Re: [LARTC] Traffic shaping on multiple interfaces

[Alexandru Dragoi <alex@zoomnet.ro>]

Terry Baume wrote:
> I'm trying to setup traffic shaping on my linux gateway/router.
>
> The system has 3 interfaces:
> eth0 - My LAN - with IP address 192.168.0.254
> eth1 - The ethernet connection to which my ADSL modem is connected. 
> This has a 10.25.x.x IP, more on this later. The ADSL link has an 
> upstream of ~1.2mbit.
> ppp0 - The PPP connection which is my WAN connection, with a real 
> world IP.
>
> The system acts a router, performing NAT for my LAN. This works 
> perfectly, as does traffic shaping on ppp0 - I get very good results.
>
> The trouble is that my ISP allows me to user another service over my 
> ADSL line, as a bonus. Basically the modem has 2 virtual circuits, one 
> being for my WAN connection, and the other being a private network 
> between other users of the same ISP, on the same telephone exchange - 
> this is where the 10.25.x.x IP on eth1 comes from. To make things 
> clear, low latency on the eth1 interface is not important, this 
> interface is only used for file sharing and such. Latency on ppp0 is 
> obviously important, being my WAN connection.
>
> My IPTables rules provide NAT for both connections, the only thing I 
> cannot get working correctly is traffic shaping.
>
> So far, I have experimented with wondershaper, shaping on the ppp0 
> interface. This works well to keep latency down when traffic is on the 
> ppp0 interface. If there is traffic on eth1 (the 'private' network of 
> 10.25.x.x), with no traffic on the ppp0 interface, latency on ppp0 
> remains low, regardless of whether traffic shaping is active. I 
> believe this has something to do with the way my ISP has configured 
> priorities at the telephone exchange. I begin to run in to trouble 
> when I am uploading heavily on eth1 & ppp0 simultaneously. Once this 
> happens, ping times over ppp0 rise dramatically, to well over 1200ms 
> (normal is around 7ms). I have tried shaping on eth1 instead of ppp0 
> (as eth1 should contain all the packets for ppp0, I believe), but this 
> does not yield lower latency, though I did note that it did limit the 
> speed of the connection if I set the upstream and downstream values 
> absurdly low.
>
> I think what I need to do is somehow setup a script where traffic 
> directed to 10.25.0.0 on eth1 is somehow counted against the bandwidth 
> specified for ppp0, but I'm really not sure. Could someone offer some 
> advice?
>
> Thanks.
>
> I believe this is due to the fact that as outbound traffic is 
> occurring on both interfaces, tc does not worry about queues etc, as 
> it does not look as though ppp0 is being maxed out (ppp0 would only be 
> using roughly half of 1.2mbit), when the ADSL link itself is being 
> maxed out.
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