[kwlug-disc] [OT] QOS router

John Van Ostrand john at netdirect.ca
Mon Nov 1 15:40:00 EDT 2010

In Linux there are several queue disciplines to choose from. The normal one 
is a fifo. There are class based queues as well as bandwidth limiting ones. 
They can and usually are layered to achieve the desired result.

One may say that a certain type of packet has first priority but is limited 
to a certain bandwidth cap. This prevents one class from overwhelming 

----- Original Message -----
From: kwlug-disc-bounces at kwlug.org <kwlug-disc-bounces at kwlug.org>
To: KWLUG discussion <kwlug-disc at kwlug.org>
Sent: Mon Nov 01 14:30:52 2010
Subject: Re: [kwlug-disc] [OT] QOS router

On 10-11-01 11:19 AM, Jeff Welling wrote:

> QoS is a way of classifying packets, commonly done by looking at the
> DiffServ/TOS field in IP packets and grouping them together into
> different classes of service.  Packets are then pulled from the
> highest priority queue and are sent out over the line until that
> queue is empty, at which point it moves on to the next highest
> priority queue and repeats until the outbound speed limit is met or
> it runs out of packets to send.

I don't think it can be that simple.  If so, any incoming traffic on
Queue 1 would block all traffic in lower queues.

Another queue algorithm I'm familiar with (GW e-mail priority queues)
pulls stuff out of queues in the following order: 1, 1 2, 1 2 3, 1 2 3
4, 1, 1 2, 1 2 3, 1 2 3 4 (but for 8 queues).  This way queue 1 gets
serviced most frequently, but queue 4 (or queue 8) doesn't stagnate


Bob Jonkman<bjonkman at sobac.com>          http://sobac.com/sobac/
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