[LARTC] Backlog with less rate than defined

[Andy Furniss]

Luciano wrote:
> Hi all,
> 
> I setup a Linux machine to act as Lan Authentication server. So, the
> same script that redirect the http connection to a login web page, it
> create some queues to limit traffic, login by login. 
> 
> The PC uses only 1 ethernet interface that receive the packets source
> routed to it and forward/nat to the external gateway using the same
> interface.
> 
> For each login I create a queue like that:
> 
> tc class add dev '.$if_externa.' parent 1:1 classid 1:'.$filaDown.' htb
> rate '.$banda_down.'kbit ceil 	'.$banda_down.'kbit prio 1'
> tc filter add dev $if_externa protocol ip parent 1:0 prio 1 handle
> ::$filaDown u32 match ip dst $ipcliente/32 flowid 	1:$filaDown
> 
> My problem is that most of the queues created does NOT get full rate as
> defined. I can see the packets entering backlog with much less rate than
> defined, ex:
> 
> class htb 1:b1 parent 1:1 prio 1 rate 256Kbit ceil 256Kbit burst 1926b
> cburst 1926b
>  Sent 6644151 bytes 5435 pkts (dropped 0, overlimits 0)
>  rate 669bps backlog 107p

Htb rate average can be quite long and misleading.

I would tcpdump and see whether the rate looks OK with that.

If not see what the dequeue behaviour is - you don't show all your 
rules, if you are using htb default class on root and shaping eth 
remember arp will get delayed there unless you filter it elsewhere.

Andy.