Panasonic UF-E1, Service Manual

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UF-E1
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The Name resolution flow is shown in the illustration above and follows the sequence below:
1. Query the local DNS Server.
2. Query the root DNS Server because the domain belongs to a destination outside of the company.
3. Com root DNS Server sends the query to the jp root DNS Server.
4. The procedure repeats until a final name resolution is available.
5. The panafax.co.jp server responds with an IP address for the query name.
6. Finally, the name resolution is completed and the destination IP address is determined.
All DNS servers makes an effort to resolve the query name with an IP address, however, a response is not
always sent out every time. Once a name resolution is completed, the information from the DNS Server IP
address table is kept in cache memory at each DNS server in accordance with a minimum TTL (Time To
Live) of SOA (Start Of Authority) record. There are two types of Name Servers, Primary and Secondary
Name Server.
6.5.5.2. Primary Name Server
A primary server has the original copy of a zone file. Any changes made to the zone file are made to the
copy on the primary server. When a primary server receives a query about a host name in its own zone, it
retrieves the host resolution locally from its own zone files.
6.5.5.3. Secondary Name Server
A secondary server gets a copy of zone files from another server. This zone file is a read-only copy of the
original file from the primary server. Any changes made to the zone file are made at the primary server,
then the changes are copied down to the secondary server through a zone transfer. Multiple secondary
servers in a domain improves performance.