QoS minimum requirements

[Juraj Papic]

Hello,

I would like if having a 50 mb bandwidth will be a best practices to apply QoS.

Thanks. 

[Karsten Iwen]

First you have to analyse and classify the applications that are running in your network. If you don't have that or you can't do that, one of the golden rules of QoS is that no QoS is often better than wrong QoS.

[Juraj Papic]

I already know all the apps that are running, what I would like to know if having a 50mb bandwidth will be worth it to do a QoS.

thanks. 

[Elliot Dierksen]

Are any of the applications passing over this link sensitive to delay/loss like VoIP or video? Are any of the ones you consider less important consuming enough bandwidth to slow down applications you consider more important? There is no "one size fits all".

[Juraj Papic]

The most important think i have is voice and I was not sure if with 50 mb apply a QoS would be a best practices.

thanks

[Karsten Iwen]

On a 50 MBit link a bursty application can easily saturate the link and impact the voice quality. I would go for a LLQ implementation.

[Juraj Papic]

I never applied LLQ but I will check it .

thanks. 

[Joseph W. Doherty]

BTW, LLQ is a QoS feature found on many Cisco routers.  On Cisco switches, PQ would be something similar.

[Juraj Papic]

I was reading about the LLQ, and for the Cisco version I have 12.x  thanks.

[Joseph W. Doherty]

If you have a router, with something like a FE hand-off, to a circuit providing 50 Mbps, you would want something like this:

class-map match-all real-time
match dscp EF !you must somehow match your real-time (e.g. VoIP) traffic

policy-map CBWFQ-example-shaper
class class-default
shape average 42500000 !about 15% less, to allow for average L2 overhead
service-policy CBWFQ-example

policy-map CBWFQ-example
class real-time
priority percent 33 !this is LLQ
class class-default
fair-queue
remaining percent 100

interface ?
service-policy output CBWFQ-example

[Joseph W. Doherty]

Actual bandwidth is irrelevant.

What's relevant is whether there's sufficient congestion that's adverse to your traffic's service needs and whether QoS can help.