question about qos

[dave dave]

hi! for a p2p lease line of latency below 20ms and bandwidth utlilization of <50% of a 2mb line. do you think it's necessary to have qos configured for voice? Is a seperate vlan required for voice? If qos is required any simple example to follow on this? I'm new to qos. Thanks.

Another question about p2p wan link is that, do you think a wan optimizer is required if traffic is pretty low?

[Peter Paluch]

Hello Dave,

What kind of leased line is it - MPLS pseudowire, PPP, HDLC, Frame Relay, Ethernet, or a real physical leased line with your encapsulation on it?

Another question is - what is the expected total amount of voice traffic on the line? Can you also specify the voice codec that is being used?

Best regards,

Peter

[dave dave]

hi! I think it's a ethernet. Normally what;s the bandwidth used per voice call session? The sites are quite small (20 users max). I would think that the max concurrent call is 70% of that 20 people which is around 14 concurrent calls.

Just curious, What different does it make between the different types of lease lines you mentioned in terms of the needs for qos? Thanks.

[Reza Sharifi]

Qos is only useful if you deploy it end-to-end.  For voice you usually need to apply qos. (see link below)

Is a seperate vlan required for voice

Yes, it is a good idea to have a separate vlan/subnet for your phones.

Another question about p2p wan link is that, do you think a wan optimizer is required if traffic is pretty low?

If the traffic is low and you have no issues, you do not need an optimizer

Here is a good doc with QOS design principals and examples:

http://www.cisco.com/en/US/docs/solutions/Enterprise/WAN_and_MAN/QoS_SRND_40/QoSCampus_40.html

HTH

[Joseph W. Doherty]

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Posting

dave dave wrote:
hi! for a p2p lease line of latency below 20ms and bandwidth utlilization of <50% of a 2mb line. do you think it's necessary to have qos configured for voice? Is a seperate vlan required for voice? If qos is required any simple example to follow on this? I'm new to qos. Thanks.
Another question about p2p wan link is that, do you think a wan optimizer is required if traffic is pretty low?

QoS necessary for VoIP on a 2 Mbps link, even with <50% utilization? - yes (to protect against transient congestion)

Separate VoIP vlan required? - depends, advisable (protects VoIP devices from unnecessary broadcast)

simple example:

class-map voip

match any (something to match your voip traffic)

policy-map example

class voip

priority percent 35

class class-default

fair-queue

interface serial

service policy example output

WAN optimizer? depends, your "mileage may vary" (with your low utilization and low latency you might not see as much benefit)