Comments
yourfanat wrote: I am using another tool for Oracle developers - dbForge Studio for Oracle. This IDE has lots of usefull features, among them: oracle designer, code competion and formatter, query builder, debugger, profiler, erxport/import, reports and many others. The latest version supports Oracle 12C. More information here.

2008 West
DIAMOND SPONSOR:
Data Direct
SOA, WOA and Cloud Computing: The New Frontier for Data Services
PLATINUM SPONSORS:
Red Hat
The Opening of Virtualization
GOLD SPONSORS:
Appsense
User Environment Management – The Third Layer of the Desktop
Cordys
Cloud Computing for Business Agility
EMC
CMIS: A Multi-Vendor Proposal for a Service-Based Content Management Interoperability Standard
Freedom OSS
Practical SOA” Max Yankelevich
Intel
Architecting an Enterprise Service Router (ESR) – A Cost-Effective Way to Scale SOA Across the Enterprise
Sensedia
Return on Assests: Bringing Visibility to your SOA Strategy
Symantec
Managing Hybrid Endpoint Environments
VMWare
Game-Changing Technology for Enterprise Clouds and Applications
Click For 2008 West
Event Webcasts

2008 West
PLATINUM SPONSORS:
Appcelerator
Get ‘Rich’ Quick: Rapid Prototyping for RIA with ZERO Server Code
Keynote Systems
Designing for and Managing Performance in the New Frontier of Rich Internet Applications
GOLD SPONSORS:
ICEsoft
How Can AJAX Improve Homeland Security?
Isomorphic
Beyond Widgets: What a RIA Platform Should Offer
Oracle
REAs: Rich Enterprise Applications
Click For 2008 Event Webcasts
SYS-CON.TV
Today's Top SOA Links


The Limits of Cloud: Gratuitous ARP and Failover
Understanding the limitations of cloud will better enable a successful migration strategy

Cloud is great at many things. At other things, not so much. Understanding the limitations of cloud will better enable a successful migration strategy.

One of the truisms of technology is that takes a few years of adoption before folks really start figuring out what it excels at – and conversely what it doesn't. That's generally because early adoption is focused on lab-style experimentation that rarely extends beyond basic needs.

It's when adoption reaches critical mass and folks start trying to use the technology to implement more advanced architectures that the "gotchas" start to be discovered.

Cloud is no exception.

whatclouddoesrightandwrong

 

A few of the things we've learned over the past years of adoption is that cloud is always on, it's simple to manage, and it makes applications and infrastructure services easy to scale.

Some of the things we're learning now is that cloud isn't so great at supporting application mobility, monitoring of deployed services and at providing advanced networking capabilities.

The reason that last part is so important is that a variety of enterprise-class capabilities we've come to rely upon are ultimately enabled by some of the advanced networking techniques cloud simply does not support.

Take gratuitous ARP, for example. Most cloud providers do not allow or support this feature which ultimately means an inability to take advantage of higher-level functions traditionally taken for granted in the enterprise – like failover.

GRATUITOUS ARP and ITS IMPLICATIONS

For those unfamiliar with gratuitous ARP let's get you familiar with it quickly. A gratuitous ARP is an unsolicited ARP request made by a network element (host, switch, device, etc… ) to resolve its own IP address. The source and destination IP address are identical to the source IP address assigned to the network element. The destination MAC is a broadcast address. Gratuitous ARP is used for a variety of reasons. For example, if there is an ARP reply to the request, it means there exists an IP conflict. When a system first boots up, it will often send a gratuitous ARP to indicate it is "up" and available. And finally, it is used as the basis for load balancing failover. To ensure availability of load balancing services, two load balancers will share an IP address (often referred to as a floating IP). Upstream devices recognize the "primary" device by means of a simple ARP entry associating the floating IP with the active device. If the active device fails, the secondary immediately notices (due to heartbeat monitoring between the two) and will send out a gratuitous ARP indicating it is now associated with the IP address and won't the rest of the network please send subsequent traffic to it rather than the failed primary. VRRP and HSRP may also use gratuitous ARP to implement router failover.   how-failure-lb-works

Most cloud environments do not allow broadcast traffic of this nature. After all, it's practically guaranteed that you are sharing a network segment with other tenants, and thus broadcasting traffic could certainly disrupt other tenant's traffic. Additionally, as security minded folks will be eager to remind us, it is fairly well-established that the default for accepting gratuitous ARPs on the network should be "don't do it".

The astute observer will realize the reason for this; there is no security, no ability to verify, no authentication, nothing. A network element configured to accept gratuitous ARPs does so at the risk of being tricked into trusting, explicitly, every gratuitous ARP – even those that may be attempting to fool the network into believing it is a device it is not supposed to be.

That, in essence, is ARP poisoning, and it's one of the security risks associated with the use of gratuitous ARP. Granted, someone needs to be physically on the network to pull this off, but in a cloud environment that's not nearly as difficult as it might be on a locked down corporate network. Gratuitous ARP can further be used to execute denial of service, man in the middle and MAC flooding attacks. None of which have particularly pleasant outcomes, especially in a cloud environment where such attacks would be against shared infrastructure, potentially impacting many tenants.

Thus cloud providers are understandably leery about allowing network elements to willy-nilly announce their own IP addresses.

That said, most enterprise-class network elements have implemented protections against these attacks precisely because of the reliance on gratuitous ARP for various infrastructure services. Most of these protections use a technique that will tentatively accept a gratuitous ARP, but not enter it in its ARP cache unless it has a valid IP-to-MAC mapping, as defined by the device configuration. Validation can take the form of matching against DHCP-assigned addresses or existence in a trusted database.

Obviously these techniques would put an undue burden on a cloud provider's network given that any IP address on a network segment might be assigned to a very large set of MAC addresses.

Simply put, gratuitous ARP is not cloud-friendly, and thus it is you will be hard pressed to find a cloud provider that supports it.

What does that mean?

That means, ultimately, that failover mechanisms in the cloud cannot be based on traditional techniques unless a means to replicate gratuitous ARP functionality without its negative implications can be designed.

Which means, unfortunately, that traditional failover architectures – even using enterprise-class load balancers in cloud environments – cannot really be implemented today. What that means for IT preparing to migrate business critical applications and services to cloud environments is a careful review of their requirements and of the cloud environment's capabilities to determine whether availability and uptime goals can – or cannot – be met using a combination of cloud and traditional load balancing services.

Read the original blog entry...

About Lori MacVittie
Lori MacVittie is responsible for education and evangelism of application services available across F5’s entire product suite. Her role includes authorship of technical materials and participation in a number of community-based forums and industry standards organizations, among other efforts. MacVittie has extensive programming experience as an application architect, as well as network and systems development and administration expertise. Prior to joining F5, MacVittie was an award-winning Senior Technology Editor at Network Computing Magazine, where she conducted product research and evaluation focused on integration with application and network architectures, and authored articles on a variety of topics aimed at IT professionals. Her most recent area of focus included SOA-related products and architectures. She holds a B.S. in Information and Computing Science from the University of Wisconsin at Green Bay, and an M.S. in Computer Science from Nova Southeastern University.

Web 2.0 Latest News
Silver shows that predictions in areas such as economics have been less successful, e.g. he examines why many economists missed the recession, and why supposedly expert forecasters get election predictions wrong so often. For example, before the recession of 2008, the assumption was ma...
When we talk about the impact of BYOD and BYOA and the Internet of Things, we often focus on the impact on data center architectures. That's because there will be an increasing need for authentication, for access control, for security, for application delivery as the number of potentia...
Despite the data privacy protections supposedly conferred by regulations like HIPAA and HITECH, consumers’ confidential health and personal information is still not safe enough. That’s the lesson to be learned from Franklin, TN-based Community Health Systems’ (CHS) August 18 regulatory...
Putting on a rock show is like piloting the Millenium Falcon – it’s simultaneously the fastest ship in the galaxy while being a “piece of junk.” The stage lights are so hot you start to sweat immediately, hoping those Jager-bombs are escaping through your pores and delaying the impend...
The IT infrastructure of modern businesses require a number of seemingly never-ending cycles to track assets. As these assets go through different stages of usefulness or functionality, IT teams must constantly manage the process, which takes them away from other more important tasks a...
Subscribe to the World's Most Powerful Newsletters
Subscribe to Our Rss Feeds & Get Your SYS-CON News Live!
Click to Add our RSS Feeds to the Service of Your Choice:
Google Reader or Homepage Add to My Yahoo! Subscribe with Bloglines Subscribe in NewsGator Online
myFeedster Add to My AOL Subscribe in Rojo Add 'Hugg' to Newsburst from CNET News.com Kinja Digest View Additional SYS-CON Feeds
Publish Your Article! Please send it to editorial(at)sys-con.com!

Advertise on this site! Contact advertising(at)sys-con.com! 201 802-3021




SYS-CON Featured Whitepapers
ADS BY GOOGLE