Setup VoIP Outside of QOS for Best Call Quality

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DD-WRT Novice

Joined: 29 Jul 2015
Posts: 2

PostPosted: Wed Jul 29, 2015 16:00    Post subject: Setup VoIP Outside of QOS for Best Call Quality Reply with quote
The Background:

I work for an eCommerce company that receives a large number of phone calls at our office on a daily basis.

We have about 25 computers and 20 VoIP phones connected to two unmanaged switches that are then connected to ports 1 & 2 of a Buffalo Router running "DD-WRT v24SP2-MULTI (09/27/12) std".

All devices have static IP addresses reserved and delivered via DHCP.

When planning for maximum possible bandwidth usage of the VoIP phones, I assumed at most 2 consecutive calls per device (40 max consecutive calls at any given time). It is very rare that this maximum ever gets reached, so it's a safe estimate for me to use.

Our VoIP systems are hosted through a 3rd party (Vonage Business - Previously Vocalocity), and they provide, on their website, a list of services used by the phone and their respective port ranges, as well as a formula for calculating the amount of bandwidth usage needed for optimum call quality per each call.

Using their formula I came up with 3.4Mbps needed for 40 consecutive calls at maximum call quality.

We are connected to a fiber-optic line from our ISP and have a dedicated 10Mbps up & 10Mbps down (this is set at the power company). I've consistently confirmed these numbers using and watching the WAN traffic numbers in the bandwidth graph of DD-WRT.

One additional bit of information. All of our computer traffic running through Ports 80 & 443 route through an internal proxy server, then to our router, and on to the internet. All port 80 traffic is cached on this proxy server (freeing up much of our available WAN bandwidth for use by other traffic).

The Setup:

Top priority for us is VoIP (sip & rtp), followed by SVN (for our web development team).

So I first made the following calculations -

  1. I took 95% of both up and down limits provided by our ISP (10,000Kbps x .95 = 9500Kbps).
  2. I then subtracted the total bandwidth needed for maximum call quality (using our very conservative number of consecutive calls) from the number in my first calculation. (9500Kbps - 3400Kbps = 6100Kbps).

Using those calculations I then configured QOS as follows -

QOS Settings
  • Port: WAN
  • Packet Scheduler: HTB
  • Uplink: 6100
  • Downlink: 6100

Services Priority
  • Bulk: Youtube, Dropbox, iTunes, Facebook, Bittorent, PDF, Skype, Twitter
  • Express: Subversion, DNS
  • Exempt: Sip, Rtp (both as custom services on the ports supplied by our VoIP provider)

No other QOS settings are configured.

The Question:

Everything I've read on the subject always says to set Uplink & Downlink at 80%-90% of the actual speeds from our ISP, then to set the Sip & Rtp services to Premium or Express.

It wasn't working well for us, so instead I allocated maximum bandwidth for use by all router traffic at an amount minus what we need for VoIP and set Sip & Rtp services to be exempt from those bandwidth limits. (Essentially allocating, at minimum, 3.4Mbps to VoIP).

I don't see this as being a feasible solution if setup in the same way for other services that have the potential to utilize our total maximum bandwidth. But because our VoIP setup would never utilize our total maximum bandwidth, we can bet there will always be available bandwidth for all other traffic running under QOS, and we can then shape their traffic priorities separate from VoIP.

So, are there any issues with setting it up in this way?

It seems to have fixed all of our VoIP issues. No more dropped calls, and no complaints of trouble hearing or voice breaking up.

Are there any other areas in which this particular setup may cause problems?

I worry because if this is a valid working configuration, why do I not find anyone else suggesting to set it up in this way? Rather they always suggest including the VoIP services under the umbrella of QOS limits.
DD-WRT Novice

Joined: 29 Jul 2015
Posts: 2

PostPosted: Thu Sep 17, 2015 14:28    Post subject: Reply with quote
No thoughts or advice on this?
Fried Chicken

Joined: 12 Jun 2019
Posts: 54

PostPosted: Wed Aug 21, 2019 7:13    Post subject: Reply with quote
You don't get much help in the advanced routing section...

I'm currently trying to set up QOS on my router for VOIP, but I'm not even sure I need it.

I have a gigabit internet connection from which I can peak around 750/50 due to my modem.

That being said, I rarely maximize bandwidth, but I do need low latency for cs:go and VOIP. I was getting ping problems in cs:go that disappeared when I set up QOS, but again, badniwdth was never the issue. QOS must have done something.

For VOIP I'm not even sure what service to use or what flags to target. Now that I think about it I could prioritize my voip modem, but again, bandwidth isn't an issue, latency is.
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