Quality of Service - does it work and should you bother?

Will ticking the 'QoS' box in your router setup make any difference? Ian Yates kicks off a three-part interview exploring that very question.

It should work if you enable it on all your routers within your company but would anybody outside the network upstream be listening, will your ISP honour these requests? We asked Adam Radford, Consulting Systems Architect, at Cisco if he could shed some light on the subject.

Ian Yates: Adam, we've all seen the QoS buttons on the menu in the routers, is it worth pressing the button, does it does anything?

Adam Radford: Well QoS is something that we see in everyday life as well as in networking. If you think about whether you go to a Qantas Club check in versus normal check in, whether you have an E-tag versus cash on the Harbour Bridge or whether you are a registered user of a web site or a guest then there is some differentiation in the way that you access resources. So in networking terms whether it makes sense to turn on quality of service or not really depends on whether you have a requirement around differentiate access to network resources. What we see is that more and more, particularly in a wide area environment there is a requirement around providing some level of differentiation.

IY: So that would not always apply if your ISP wasn't playing the game as well would it?

AR: Well it depends because there is really two ways of providing that differentiation. There is providing it end to end where you have a bi-directional traffic flow, where I want to prioritise what goes out as well as what comes in. But I could think of a simple example in maybe internet banking is an example, where I may want to prioritise the traffic that actually goes out and leaves my organisation. For example I may want to make sure that premium banking customers, not that I am one but if I was I have got better access to a specific application then a normal banking user.

IY: Yeah. Okay. That makes it slightly different from the real world examples you gave which were quite good because that is the first time someone has explained that way which makes sense, that we always take it for granted in the real world. But it also means I am thinking about it, that what you are suggesting there being able to differentiate between customers would almost be like having in your hand a Qantas business lounge membership but standing in the normal queue and still getting better service.

AR: Well, I think the thing about QoS and quality of service from an implementation point of view. There is actually two key concepts. There is the identification of a particular type of a particular class of user. Then there is what you would do with them which is the queuing aspect.

IY: Okay.

AR: That is where the network plays a role because it has the ability to do both the classification as well as the queuing or the access to the resource. So in the example that I mentioned which we internet banking the network can actually identify whether it is a premium customer or not. So mark those packets accordingly. So give you your ticket and then once you get to the interface, once you get to the point in the network where you go out into the broader internet it can identify whether you know, the premium banking customers get first access to that or not.

IY: Right, okay. I guess the good thing about that is that on application by application basis they may all get the same level of access to certain bits of things and some might get better access to what they consider more critical for that customer.

AR: Absolutely.

IY: So normally you only hear about people talking about for VoIP, that is the obvious one that everybody says, oh God I need some VoIP and so forth I need some QoS because I am getting swamped. But it is not just VoIP that can benefit from quality of service and of course VoIP is probably the one that can least benefit in the wider scheme of things because you don't control the whole pipe most of the time.

AR: Well it depends, again it depends on the environment that you are using. If you look at the typical ways that the quality of service is provided or implemented it is implemented internally and that is really about efficiency.

IY: Right.

AR: Providing better efficiency of the network resources that I have and VoIP is a very good example of that where voice, video and data share the same pipe. Then the other place that you can use it is the example that I mentioned earlier which is probably less well known but where you can actually define the response time to applications and define how application traffic leaves your network.

IY: Right so you can give a little bit of tweak even if you are not getting a total commitment from your ISPs to have end to end. You can still improve the way that it leaves and reaches the ISP so that you take out one factor.

AR: Exactly.

IY: Okay.

AR: You know increasing we are starting to see services from ISPs that are QoS enable and again if you look particularly services that are provided LAN connections, for enterprise customers, the majority of those are QoS enabled.

IY: So you want it, you pay for it, they have got it.

AR: Yeah, that's right.

IY: Okay. So therefore we should not ignore that button, but we also should not just press it, we should find out exactly how it works and what we can do with it.

AR: You are hitting the key issue that I have seen in terms of the way the customers deploy quality of service or think about quality of service. There is really two ways that this conversation goes. The first one is the technology lead conversation which is IT goes to the business and says we have got this QoS thing, we would like to turn it on. We would like to understand the prioritisation of your application. Normally the response that comes back from the business is well hours are all gold. The business unit that you are talking to reckons that their application is most mission critical in the entire organisation.

IY: That's it.

AR: The challenge with that is that they don't have any context to understand how to prioritise those applications. So normally the conversation that is most successful is that if you explain to the business that the LAN resources that are a scarce resource and what we are looking to do is try to prioritise access to those so of your application which will you choose and you have to choose are going to have gold, silver, bronze access to that bandwidth. You come up with a more meaningful discussion.

IY: Right. Yes, I can imagine that would be the case. You go and ask each different department and it would be like here, yes and marketing it would be power point.

AR: Yes exactly. Exactly right for better or worse.

IY: Yes. All right. Well there are some things to think about but obviously it is something that needs to be understood.

AR: Aligned with the business outcome as well.

NEXT: Quality of service for smaller networks


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