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Round-trip time is an important metric in networking that can indicate the quality of communications between two endpoints. RTT can be directly impacted by a range of architecture design decisions, especially by your network topology. What is Round-Trip Time (RTT)?In networking, round-trip time (RTT), also known as round-trip delay time (RTD) is defined as a metric that measures in milliseconds the amount of time it takes for a data packet to be sent plus the amount of time it takes for acknowledgement of that signal to be received. This time delay includes propagation times for the paths between the two communication endpoints. RTT vs. Ping – What’s the difference?Round-trip time and ping time are sometimes considered synonymous. Although ping time can provide a good RTT estimate, the difference is that ping tests are usually performed within a transport protocol that uses ICMP packets. In contrast, RTT is measured at the application layer (layer 7 of OSI/ISO) and includes additional processing delays caused by higher-level protocols and applications (e.g. encrypted communication by HTTPs). RTT vs. Latency – What’s the difference?Network latency is closely related, but different from RTT. Latency is the time required for a data packet to travel from the sending endpoint to the receiving endpoint (only one trip). Many factors may affect this path. The latency is not definitely equal to half of the RTT, because the latency may be asymmetric between any two given endpoints. RTT includes the processing delay at the echo endpoint. What is a good round-trip time?Every type of application will have its own requirements and it’s almost impossible to give a concrete time. What is bearable for one application may be unbearable for another. For instance, AWS WorkSpaces, which is a fully managed and persistent desktop virtualization service that enables users to access their applications and the resources they need, has these thresholds for RTT:
So based on this, your users should have 100ms RTT for normal usage of your application and a maximum of 200ms before your application will degrade the quality of your service. Why is RTT in networking important?Network round-trip time tends to have a great impact on your end-user experience in interactive applications, such as web browsing. Network administrators can use it to diagnose the speed and reliability of the network connection and many web applications disconnect if RTT is too high. How to calculate or measure RTTRTT calculationThe best way to calculate RTT is to understand that when a user loads a web page in a browser, they must first send out a request to load the page. This requires at least one RTT to get the response to the user. RTT is a complex metric that has several components. It includes propagation delay, processing delay, queuing delay, and encoding delay. But normally processing delay, queuing delay, and encoding delay have negligible values. Propagation delay is the length of time taken for a request to reach its destination. The propagation delay is usually the dominant component in RTT and you can get a good estimate of RTT by a simple formula: RTT = 2 x Propagation delay. You should also understand that it generally takes more than a single request to load the entire page. The page might consist of images, scripts, etc., each requiring a separate request to load. If the page consists of 20 components, it may take RTT x 20 to request the entire page. Measure RTTAlthough it is not the most accurate way to estimate RTT, the most common tool used to measure the RTT is a ping) command. A ping command sends Internet Control Message Protocol (ICMP) echo request packets to the destination and then reports the time, in milliseconds, that it takes to receive a response signal. As you can see below, it can be used in Windows command-line (CMD) by typing ping “server ip or link”. You can use the following Linux command to measure average, maximum, and minimum RTT for a specified server.
If you need to know more information about the “route” from the starting-point to the origin server, you can use the command traceroute and get information about how much time every hop in the route takes. What influences RTTThese are some basic things that can influence RTT:
How to reduce RTTThis section is separated into two – General and CDN, because the CDN is a separate way to reduce the overall RTT. General ways to reduce RTT:
Reducing RTT using Amazon CloudFront CDN distributionOne of the original issues CDNs (Content Delivery Networks) were designed to solve was to reduce RTT. They have been largely successful, and it’s now reasonable to expect a decrease in your RTT of 50% or more after onboarding a CDN service. You will read about the main reasons why this is possible in the section below. StormIT recommends using cloud-based CDN such as Amazon CloudFront, which is a network of strategically placed servers, each holding a copy of your content. CloudFront works seamlessly with any AWS origin, such as Amazon S3, Amazon EC2, Elastic Load Balancing, or with any custom HTTP origin. CDN is able to address the factors influencing RTT in the following ways:
StormIT offers custom Amazon CloudFront pay-as-you-go pricing and you pay only for what you use. There is no minimum fee and you can start as low as 1TB/month. Learn more about Amazon CloudFront and how StormIT can help you reduce costs associated with using it or contact us for a free consultation. What is the delay in the amount of time for data to travel between two points on a network Goodput bandwidth throughput latency navigation bar?Latency is a term used to indicate delay when getting a packet from one point to another.
What is the data latency?Data latency is the time it takes for data packets to be stored or retrieved. In business intelligence (BI), data latency is how long it takes for a business user to retrieve source data from a data warehouse or BI dashboard.
What type of network is defined by two computers that can both send and receive requests from resources?Local Area Network (LAN).
What is latency in network?Network latency is the amount of time it takes for a data packet to go from one place to another. Lowering latency is an important part of building a good user experience.
What is the time taken by data to travel from one source point to another destination point?Transit time: It is the time taken by data to travel from one source point to another destination point.
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