that is a guess? Numbers/real data would be better; that said
with even windows update allowing peer-to-peer distribution of updates
bit-torrent-like traffic probably is something most home-users will see
occasionally.
>
> Best Regards
> Sebastian
>
>
> >
> > 2016年10月12日 下午8:04，"moeller0" <moeller0 at gmx.de>寫道：
> > Hi Ching?
> >
> > > On Oct 12, 2016, at 12:17 , ching lu <lsching17 at gmail.com> wrote:
> > >
> > >
> > > 2016年10月12日 下午6:05，"moeller0" <moeller0 at gmx.de>寫道：
> > > >
> > > > Hi Ching,
> > > >
> > > > > On Oct 12, 2016, at 11:35 , ching lu <lsching17 at gmail.com> wrote:
> > > > >
> > > > > How to archive "cake follows iptables"? is it “wan ingress ->
iptables
> > > >
> > > > Yes.
> > > >
> > > > > -> wifi egress/LAN egress -> ifb egress -> cake”?
> > > >
> > > > Except that if you instantiate cake on the interface
connecting to the outers LAN/WLAN side (lets call this LAN for short), cake
will reside on that interfaces egress and hence you require no ifb for
traffic coming in from the internet (as a plus cake will even without the
fancy new deNAT options see the full intrnal IP addresses, useful for dual
and triple isolation options). In the direction facing the internet you can
instantiate cake on an ifb interface for LAN and then put the iptables DSCP
cleaner on the WAN egress side (and the WAN ingress side, unless you trust
your ISP to deliver reasonable DSCP values, which should be like never*)
> > >
> > > The bandwidth shaper won’t work correctly if cake(s) are registered
on multiple LAN interface, ifb is necessary
> > >
> > > e.g. if ingress bandwidth limit is 100M, then setting 50M on wifi,
and 50M on LAN ?
> >
> > Yes that seems true, if you instantiate cake on br-lan (which I
believe would be the relevant interface) you will shape both wireless and
wired traffic, but most likely also internal traffic… But that can be
solved by one more router/AP ;)
> >
> > >
> > > I think the diffserv support of cake model is not suitable for home
network currently.
> >
> > I have no real opinion on that, but could you explicitly state
what short coming you see that is a showstopper? DSCP cleaning on ingress
is BTW not really required to happen before cake, as long as cake is set to
besteffort it will ignore DSCP markings anyway, and if you want to
re-map/re-classify packets vie DSCP on ingress you are pretty much out of
scope for a typical home network. Cleaning up on egress, as to not leak
internal configuration to the upstream seems indeed sub-optimal, but cake
is not alone in that regard…
> >
> > > The setup is much more complex
> >
> > Well, DSCP setup is complex no matter how you slice and dice
it… but maybe you have an idea what a shaper (like cake) could/should do to
make this simpler?
> >
> > Best Regards
> > Sebastian
> >
> > >
> > >
> > >
> > > >
> > > > Best Regards
> > > > Sebastian
> > > >
> > > > 8) DSCP are only ever guranteed to be meaninful inside a dscp
domain, and in reality your home net is a different domain from the ISP’s.
It would have been nice if the DSCP field would have been separeted into 2
3bit fields, the first for the actual sender to request one of 8
differential classes and the other 3bits for the current domain to store
its actually used DSCP bits. I claim the 3 bits should be enough for
anybody ;)
> > > >
> > > >
> > > > >
> > > > >
> > > > > On Wed, Oct 12, 2016 at 5:10 PM, moeller0 <moeller0 at gmx.de> wrote:
> > > > >> Hi,
> > > > >>
> > > > >>
> > > > >>> On Oct 12, 2016, at 10:11 , ching lu <lsching17 at gmail.com>
wrote:
> > > > >>>
> > > > >>> For egress, setting DSCP field should work.
> > > > >>>
> > > > >>> iptables -> wan egress -> cake
> > > > >>>
> > > > >>> But is it possible to set DSCP to 0x0 after cake's
classification? i
> > > > >>> do not know how ISP handle non-zero DSCP, there seems to be no
> > > > >>> standard for this.
> > > > >>
> > > > >> Interestingly cake, at some point in the past offered
exactly that functionality, but it got removed due to added complexity with
very little practical applicability (and a potential layering violation,
but one could equally argue that the current layering is partly
sub-optimal/wrong and hence violating it to better reflect reality might be
acceptable). But current cake does not offer this. If you are willing to
daisy-chain two routers, you could run cake on the respective egress
interfaces connecting both routers, and do the DSCP cleaning on the outer
router’s egress interface toward the internet…
> > > > >>
> > > > >>>
> > > > >>>
> > > > >>> For ingress, DSCP field may not be set by network peer at all,
and i
> > > > >>> have multiple LAN interfaces
> > > > >>>
> > > > >>> AFAIK, the order is "wan ingress -> ifb egress -> cake ->
iptables"
> > > > >>>
> > > > >>> The trick of setting DSCP by iptables do not work because cake
comes first
> > > > >>
> > > > >> Hence Jonathan’s recommendation to make sure that cake
follows iptables, by setting it up on egress interfaces only…
> > > > >>
> > > > >> Best Regards
> > > > >> Sebastian
> > > > >>
> > > > >>>
> > > > >>> On Wed, Oct 12, 2016 at 3:26 PM, Jonathan Morton <
chromatix99 at gmail.com> wrote:
> > > > >>>>
> > > > >>>>> On 12 Oct, 2016, at 08:52, ching lu <lsching17 at gmail.com>
wrote:
> > > > >>>>>
> > > > >>>>> I deprioritize bittorrent traffic by marking related
connections in
> > > > >>>>> iptables (e.g. detect by port number) and route them to
corresponding
> > > > >>>>> HTB class and qdisc.
> > > > >>>>>
> > > > >>>>> How can i archive the same goal using the cake qdisc?
> > > > >>>>
> > > > >>>> Modify your iptables rules to set the DSCP rather than a
kernel-internal mark. You probably want "-j DSCP —set-dscp-class CS1”, as
CS1 is the “bulk low priority” code. Cake’s default Diffserv mode will
pick that up appropriately.
> > > > >>>>
> > > > >>>> You also need to make sure Cake sees your packets *after*
they’ve been through the firewall, which generally means attaching it to
the egress port in each direction, not the ingress port. You’ve probably
already done this, if you’re happy with your HTB setup.
> > > > >>>>
> > > > >>>> If you have multiple LAN interfaces (eg, both Ethernet and
wifi), you should loop the inbound traffic through a common IFB device (and
attach Cake to that instead of the physical interfaces) to simplify
configuration.
> > > > >>>>
> > > > >>>> - Jonathan Morton
> > > > >>>>
> > > > >>> _______________________________________________
> > > > >>> Cake mailing list
> > > > >>> Cake at lists.bufferbloat.net
> > > > >>> https://lists.bufferbloat.net/listinfo/cake
> > > > >>
> > > >
> > >
> >
>
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