Is there a QOS method that really gives priority to select traffic? (ASA 5510)

[todd.townsend]

Before today my concept of priority queuing was that if two packets wanted to go and there was only room for one, the higher priority packet would go and the other would wait.  In other words, if I prioritize VOIP then those packets will travel uninterupted no matter how many downloads I start.

Today a Cisco tech told me that if I really wanted to protect the VOIP traffic, I would also have to police all other traffic -- permenantly make everything else slower just in case there was some VOIP that wanted to go through.

1. Is this true?

2. If so, is there a way to do what I described first?

3. If the ASA 5510 can't do it, is there another device that can?

[todd.townsend]

Good point.  What do you recommend?

[sofianecirat]

There're actually many QoS .....and use them depending and what is it that you want to achieve... many times MQC is used time for VoIP,  also if you want to get more granular you can even combine MQC and NBAR....

[todd.townsend]

I want VOIP traffic to travel uninterrupted even when bandwidth is maxed out.  I do not want to permanently throttle all other traffic just so the occasional VOIP traffic has room.  Did I mention that I am a Cisco newbie who uses only ASDM?

[todd.townsend]

https://supportforums.cisco.com/docs/DOC-1230 says, "Priority queueing needs to be used with policing or traffic shaping."

Based on this article and my interactions with Cisco support, there is no way to prioritize a type of traffic without first permenantly reducing your total bandwidth to everything else.  This is not my area of expertise, but I am surprised and dissapointed that a high-end firewall like the ASA 5510 can't just let let the the important traffic go first.

[Julio Carvajal]

Hello Todd,

Since day One I told you that

06-sep-2012 22:08 (en respuesta a Todd Townsend)

The priority will start to happen as soon as the ASA gets oversubscripted ( this means the hardware queue got full, then the software queue it will start working and here is where the priority magic happens ( we have the 2 best effor queue {Default} and the priority queue)

So for that is why you will need to configure policing or shapping!

Check this blog:

"http://brian-kayser.blogspot.com/2010/10/doing-asa-quality-of-service-qos.html"

Regards,

Julio

[todd.townsend]

Sorry.  I didn't understand your original comment about the ASA getting oversubscribed. 

Thanks for the additional article, but did you notice what he said about QOS on incoming traffic? "It may have helped just slightly but the loss of available download bandwidth wasn't worth it."

[Julio Carvajal]

Hello Todd,

Not a problem

Yes, I see what you mean. To be honest with you I have seen this in a lot of scenarios because of the amount of traffic on the customer networks but this because the link was getting overloaded so the Priority started to take place.

That is what you need to ask yourself... Is this going to happen without the shaping or police?

Remember to rate all the helpful posts

Julio