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New Member

Do I really need QoS because of BW?

My question is do we have avaialble BW on the egress uplink port (2 Gbps) of the CAT4003 to support 75 users (100Mbps-Full/User=7.5Gbps) ??? OR I have to implement QoS on that?

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We have few CAT4003 (CATOS v6.3-3a, Pure L2 switch, No L3 Engine)

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Let us focus on only 1 CAT 4003 for NOW which is connected to CAT6509

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CAT4003 is connected CAT6509 over DUAL 1GIG Fiber. 75 users are connected to switch ports over 100Mbps/full link. User's PC are connected to IP Phone and IP Phone is directly connected to switch ports.

(Likewise 75 IP Phones connected to 75 switch ports). Switch has 2 VLAN, 1native VLAN=3 for PC-DATA and 1 AUX VLAN=99 for Voice.

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I just want to find out How much BW will be used by PC and Phone? Each port has available BW of 100Mbps which is jointly shaed by IP Phone and PC. Now..There are 75 connected switch ports so total available BW for all ports are 75x100=7500Mbps, Which is equal to 7.5 Gbps. And as i mentioned switch has DUAL 1-Gbps uplink ports which equals 2Gbps.

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Both Voice and Data Traffic pattern is quite variable.

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My understanding is If i want to prioritize the VOICE traffic over regular DATA then i have to implement certain QoS rules so all my VOICE traffic can utilize 2Gbps available BW og UPLINK ports?

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As IP Phone is sending L2QoS so i can implement QoS rules based on that value on the entire switch.? Is it a good idea?

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I forget to mention that some IP Phone are restarting in indefine timely faishon. I guess that is because of GK is seating to CAT6509 and IP Phone are seating on CAT4003. So it looks like RAS messages from the IP Phones might get dropped at CAT4003 uplink port as there is no QoS yet. Is that correct?

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How would i measure BW utilization on the uplink port? so i can find out Do i

really need QoS?

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Kal

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1 REPLY
New Member

Re: Do I really need QoS because of BW?

In general, any link that has the potential of being oversubscribed and is carrying voice should use some form of QoS. It won't hurt you if the line doesn't get fully utilized, but it will certainly help if it does. Look at it this way, you have a max of 2 Gb. This means that you only need 20 workstations to log on at once, or save a file at the same time, to mess with someone's voice call. And if that someone is the CEO...

I would look at prioritizing voice over data (from what I read, you can only do this at L2, but it should still work okay) and also at some sort of WRED applied to the data traffic in case the queues do start getting overloaded.

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