Apple 034-2351_Cvr manual NTP Service, How NTP Works

Page 79

NTP Service

6

 

Network Time Protocol (NTP) is a network protocol used to synchronize the clocks of computers on your network to a time reference clock. NTP is used to ensure that all the computers on a network are reporting the same time.

If an isolated network, or even a single computer, is running on wrong time, services that use time and date stamps (like mail service, or web service with timed cookies) will send wrong time and date stamps and be out of synchronization with other computers across the Internet. For example, an email message could arrive minutes or years before it was sent (according to the time stamp), and a reply to that message could come before the original was sent.

How NTP Works

NTP uses Universal Time Coordinated (UTC) as its reference time. UTC is based on an atomic resonance, and clocks that run according to UTC are often called “atomic clocks.”

Internet-wide, authoritative NTP servers (called Stratum 1 servers) keep track of the current UTC time. Other subordinate servers (called Stratum 2 and 3 servers) query the Stratum 1 servers on a regular basis and estimate the time taken across the network to send and receive the query. They then factor this estimate with the query result to set the Stratum 2 or 3 servers own time. The estimates are accurate to the nanosecond.

Your local network can then query the Stratum 3 servers for the time. Then it repeats the process. An NTP client computer on your network then takes the UTC time reference and converts it, through its own time zone setting to local time, and sets its internal clock accordingly.

79

Page 78 Page 80
Image 79
Page 78 Page 80
Contents Mac OS X Server Network Services Administration 034-2351/9-20-03 Contents Glossary Index Using This Guide How to Use This GuideWhat’s Included in This Guide Getting Help for Everyday Management Tasks Setting Up Mac OS X Server for the First TimeGetting Additional Information Before You Set Up Dhcp Service Dhcp ServiceLocating the Dhcp Server Using Static IP AddressesCreating Subnets Assigning IP Addresses DynamicallyAssigning Reserved IP Addresses Setting Up Dhcp Service for the First TimeUsing Multiple Dhcp Servers on a Network Interacting With Other Dhcp ServersSet up logs for Dhcp service Managing Dhcp ServiceStarting and Stopping Dhcp Service Creating Subnets in Dhcp ServiceTo change subnet settings Changing Subnet Settings in Dhcp ServiceSetting the DNS Server for a Dhcp Subnet Deleting Subnets From Dhcp ServiceChanging IP Address Lease Times for a Subnet Setting Wins Options for a Subnet Setting Ldap Options for a SubnetTo set Ldap options for a subnet Disabling Subnets Temporarily Monitoring Dhcp ServiceViewing the Dhcp Status Overview Viewing Dhcp Log Entries Setting the Log Detail Level for Dhcp ServiceViewing the Dhcp Client List Where to Find More Information DNS Service DNS and Bind Before You Set Up DNS ServiceSetting Up DNS Service for the First Time Setting Up Multiple Name ServersLearn and plan Start DNS service Configure basic DNS settingsSet up a mail exchange MX record optional Configure the reverse lookup zone optionalEnabling or Disabling Recursion Managing DNS ServiceStarting and Stopping DNS Service Enabling or Disabling Zone TransfersAdding a Master Zone Managing ZonesTo add a master zone Adding a Slave ZoneTo add a slave zone To duplicate a zone Adding a Forward ZoneDuplicating a Zone To add a forward zoneTo modify a zone Managing RecordsModifying a Zone Deleting a ZoneTo add a record Adding a Record to a ZoneTo delete a record Modifying a Record in a ZoneDeleting a Record From a Zone To modify a recordViewing DNS Log Entries Viewing DNS Service StatusViewing DNS Service Activity Monitoring DNSViewing DNS Usage Statistics Changing DNS Log File LocationTo change the log detail level To see DNS usage statistics Securing the DNS ServerDNS Spoofing Server MiningTo alter BIND’s version response DNS Service ProfilingDenial-of-Service DoS To specify zone transfer IP addressesService Piggybacking Setting Up MX Records Common Network Administration Tasks That Use DNS ServiceExample.com Edit the MX record of the primary mail server Configuring DNS for Mail ServiceTo enable MX records Enabling Redundant Mail ServersTo enable backup or redundant mail servers Setting Up Namespace Behind a NAT RouterNetwork Load Distribution aka Round Robin Setting Up a Private TCP/IP NetworkHosting Several Internet Services With a Single IP Address Configuring Bind Using the Command LineWhat Is BIND? Zone Data Files Bind Configuration FileBind on Mac OS X Server Practical ExampleTo set up the sample files Setting Up Sample Configuration FilesConfiguring Clients If you are using Mac OS X Server as your Dhcp Server Using DNS With Dynamically Assigned IP AddressesCheck Your Configuration Request For Comment Documents For more information on DNS and BIND, see the followingPage IP Firewall Service IP Firewall Service Subnet Mask What is a Filter?Understanding Firewall Filters IP AddressCidr Rule Mechanism and Precedence Using Address RangesMultiple IP Addresses Add filters to the IP filter list Setting Up Firewall Service for the First TimeStart firewall service Create an IP address group that filters will apply toSave firewall service changes Managing Firewall ServiceStarting and Stopping Firewall Service Opening the Firewall for Standard ServicesCreating an Address Group To open the firewall for standard servicesTo create an address group To edit or delete an address group Editing or Deleting an Address GroupDuplicating an Address Group Creating an Advanced IP Filter for TCP portsTo create an IP filter for TCP ports Creating an Advanced IP Filter for UDP PortsTo create an IP filter for UDP ports NFSTo edit advanced IP filters Changing the Default FilterTo change the Default setting Editing Advanced IP FiltersViewing the Firewall Log Monitoring Firewall ServiceSetting Up Logs for Firewall Service Viewing the Firewall Status OverviewTo view denied packets Viewing Denied PacketsViewing Packets Logged by Filter Rules Log ExampleTo do this Block Access to Internet UsersPractical Examples Block Junk MailAllow a Customer to Access the Apple File Server To prevent ping denial-of-service attacks Preventing Denial-of-Service DoS AttacksControlling or Enabling Peer-to-Peer Network Usage Controlling or Enabling Network Game Usage Advanced ConfigurationBackground Creating IP Filter Rules Using ipfw PrecautionsCreating IP Filter Rules Reviewing IP Filter RulesDeleting IP Filter Rules Port ReferencePptp VPN UDP port Used for Reference For more information about ipfw Starting and Stopping NAT Service NAT ServiceTo start NAT service Viewing the NAT Status Overview Configuring NAT ServiceMonitoring NAT Service To configure NAT serviceFor more information about natd To view the NAT divert logPage VPN Service Point to Point Tunneling Protocol Pptp Authentication MethodVPN and Security Transport ProtocolsEnabling and Configuring L2TP Transport Protocol Before You Set Up VPN ServiceManaging VPN Service Starting or Stopping VPN ServiceTo enable L2TP Enabling and Configuring Pptp Transport ProtocolTo enable Pptp To set routing definitions Configuring Additional Network Settings for VPN ClientsConfiguring VPN Network Routing Definitions To configure addition network settingsViewing a VPN Status Overview Monitoring VPN ServiceSetting the Log Detail Level for VPN Service Setting the VPN Log Archive IntervalTo view client connections Viewing the VPN LogViewing VPN Client Connections To view the logPage How NTP Works NTP ServiceSetting Up NTP Service Using NTP on Your NetworkTo set up NTP service To configure NTP on clients Configuring NTP on ClientsPage IPv6 Support Notation IPv6 Enabled ServicesIPv6 Addresses in the Server Admin IPv6 AddressesIPv6 Addressing Model IPv6 Reserved AddressesIPv6 Address Types Where to Find More Information Glossary GlossaryGlossary Glossary Name server See DNS Domain Name System Search path See search policy UCE unsolicited commercial email See spam Glossary Page Index Dhcp VPN

034-2351_Cvr specifications

The Apple 034-2351_Cvr is a remarkable product designed to enhance the user experience for various Apple devices. Known primarily as a protective cover, the 034-2351_Cvr is tailored to meet the demands of both functionality and style.

One of the main features of the 034-2351_Cvr is its premium materials that provide durability while maintaining a lightweight profile. Made from high-quality polycarbonate and soft-touch silicone, the cover not only protects devices from scratches and minor drops but also offers a comfortable grip. The edges of the cover are reinforced to absorb shocks, ensuring your device remains secure under everyday use.

Another defining characteristic is the precise cutouts and tailored design that allows for seamless access to all ports and buttons. Users can easily charge their devices, utilize speakers, and access buttons without needing to remove the cover. This focus on user accessibility aligns perfectly with Apple’s ethos of simplicity and ease of use.

In terms of technology, the 034-2351_Cvr features advanced features that cater to modern-day needs. It provides compatibility with wireless charging, ensuring that users can charge their devices without the hassle of removing the cover. This convenience is especially valuable for users who travel frequently and rely on wireless charging solutions.

Additionally, this cover incorporates antimicrobial properties, helping to reduce the growth of bacteria on its surface. This is increasingly important for users who are aware of hygiene, especially during a time when sanitization has become a priority in everyday life.

Design-wise, the 034-2351_Cvr is available in a range of colors and finishes, allowing users to personalize their devices according to their style. Whether one prefers a sleek matte look or a vibrant glossy finish, there is an option to suit every aesthetic.

Furthermore, the cover is designed to fit securely without adding bulk, preserving the slim profile of the device it protects. This maintains the sleek Apple design language while offering essential protection.

In conclusion, the Apple 034-2351_Cvr is more than just a protective accessory. With its combination of high-quality materials, advanced technologies, and stylish design, it embodies the essence of modern device protection, making it an essential accessory for Apple device users.
Top Page Image Contents