This illustration depicts the “TCP 3-Way Handshake” that serves to initialize a connection between two network end systems, such as web client and web server<\/figcaption><\/figure>\nIn TCP\/IP protocol, only after the initial 3-way handshake does the server begin transmitting data back to the client. This requires a total of 2RTT<\/strong>. Keep that in mind; it’s important in differentiating persistent vs. non-persistent HTTP connections.<\/p>\nFor non-persistent connections; the 3-way handshake has to be completed for every object being requested<\/em>. That level of network traffic starts to add up fast and can result in timeouts, dropped packets, and even server crashes.<\/p>\nIn persistent HTTP connections, the socket between client and server remains open<\/strong> and subsequent requests don’t require the 3-way handshake.<\/p>\nNon-Persistent Connections<\/h2>\n
Non-persistent HTTP connections were the defacto means of communication in early HTTP implementations. It’s not that this method was chosen\u00a0over<\/em> persistent connection protocols\u2014rather, persistent protocols didn’t exist yet.<\/p>\nModern web browsers like Chrome, Firefox, and Opera use persistent HTTP connections by default. As such, non-persistent connections are very widely used in modern network applications. However, there are still some advantages.<\/p>\n
Advantages<\/h4>\n\n- Unused resources are freed immediately after use<\/li>\n<\/ul>\n
Disadvantages<\/h4>\n\n- 2 RTT’s per object requested<\/li>\n
- Greater CPU overhead<\/li>\n<\/ul>\n
Persistent Connections<\/h2>\n
Persistent HTTP connections are designed to allow multiple request\/response exchanges without establishing new connections for each. In TCP, this can considerably reduce network congestion and resource use by eliminating the need for the TCP 3-way handshake for each request. One “introduction” between client and server is all that’s needed.<\/p>\n
Advantages<\/h4>\n\n- Lower CPU and memory usage<\/li>\n
- Allows for HTTP Pipelining<\/li>\n
- Reduced network congestion<\/li>\n
- Reduced latency for subsequent requests<\/li>\n
- Errors can be reported without TCP connection termination<\/li>\n<\/ul>\n
Disadvantages<\/h4>\n\n- Resources may be unaccessible even when unused<\/li>\n<\/ul>\n
Review<\/h2>\n
Understanding the benefits of persistent HTTP protocols can help realize the path to better network applications by reducing congestion, freeing up resources, and parallelizing high-demand use cases. While HTTP has evolved considerably since HTTP\/1.0, its reliance on TCP\/IP transport protocols still results in many of the same application concerns.<\/p>\n","protected":false},"excerpt":{"rendered":"
Hypertext Transfer Protocol (HTTP) outlines several ways by which two networked devices can transfer information. Persistent vs. Non-Persistent HTTP connections are among two of the most differentiating aspects of HTTP protocol. Comparing the advantages and disadvantages of each can help determine the best protocol to use given an application’s demand and\/or goals. Before diving in, […]<\/p>\n","protected":false},"author":2,"featured_media":152,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":""},"categories":[3],"tags":[78,79,80,6],"acf":[],"_links":{"self":[{"href":"https:\/\/www.alpharithms.com\/wp-json\/wp\/v2\/posts\/148"}],"collection":[{"href":"https:\/\/www.alpharithms.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.alpharithms.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.alpharithms.com\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.alpharithms.com\/wp-json\/wp\/v2\/comments?post=148"}],"version-history":[{"count":2,"href":"https:\/\/www.alpharithms.com\/wp-json\/wp\/v2\/posts\/148\/revisions"}],"predecessor-version":[{"id":151,"href":"https:\/\/www.alpharithms.com\/wp-json\/wp\/v2\/posts\/148\/revisions\/151"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.alpharithms.com\/wp-json\/wp\/v2\/media\/152"}],"wp:attachment":[{"href":"https:\/\/www.alpharithms.com\/wp-json\/wp\/v2\/media?parent=148"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.alpharithms.com\/wp-json\/wp\/v2\/categories?post=148"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.alpharithms.com\/wp-json\/wp\/v2\/tags?post=148"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
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