[Cake] New to cake. Some questions

Kevin Darbyshire-Bryant kevin at darbyshire-bryant.me.uk
Thu Jun 9 17:36:13 EDT 2016

On 09/06/16 21:58, Dennis Fedtke wrote:
> Hi
> Currently im running lede + cake + sqm_scripts and i have some questions:
> 1. What is considered the "optimal" setup atm for cake?
> e.g. which cake script should i use piece or layer cake?
Piece of cake doesn't use diffserv hence doesn't 'soft shape' traffic 
into bandwidth categories.  Layer cake uses DSCP to divide packets into 
relevant flow types and 'soft shape/limit' them.  Also do you mean 'at 
the moment' or do you mean 'ATM - Async Transfer Mode'?
> 2. Recently squash and wash was removed.
> But the sqm scripts were not updated. In the advanced options should i 
> set that the dcsp marks are kept?
On point 2: sqm-scripts was never actually updated to take advantage of 
the 'squash' (synonym for besteffort wash) or 'wash' option anyway.  It 
used and continues to use iptables rules to set DSCP marks to '0', in 
combination with 'besteffort' to get cake to ignore the DSCP codes.
> 3. Should i use advanced options in sqm scripts and set triple-isolate 
> + diffserv8 ?
There's almost certainly no point in going to 'diffserv8' - it is 
reliant on suitable DSCP markings to put traffic in each tin and I'd be 
gobsmacked if you had that many different DSCP markings in use. 
Triple-isolate is more interesting and needs a lot more testing...if we 
can ever work out how to test it :-)  Another potential problem is 
'where are you putting the cake qdisc?'  If you're putting this on a WAN 
interface of your standard NAT router, then it won't be seeing you're 
internal IP addresses anyway...all the traffic is coming from/going to 
your router's external Internet facing IP..it doesn't see the 
de-masqueraded addresses of your internal LAN.
> 4. Is it recommend to enable diffserv on ingress?
I guess it depends if you see different DSCP markings on your ingress 
traffic or if your ISP mangles them somehow anyway.  'tc -s qdisc show' 
would show if any packets have been placed in different tins.  I happen 
to use diffserv4 on ingress even though my ISP seems to mangle them 
anyway :-)
> 5. Is there still the udp packet dropping problem? e.g. games that are 
> using udp.
> If yes does it make sense to apply diffserv classes manually? How to 
> do this?
What udp packet problem?
> 6. is the autorate_ingress still under development?
> This very interesting feature. especially for docsis networks. Will it 
> be possible to set target ping time?
no idea
> 6. What difference does it make to set a different rtt?
> Setting lower rtt will reduce download speed i guess but will it allow 
> better ping times (because of lower downloadrate uh)?
> What happens if rtt is set way higher?
Don't mess with the rtt parameter unless you're on either extremely fast 
links 10gbit+ OR you have a high latency link (satellite)  If you really 
must know more lookup info on 'codel interval' and look at 
http://queue.acm.org/detail.cfm?id=2209336  CAKE uses codel for its flow 
queueing management.
> Thank you!
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