Solving issues related to poor Application Response Time (ART) is a key task that network engineers have to tackle all the time. Is it the application itself or a slow network that is driving users mad? Maybe it’s the server that’s simply stalling too much?
Finding the cause of your users’ frustration – the application or the network – is important because knowing exactly where to look is the first step to solving slow response times. Here are four factors that affect network performance you might want to check when faced with network issues:
Latency: Think of latency as the speed limit on a highway. Traffic speed on a motorway is affected by many variables such as weather, other traffic, and highway signs. Likewise, data packets traversing a network are affected by many variables as well. The first step in mitigating latency is to break down the overall latency into that due to the network and that due to the application and its associated servers. With that determination made, visually graph both the application and network latency to help identify patterns and anomalies that deserve closer attention so that you can later drill down and figure out exactly what is causing the bottleneck.
Throughput: Throughput is the amount of traffic a network can carry at any one time. Like the analogy of traffic used to explain latency above, think of throughput as analogous to the number of lanes on a highway. The more lanes, the more traffic a highway can accommodate. When thinking of networks, the higher the bit rate, the faster files transfer. Slow response times might be an issue with your network not having enough throughput.
Packet Loss: Glitches, errors, or network overloading might result in the loss of data packets. Sometimes routers or switches might shed traffic intentionally to maintain overall network performance or to enforce a particular service level. In a well-tuned network intentional packet loss is hopefully a rare occurrence, though packet loss is still something that happens regularly due to a host of other reasons, and must be monitored closely to ensure overall network performance.
Retransmission: When packet loss does occur, those lost packets are retransmitted. This retransmission process can cause two delays; one from re-sending the data and the second delay resulting from waiting until the data is received in the correct order before forwarding it up the protocol stack.
These factors are not exclusive, but they do help paint a picture of the many things that can contribute to a slow network. Hopefully, armed with this information, you can start accurately diagnosing your network before performance issues arise.