Edge servers are a primary component of making the Internet fast.
What is a CDN edge server?
A CDN edge server is a computer that exists at the logical extreme or “edge” of a network. An edge server often serves as the connection between separate networks. A primary purpose of a CDN edge server is to store content as close as possible to a requesting client machine, thereby reducing latency and improving page load times.
An edge server is an edge device that provides an entry point into a network. Other edge devices include routers and routing switches. Edge devices are often placed inside Internet exchange points (IxPs) to allow different networks to connect and share transit.
How does an edge server work?
In any particular network layout, several different devices will connect using one or more predefined network patterns. If a network wants to connect to another network or the more extensive Internet, it must have some form of bridge for traffic to flow from one location to another. Hardware devices that create this bridge on the edge of a network are called edge devices.
Networks connect across the edge
In a typical home or office network with many devices connected, mobile phones or computers connect and disconnect to the network through a hub-and-spoke network model. All of the devices exist within the same local area network (LAN), and each device connects to a central router through which they can connect.
To connect a second network to the first network, at some point, the connection must be made between the networks. The network’s connection device is, by definition, an edge device.
Now, if a computer inside Network A needs to connect to a computer inside Network B, the connection must pass from Network A, across the network edge and into the second network. This same paradigm also works in more complex contexts, such as when a connection is made across the Internet. The ability for networks to share transit is bottlenecked by the availability of edge devices between them.
When a connection traverses the Internet, even more intermediary steps must be taken between networks A and B. For the sake of simplicity, let’s imagine that each network is a circle, and the place in which the circles touch is the network’s edge. For a connection to move across the Internet, it typically touches many networks and moves across many edge nodes. Generally speaking, the farther the connection must travel, the greater the number of networks that must be traversed. A connection may traverse different Internet service providers and Internet backbone infrastructure hardware before reaching its target.
A CDN provider will place servers in many locations, but some of the most important are the connection points at the edge between different networks. These edge servers will connect with multiple networks and allow traffic to pass quickly and efficiently between networks. Without a CDN, transit may take a slower and/or more convoluted route between source and destination. In worst-case scenarios, traffic will “trombone” large distances; when connecting to another device across the street, a connection may move across the country and back again. By placing edge servers in key locations, a CDN can quickly deliver content to users inside different networks. Explore how CDN performance works to learn more about the improvements of using CDN.
What is the difference between an edge server and an origin server?
An origin server is the web server that receives all Internet traffic when a web property is not using a CDN. Using an origin server without a CDN means that each Internet request must return to the physical location of that origin server, regardless of where in the world it resides. This increases load times, which increases the further the server is from the requesting client machine.
CDN edge servers store (cache) content in strategic locations to take the load off of one or more origin servers. By moving static assets like images, HTML, and JavaScript files (and potentially other content) as close as possible to the requesting client machine, an edge server cache can reduce the time it takes for a web resource to load. Origin servers still have an essential function to play when using a CDN, as necessary server-side code, such as a database of hashed client credentials used for authentication, typically is maintained at the origin.
