What Is a Congestion Window?

Protocol Systems

• Protocol systems are the infrastructure of data transfers. In the internet age, these systems were revamped and rebuilt to deliver billions of gigabytes of memory rapidly, with minimal memory loss. The purpose of these systems is to transfer data without clogging up the system. The regulatory structure that prevents this is called the Congestion Window, but the CW is dependent on other “windows” that regulate other aspects of data transmission.

Data Regulation

• “Congestion” here refers to the backup of data. More specifically, it refers to the amount of data a computer can receive without freezing up. A network can only receive so much data before becoming overloaded. The data, therefore, must be regulated. The TCP uses what Stevens called the “three way handshake” that is behind the transfer and reception of all data. There is a sender and a receiver, but there must also be a network structure that processes and decodes all data that is sent. In other words, there may be two computers communicating, but this implies a third “master computer” network. These are controlled by firms like AT&T, Sprint and AOL/Time Warner. There are also smaller networks that can also perform these tasks.

Congestion Window

• There is a maximum amount of data that two computers — or two sets of computers — can send and receive at any one time. The data and the computers' ability to either send or receive it are regulated by a group of “windows” the theoretical structure of which was developed by Stevens. The CW sets limits to the amount of data sent. If it is too much, it will be forced to “wait” in the queue system. If it waits too long, it may have to be resent. This is the job of the Restart Window. The Loss Window regulates the Congestion Window. If data is lost through error, the CW can then accommodate more data. If the Restart Window decides to resend the data, then the CW becomes larger until that data is resent. In other words, these windows are self-regulating and constantly interacting to keep data flow at its maximum – but no more.

Congestion Control

• The CW can be pictured as a coordinator – it is a regulator that keeps both the sending computer and the receiving computer apprised of each other. It is a part of the network that oversees internet data transfers and therefore is a part of the network's structure. The web could not function for a minute in an anarchic situation where there were no controls over the amounts and speed of data movement. If the receiver sends too much too quickly, the CW then takes action, slowing the data's reception into the receiving computer.