[e2e] Is RED dead?

John Kristoff jtk at northwestern.edu
Sun Oct 16 20:53:36 PDT 2005


On Mon, 17 Oct 2005 11:33:32 +0800 (CST)
Jing Shen <jshen_cad at yahoo.com.cn> wrote:

> > In my own experience with some Cisco gear, I suspect
> > a fair number of
> > people have WRED on a number of interfaces where
> > they have turned on
> > the QoS knobs for the box, primarily it seems as
> > part of a VoIP
> > roll-out.
> 
> That's may be the key reason for only EF class
> implemented in some enterprise networks. But, would
> WRED act with EF class traffic ?

No.  By default EF traffic will be put in a strict priority queue.
At least on the gear I've seen.  Note, other DiffServ codepoints are
often supported and enabled by default for some applications, such
as video.  However, I bet many if not most organizations are ignoring
those other codepoints or resetting them to best effort (CS-0).

Regardless of whether this is the right approach or not (it wipes out
scavenger, which is may not what you might want to do).

More specifically it seems that EF is supported and set by using a
packet filter to match on what looks like voice traffic (e.g. ef set,
UDP,  ports set to fit [x1-x1,y1-y2], IP src/dst) and everthing else
is remarked best effort if it isn't already.

> I'm not sure but to my experience I have to config
> packet dropping policy explicity with Cat6509. 

In versions I've used, once you set 'mls qos' globally, you get the
default queueing parameters as they are hard wired to the physical
interface (modules).

John


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