How Does Packet Loss Impact Application Performance?
Packet loss is the occurrence of missing data packets in a network transmission resulting in an incomplete transmission, which is dire enough can noticeably degrade real-time transmissions. Incomplete file transmissions typically trigger a recall of missing data packets, which can be noticed, for example, when web pages load slowly. In real-time video and voice, packets typically are not recalled if they are not available when it is time for their playback (known as deadline expiry), this is what gives weak real-time transmissions their “stuttering” characteristic.
How is packet loss measured?
Using standard ping tools found on most computers, packet loss can be tested easily from the command line. Two measurements are typically used to express packet loss, packet loss ratio, and frame loss rate.
The packet loss ratio is the ratio between the number of lost packets to the total number of packets sent. Whereas, the frame loss rate is the ratio between the number of frames received at the destination and the number of frames sent. Depending on the network protocol, packets and frames may be the same size (like in TCP/IP), meaning their ratios will be the same or similar, otherwise, protocols with different packet and frame sizes will have greater differences. In practice, inter-frame dependencies (those packets that span multiple frames) can cause a 3% packet loss ratio to convert into a 30% frame loss rate.
What is acceptable packet loss?
Because packet loss is highly associated with quality of service (QoS), acceptable packet loss is dependent on what data is sent. Typically, real-time applications demonstrate significant quality loss due to small amounts of packet loss. Some have described a 1-2.5% as “acceptable” where others have described 5-10% packet loss as a significant impact on the quality of the session, in some cases even making the session unusable. But, in cases of file transmissions, like web pages or downloads, dropped packets are typically recalled, and packet loss rates can be higher than real-time applications without showing noticeable quality loss.
Application Performance and Packet Loss
Measuring application performance and packet loss, focus will be placed on capturing data traffic on the points involved – both the sender and the receiver – and subsequently determining the number of packets that didn’t get to their destination.
What are the effects of packet loss?
Packet loss directly impacts throughput in two major ways. Lost packets directly reduce sender throughput, further, packet loss indirectly reduces throughput at the transport layer when certain protocols interpret this loss as congestion and make adjustments to correct and avoid this congestion. In effect, minor packet loss can cause cascading delays throughout the network.
This throughput, which is the actual measure of data transfer compared to bandwidth, which is the theoretical measure of data transfer, shares a direct relationship with application performance. As throughput drops, so does application performance resulting in laggy apps.
Common Causes of Packet Loss
- Network congestion—Network congestion causes packets to wait in a routing queue before they are directed to their destination. If congestion grows beyond the network’s capacity to route, to improve network performance, network hardware must manage traffic by dropping packets.
- Software bugs—Bugs within system software can disrupt network performance. This can be a more difficult cause to diagnose and fix. But, if all other causes have been addressed without improving network performance, then assess the software running on the network for patch fixes and updates.
- Problems with network hardware—Network hardware becomes outdated and glitchy over time. If the traffic load on the network increases significantly then the firewalls, routers, and network switches that support that network must also grow to ensure the free flow of traffic.
- Security threats—Traffic is a key weapon for security hackers. Cybercriminals have been known to deliberately tamper with networks directing routers to drop packets and deny services. Additionally, a classic attack is the denial-of-service attack (DoS) where hackers flood a network with traffic in an attempt to overload and crash the system.
How to Prevent Packet Loss
Packet loss occurs on all networks. Sometimes all that must be done to improve performance is to check their connections, restart the network or computer, update software, or remove any non-essential devices from the network.
In enterprise settings, networks serving high amounts of traffic and requiring high standards of security, network visibility has become the key to understanding network traffic and packet loss. Special network monitoring software has been developed to give admins a clearer picture of the activity on their networks. By pinpointing the offending culprits of packet loss, IT departments are far ahead of the curve of setting out an effective solution to return to a high performing network.
Network jitter, a.k.a. packet delay variation (PDV), is a stuttering like effect in signal quality because of inconsistent packet delays in a data transmission. Each packet in the transmission may be routed differently to its destination causing packets to arrive out of order or not at all (called packet loss). Though technology will handle this situation and put the packets back in order, it does cause delays. To illustrate the impact, in cases of high jitter video calls or VoIP, users will experience stuttering video, intermittent voice or dropped calls when speaking to others over the internet.
Quality of Service (QoS) is a qualitative measurement of the overall performance of services like telephony, computer networks, and cloud computing. QoS may also refer to the set of technologies and strategies that organizations deploy, aimed at optimizing network traffic in order to improve the user experience of their apps. QoS approaches are commonly applied to real-time applications, such as VoIP, video-on-demand, streaming video, or online gaming where transmission quality is at a premium.