Latency: The Achilles Heel of Cloud Computing
End-user requirements must take precedence in the decision to deploy applications in the cloud
By: Robert Minnear
Mar. 9, 2011 10:15 AM
Today, cloud computing is proliferating. For IT and corporate business units alike, there is strong interest in deploying applications in a cloud environment for its increased business flexibility and cost savings. However, common cloud computing solutions can introduce unexpected costs associated with the broader issue of latency from the cloud edge to the end user.
IT and individual business units tend to focus on the aspect of performance within the cloud environment when deploying applications to the cloud, rather than the question of performance and reliability of the overall application and content delivery chain from the cloud environment to the end user.
This is a serious miscalculation for two reasons. First, the cloud computing provider's choice of network carrier shouldn't penalize the cloud user when network performance is degraded. Second, end users will abandon applications and websites based on the smallest performance delays or downtime, jeopardizing the perceived value of the cloud initiative. For these reasons, it is critical that the discussion around cloud latency shift away from IT or business unit-defined acceptable levels of latency to end-user behavior judgments as to what level of latency is acceptable.
Using a systemic approach, CIOs and business unit executives can effectively gratify their end users when deploying their business-critical and revenue-centric applications in the cloud.
Slow or Unresponsive Application and Website Performance Matter to End Users
Aberdeen Group provides a similar snapshot of demanding user requirements for website performance in a recent study on the performance of web applications.
Latency across the Internet is typically the culprit behind slow or unresponsive applications and websites, and represents a major issue for cloud computing. Geography and network distance play a key role in determining latency - the further the cloud environment is from your internal network systems or the end user, the greater latency across the network.
A Narrow Focus on Cloud Infrastructure
KPMG surveyed current cloud adopters to identify realized benefits of cloud and what respondents would like to see improved. Neither "performance" nor "availability" was cited as realized benefits. Instead, both were identified as areas that should be improved. In the Aberdeen Group study on cloud infrastructure performance, only 5 percent of respondents indicated their applications experienced a performance improvement. Thus, IT and corporate business units want to see stronger performance and reliability within the cloud environment. Unfortunately, this focus on performance and availability within the cloud environment ignores the aspect of the "network" path by which latency and jitter affect the performance of application content delivery to end users.
Both aspects, the cloud computing platform and the network or "Internet," have the potential to adversely impact the end-user experience. The combined latency or degraded performance can manifest itself as a simple echo annoyance on a VoIP call, or can spell disaster for a Massive Multiplayer Online Game (MMOG) provider with thousands of users playing performance-sensitive games at any given time. When this happens, high latency within the cloud and/or across the network will cost your organization money.
Cloud infrastructure performance and the "network" must be given equal consideration. They are two sides of the same coin, and the ultimate success of any application deployment in the cloud relies on both aspects performing reliably at a level acceptable to the end-user.
Is Your Carrier the Weak Link in Application Performance in the Cloud?
The problem with this approach is that no one or combination of two (or three or four) carriers ensures an optimal connection to the Internet. Redundancy may keep the connections up, but they are not addressing a core need - which is optimal routing of traffic to reduce latency, jitter and packet loss. Indeed, brown outs or less-than-optimal network performance may cumulatively prove more costly to an organization over time than actual downtime during the same period.
Manually selecting a combination of carriers that somehow comprise a more efficient routing solution for web-based applications is a "hit or miss" proposition. Finding the optimal path across carriers is a fluctuating objective, if not incomprehensible to determine and manage due to standard networking practices like Border Gateway Protocol (BGP) and carrier SLAs.
Latency from the Cloud to Your End User
CL1 + NL2 = TSL
Where CL equals intra-cloud latency, NL equals network or Internet latency, and TSL equals total system or systemic latency.
It's important to recognize that network latency will be significantly greater than cloud-based latency as represented here:
L2 >> L1
Ultimately, TSL is the statistic that the application or website should be measured against in terms of end-user requirements as represented in the extension of the formula:
TSL < End-User Requirements
Is Your Cloud Provider's SLA Strong Enough for What Cloud Computing Requires?
The critical questions that cloud customers should ask their providers when considering downtime include the following:
In the end, it's not what the provider says it will do, or what the provider guarantees it will do, but what the provider actually has proven to deliver. Lost revenue will very likely far exceed any credits for downtime you may receive. As a result, it's much more critical to have a highly available cohesive cloud computing and network solution to minimize potential loss in the first place.
Of course, this aspect of the SLA doesn't address the issue of latency or delay in terms of measurable performance metrics and guarantees.
Today, SLAs across cloud providers fail to align with market realities that dictate the need for a highly responsive application or website experience. Often, the cloud provider will guarantee levels of uptime but won't guarantee any latency threshold. Some cloud vendors will go so far as to guarantee a threshold for latency, but this is calculated only for intra-cloud operations and completely ignore the aspect of application content delivery across the Internet which, by its nature, is harder to control.
Promises for performance, especially when they relate to such a complex system involving the cloud infrastructure and the network, must be backed by SLAs that mean something.
Take a Systemic Approach to Minimize Latency
The total latency should not exceed any estimated acceptable performance requirement from the end-user's perspective. Anything above acceptable performance levels raises the risk and likelihood that end users will penalize an application or website by abandonment.
Thus, enterprise organizations seeking a cloud service provider should do their due diligence to ensure their service is built on the following components:
Given the level of trust that customers must have to place applications and information in the cloud environment, cloud vendors must offer higher-level SLA and support models to address cloud performance/reliability and customer-related inquiries. Some key aspects of next-generation SLAs to look for include:
Cloud Computing's Promise
Looking out into the not-too-distant future, cloud computing will no longer be considered innovative, but simply the way we deliver applications. The term "cloud" won't be used anymore - it won't be necessary.
This vision will be fully realized if we deploy a regimen across the Internet that serves to minimize latency where possible and accelerate IP traffic to a much greater level.
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