Troubleshooting the Network
There are four factors that affect network performance:
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 those caused by the network and those caused by 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.
Packet-level monitoring is ideal for accumulating data. By visually inspecting a packet-level conversation between a client and a poorly performing application, one can see whether the network (or a network device) is the source of the delay or if the application is the bottleneck. This is done by comparing the responsiveness of the TCP ACK to a client request versus the application response, which includes actionable payload data. The use of our Sync Stress tool can help with identifying the latencies.
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. A simple Ping test or file copy across the network can help determine the throughput.
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 a number of other reasons, and must be monitored closely to ensure overall network performance. Packet sniffer tools like WireShark can be used to detect packet loss.
When packet loss does occur, those lost packets are retransmitted. This retransmission process can cause two delays:
- Delays re-sending the data
- Delay resulting from waiting until the data is received in the correct order before forwarding it up the protocol stack
