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Video: Traffic Engineering Using 128T 

05-23-2018 00:23

Most forecasts for networks indicate dramatic growth, both in bandwidth and the numbers of endpoints driving network utilization. 

This ensures that network resources will be constantly contended for, especially in places such as the last mile of wide-area networks, where relatively low-speed links are still commonplace.

The service oriented nature of the 128T Networking Platform (128T) provides a powerful set of tools for making efficient use of network bandwidth, providing true determinism based on sessions, in order to prevent congestion and increase utilization at the same time.

However, sometimes congestion is unavoidable. 

The video above presents a demo of a 128T router's ability to handle congestion, using state of the art traffic engineering and queuing to ensure that critical services and applications are prioritized.

The demo setup is using the default production router at the 128 Technology Seattle branch site. The PC is sitting behind device interface glacier:5 which is set up with a capacity of 15 megabits /second, and is currently operating at around 8-9 mbps, a little below what is provisioned.

All packets arriving at the 128T forwarding plane undergo classification, either based on system default session-types, by service, or by incoming DSCP value. Across the authority we maintain a Gold, Silver, Bronze, and Best Effort service classification, but note that this is completely customizable. 
In this case, we've used a service-policy to explicitly assign four different services to those classifications. The four videos playing in the background are real-time, RTP streaming from each of the four services.

The streams will represent a qualitative measure of what the quality of experience might be like for an end application, such as a video call.

The 128T router indicates each of these streams is consuming between two and three megabits /second.


As you can see, without any congestion, all packets are being promptly forwarded, and the video streams are operating flawlessly.

These streams are ordered from top to bottom by their priority, with Gold on top, then Silver, Bronze, and Best Effort at the bottom.

Now let’s observe what happens when we put the network into a congestion situation. I'm going to use iPerf, an open source traffic generation tool, to create a number of new sessions to contend with the video streams for network bandwidth.


Note that the traffic I'm sending with iPerf is currently being classified into the Best Effort service-class, and given lowest priority. You can see the video stream in the Best Effort service class is impacted, while the Gold, Silver, and Bronze streams are not.

If I add additional traffic to the Bronze service class, you can see that the corresponding video stream now feels the effects of the congestion along with the best effort stream, while the Gold and Silver streams remain flawless.

Removing the contentious traffic, we see the videos restore to full quality.


But what if the network is being congested by traffic in the Gold service-class, which has top priority? Let's create contention by generating seven megabits /second of UDP traffic into the Gold service-class. 

Note that the best effort service is noticeably impacted, while the impacts to video streams in Silver and Bronze service classes are only slightly visible. 

This is because the 128T scheduling algorithm provides fairness between the traffic belonging to the different priorities. 

This is important, as it prevents complete and total starvation of traffic when congestion is happening at higher prioritizations, and allows for flexible bandwidth reservation across the traffic classes.

Last of all let’s take a look at what happens if we add congestion in the form of Best Effort traffic when there is no traffic occurring in Silver and Bronze classifications. As expected, the Gold service remains unaffected under congestion. 


However, note that the best effort utilization has expanded far beyond its guaranteed reservation, to take advantage of the unused bandwidth from Silver and Bronze. 

As I add some traffic to the Silver classification, the utilization of best effort shrinks dynamically to allow room for the new traffic at higher priority. 

This elasticity in the hierarchical scheduler of the 128T router offers key advantages over the traditional packet scheduling done on most legacy routers, and delivers a superior quality of experience in varying network conditions.

#TrafficEngineering #QOS #video #Demo

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