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New Member



I would like to appologoize for this long descripltion due to setup complexity.

I have a complicated customer setup in which he is running Voice over IP and he is suffering from bad Voice quality ; due to complextiy of the network setup i am asking where should i apply my QoS policiy in order to reserve requesteded bandwith for voice traffic to assure a good quality in case of congestion .

this customer has two branches in two remote areas interconnected together using our ATM to Frame relay mapping cloud ,and for that we are using a cisco router 3620 at customer premises labeled as A, connected from one side to a PBX via FXO interfaces and to an another 3620 labeled as B,also located at CPE side , via fast Ethernet interface.

B is connected to our CISCO router labeled as C ,located in our premises ,through serial connection running HDLC , C is connected to our remote router ,labeled as D, via ATM to Frame relay cloud then D is connected by HDLDC to a a 2620 router,labeled as E at the remote customer Side ,which in turn connected to a PBX by FXO interface and to the remote LAN by Fast ethernet interface , the setup looks like the folloing:

LAN and PBX <. ethernet and fxo.> A <.Ethernet.> B <.HDLC.> C <.ATM to Frame RelaY Cloud.> D < .HDLC.> E <.FXO and Ethernet > PBX and LAN.

the capacity of the Link is 128 kbps and we have two FXO interfaces to interconnect plus IP data trafic .

referring to this scenario where should i apply QoS policy in order to guarantee at least 32 kbps for VoIP traffic?

anyone could help?

i would appreciate your fast responses because it s an urgent case .

Jacob ,

Network Supervisor .


  • Voice over IP

Re: QoS

In order for QoS methods to be used in your network, traffic must be classified into higher and lower priorities. Each classification must then be marked so the network knows which QoS methods to apply. This process(marking) is completed at the ingress points to the network. Queuing and shaping methods can then be applied throughout the network.

New Member

Re: QoS


Thanks for your reply ,

referring to diagram posted in my email , could you please elaborate a little bit on your reply and indicate which routers should be in involved in this QoS mechanism ? i have recently read about the feature autoqos available in new Cisco IOS releases , will be enough to apply this command at serial interfaces (configured with HDLC encapsulation but they are not on the same IP subnet due to Network setup used , plesae refer to the diagram ) of both routers at customer side CPE ?

i am feeling a little bit confused, it will be more clear to me to indicate which router in the diagram must participate in establishing QoS through out the network and how should be configured for that .

Thanks in advance for your help,


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