Quality of Service (QoS) -- NBN Services/Connections Print

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The National Broadband Network (NBN) has created some very interesting challenges for users switching to its services, especially as it relates to connecting to third-party voice services providers such as us Digital Hybrid and our hosted PBX services.

New NBN users across Australia report a loss of registration to voice servers, voice data not flowing normally, if at all, and general instability with their handsets and voice service.

NBN Co have published, but not made obvious, the incredibly tight restrictions placed on voice data packets and how they must be dealt with on when connected to the NBN.

As a result, we have taken steps to compile this guide to help you avoid the almost-certain pain you will experience if and when you switch to using the NBN while continuing to use our hosted PBX services.


NBN Specifications for Voice Traffic

For VoIP class traffic, the NBN only recognises DSCP markings of (decimal) 40 to 47, and will drop any unrecognised voice packets with a DSCP marking outside that accepted range, rather than routing them as generic traffic.

We've provided the current NBN specifications guide HERE.

Specifically note section 4.8 Priority Encoding on pages 21 and 22, as this clearly outlines the requirements and what action the NBN will take with incorrectly marked voice data packets.


Getting it Right

Our tests reveal that a DSCP marking of (decimal) 40 does not work as well as a DSCP marking of (decimal) 46.

Therefore, all recommendations that follow in this guide will use (decimal) 46, which translates to DSCP markings of:

  • EF, priority 5
  • TOS 0xb0


Cisco SPA-range Handsets

The Cisco SPA range of handsets are extremely intelligent and include on-board NAT and QoS/TOS capbilities. It's for this and many other reasons we strongly recommend their use with our voice services.

By default, the handsets will mark all voice packets leaving them, even if QoS rules are not in place on your router.

The default DSCP marking for these handsets is 0x68 for SIP and 0xb8 for RTP.

This translates to SIP packets being marked (decimal) 40 and RTP packets being marked (decimal) 46.

Based on our tests as outlined above, this means that SIP traffic will still experience problems is the TOS DSCP marking is not updated.

The following changes must now be made on these handsets' Extension or Line tabs, to make them NBN-compliant:

  • SIP TOS/DiffServ Value: 0xb8
  • RTP TOS/DiffServ Value: 0xb8

This change is now included in our Cisco SPA-Range configuration guide HERE.


Siemens Gigasets

we've updated the configuration guide for the cordless Siemens Gigasets to include a change that will assist their behaviour and performance when connected to us via the NBN.

You will find the guide HERE.

The NBN-related setting to pay attention to is:

  • Outbound Proxy Mode: Auto
  • Outbound Proxy: proxy.ezytel.net.au
  • Outbound Proxy: Port 5070


Router-Level QoS

The simplest illustration of the QoS rules we recommend for use with the NBN is to show you an example screenshot of the rules currently in place on a customer's Billion BiPac router.

You should match your router's QoS settings to match the equivalent of those in the screenshot:

These settings will not only give you the best overall results, but will also make you NBN-compliant.


For Your Reference

We've made a DSCP TOS CoS Precedence Conversion Chart available that we hope will be beneficial in helping you understand DSCP markings and how they're prioritised by your router.

You will find the chart HERE.



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