> ## Documentation Index > Fetch the complete documentation index at: https://docs.hologram.io/llms.txt > Use this file to discover all available pages before exploring further. # Data metering > Usage information posted on the Dashboard comes directly from our carrier partners, all of whom are members of the GSM Association. They all use standard protocols and interfaces, and provide us with the information as reported from the gateway. This guide reviews how data metering at Hologram works with data sessions. ## Networking overhead Due to networking overhead, the bandwidth used by a device will be higher than the sum of bytes your application sends and receives. Each TCP packet (and therefore each Hologram Cloud message) incurs an **overhead of about 500-700 bytes**. This means that to reduce data charges, you should prefer fewer large messages over more small messages. Messages larger than about 2kB may be split into multiple packets, so this optimization is mainly relevant for very small messages. Also, keep in mind that higher-level protocols such as HTTP have their own headers which may inflate the per-message overhead. ## Inbound and outbound data Usage data includes both inbound and outbound traffic for a device. ## Data sessions Data usage is reported via **data sessions**, which are the periods of time when a device is connected to a network and transmitting data. Data usage is calculated at the **end of each closed data session**, at which time checks are made for data usage limits and transaction charges and sessions populate in data usage reports. Some checks like usage warnings are checked live during mid-session updates, but most are made at the end of the session. Information about data sessions is provided in **near-real-time**, as frequently as we receive it from carriers. Some carriers and networks provide intra-session data usage updates, some provide updates only at the end of the session, while others provide updates at the end of a block of time which we call a "reporting window". * **API data usage** is provided in near-real-time. * **Recent data usage** reports and last connection details in your dashboard are provided in near-real-time. * **Historical data usage** reports available to contracted accounts and larger organizations are updated every 60 minutes. * **USA-2** and **USA-1** profile data usage is reported only in reporting windows, every 120 minutes for US2 and every 6 hours for US1. ## Network activity monitoring tools Measure device traffic using standard tools: * `tshark`: [Wireshark tshark](https://www.wireshark.org/dashboard/man-pages/tshark.html) * `bmon`: [Bandwidth Monitor](https://github.com/tgraf/bmon) * `tcpdump`: [tcpdump](https://www.tcpdump.org/) If your device is using odd or unexpected amounts of data, please refer to our [guide on unexpected data usage](/guides/troubleshooting/unexpected-data-usage). ## Manage data usage in the Dashboard