[j-nsp] CoS value of return traffic

[wojtas at wizja.net.pl]

So, asumming Your guess and the fact that router is preserving DSCP  
values in reflected packets one could do something like this:

Set firewall family inet filter FILTER1 term T1 from dscp XYZ;
Set firewall family inet filter FILTER1 term T1 then dscp XYZ;
Set firewall family inet filter FILTER1 term T2 then accept;

And this could set 802.1p bits to 3 most significant bits from DSCP  
XYZ. Please correct me if I am wrong.
Thanks

Wojtek

-----Original Message-----
From: juniper-nsp-bounces at puck.nether.net  
[mailto:juniper-nsp-bounces at puck.nether.net] On Behalf Of ext Danny  
Vernals
Sent: Wednesday, October 19, 2011 10:02 AM
Cc: Juniper-Nsp
Subject: Re: [j-nsp] CoS value of return traffic

On Tue, Oct 18, 2011 at 11:14 PM, Ben Dale <bdale at comlinx.com.au> wrote:
> Hi there,
>
> We are experiencing an issue caused by exactly this behaviour  
> (Control traffic from the RE being automatically marked as CoS 6),  
> and I think the current answer regarding changing the value is no.   
> We are currently getting around it by looping traffic back into the  
> MX80 (using physical ports) in order to strip 802.1p off transit  
> traffic, which is an expensive hack to say the least.
>

I haven't tested this on an MX80 but on a MX960 (both DPC + MPC,
running 10.4 irrc) if you use an egress lo0 firewall filter with a
term with "then dscp #": 802.1p will inherit the value of the 3 most
significant bits of the DSCP you have set.

> When I get some more time in the lab I'll try using lt interfaces to  
> do the same.
>
> Cheers,
>
> Ben
>
> On 18/10/2011, at 9:40 PM, wojtas at wizja.net.pl wrote:
>
>> Hello,
>> Is there a possibility to set the CoS (802.1p) value of return  
>> traffic from RE ?
>> I know that You can do it for, at least , DSCP using:
>> set class-of-service host-outbound traffic  
>> <dscp-code-point|forwarding-class)

I couldn't say definitively but if I had to guess I'd say this would
have the same effect as setting DSCP via egress firewall filter, i.e.
802.1p would inherit MSB values.

>> Each time I send UDP echo probes to MX80 with different CoS values  
>> , the router responds with the same pattern 100(binary). The best  
>> workaround in this case would be to set CoS values according to the  
>> particular DSCP (which is preserved in this case).
>> Thanks in advance for Your help!
>>
>>
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>
>
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