Author Archives: elsteadmontague

About elsteadmontague

Passionate about App performance

Don’t put all your eggs in the CoS basket

CoS, what is it good for? Maybe not “absolutely nothing” but not far short.

With the exception of the EF class for real-time apps, CoS actually delivers almost none of the expected benefits promised by the marketing gloss. Let’s pull it apart and see why.

CoS only operates on outbound links (no point in queuing traffic after it’s already traversed the WAN). OK, but managing traffic outbound from each end does give bi-directional control, right? Wrong. CoS bandwidth allocations are proportional to the overall outbound bandwidth which is usually much bigger at the DC end than any of the branches. Traffic in any individual CoS leaving the DC could easily flood the smaller inbound branch links.

OK how about outbound from the branch? Nope, not much better. Normally the outbound branch traffic runs at a lower volume than inbound. CoS only kicks in when the link reaches capacity and this rarely happens. Worse still, the sum of many branch networks can oversubscribe the inbound DC bandwidth and as there’s no inbound control at the DC end the traffic profile can be chaotic.

In summary, CoS has no meaningful control of traffic outbound from the DC or outbound from the branch. CoS cannot help with inbound control. Include the possibility of branch to branch traffic wrecking best laid plans and any notion that CoS is useful flutters out the window.

If you want to monitor CoS utilization and other end-to-end Path characteristics like packet loss, RTT and jitter try PathView . If you need to manage traffic it’s far better to use traffic engineering devices like PacketShapers, even if you can only put one in the DC. We provide PathView and PacketShapers separately or bundled in low cost service options.

Network traffic considerations with Virtualised Desktop

I was wondering about the future for many of the traditional network vendors when desktop virtualization is widely deployed. What happens when each user’s network traffic is just a single stream, likely encrypted, representing their entire suite of business applications?

I’m not talking about yet more tweaks for traditional thin client stuff such as Citrix and the like. UDP makes sense to get the snappiest performance but that brings issues for many WAN optimisation vendors for out-of-the-box operations.

Will there even be a place for WAN optimisation? How will traditional visibility vendors decode a single stream that, by intent, has minimised and encrypted the I/O activity for multiple applications? Even if they could, what’s the point? Conventional bandwidth management and QoS techniques are meaningless if the traffic of the individual applications cannot be separated out because it’s just one ‘TV’ channel

How about security? Some devices at the user end don’t even run software. What’s to infect? There’s no data at the user end to steal. Surely that’s the point.

I can see a place for the traditional vendors between the Data Centre and Cloud/Internet third party services but not between the Data Centre and the users. I am, and for a while at least will be, a big proponent of comprehensive network traffic visibility and the often jaw-droppingly magical qualities of WAN optimisation. I’ve made a living from these exclusively for the last 15 years but am increasingly nervous about their future relevance.

The common denominator is the network.

I read an article at TMCnet entitled “The Unvarnished Truth about VDI Desktop Virtualisation”

One paragraph jumped out at me”…One thing is certain: VDI places significant loads on your network infrastructure. If you have limited bandwidth and high-latency connections, problems with performance and reliability are sure to rear their ugly heads…

It struck me that the quality and integrity of the network infrastructure, hardly the most sexy aspect of business technology, is increasingly critical to the successful deployment of (whoa, possible oxymoron approaching) a fully virtualised realisation of an enterprise’s IT communications strategy.

If like me, you’ve seen WAN optimisation evaluations humbled by a simple (but thitherto unknown) NIC duplex mismatch, you will know and despise the crippling effects of a less than perfect network infrastructure.

With all of this in mind in mind I have developed a passionate obsession with PathView Cloud from AppNeta ( Clear and straightforward business-friendly SLA reporting for all the relevant aspects of an entire IT infrastructure drilling down seamlessly to monitoring, notifications and deep diagnostics of an individual communications path.

I dread to think how many network management vendors aspirations would have been cut short if PathView Cloud been around 20 years ago.

For an enlightened view of your own network infrastructure go to and pay attention to PathView Cloud. I guarantee you will not regret it. You really don’t want to be the last one to get on board!

Cheers, Cliff.