(1) (Time To Live) A parameter in a network packet that sets a time limit to its validity. In order to prevent an IP packet from propagating endlessly through the network, the value in the TTL field is reduced by each router. When TTL reaches 0, the packet is discarded.
In the DNS system, which converts host names to IP addresses, responses use a TTL field to keep the IP address in the user's cache for a set time. If a company is preparing to change its IP addresses, it can lower the time in the TTL field before the actual change is scheduled. If the address is then cached in the user's computer, it is valid for only a short time, and the company's name server will be queried more frequently. See DNS and DNS rebinding.
(2) (Transistor Transistor Logic) A digital circuit composed of bipolar transistors wired in a certain manner. Widely used since the early days of digital circuitry, a "TTL" designation on an input or output port of a device indicates that it is a digital circuit in contrast to an analog circuit. See ECL, I2L and bipolar.
In the DNS system, which converts host names to IP addresses, responses use a TTL field to keep the IP address in the user's cache for a set time. If a company is preparing to change its IP addresses, it can lower the time in the TTL field before the actual change is scheduled. If the address is then cached in the user's computer, it is valid for only a short time, and the company's name server will be queried more frequently. See DNS and DNS rebinding.
(2) (Transistor Transistor Logic) A digital circuit composed of bipolar transistors wired in a certain manner. Widely used since the early days of digital circuitry, a "TTL" designation on an input or output port of a device indicates that it is a digital circuit in contrast to an analog circuit. See ECL, I2L and bipolar.
 | Reproduced with permission from Computer Desktop Encyclopedia. Copyright (c) 1981-2008 The Computer Language Company Inc. All rights reserved. |
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