It is important to keep in mind that round trip time is an estimate, not a guarantee; the path between two locations can change over time and other factors such as network congestion can play a role, affecting the overall transit time. Regardless, RTT is an important metric in understanding whether a connection can be made, and if so, approximately how long the trip will take.

What Are the Common Factors That Affect RTT?

Infrastructure components, network traffic, and the physical distance along the path between the source and destination are all potential factors that can affect RTT.

List of Factors That Affect RTT:

• Nature of the transmission medium – The way in which communications are conducted affects the speed at which the connection moves; links carried over fiber optics will behave differently from links made over copper. Similarly, a connection made over radio frequency will behave differently from one made via satellite.
• Local Area Network (LAN) traffic – The volume of traffic on the local network can bottleneck the connection before it reaches the broader internet; for example, if many users are using a video streaming service simultaneously, round trip time may be impeded even though the external network has surplus capacity and is operating normally.
• Server response time – The amount of time it takes a server to process a request and respond represents a potential obstacle in network latency; when a server is overwhelmed with requests, as during a DDoS attack, its ability to respond efficiently can be hindered, leading to increased RTT.
• Number of nodes and congestion – Depending on the path the connection takes across the internet, it may be routed or “hop” through a varying number of intermediate nodes. Generally, the more nodes a connection touches, the slower it will be. A node may also experience network congestion due to other network traffic, slowing the connection and increasing round trip time.
• Physical distance – Although a CDN-optimized connection can often reduce the number of hops required to reach a destination, there is no way around the limitations imposed by the speed of light; the distance between the starting point and the endpoint is a limiting factor in network connectivity that can only be reduced by moving content closer to the requesting users. To overcome this obstacle, a CDN will cache content close to requesting users, thereby reducing RTT.

How Can a CDN Improve RTT?

By maintaining servers within internet exchange points and through having preferred relationships with internet service providers and other network carriers, a CDN is able to optimize network paths between locations, resulting in reduced RTT and improved latency for visitors accessing content cached within the CDN.

Explore the CDN performance lesson to learn how caching,

data center placement, file size reduction, and other optimizations reduce latency and improve RTT. Learn how CDN is used to improve RTT.