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VOIP Delay...traffic marking for Qos?

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Goldsound
Occasional Visitor

VOIP Delay...traffic marking for Qos?

We use a VOIP phone system from Mitel called MiCloud. Since day one, August of 2014, the delay we experience on phone calls has been awful. I have set up Qos settings on my router but it has not made a difference. Mitel has asked me to check with Comcast to see if they can "mark" traffic for us in order to truly priortize our phone traffic. I'm not sure calling the 800 number would get me the answer so I am hoping somone here is knowledgable enough to assist us....

 

They have stated that the following settings are necessary on the ISP side to achieve minimum delay over our phones...

 

DSCP signaling - 26

DSCP voice - 46

DSCP other - 46

L2 priority voice - 6

L2 priority signal - 6

L2 priority other - 6

 

I'm not an expert in this area and would really appreciate any help in solving this...I signed us up for Comcast Business in the hopes that it would do all we needed for our new phone system, please help reassure me that I made the right choice!

 

Accepted Solution

Re: VOIP Delay...traffic marking for Qos?

Hi, thanks for the reply.

 

I already have the VOIP system behind a QoS capable router with a public IP address, but the router is behind the Comcast gateway.

 

We're using the Comcast connection for all our internet needs as well....

 

Are you saying I need to ditch the Comcast gateway all together and buy a modem that also supports Qos? 

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Accepted Solution

Re: VOIP Delay...traffic marking for Qos?

If your Comcast modem is in passthrough mode and you are using your own router, it sounds like you are already setup how Comcast_John was recommending. If you are not in passthrough mode and are using double NAT, that would be the first thing to correct.

 

You may be able to control QoS on your own router to make sure traffic is prioritized going out your router, but Comcast does not provide any kind of QoS once you reach their network/Internet and even if they did, your traffic is likely routed through other networks and QoS is not guaranteed to be honored. Inbound QoS is even more complex. High end business Internet service sometimes do guarantee QoS, but you aren't going to find that with $100-$250 service from Comcast cable.

 

I deal with VoIP systems from Vertical. QoS is normally tagged by the devices, not the router. Routers job is to recognize and prioritize the traffic. So that would be the question I'd ask Mitel, is the traffic being tagged and are you saying the routers need to prioritize those QoS queues. If that is the case, as I suspect it is, you aren't going to get Comcast to do any more prioritizing than is already happening.

 

My favorite config is Comcast in passthrough with a pfsense firewall. With that I can prioritize outbound traffic to make sure RTP (VoIP packets) are being prioritized as much as possible. I'm also able to setup limits on bandwidth use by other protocols such as HTTP or just other LAN devices to make sure no other device takes up all the bandwidth. This has generally made VoIP reliable (although currently I'm having jitter issues).

 

Also, you may want to find out how your traffic is being routed. If you can find out from Mitel what IP or hostname the RTP packets are coming from, you can do a tracert to see how your traffic is being routed. Comcast often has some interesting routing with traffic sometimes traversing the country before reaching it's destination. I don't know if there is anything that can be done about that though.

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Trusted Forum Contributor

Re: VOIP Delay...traffic marking for Qos?

Unfortunately, I don't believe any of the current Comcast leased modem/gateways support VLAN/QoS tagging of any sort. I know that Metro Ethernet (Comcast's fiber service) supports it to some degree.

 

How is your internet browsing experience / speeds outside of VoIP? Do you always get your full provisioned speed, and do sites like http://pingtest.net report any packet loss or latency issues? As well, what kind of router do you have?

Community Manager
Community Manager

Re: VOIP Delay...traffic marking for Qos?

HI Goldsound.  QoS is not available on the Comcast Gateway Routers. All traffic thru the Internet devices is FIFO or best effort. Other forum members have noted success with placing their VoIP system behind  their QoS capable network router that has a statically assigned public IP address as well as placing a stand alone modem or a bridged gateway device, without a static IP address in front of the QoS capable router. As QoS is not available in the Comcast gateways please let us know if you need to make changes to the device.

 

Thank You

Goldsound
Occasional Visitor

Re: VOIP Delay...traffic marking for Qos?

Hi, thanks for the reply.

 

I already have the VOIP system behind a QoS capable router with a public IP address, but the router is behind the Comcast gateway.

 

We're using the Comcast connection for all our internet needs as well....

 

Are you saying I need to ditch the Comcast gateway all together and buy a modem that also supports Qos? 

Goldsound
Occasional Visitor

Re: VOIP Delay...traffic marking for Qos?

Hey Comcast_John can you please clarify?

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jamesdav1
New Contributor

Re: VOIP Delay...traffic marking for Qos?

If your Comcast modem is in passthrough mode and you are using your own router, it sounds like you are already setup how Comcast_John was recommending. If you are not in passthrough mode and are using double NAT, that would be the first thing to correct.

 

You may be able to control QoS on your own router to make sure traffic is prioritized going out your router, but Comcast does not provide any kind of QoS once you reach their network/Internet and even if they did, your traffic is likely routed through other networks and QoS is not guaranteed to be honored. Inbound QoS is even more complex. High end business Internet service sometimes do guarantee QoS, but you aren't going to find that with $100-$250 service from Comcast cable.

 

I deal with VoIP systems from Vertical. QoS is normally tagged by the devices, not the router. Routers job is to recognize and prioritize the traffic. So that would be the question I'd ask Mitel, is the traffic being tagged and are you saying the routers need to prioritize those QoS queues. If that is the case, as I suspect it is, you aren't going to get Comcast to do any more prioritizing than is already happening.

 

My favorite config is Comcast in passthrough with a pfsense firewall. With that I can prioritize outbound traffic to make sure RTP (VoIP packets) are being prioritized as much as possible. I'm also able to setup limits on bandwidth use by other protocols such as HTTP or just other LAN devices to make sure no other device takes up all the bandwidth. This has generally made VoIP reliable (although currently I'm having jitter issues).

 

Also, you may want to find out how your traffic is being routed. If you can find out from Mitel what IP or hostname the RTP packets are coming from, you can do a tracert to see how your traffic is being routed. Comcast often has some interesting routing with traffic sometimes traversing the country before reaching it's destination. I don't know if there is anything that can be done about that though.

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