I've been dealing with occassional one-way audio dropouts for a couple years now. Our ISP blames our gateway (Sophos) and vice versa. Now I'm beginning to think it's been the switch all this time.
But now I'm thinking: If Auto-VOIP (OUI Based) is putting the phones on VLAN 4088, but VLAN 4088 doesn't have COS Override Mode enabled, is it doing anything? The phones don't have DSCP set up, and SIP, RTP, and RTCP Priorities are set to 0, so maybe the traffic isn't getting tagged for priority treatment at all? Is that posssible, or does Auto-VOIP and VoiceVLAN give priority to voice traffic regardless what the COS setting is.
In short: should I enable CoS Override Mode on all my phone ports so VLAN 4088 actually gets prioritized?
Thanks,
Jeff
Model: GS752TPv2|48-Port Gigabit Ethernet PoE+ Smart Managed Pro Switch with 4 SFP Ports (380W)
Similarly, should I set a DSCP Value of 46 in my voice VLAN Configuration page to ensure the traffic is prioritized?
Hopefully someone out there sees these ... the Netgear documentation is great at explaining HOW to do things but not so much about WHY you would want to (or not).
Don't mix up L2 QoS fetaures like the CoS tag, defining the queue the frames are handled within the switch and between switches) and the L3 QoS features like DSCP tag which is used as part of the routing process. permitting your router, the Internet provider does allow passing to the VoIP provider, and the VoIP provider taking care of.
It's definitivley not wrong to enable amd configure the CoS override, eg. in case the the VoIP devices are not configured to add these. While adding slightly more load to the switch, it makes it much easier for the management. This allows to send the VoIP traffic to the higher prio queue on the switching core, and the next L2 hop switch, which can bring some advantage over the normal prio L2 network traffic.
So, practically speaking, does that mean that in this example:
... voice traffic from the phone on Interface g36 will be assigned a DSCP value of 46, which according to this table
-- will set its queue at 2, which gives it a higher priority ("Expedited Forwarding")? Would I have to explicitly ensure that VLAN 4088 is also expedited at each node (eg on the links connecting the switch to the router and any switches between them)? Or, once it's marked as "Expedited" all equipment along the path will read this and will give it priority? In short: should I set DSCP to 46 for VLAN 4088 on the uplink ports?
Also, and I right in thinking I should also set the interface trust mode to DSCP since that's what I'm using to shape the traffic?
I'm trying to make sure that my settings are actually accomplishing what I think they are ... to prioritize voice traffic.
