22 Replies Latest reply on Sep 6, 2013 10:11 AM by levi

    Voice over IP via 2 netvanta 3448 issues

    dlazure New Member

      I have a customer where we installed two netvanta 3448 to connect two site together. they use the link to connect two IP phone on the remote site and share files.

      they complain about the voice being cut all the time. I programmed QoS but i am not sure if it is done correctly

       

      can i get some help please

       

      i joined both config

        • Re: Voice over IP via 2 netvanta 3448 issues
          levi Employee

          dlazure:

           

          Thank you for asking this question in the support community.  When you get a chance, can you provide some additional information about the nature of the application?  Are the phones from the remote site registering to the phone system at the main site?  Are the phones going over the VPN?  Are the phones and the phone system using SIP?  You mentioned the phones will work for a while, and then what happens?  Do they drop in the middle of the call, does the audio become choppy, or something else?

           

          Again, thanks for posting this question, and let me know some additional information, and I'll be happy to help in any way I can.

           

          Levi

            • Re: Voice over IP via 2 netvanta 3448 issues
              dlazure New Member

              ? Are the phones from the remote site registering to the phone system at the main site? 

              Yes


              Are the phones going over the VPN?

              Yes


              Are the phones and the phone system using SIP? 

              Yes


              You mentioned the phones will work for a while, and then what happens?

              they work all the time, but when you speak to someone the voice quality is bad and some audio is being cut and sometime the call drop


              Do they drop in the middle of the call, does the audio become choppy, or something else?

              The call drop or become choppy

            • Re: Voice over IP via 2 netvanta 3448 issues
              rcohen New Member

              You've got a few issues to resolve.

              First remember that this is the Internet, that means no QoS no matter how you tag your traffic. I have seen ISPs offer QoS within their own core, but it would have to be something they are specifically providing.

               

              Next, traffic shaping. Unless both directions have a 100Mbps synchronous connection to the Internet you want to be sure the router is aware that port speed is not the available bandwidth.

               

              Now the big one. You are prioritizing outbound traffic to the Internet based on the UTP ports. BUT, those UTP packets are being encapsulated within the VPN packets which are TCP and from the outside they all look the same regardless of the traffic type/port. Also, encryption in general can cause quality issues because of increased latency. So I've worked around this a couple ways. You can do two VPN tunnels and prioritize the voice tunnel. This requires multiple IPs and really isn't my preferred. Another solution is to use the VPN only for data. Enable the ALG for SIP traffic, use static translations, and absolutely set up ACLs for inbound SIP traffic or you'll be hacked and calling other countries in no time.

               

              Yes, this means you VoIP communications is unencrypted across the internet. But as long as you use the ACLs and your security is set up correctly the risk is low that someone would be able to intercept the traffic in a way that the participants wouldn't notice (such as one-way audio).

               

              A variant of the two VPN tunnels is a Data VPN and a VoIP GRE. Prioritize the GRE, remember it's encapsulated. A little more secure but no encryption.

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                • Re: Voice over IP via 2 netvanta 3448 issues
                  dlazure New Member

                  Thanks rcohen for the reply

                   

                  I want to program the qos by matching ip precedence

                   

                  (config)#qos map VOIP 10

                  (config-qos-map)#match precedence 5

                  (config-qos-map)#bandwidth 640

                   

                  my phone system is taging RTP traffic with a priority of 5

                   

                  Can't i just apply this qos map to the vpn?

                   

                  i know in cisco we can take the ip precedence value on the packet and place it outside the IPSEC payload during encryption.

                   

                  Is there a way in AOS ?

                   

                  thanks

                    • Re: Voice over IP via 2 netvanta 3448 issues
                      rcohen New Member

                      That is a good question.

                      I haven't heard of AOS being able to tag VPN packets with IP Precedence to match the payload, but maybe I missed it, I'll leave this to Adtran to answer. Adtran, please post the answer as I too am very interested to know.

                      I do know that ISPs commonly strip QoS tags in transport, but you can't prioritize incoming traffic anyway.

                       

                      AOS is a second language to me, IOS being my first. There is a lot you can do with IOS that AOS can't, but you get to pay a LOT more for it. For your basic one or two T1s, or <=75Mbps routing it's a great router. It also works very well with VoIP traffic, and is extremely reliable, but sometimes you need more. BTW when I talk about Cisco I mean the real IOS based Cisco, not that web-only, linksys-like **** they put the Cisco label on.

                      • Re: Voice over IP via 2 netvanta 3448 issues
                        levi Employee

                        dlazure:

                         

                        Please, review the following post on VPN & QoS:  https://supportforums.adtran.com/message/1731#1731

                         

                        Since you are going over the Internet, there is some QoS limitation because you have no control as to how traffic is prioritized over the connection. Although it is not as clear-cut as setting up QoS over a private network, we can set up a QoS policy to at least ensure that the NetVantas prioritize certain traffic types. When setting up QoS for voice traffic going over a VPN, you must match either the DSCP value or IP precedence value. Matching by any other parameter will not work as those other parameters will be encrypted before QoS has a chance to prioritize how the traffic is sent out.


                        Therefore, the QoS map you suggested is accurate, however, since the voice traffic is low latency, I would recommend the priority command instead of the bandwidth command, as follows:


                        (config)# qos map VOIP 10

                        (config-qos-map)# match precedence 5

                        (config-qos-map)# priority 640

                         

                        I hope that makes sense, but let me know if you have any further questions.

                         

                        Levi

                          • Re: Voice over IP via 2 netvanta 3448 issues
                            dlazure New Member

                            Thanks Levi for the reply

                             

                             

                             

                            I have some other questions

                             

                             

                             

                            Do I need to tag the RTP and SIP value with different priority?

                             

                             

                             

                            How much bandwidth SIP need per phone call?

                             

                             

                             

                            Can I log remotely to the 3448 and disable the actual qos map and aply the new one without droping the interface?

                              • Re: Voice over IP via 2 netvanta 3448 issues
                                levi Employee

                                dlazure:

                                 

                                The configuration files you submitted previously were for NetVanta 3120s.  Are the units you have questions on NetVanta 3120s or NetVanta 3448s?  What is the type of WAN/Internet interface that the QoS map is applied to?  Applying a QoS Map to a PPP or demand interface will cause the interface to drop briefly.  This causes a temporary service interruption and the interface should come back up momentarily.

                                 

                                The amount of bandwidth usage per call, depends on the CODEC.  Typically G.711 uses approximately 90 Kbps per call, and G.729 uses about 40 Kbps per call.

                                 

                                Most likely, for a QoS over VPN application, the phones will mark their traffic with a DSCP or IP Precedence value, and that is what you will need to prioritize in the QoS map.  For additional information on QoS, the links below go over how to configure a basic QoS map over the web interface and CLI:

                                 

                                Configuring QoS in AOS in the GUI (video) - https://supportforums.adtran.com/videos/1046

                                Configuring QoS for Voice over PPP WAN Interface (CLI) - https://supportforums.adtran.com/docs/DOC-2654

                                Configuring QoS for Voice over Ethernet WAN Interface (CLI) - https://supportforums.adtran.com/docs/DOC-3406

                                 

                                Please, let me know what additional questions you have.

                                 

                                Levi

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                                  • Re: Voice over IP via 2 netvanta 3448 issues
                                    dlazure New Member

                                    We changed the 3120 for 3448 because adtran told me 3120 cpu were to weak to manage voip.

                                     

                                    I applied my 3130 config over the 3448

                                     

                                     

                                    So i am using two 3448 now

                                     

                                    I dont understand one thing

                                     

                                    You seem to include the sip and rtp bandwidth in the required bandwidth

                                     

                                    I want to know i lf i need to tag the sip packet and rtp with different priority value ?

                                     

                                    Dominic lazure

                                    Luminet solutions

                                     

                                    Message was edited by: levi (Removed Contact Information)

                          • Re: Voice over IP via 2 netvanta 3448 issues
                            levi Employee

                            dlazure:

                             

                            I went ahead and flagged the "Correct Answer" on this post to make it more visible and help other members of the community find solutions more easily. If you don't feel like the answer I marked was correct, feel free to come back to this post and unmark it and select another in its place with the applicable buttons.  If you still need assistance, we would be more than happy to continue working with you on this - just let us know in a reply.

                            Thanks,

                             

                            Levi