In the first part of this post we highlighted Twitter as an example of how a business might apply rate limiting to users of a particular service. Below, I will explore some of the first steps a business might look to deploy as a more elegant way to rate limit.
In the first instance, organizations could measure the performance of the infrastructure and services with Service Level Monitoring. At this point, if the services response time rises above a certain threshold it would suggest that the infrastructure performance level has dropped. Taking action at this point is all very well, but against which type of users of the service? So, before any action is taken, we would need to classify the users of the service in some way as to differentiate between them. We are then able to decide which users of the service we would want to rate limit. Because of the unique way that Zeus Traffic Manager inspects client requests we are able determine the location, content or frequency of the request and then classify the user accordingly. So, in the case of Twitter we might wish to classify bots that are sending too many tweets/requests per minute based on what would be reasonable if a human were sending them. We might decide that any Twitter user who is sending more than 5 tweets per minute be classed as an abusive bot.
Once we have decided on when to apply a rate shaping class and which users it will affect, it is at this point we apply the rate shaping class. So, when the service and infrastructure starts to become over-loaded we will limit the users in the class to only 1 tweet per minute. The result of this action is that legitimate users of the service will continue to receive the same high quality of service despite the infrastructure being over-loaded. This solution is much more elegant than the blanket approach of limiting all users all the time.
This is just one example of how Zeus' request rate shaping might be applied in a real world situation. SeeTickets, a current Zeus customer, is an example of how request rate shaping and Trafficscript has been used to ensure its website is always online and fast, even during extreme-peaks in traffic, so valued customers receive an excellent online service. Read the full case study.
For those of you who would like to get a more detailed insight into our request rate shaping capabilities, the following white paper will be of interest: Traffic Valuation and Prioritization with Zeus Traffic Manager.
Next week I plan to discuss how Zeus might assist organizations that are under attack from a DDoS attack.
Mark Gyles
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