Dealing with Slow Networks -TCP/IP

Slow TCP/IP Network Troubleshooting

Network performance is a major concern for many organizations. Slow networks can have significant impacts on productivity and efficiency, as well as customer satisfaction.

Now obviously there can be very simple solutions, if you’re overloading the network you’ll simply need to upgrade.   If your network slows to a crawl every lunchtime, it’s likely everyone is streaming from sites like BBC iPlayer and YouTube whilst eating their lunch.

However, a slow network could be the result of issues with TCP/IP that need to be addressed in order to ensure optimal performance. This article will discuss various strategies for dealing with slow networks related to TCP/IP, including examining common causes of slowness and how they can be resolved.

It will also provide recommendations on how to best monitor and maintain network performance going forward.

TCP Error Recovery Features

In order to improve the performance of networks using TCP/IP, various error recovery features have been designed. These include timeouts, acknowledgements and fast retransmission algorithms.

Timeouts are used by a device on one end of a connection when it has not received any data from its peer after a certain period of time. If no response is received within this window, the device will re-transmit the packet in an attempt to recover from lost or delayed packets.

Acknowledgments (ACKs) are sent between two devices to indicate that the previous data was received successfully and can be used for flow control purposes as well as detecting errors.   They can be used to identity quickly errors like duplicate and fake IP addresses or malfunctioning network cards.

The Fast Retransmission algorithm reduces the amount of latency experienced due to timeout detection by quickly identifying lost or corrupted packets and triggering their re-transmission without waiting for a timeout event.

By utilizing these techniques, slow network speeds caused by poor connectivity can often be improved significantly.

TCP Retransmissions

Network performance is often impacted by the occurrence of TCP retransmissions. These retransmission events occur when a segment that has already been sent and acknowledged by one side fails to arrive at its destination in time, or it arrives corrupted. This creates a need for additional data transmission across the network and can lead to noticeable delays in applications depending on the amount of lost packets.

To understand how this works, consider the following 3 points:

  • When an application sends out some data (a “segment”) via TCP/IP protocol, both sides acknowledge each other that they have received the segment with no errors.
  • If either side does not receive an acknowledgement in due time, it assumes that something went wrong during transmission and will resend (retransmit) the segment until it receives confirmation from the other end.
  • Retransmitting segments uses up extra resources such as bandwidth, thus leading to slower connection speeds overall.

The effect of these retransmissions is especially pronounced if network conditions are suboptimal; high latency connections will be particularly vulnerable to excessive packet drops and therefore more frequent retransmissions may take place than expected. Understanding how these issues affect your infrastructure is essential for identifying where improvements should be made so that service quality remains consistent for customers accessing your services over long distances or low bandwidth links.

TCP Duplicate Acknowledgements

TCP Duplicate Acknowledgements are a common occurrence in slow networks where packets may take longer to traverse the network, leading to retransmissions.

This can also lead to other issues such as buffer overruns or congestion if left unchecked.

When dealing with a slow network, it is important to monitor for duplicate acknowledgments and ensure that they do not become too frequent, as this could indicate an underlying issue with the performance of the network.

If detected early enough, corrective measures such as increasing available bandwidth or optimizing routing protocols may be taken to improve overall performance.

In addition, monitoring applications should be used to track changes over time and alert administrators when thresholds are exceeded.

With these tools in place, issues related to TCP Duplicate Acknowledments can be avoided and system reliability maintained.

TCP Flow Control

The TCP protocol provides mechanisms for dealing with slow networks, such as the Duplicate Acknowledgements mechanism which can be used to detect lost packets. However, in some cases a more proactive approach may be required – this is where flow control comes into play.

Flow control allows the sender and receiver of data to adjust their speeds depending on the current conditions of the network, increasing or decreasing throughput accordingly. Flow control works by having the sender send out an initial window size before beginning transmission of data. This window size indicates how much data it expects to receive from the receiver at any given time.

If too much data arrives at once, then congestion occurs and packet loss is likely. The receiver will therefore send back a reduced window size which tells the sender that they need to throttle down its transmissions until further notice. This cyclic process ensures that each side never sends too much traffic than what the other end can handle, allowing for a smooth flow of communication over a potentially unstable connection.


Network performance can be improved when dealing with a slow network.

  • TCP error recovery features, such as retransmissions and duplicate acknowledgements help reduce the effects of lost packets and misordered packets across the network.
  • Flow control works by adjusting the transmission rate to match the receiving device’s buffer size in order to avoid overflowing it.

Together, these techniques enable reliable data transfer over networks that are experiencing varying degrees of congestion or latency.   As such, understanding how to use them effectively is key for improving overall network performance.