<P> Network congestion is a cause of packet loss that can affect all types of networks . When content arrives for a sustained period at a given router or network segment at a rate greater than it is possible to send through, there is no other option than to drop packets . If a single router or link is constraining the capacity of the complete travel path or of network travel in general, it is known as a bottleneck . In some cases, packets are intentionally dropped by routing routines . Packet loss can also be caused by a packet drop attack . </P> <P> Packet loss can reduce throughput for a given sender, whether unintentionally due to network malfunction, or intentionally as a means to balance available bandwidth between multiple senders when a given router or network link reaches nears its maximum capacity . </P> <P> When reliable delivery is necessary, packet loss increases latency due to additional time needed for retransmission . Assuming no retransmission, packets experiencing the worst delays might be preferentially dropped (depending on the queuing discipline used), resulting in lower latency overall at the price of data loss . </P> <P> During typical network congestion, not all packets in a stream are dropped . This means that undropped packets will arrive with low latency compared to retransmitted packets, which arrive with high latency . Not only do the retransmitted packets have to travel part of the way twice, but the sender will not realize the packet has been dropped until it either fails to receive acknowledgement of receipt in the expected order, or fails to receive acknowledgement for a long enough time that it assumes the packet has been dropped as opposed to merely delayed . </P>

What is the chief cause of packet delay and loss in the internet