TCP Optimization!
What does Cisco SD-WAN have in common with YouTube? TCP Optimization! Learn how Google's BBR algorithm significantly improves throughput on high latency WAN links.
High latency on a WAN link between two SD-WAN sides causes bad application performance. You have critical TCP traffic, which must be optimized.
When you use TCP Optimization feature, you improve the average TCP throughput for critical TCP flows between two SD-WAN sites. Take a look at the overview and differences between TCP Optimization on cEdge Bottleneck Bandwidth and Round-trip (BBR) and vEdge (CUBIC) Fast BBR propagation time algorithm is used in the XE SD-WAN implementation (on cEdge).
Viptela OS (vEdge) has a different, older algorithm, called CUBIC. CUBIC takes mainly packet loss into consideration and is widely implemented across different client operating systems. Windows, Linux, MacOS, Android already have CUBIC built-in. In some cases, where you have old clients running TCP stack without CUBIC, enabling TCP optimization on vEdge brings improvements. One of the examples, where vEdge TCP CUBIC optimization benefited, is on submarines that use old client hosts and WAN links experiencing significant delays/drops. Note that only vEdge 1000 and vEdge 2000 support TCP CUBIC. BBR is mainly focused on round-trip time and latency. Not on packet loss. If you send packets from US West to East coast or even to Europe across the public internet, in the majority of the cases you don't see any packet loss. Public internet is sometimes too good in terms of packet loss. But, what you see is delay/latency. And this problem is addressed by BBR, which was developed by Google in 2016.
In a nutshell, BBR models the network and looks at each acknowledgement (ACK) and updates max Bandwidth (BW) and minimum Round Trip Time (RTT). Then control sending is based on the model: probe for max BW and min RTT, pace near estimate BW and keep inflight near Bandwidth-Delay-Product (BDP). The main goal is to ensure high throughput with a small bottleneck queue.
Read the full solution here:
Configure TCP Optimization Feature on Cisco IOS® XE SD-WAN cEdge Routers
