[AusNOG] Telstra NBN - DSCP Filtering

[Matt Carter]

Coming in a bit late but this is most certainly the expected behaviour for a DSCP mapped service…


·         A default mapped service will remark all non-compliant ingress frames to DSCP BE at the NTD.

·         A DSCP mapped service will drop all non-compliant ingress frames at the NTD

That is, on a DSCP mapped service, DSCP 46-48 is mapped to Traffic Class TC-1 and DSCP 0 is mapped to Traffic class TC-4, everything else that cannot be 1:1 mapped is dropped on the floor. (as per the NEBS technical specification) Remember at the head end TC-1 is coming into the BNG with S/C-TAG (Inner&Outer Vlan) CoS of 5 on top of the DSCP marking and that TC-1 is a priority class within TC-4 which costs money, so it is unsurprising to me that TC-1 ends up at Telstra’s Voice product and it can’t  be used for other purposes. (Do you even have TC-1 provisioned?)
At the end of the day, all we’re talking about here is ye old LLQ at the CPE and the DSCP simply allows traffic to be aligned to the correct policer class inside NBNco such that it is offered a different rate (Eg DSCP 46-48 = TC-1 = 150Kbps) but  from a traffic management point of view if you ingress to the NTD at a rate that exceeds the subscribed rate you will get drops on both traffic classes, it is ultimately the responsibility of the CPE to ensure any egress traffic is shaped accordingly and that TC-1 is prioritised above TC-4 such that TC-1 is lossless when the AVC is contended with TC-1 and TC-4.

Interesting to see there’s no NBNCo voice on this list??

From: AusNOG [mailto:ausnog-bounces at lists.ausnog.net] On Behalf Of Greg Lipschitz
Sent: Friday, 7 August 2015 4:23 PM
To: Dino Sosic; ausnog at lists.ausnog.net<mailto:ausnog at lists.ausnog.net>
Subject: Re: [AusNOG] Telstra NBN - DSCP Filtering

Yep, seen this one before and I believe I posted about it here previously.

Telstra are only allowing EF towards their SIP servers, thus avoiding to have to pay for the UNI-D ports and COS1 NBN traffic.
Then they’re selling a Netgear Router with a VoIP ATA Built in and essentially forcing customers to use Telstra for calls rather than another VoIP provider.

We got around this by using a non-Telstra router and re-writing the packets as they hit the router (from EF to BE) so that it would flow.

Cheers,

Greg



Greg Lipschitz | Director | The Summit Group

E: Greg at thesummitgroup.com.au<mailto:Greg at thesummitgroup.com.au> | W: www.thesummitgroup.com.au<http://www.thesummitgroup.com.au>

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From: AusNOG [mailto:ausnog-bounces at lists.ausnog.net] On Behalf Of Dino Sosic
Sent: Friday, 7 August 2015 2:02 PM
To: ausnog at lists.ausnog.net<mailto:ausnog at lists.ausnog.net>
Subject: [AusNOG] Telstra NBN - DSCP Filtering

Hi guys,

Something I discovered after an extensive tshooting. Telstra service on NBN ( TID Service ) actually drops all non 0 marked DSCP markings. They say it’s actually NBN doing that, but I do not see this on other providers. I had phones trying to register across the IPsec through that NBN, that were failing to do so as long as they were sending marked packets (phones mark it EF by default ). Once I remarked the voice traffic to DSCP 0(default), the SIP registered immediately. Some heavy traffic manipulation or what? ☺ So much for unhindered transport from A to B.
Interesting part was also, even though the voice traffic is inside the ESP packet, those packets get dropped, I am guessing due to size+DSCP marking copied to ESP packet. Anyone seen this before?

Dino
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