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Major Changes for Big-IP

The feature in Big-IP that lets it respond to applications via Web services has been a part of the product line for nearly two years, but developers can just now take advantage of it. Although SNMP typically can be used within an application, developers often hesitate to use it because of its inherent complexity (see sidebar below for more on SNMP versus Web services for load-balancing).

Applications use SOAP (Simple Object Access Protocol) to manage the Big-IP 4.5. For example, an application overburdened with requests can remove the server on which it runs for scheduled maintenance. It later can have the server added back to the pool by making a simple SOAP-based call to the Big-IP. This lets developers design applications that can leverage Web services to control the load sent.

All is not perfect in Big-IP land, however. Although you can route traffic based on content in the TCP payload, the task must be done manually--including the conversion of string-based content to hexadecimal values. The work is nightmarish, but once you're done, the system works like a charm.

Good
• Routes traffic and persists connections based on TCP payload.

• Web services management puts apps in control.
• Supports HTTP, HTTP/S, SOAP and custom protocols.

Bad
• TCP payload switching rules must be written manually, and content must be represented hexadecimally.
• Some protocols, such as POP3 and SMTP, won't benefit from the new switching capability.

Admins also need to be aware of introducing latency. The location of the data in the packet stream affects the amount of time it takes to process the request. The Big-IP must buffer the packets until it can find matching content. The default buffer size is 16 KB, and F5 says performance is likely to degrade with larger buffers.

Even if you don't use Big-IP 4.5 for Web services deployments, you can route traffic and persist connections based on any HTTP header. This gives you more control over application traffic and more flexibility in server-farm design than you get with most load-balancing solutions.