Resource: Windows 2000 Server Resource kit TCP/IP Core Networking Guide  

DNS > Example of Queries (Query for a Name in the External Namespace)

Example of Queries (Query for a Name in the External Namespace)
 

در شکل زیر مشاهده می کنید که Client برای شروع query خود را به Proxy serv می فرستد چون آن یک Proxy Client می باشد

برای شروع از طریق PAC Files متوجه می شود که Namespace مورد نظر Internal Namespace نمی باشد پس Query بطرف

Internal DNS Server ها نمی رود. در مرحله بعد این Query بطرف آن Public (External) DNS Server می رود

که در Internet آماده شده برای دریافت Query از Reskit.com  که نام آن سرور Server.reskit01-ext.com می باشد سپس این Query

برای پیدا کردن Host.isp01-ext.com از طریق سرورهای Public root DNS به سرور DNS  با نام Server2.isp01-ext.com فرستاده

می شود تا از آن جواب بگیرد در مورد IP Address سیستمی  بانام Host و DNS Suffix بنام ISP01-EXT.COM و الی آخر .

(PAC) file

Note: proxy autoconfiguration (PAC) file. A list of DNS suffixes and exact names that are internal or external.

Figure 6.30 Query in the Domain Reskit.com for a Name on the Internet

The query proceeds as follows:
  1. Because the client is a proxy client, it consults its exclusion list or its PAC file and determines that the name is not in the internal namespace. Therefore, the client sends the request to the proxy server.
  2. The proxy server sends a query to the DNS server to which it is configured to send queries. In this case, the server is server.reskit01-ext.com.
  3. The server server.reskit01-ext.com sends a query to the Internet root server.
  4. The Internet root server returns a referral to a server that is authoritative for the Internet zone com.
  5. The server server.reskit01-ext.com queries the server that is authoritative for the com zone.
  6. The server that is authoritative for the zone com returns a referral to the server that is authoritative for the zone isp01-ext.com.
  7. The server server.reskit01-ext.com queries the server that is authoritative for the zone isp01-ext.com.
  8. The server that is authoritative for the zone isp01-ext.com returns the IP address that corresponds to the name host.isp01-ext.com.
  9. The server server.reskit01-ext.com returns the response to the proxy server.
  10. The proxy server uses the IP address to contact host.isp01-ext.com and provides necessary information to the client.

Example of Queries    (Query for a Name in the External Namespace)

Query in the Domain Acquired01-int.com  for a Name on the Internet
اما در Acquired01-int.com سرور Proxy وجود ندارد .پس Client یک Query به Local DNS Server خود می فرستد .وقتی سرور
First.Acquired01-int.com در Cache خود جوابی برای آن پیدا نکند این Query را به سرور Parent خود Acquired01.int.com
می فرستد یا در واقع Forward می کند .و آن نیز این Query را بدلیل اینکه در مربوط به Internet می باشد از طریق Firewall به سرور مربوطه بنام
Acquired01-ext.com موجود در Internet می فرستد  و آن نیز به Public Root DNS Server می فرستد و الی آخر .
در اینجا نیز مانند مثال بالا Client بدنبال سیستمی بانام Host.isp01-ext.com  در  Internet می باشد .

Figure 6.31 Query in the Domain Acquired01-int.com for a Name on the Internet

The query proceeds as follows:
  1. The computer queries its local DNS server, server.first.acquired01-int.com.
  2. If the server cache does not contain the requested data, the local DNS server forwards the query to the DNS server that is authoritative for the zone acquired01-int.com, server.acquired01-int.com.
  3. The server server.acquired01-int.com forwards the query to the external server, server.acquired01-ext.com, through the firewall.
  4. The server server.acquired01-ext.com sends a query to the Internet root server.
  5. The Internet root server returns a referral to a server that is authoritative for the Internet zone com.
  6. The server server.acquired01-ext.com queries the server that is authoritative for the zone com.
  7. The server that is authoritative for the zone com returns a referral to the server that is authoritative for the zone isp01-ext.com.
  8. The server server.acquired01-ext.com queries the server that is authoritative for the zone isp01-ext.com.
  9. The server that is authoritative for the zone isp01-ext.com returns the IP address that corresponds to the name host.isp01-ext.com.
  10. The server server.acquired01-ext.com returns the IP address to server.acquired01-int.com through the firewall.
  11. Server.acquired01-int.com returns the IP address to the local DNS server, server.first.acquired01-int.com.
  12. Server.first.acquired01-int.com returns the IP address to the client. The client can then contact the host through the firewall and download the desired Web page.

Last Updated: October 01, 2006

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DNS > Example of Queries (Query for a Name in the External Namespace)

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