Updates using idle bandwidth

[Ralf Ertzinger]

Hi.

On Tue, 11 Mar 2008 22:15:47 -0500, Bruno Wolff III wrote:

> If you are talking about the qos flags in IP packets, the answer is
> no. There aren't that many states and generally you can only describe
> broad things about packets (such as I want low latency or I want high
> throughput) not detailed bandwidth allocations.

You can do bandwidth allocation based on QoS flags (with the newer DSCP
interpretation of the relevant IP header flags you get 64 possible traffic
classes, which is quite a lot).

> Also I tried a few
> experiments with testing qos bits and found that they seemed to be
> getting stripped (I expected them to be ignored, but that at least
> they would be preserved) in transit. I didn't do enough experiments
> to see where this was happening or to get a good idea of how common
> this was.

On the other hand QoS is very much an end-to-end process, which means
that all involved devices (as in: routers) have to agree on the QoS
policy (which DSCP flag signifies which traffic class, and what preference
this traffic gets). This is why it is does not work over the internet
as a whole. Your provider usually has a diffenent view on what constitutes
important traffic, and thus strips your classification (or does not strip
it but ignores it).