Maximizing EC2 Throughput with ENA Express

Technology provides great utility in almost every aspect of our lives but can prove to be frustrating to work with at times. As technology gets better and better, our expectations for how applications should perform continue to increase. Now, what expectations do you ask? I’m referring to the impatience you feel when a page doesn’t load in 0.5 seconds, when a button click doesn’t give you almost instantaneous feedback, or when your favorite website is down due to network issues. Frustrating, right? In order to fuel our increasing expectations for performance, innovations with how we transport data across the internet need to happen. Luckily, we have great companies that are making strides to satisfy our demands. 

In this blog, we’ll take a look at how the standard TCP protocol works at a high level, talk about Scalable Reliable Datagram (SRD) and the benefits it brings over the traditional TCP networking protocol, and how AWS’s Elastic Network Adapter (ENA) Express is leveraging these performance improvements.

Transmission Control Protocol

The backbone of the internet is derived from the Open Systems Interconnect (OSI) model which is made up of seven layers: the physical layer (L1), data link layer (L2), the network layer (L3), the transport layer (L4), the session layer (L5), the presentation layer (L6), and the application later (L7). The transport layer is responsible for the end-to-end data transmissions between devices. The best known example of the transport layer is the TCP protocol which is built on top of the IP protocol that resides in the network layer, commonly referred to as TCP/IP. The transport layer is responsible for breaking apart data into smaller segments before sending it to the network layer. The transport layer on the receiving device is responsible for taking these segments and reconstructing the original piece of data that was transmitted. The transport layer is also responsible for data flow control, which dictates the optimal data transfer speeds and error handling to ensure missing or dropped pieces of data are retransmitted. 

Transmission Control Protocol (TCP) is one of the basic communication standards that define the rules of the internet and used to transport packets (pieces of data) across the internet. To put it simply, it ensures that the packets of data you send when you click that button makes it to their destination. TCP requires a virtual connection to be made between a client and a server before transmitting packets and also guarantees the order in which those packets were transmitted. This is an important concept to understand for the rest of the blog post. There are other protocols like User Datagram Protocol (UDP) that don’t require an established connection between the client and server or guarantee ordering which makes it faster and cheaper than TCP, albeit less reliable, but we won’t dive deep into those in this article.

To make developers’ lives easier, the TCP protocol works to ensure that each packet gets sent down the same set of paths and reorders packets on the receiving end to ensure the integrity of the message (A->B->C->D->E->F->G).