Vocabulary of Internet Performance
This article describes the terms and tools that are commonly used in the field of internet performance. We have taken the liberty, for a broader audience, of simplifying these concepts and using common analogies hopefully without any loss of relevant understanding.
TERMS
These are commonly used terms when discussing Internet Performance:
Packets are the fundamental unit of information transport in all modern networks. When any data (web traffic, email, video, etc.) is sent across the Internet it is divided up into packets. Each packet contains some data plus the addresses of the source and destination. If there is more data than can fit in a single packet it is split across multiple independent packets.
Latency or Delay is the time it takes for a packet to go from a designated point (source) to the destination. Packet delays are typically measured in thousandths of a second or milliseconds (ms). If you think of a highway metaphor, then while the number of lanes between the two cities is the bandwidth, the time it takes for one car to travel between them is the delay.
Jitter (Delay Variation) is defined as the variation in the delay of received packets. Some applications (e.g. Skype Voice) transmit packets in an evenly spaced stream, as the application expects an “even” real-time playout (like listening to someone on the phone). Because of network congestion or path changes the delay of each packet can vary instead of remaining constant, this is called jitter or delay variation.
Packet loss occurs when one or more packets of data travelling across a computer network fail to reach their destination, or arrives with errors. Most applications will need to retransmit the lost or errored packets. This delays the application and can significantly impact user experience if it happens frequently enough. Packet loss is typically caused by network congestion. Packet loss is measured as a percentage of packets lost with respect to packets sent.
Bandwidth is used to define the amount of data the network can carry and is usually expressed in bits per second (bps). Modern networks typically have bandwidth measured in the millions of bits per second (Megabits per second, Mbps) or billions of bits per second (Gigabits per second, Gbps).
Throughput is the rate of data moved successfully from one place to another and is typically measured like Bandwidth in bits per second (bps), Megabits per second (Mbps) or Gigabits per second (Gbps).
Bandwidth, Throughput and Speed are often used interchangeably: When people say "speed" they usually mean bandwidth or throughput. You can think of Internet bandwidth as the number of lanes on a highway between two cities -- it tells you how many cars you can pack on that highway.
Lag is a term used to talk about delays in the transfer of packets. This is commonly used instead of latency (see above). This term is common in online gaming where high latency leads to “lag” in the gaming experience.
Domain Name Service (DNS): Websites are often referred to by their names or URLs (e.g. www.google.com). But the names themselves are not actually the address of the sites. The first time your browser asks for the website, it resolves the name using the Domain Name Service (DNS). Why not just type the IP address in? It is hard to remember numbers, and also often there is not a single server for the same website -- the DNS will also pick the closest server to you that has the website based on the rules the website has set. Your ISP will usually provide your primary and secondary DNS servers.
Does higher bandwidth guarantee better experience? Using the highway analogy, if you have an accident on the highway or construction it will affect the actual carrying rate of the highway (or the throughput of the highway). In a similar way, a lower bandwidth connection that runs clean almost always produces a better user experience than a higher bandwidth connection that experiences timeouts and retransmissions.
A Note on Bandwidth vs Delay or Latency People have used “speed” and “fast” to describe the bandwidth of the connection, because it is faster to download a given size file with a connection of larger bandwidth. But bandwidth is not speed, it is carrying capacity. As a result a higher bandwidth router may or may not, for example, improve gaming delay as there are other factors that impact delay.
TOOLS
There are several common tools used to measure performance:
Ping is a command used to see if a computer can reach another computer. And it also measures how fast a packet can be transferred from the source to the destination and back. Typically the ping command is followed by a target DNS name, web URL or IP address.
Traceroute is a command that exposes the actual path from one computer to the other. Each stop (hop) on the way typically represents a physical router that is traversed and is shown by its IP address and DNS name. Traceroute also measures the time it takes from the source to each of the hops in the path. Some hops in the path route may prohibit the details from being published.
Speed Test is a common tool provided by Internet Service Providers or third parties to measure the time it takes to upload and download a relatively large chunk of data. This test sends data to a known server (upload) and receives data back (download) to measure the rate of transfer. A Speed Test measures the throughput seen when sending and receiving the maximum possible amount of traffic on your connection (by saturating your link).
This article describes the terms and tools that are commonly used in the field of internet performance. We have taken the liberty, for a broader audience, of simplifying these concepts and using common analogies hopefully without any loss of relevant understanding.
TERMS
These are commonly used terms when discussing Internet Performance:
Packets are the fundamental unit of information transport in all modern networks. When any data (web traffic, email, video, etc.) is sent across the Internet it is divided up into packets. Each packet contains some data plus the addresses of the source and destination. If there is more data than can fit in a single packet it is split across multiple independent packets.
Latency or Delay is the time it takes for a packet to go from a designated point (source) to the destination. Packet delays are typically measured in thousandths of a second or milliseconds (ms). If you think of a highway metaphor, then while the number of lanes between the two cities is the bandwidth, the time it takes for one car to travel between them is the delay.
Jitter (Delay Variation) is defined as the variation in the delay of received packets. Some applications (e.g. Skype Voice) transmit packets in an evenly spaced stream, as the application expects an “even” real-time playout (like listening to someone on the phone). Because of network congestion or path changes the delay of each packet can vary instead of remaining constant, this is called jitter or delay variation.
Packet loss occurs when one or more packets of data travelling across a computer network fail to reach their destination, or arrives with errors. Most applications will need to retransmit the lost or errored packets. This delays the application and can significantly impact user experience if it happens frequently enough. Packet loss is typically caused by network congestion. Packet loss is measured as a percentage of packets lost with respect to packets sent.
Bandwidth is used to define the amount of data the network can carry and is usually expressed in bits per second (bps). Modern networks typically have bandwidth measured in the millions of bits per second (Megabits per second, Mbps) or billions of bits per second (Gigabits per second, Gbps).
Throughput is the rate of data moved successfully from one place to another and is typically measured like Bandwidth in bits per second (bps), Megabits per second (Mbps) or Gigabits per second (Gbps).
Bandwidth, Throughput and Speed are often used interchangeably: When people say "speed" they usually mean bandwidth or throughput. You can think of Internet bandwidth as the number of lanes on a highway between two cities -- it tells you how many cars you can pack on that highway.
Lag is a term used to talk about delays in the transfer of packets. This is commonly used instead of latency (see above). This term is common in online gaming where high latency leads to “lag” in the gaming experience.
Domain Name Service (DNS): Websites are often referred to by their names or URLs (e.g. www.google.com). But the names themselves are not actually the address of the sites. The first time your browser asks for the website, it resolves the name using the Domain Name Service (DNS). Why not just type the IP address in? It is hard to remember numbers, and also often there is not a single server for the same website -- the DNS will also pick the closest server to you that has the website based on the rules the website has set. Your ISP will usually provide your primary and secondary DNS servers.
Does higher bandwidth guarantee better experience? Using the highway analogy, if you have an accident on the highway or construction it will affect the actual carrying rate of the highway (or the throughput of the highway). In a similar way, a lower bandwidth connection that runs clean almost always produces a better user experience than a higher bandwidth connection that experiences timeouts and retransmissions.
A Note on Bandwidth vs Delay or Latency People have used “speed” and “fast” to describe the bandwidth of the connection, because it is faster to download a given size file with a connection of larger bandwidth. But bandwidth is not speed, it is carrying capacity. As a result a higher bandwidth router may or may not, for example, improve gaming delay as there are other factors that impact delay.
TOOLS
There are several common tools used to measure performance:
Ping is a command used to see if a computer can reach another computer. And it also measures how fast a packet can be transferred from the source to the destination and back. Typically the ping command is followed by a target DNS name, web URL or IP address.
Traceroute is a command that exposes the actual path from one computer to the other. Each stop (hop) on the way typically represents a physical router that is traversed and is shown by its IP address and DNS name. Traceroute also measures the time it takes from the source to each of the hops in the path. Some hops in the path route may prohibit the details from being published.
Speed Test is a common tool provided by Internet Service Providers or third parties to measure the time it takes to upload and download a relatively large chunk of data. This test sends data to a known server (upload) and receives data back (download) to measure the rate of transfer. A Speed Test measures the throughput seen when sending and receiving the maximum possible amount of traffic on your connection (by saturating your link).
