WT4070...DNS cache and dynamic update support for DNS/WINS

15:00/05-21-2009
4 hour
WT4070
CE5.0
1890792

Customer needs to know if a WT4070/CE5.0 connected via WLAN will cache DNS info and if it will dynamically update the DNS and WINS server updates.

Jarod Fox
11:59 05/27/2009 Take a look

11:59 05/27/2009
Take a look at the following http://msdn.microsoft.com/en-us/library/aa915732.aspx

By default DNS Update is turned off, but can be enabled using the
HKEY_LOCAL_MACHINE\Comm\AFD\ UpdateDnsName
registry value.  Additionally, you can enable DNS caching (and age-out values) with the keys
HKEY_LOCAL_MACHINE\Comm\AFD\ResolverCheckCacheFirst
HKEY_LOCAL_MACHINE\Comm\AFD\MaxPositiveCacheTTL

Also, on CE (NOT Windows Mobile) You can use ipconfig /flushdns to clear the dns cache. 
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Howard Laser
Customer wanted to know some

Customer wanted to know some further info, if possible: Do we cache the resolved IP from a prior connection....he references the 'time to live' value  obtained form a PC with command ipconfig /displaydns...so in this example a request done to same name will use the Host record cached until 691 seconds passed , and then it will need to query dns again.
 Record Name . . . . . : de01dsdc01.am.mot.com
 Record Type . . . . . : 1
 Time To Live  . . . . : 691
 Data Length . . . . . : 4
 Section . . . . . . . : Additional
 A (Host) Record . . . : 10.176.4.221

Additionally, does or device update the DNS and WIN servers with our information as per IP address and /or device name?

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Howard Laser
George, the customer

George, the customer responded  to  the info in your latest post with the following:

This
is an incorrect statement:


The
terminal does NOT actively update DNS or WINS servers.  In fact, no node
(desktop, laptop or mobile) performs this function”


 


DDNS
and WINS update is a function of the stack for all operating systems.  A simple
sniffer trace will show this after a DHCP renewal, assuming the options are
presented in DHCP scope options. According to Microsoft Windows CE is able to it
also.  We were trying to see if Symbol ripped that feature
out.


 


Secondly
I understand the TTL is followed, which make me believe you have a local DNS
cache.  Is there an ipconfig /flushDNS option available for the CE
OS?


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George Dellaratta
This functionality is part of

This functionality is part of the network stack which is owned by Microsoft, not Motorola.

This type of information is cached, but the terminal will not actively update the table.  The update happens as part of a communication session being initiated from the upper layers.  For example, if someone were to try to connect to www.motorola.com through IE, the stack would query the cache and if that name is NOT in the cache it will send a DNS request.  As the communications session continues this cached item will be maintained.  It ages out if not used after some amount of time (I don't know the timeout period).

The terminal does NOT actively update DNS or WINS servers.  In fact, no node (desktop, laptop or mobile) performs this function.

Time To Live has nothing to do with cache timeout.  It is the maximum period of time an IP datagram remains in the system before it is discarded.
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Howard Laser
Thanks, George.

Thanks, George.
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George Dellaratta
Gee, my statement is NOT

Gee, my statement is NOT incorrect.  I'm referring to the default behavior.  As the customer stated, "...assuming the options are presented..."  I'm not willing to make that assumption.

I know of no method to flush the DNS cache.

(Don't bother responding to his comment about the statement being incorrect.  Let's not start an argument...it's not worth it)
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George Dellaratta
I don't think the customer

I don't think the customer understands how this works....

First of all, WLAN doesn't cache any of this type of information...that's the responsibility of the network stack.  Second, there's no such thing as "dynamic" updates to DNS and WINS values.  Specific network messages perform this function.

Here's what you say to the customer:  "The WT40XX product family uses Microsoft's network stack to handle layer 3 and layer 4 functions.  WINS and DNS information are typically provided to the terminal through DHCP and these values are maintained in the registry until the network connection cycles through a disconnect and re-connect."
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Howard Laser
Thank you!

Thank you!
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Howard Laser
Thanks George !

Thanks George !
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