Welcome!

Machine Learning Authors: Zakia Bouachraoui, Liz McMillan, Yeshim Deniz, Pat Romanski, Elizabeth White

Blog Feed Post

TCP Pace Yourself

TCP congestion control strives to optimize network goodput while minimizing packet loss by moderating transmission speed. Unfortunately, the way that congestion control moderates transmission often results in microbursts which can overflow buffers on switches and routers. This packet loss in turn triggers congestion control to moderate transmission speeds by reducing the congestion window; TCP then ramps up and the cycle repeats. This oscillation between under and over utilization of the network, combined with retransmission delays due to packet loss, cause application performance challenges and poor user experience.

How does congestion control work?

TCP moderates its transmission speed by calculating a target number of packets to keep in flight. This is the congestion window (cwnd). Typically, the congestion window starts out small and is increased each time the remote system acknowledges receipt of the packet. In addition to adjusting the congestion window, TCP compares the congestion window to the number of packets in flight on the network. In the event that the congestion window is greater than the number of packets in flight, the stack will transmit the difference between the two.

When do packet bursts occur?

Stretch ACKs are acknowledgements that cover 2 or more segments of unacknowledged data. It is possible based on network conditions that a stretch ACK will result in the acknowledgement of all the in-flight packets. When this happens, the TCP stack’s accounting of the number of packets in flight goes to zero and the stack transmits a sudden burst of traffic to bring the in-flight total back up to the calculated congestion window value.

The exponential growth phase of TCP can also trigger packet bursts. During the exponential growth phase, the TCP stack doubles the number of packets in flight each roundtrip time. On high bandwidth high delay networks, these packets travel as a tightly packed group. Once they arrive at the receiver, ACKs will be generated in response. Because of the close arrival time of each of the data packets, the ACKs will also travel as a group. When this tight cluster of the returning ACKs arrives back at the sending system, a burst twice as large as the previous one is generated.

Rate Pacing to the Rescue RatePacingImageRatePacingImage

To mitigate this bursty behavior, F5 introduced rate pacing to TCP Express in v11.5 of BIG-IP. Rate paciRatePacingImagengRatePacingImage  analyzes the traffic on a per flow basis to determine the best speed at which to transmit packets. Rate pacing sends packets at the rate of the slowest draining buffer, resulting in a much smother packet transmission as illustrated to the right. By sending data at a steady pace, large bursts of packets are prevented from traversing the network and causing buffer overflows.

 

 

 

 

 

Read the original blog entry...

More Stories By Dawn Parzych

Dawn Parzych is a Technical Product Marketing Manager at Instart Logic. Dawn has had a passion for web performance for over 15 years with a focus on how to make the web faster. As a technical product marketing manager at Instart Logic, she researches and writes about trends in the web performance space and how they impact the user experience. Prior to joining Instart Logic, Dawn worked at F5 Networks, Gomez & Empirix.

CloudEXPO Stories
DXWorldEXPO LLC announced today that Big Data Federation to Exhibit at the 22nd International CloudEXPO, colocated with DevOpsSUMMIT and DXWorldEXPO, November 12-13, 2018 in New York City. Big Data Federation, Inc. develops and applies artificial intelligence to predict financial and economic events that matter. The company uncovers patterns and precise drivers of performance and outcomes with the aid of machine-learning algorithms, big data, and fundamental analysis. Their products are deployed by some of the world's largest financial institutions. The company develops and applies innovative machine-learning technologies to big data to predict financial, economic, and world events. The team is a group of passionate technologists, mathematicians, data scientists and programmers in Silicon Valley with over 100 patents to their names. Big Data Federation was incorporated in 2015 and is ...
Dynatrace is an application performance management software company with products for the information technology departments and digital business owners of medium and large businesses. Building the Future of Monitoring with Artificial Intelligence. Today we can collect lots and lots of performance data. We build beautiful dashboards and even have fancy query languages to access and transform the data. Still performance data is a secret language only a couple of people understand. The more business becomes digital the more stakeholders are interested in this data including how it relates to business. Some of these people have never used a monitoring tool before. They have a question on their mind like "How is my application doing" but no idea how to get a proper answer.
All in Mobile is a place where we continually maximize their impact by fostering understanding, empathy, insights, creativity and joy. They believe that a truly useful and desirable mobile app doesn't need the brightest idea or the most advanced technology. A great product begins with understanding people. It's easy to think that customers will love your app, but can you justify it? They make sure your final app is something that users truly want and need. The only way to do this is by researching target group and involving users in the designing process.
CloudEXPO New York 2018, colocated with DevOpsSUMMIT and DXWorldEXPO New York 2018 will be held November 12-13, 2018, in New York City and will bring together Cloud Computing, FinTech and Blockchain, Digital Transformation, Big Data, Internet of Things, DevOps, AI and Machine Learning to one location.
Whenever a new technology hits the high points of hype, everyone starts talking about it like it will solve all their business problems. Blockchain is one of those technologies. According to Gartner's latest report on the hype cycle of emerging technologies, blockchain has just passed the peak of their hype cycle curve. If you read the news articles about it, one would think it has taken over the technology world. No disruptive technology is without its challenges and potential impediments that frequently get lost in the hype. The panel will discuss their perspective on what they see as they key challenges and/or impediments to adoption, and how they see those issues could be resolved or mitigated.