Frequently Asked Technical Questions about Allworx
Allworx Quality of Service (QoS) FAQ's
- What are the Quality of Service (QoS) features for the Allworx systems?
- Does the Allworx family of products support Quality of Service (QoS)?
- How does the Allworx family of products mark/tag voice related packets?
- How much bandwidth is required per VoIP call?
- Which codecs are supported within the Allworx family of products?
- Why is call audio that is sent over the Internet sounds choppy at the other end?
| What are the Quality of Service (QoS) features for the Allworx systems? |
QoS features present in the Allworx product line (6x, 10x, 24x, 9102 and 9112)
- VLAN (with priority) support in phones.
- DiffServ tagging of all voice traffic: value 2E.
- Call Admission Control on a per-proxy and overall PBX basis.
- priority handling of voice vs. data on LAN-to-WAN passage.
If you are setting up QoS in a third party router the simplest way is to filter on DiffServ values. All voip traffic from the PBX and phones uses a value of "2E", DSCP "46".
If you must use ports then UDP:5060 for SIP and range UDP: 16384 thru 32768 are used for RTP audio should get you by. Other ports are used for boot time downloads and BLF message activity and shouldn't affect call quality.
| Does the Allworx family of products support QoS? |
Yes.
• Priority passage of RTP audio from LAN-to-WAN
• Ability to set call limits on a server-wide and per-proxy basis
• Ability to specify jitter buffer settings on 9102/9112 handsets
• Ability to specify codec for inbound/outbound calls on 9102/9112 handsets
• Support of traffic segmentation using VLAN in 9102/9112 handsets.
• Support of CoS within VLAN frame headers in 9102/9112 handsets.
• Support of packet tagging for all VoIP traffic.
| How does the Allworx family of products mark/tag voice related packets? |
• Equipment screening the DSCP field would recognize a value of “2E”.
• Equipment screening the ToS byte would recognize this as Priority value of “1”.
• CoS bits within the 802.3 Q/P header (VLAN) can be set in the Allworx phones to 9102/9112 phones
| How much bandwidth is required per VoIP call? |
90kbps or 35kbps of bi-directional bandwidth depending the codec being used on the call.
- Refer to the Allworx VoIP White Paper for more details.
| Which codecs are supported within the Allworx family of products? |
G711 and G729a.
- Refer to the Allworx VoIP White Paper for more details.
| Why is call audio that is sent over the Internet sounds choppy at the other end? |
Poor voice quality is typically a result of packet loss or jitter.
• Packets can be dropped or discarded at any point along its path of travel. The most common point of discard is at the Cable/DSL modem or T1 router. This is known as egress blocking.
• Jitter is the variable delay between packets; if packets are delayed too much they are not available when needed by the receiving handset for audio play out.
