What is packet loss and how does it affect your network


What is packet loss?


Simply stated, packet loss is the failure of packets to arrive at their destination. This can happen for many reasons. Some are related to the design of the network. For example some TCP/IP stacks use a method called slow start in an attempt to control congestion. The slow start algorithm inserts traffic into the network until packet loss occurs. Using this algorithm, TCP/IP stacks using slow start can quickly determine the maximum rate they can insert data into the network before causing congestion. Some are related to traffic shaping by vendors and others as networks control the amount of data allowed into their systems. Still others are related to hardware / software problems including cabling. However, the most common problem is too much data for the capacity of the network. This causes congestion. Commonly, networking devices simply drop packets when congestion occurs and this causes packet loss. IsItUp can help you to stay on top of packet loss problems by monitoring the packet loss in your network and alerting you when a problem arises.



How does packet loss affect your network?


Certain protocols such as the Real Time Protocols used for streaming, Voice over IP and gaming are particularly susceptible to packet loss. Packet loss can cause degrading speech quality in VOIP and both degraded speech and video quality when streaming from audio / video feeds. Gammers often find cursors and animation sluggish making it very difficult to play real-time multi-player games. Other protocols such as HTTP, FTP, Etc. are less susceptible to packet loss. They usually only slow down as the packet losses increase transmission times due to the need to retransmit a significant number of packets.



What is an acceptable packet loss?


An acceptable packet loss depends on your situation and your tolerance for errors. However, packet losses greater than 1 to 2 per cent can cause problems for Real time protocols. This level of packet loss might make VOIP, streaming, and gaming appear choppy, sluggish, and jerky. Other protocols that are used primarily for data just slow down as the protocols retransmit to recover loss packets. For these protocols, packet losses of 3 to 5 percent begin to show effects.



How does IsItUp measure Packet Loss?


IsItUp uses the Ping Sensor to measure packet loss. It is recommended that a large number of packets be sent per test to get a reasonable measure of packet loss. We suggest at least a 100 packets be sent per test for data only links and for Real Time Protocols at least 1000. You may also want to increase the size of each packet to be similar to the normal load on your network. IsItUp keeps complete statistics both on packet loss, jitter, and round trip time. It is also worthwhile to mention that ping packets (ICMP) usually have the lowest routing priority and are the first packets to be dropped when a router or a server gets overloaded. Consequently, using ping gives only an estimate of the packet loss experienced by network users. Still, for normal practices, ping is an excellent tool for determining connectivity and packet loss.



For complete instructions on how to setup packet loss and jitter monitoring, please visit How to monitor packet loss and jitter