Vishal Digital Electronics Pvt. Ltd., Vitthalpur, Sikhar, Mirzapur

Time to live For the 1969 French film, see  Time to Live (film) . Time to live  ( TTL ) or  hop limit  is a mechanism which limits the lifespan or lifetime of data in a computer or network. TTL may be implemented as a  counter  or  timestamp  attached to or embedded in the data. Once the prescribed event count or timespan has elapsed, data is discarded or revalidated. In  computer networking , TTL prevents a data packet from circulating indefinitely. In  computing  applications, TTL is commonly used to improve the performance and manage the  caching  of data. IP packets Under the  Internet Protocol , TTL is an 8-bit field. In the  IPv4 header , TTL is the 9th  octet  of 20. In the  IPv6 header , it is the 8th octet of 40. The maximum TTL value is 255, the maximum value of a single octet. A recommended initial value is 64. [1] [2] The time-to-live value can be thought of as an upper bound on the tim...

THE RF CHALLENGES OF ATC COMMUNICATIONS David Hand C.Eng MIET Consultant Engineer - Park Air Systems Ltd. Abstract - The backbone of an Air Traffic Control system is the communication network allowing  controllers to communicate with pilots. Every civilian aircraft should be able to communicate with any  ATC system across the world which leads to unique challenges in establishing and maintaining a  standard system. Against a background of enormous growth in air traffic, upgrading a  communications system on a worldwide basis with many different stakeholders has and will continue  to place considerable demands on the RF parts of the communications networks. This non- mathematical paper will present aspects of the RF performance demanded of ground based ATC  radios and the communications systems they are used in. 1. Radios used in Civil ATC Radios used to communicate between aircraft and the ground have historically never been the same  at each end of th...