router questions

[Michael Butash]

Not in the modem, but likely in the router (the layer 3 ip router/nat 
here) itself to enable shaping to your given committed bandwidth rate 
(assuming it's stabe bw, this is dsl we're talking).

Most people don't ever do (or understand why), but shaping is pretty 
important when dealing with things like 40mbps rates on a gigabit 
interface.  Ethernet phy buffers presume your bandwidth == phy, ie. 
1gbps, but obviously your cable/dsl isn't quite yet. That's when their 
policers kick in, dropping your traffic when you send over the cir, 
knocking your bandwidth back so tcp will scale down (udp doesn't, why 
queuing is needed for voip).  If you shape the outbound to a given rate, 
ie. your 40mbps cir or whatever, then they never penalize you, and you 
get far more consistent bandwidth throughput rates.

Example - My cir with cox was 50mb, their "burst" was 60mbps.  If I 
tried to push 70, they'd penalize me, drop my cir down, protocols have 
to window down, bw drops to 30, starts working back up to 60, then 70, 
rinse/repeat.  My bandwidth tests would look like repeating steps and 
drop-off's.

Shaping plus the txqueuelen took all jerkiness out of my bandwidth 
tests, and just pegs at the cox "burst" rate now constantly without 
drop-offs.

Look at tuning your txqueuelen on the box too, setting it much lower.  I 
set mine to 32 on my ddwrt box.  This way small packets don't stay in 
buffer waiting to fill long,  Suggest the same with host system 
txqueuelen too, especially if gaming and such.

Search the tubes for "buffer bloat linux networking" for more details.

-mb


On 11/08/2015 12:25 PM, David Schwartz wrote:
> I’ve just moved and re-established my CenturyLink DSL internet account.
>
> I’ve got a C1000A modem, which hasn’t got very good WiFi in it. (They also sent me a newer one, which is also last-generation tech.)
>
> A few months back I got an ASUS TM-AC1900 router from T-Mobile that supports 1900-AC WiFi, which is good because my MacBook Pro also runs AC WiFi.
>
> I disabled the WiFi in the C1000A and plugged the ASUS modem into it via cable.
>
> The ASUS modem is only used for WiFi, not wired connections, while the C1000A has two devices plugged into the wired connections and the radio is disabled.
>
> Everything is working fine.
>
> My question is this: are there any settings in either of the modems that I can enable or (more likely) disable to improve the through-put with these two devices chained together like this?
>
> -David Schwartz
>
>
>
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