On 2/6/14, 10:50 PM, Teco Boot wrote:
> 
> Op 6 feb. 2014, om 20:39 heeft Brian E Carpenter 
> <[email protected]> het volgende geschreven:
> 
>> On 06/02/2014 20:46, Mikael Abrahamsson wrote:
>>> On Thu, 6 Feb 2014, Brian E Carpenter wrote:
>>>
>>>> We designed diffserv for this purpose and it works well and is quite
>>>> widely used in corporate networks. Wasting prefixes to distinguish
>>>> traffic types is an incredibly bad idea.
>>>
>>> Problem with DSCP is that you have to reset them for a non-qos service
>>> in your network (unless you're running some kind of encapsulation scheme
>>> such as tunnels or MPLS).
>>
>> Sorry, what, why? DSCP is a no-op for a router that doesn't
>> implement diffserv, so why would you ever need to reset them?
>> (It's normal for border routers to clear the DSCP if they want to,
>> of course; no harm, no foul.)
> 
> No harm? Hmm. Two edge networks are connected via backbone and try to use end 
> to end QoS. It is not unusual to add a tunnel, just to protect against DSCP 
> rewrites.

if you include the DSCP in your hash algorithm really funny things
happen when providers that set them differently on different parts of
the same flows (e.g. prioritizing syn/ack) fail to sanitize them at
their border. there's a lot of pollution in DSCP which means you really
should sanitize them before you employ those bits.

> Teco
> 
> 
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