If you are interested in networking, soon these letters will be in your way: TTL. Better to get familiar with their meaning and purpose now.
What TTL means?
TTL means time-to-live, and it is a value contained in every IP or Internet Protocol data packet to determine its expiration time. The TTL value is defined by network administrators (senders) based on what is more convenient for the network’s operation, higher or lower values. The TTL informs network routers how long the data packet has been around the network for them to allow it or discard it.
How does TTL work?
Every data packet sent from a host (source) to a destination (another host) will get set with a specific TTL value, established in a number of hops, in its IP header.
While traveling to its destination, the data packet will pass through different routers. Each one will reduce the data packet’s TTL value. At a certain point, the TTL value will be zero, and then, routers will discard the data packet and send to the sender an ICMP or Internet Control Message Protocol message to report “time exceeded”.
As you see, the TTL works as a sort of timer for data packets. It helps to control the maximum time or number of hops through the routers for data packets. Meaning they have to accomplish their trip (purpose) within the time defined by the sender. Once expired, they will be discarded.
What are TTL’s purposes?
Prevention of network congestion
The time-to-live value was created to control the amount of data packets circulating on networks. Without such a mechanism, imagine the number of already pointless and old data packets that could be traveling across a single network. This could be a serious obstacle for networks to work efficiently. However, having an expiry date and the means to be stopped, data packets, no matter if they multiply daily per million, can be under control.
Tracing data about data packets
You can trace through the TTL the complete route data packets have followed, and the time they have been circulating within the network.
Detection and mitigation of security threats
Some cyber attacks, like Distributed Denial of Service (DDoS), are executed by sending a large number of data packets with a high TTL value. Remember that the dark purpose is to overwhelm the target. When you (your system) detect such types of data packets, you can set up routers to discard them and mitigate the impact of the malicious attempt.
Avoidance of routing loops
Routing loops are a big issue for networks. Data packets continually routed via the same routers over and over affect the performance of the network and consume resources like bandwidth and processing power. Thanks to the TTL setup on data packets, especially if the values are low, this issue can be stopped and prevented.
Now, you know what TTL or time-to-live means. It is a versatile mechanism you can use in different ways to ensure the security and efficiency of your network’s operation.