Re: [Cerowrt-devel] Build instructions for regular OpenWRT with Ceropackages

[David Lang <david@lang.hm>]

On Tue, 30 Jun 2015, Mikael Abrahamsson wrote:

> On Tue, 30 Jun 2015, dpreed@reed.com wrote:
>
>> What happens if the SoC ports aren't saturated, but the link is GigE? That 
>> is, suppose this is an access link to a GigE home or office LAN with wired 
>> servers?
>
> As far as I can tell, the device looks like this:
>
> wifi2------
> wifi1----\|
> 	SOC2 6-|
> 	SOC1 5-|
> 	WAN  4-|
> 	LAN1 3-| (switch)
> 	LAN2 2-|
> 	LAN3 1-|
> 	LAN4 0-|
>
> LAN1-4 and SOC2 is in one vlan, and SOC1 and WAN is in a second vlan. This 
> basically means there is no way to get traffic into SOC1 that goes out SOC2 
> that will saturate either port, because they're both gige. Only way to 
> saturate the SOC port would be if the SOC itself "created" traffic, for 
> instance by being a fileserver, or if there is significant traffic on the 
> wifi (which has PCI-E connectivity).
>
> So it's impossible to congest SOC1 or SOC2 (egress) by running traffic 
> LAN<->WAN alone.

not true, the switch doesn't give any way for traffic to get from one vlan to 
the other one, so if you have gig-e connections on both sides, the traffic going 
from one to the other will have to go through the soc, so if there is more than 
1Gb of traffic in either direction the interface will be saturated.

The problem is if you have a slower connection, the bottleneck is in the switch 
not the soc. you may be able to set the soc-switch interface to 100Mb (make sure 
you have access through another interface in case you cut yourself off) and that 
would make the soc see the queue directly.

David Lang