Linux Network Internals
Linux Network internals
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Configuring a Linux-based NTP Time Server
Computer time synchronization is very important in modern computer networks, precision and time synchronization is critical in many applications, particularly time-critical transactions. Imagine buying an airline ticket just to the airport that the ticket was sold twice because it then was bought on a computer tells the will had a slower clock!
Modern computers internal clocks called Real Time Clock chips (RTC) have the time and date Information supplied. These chips are battery backed so that even during a power outage, it can keep time, but PCs are not for the perfect watch. Your Design for the mass production and have been optimized low-cost, rather than maintaining accurate time.
For many applications this is can be quite sufficient, although often machines need time to synchronize with other PCs on the network and computers are not synchronized to any other problems such as sharing network caused by files or in some environments even fraud!
Network Time Protocol (NTP) is an Internet protocol used for transmitting the precise time and offers Time information together so that an exact time can be obtained. When NTP was originally written For Linux, many Linux-based operating systems already have a version NTP installed. However, the source code is free from the NTP website are (ntp.org download) the latest version V 4.2.4.
NTP (version 4) can be maintained over time the public Internet within 10 milliseconds (1/100th of a second) and can be even better over LANs with accuracies of 200 microseconds (1/5000th of a second) under ideal conditions to perform.
NTP works within the TCP / IP suite and relies on UDP, a less complex form of NTP exists called Simple Network Time Protocol (SNTP) that it is not necessary to store information about previous communications, needed by NTP. It is in some devices and applications where high accuracy timing is not used so important.
The NTP Desktop program with the file 'ntp.conf' configured. This contains a list of public NTP server references, that can be synchronized to time. NTP Time Server on the "Server" command, all characters after the '#' comments are:
Example
Server-time-a.nist.gov # Public NTP server: Maryland
When configured, NTP can be controlled using the commands' ntpd start'' ntpd stop 'ntpq-p "(shows status)
NTP can also authenticate timing resources Note: It is strongly recommended that you configure a time server, with a hardware source rather than the Internet, where there is no authentication. Authentication codes are specified in the "ntp.keys' file.
Specialist NTP servers available, the programs can receive transmissions from GPS or national time reference. They are relatively cheap and the signal is a secure authentication time reference.
Authentication for NTP has been developed to prevent malicious system with synchronization only firewalls are designed to protect networks from attacks, but as with any system safety, it only works when it is used.
32 Network Attacks Internals eXternal Intranet and Extranet HTB 1-12 By Dario Ortiz ITS, DarioPCX
