When using SIM cards for data services in IoT and GPS tracking, the SIM card costs can become more complicated than it appears at first glance. While most users focus on how much data they consume in total, a lesser-known expense lies in how these connections are initiated and maintained. These hidden costs can add up over time, especially if your device frequently establishes new connections or constantly maintains active links to a network. Let’s dive into how networks manage data transfers and the impact of creating TCP connections, heartbeat signals, and keep-alive mechanisms.
The True Cost of a TCP Connection
Every time your device connects to the internet, it establishes a connection with a server, often using a protocol like TCP (Transmission Control Protocol). This TCP connection requires the exchange of data packets between the device and the server to initiate and maintain the connection. Even though each connection handshake might only use a small amount of data (sometimes around 200-300 bytes), the way mobile networks calculate and bill data usage can result in much larger charges.
For instance, a network might round up the data transfer for each connection to the nearest kilobyte (KB). If your device sends a 200-byte request, the network could round this up to 1 KB or even 10 KB depending on its billing policies. Over time, these small discrepancies between actual data usage and billed data can accumulate, resulting in higher overall costs. For businesses operating devices like GPS trackers or IoT devices, which often initiate multiple TCP connections throughout the day, this can be a significant, hidden cost.
Data Rounding: A Key Factor in Hidden Costs
Many mobile networks apply rounding practices that can inflate data usage. If your device establishes many short TCP connections—each only requiring a few hundred bytes of data—the network may round up each connection session, resulting in a data usage figure that is disproportionately high compared to actual usage. For example:
- Connection 1: The device sends 250 bytes (rounded to 1 KB)
- Connection 2: The device sends 300 bytes (rounded to 1 KB)
- Connection 3: The device sends 150 bytes (rounded to 1 KB)
Even though these three sessions used only about 700 bytes of data, the network may charge you for 3 KB. This adds up quickly when devices establish connections frequently.
Heartbeats and Keep-Alive Signals
In addition to the costs associated with creating new connections, maintaining active connections between a device and a server also consumes data. Devices and servers often rely on heartbeat or keep-alive signals to ensure that connections remain open and active.
- Heartbeat signals: These are periodic, small data packets that are sent to confirm that a connection is still active. While each individual heartbeat is very small—sometimes just a few bytes—the frequency of these signals can cause substantial data usage over time.
- Keep-alive mechanisms: Similar to heartbeats, these are small packets that ensure a TCP connection remains open. Servers and devices exchange keep-alive packets to prevent the connection from being closed due to inactivity.
While the data used for each heartbeat or keep-alive message may seem negligible, networks may still apply the same rounding rules, charging for each signal as if it were a much larger data transfer. This results in devices incurring extra costs even when they’re not actively sending or receiving large amounts of information.
Optimizing Server and Device Settings to Minimize Data Costs
To mitigate the hidden costs of SIM card connections, it’s essential to optimize how your devices establish and maintain connections. One strategy we employ for our customers is to adjust the settings on our server and connected devices to reduce the frequency of heartbeats and keep-alive messages.
For example, if you have a GPS tracking device, you may not need to maintain a constant connection throughout the day especially if a vehicle is parked at the same location. Instead, we can help you configure the server to accept longer intervals between heartbeat signals, reducing the number of TCP connections and associated data usage. Some specific optimizations include:
- Adjusting keep-alive timeouts: Extending the duration between keep-alive signals can reduce the number of small data packets sent, minimizing the rounding effect on your data usage.
- Using UDP for short transmissions: If your application can handle it, consider using UDP (User Datagram Protocol) instead of TCP. UDP doesn’t require the same connection setup and tear-down process as TCP, which can reduce overhead data.
Conclusion: Hidden Data Usage Adds Up
In the world of mobile data connections, every byte counts. The hidden costs of establishing TCP connections, network rounding practices, and the maintenance of active connections through heartbeat and keep-alive signals can lead to much higher-than-expected data bills. For businesses using SIM cards in GPS tracking, IoT devices, or other data-driven applications, it’s essential to understand how these factors contribute to overall data usage. At WhiteLabel Tracking, we assist our customers in optimizing server settings and carefully selecting connection protocols to minimize these hidden costs and reduce their data expenses. To find out more about how we can also help your business, contact us and we’ll schedule a call with our team of experts.
