DFS and site awareness

[gobi]

If I have a domain-based DFS root, and I add links
targeting a non-win2k machine (assuming it supports CIFS
shares), does the site awareness work for that link? Or,
does the site awareness only work with Windows 2000
machines?

Basically, I want to know if DFS gets the site information
from AD, by the IP subnet of the target machine, or by
querying the target machine for information.

thx,
Gobi

[Atul Hirpara [MSFT]]

Hi --

Site determiniation of a link target or a root target is done by looking at
the machine's IP address ranges. The target machine is not queried and
hence does not need any special functionality to announce it's site
information.

The site awareness should work even if your link target is not a W2K
machine.

I also suggest you to look at what Windows Server 2003 offers in this
regard: Here is a summary comparing the site awareness and the closest site
selection.

-------------
Site awareness: When a Windows client accesses a DFS root or link, the DFS
Server will return a list of root targets or link targets arranged in the
following order:

1.. Link or root targets in the same site as that of the client. Within
this set, the DFS lists the targets randomly.
2.. Link or root targets in other sites than that of the client. Within
this set, the DFS lists the targets randomly.
Effectively, the client will connect to a target in its site first if
available. If all the targets in its site are unavailable, it will connect
to target anywhere outside its site irrespective of the proximity of the
target from the client.

This functionality is called site awareness and it exists in all DFS flavors
of Windows 2000 and Windows Server 2003. It is enabled by default. It can
be overridden by the closest site selection mode in Windows Server 2003 DFS.

Closest site selection mode: When a Windows client accesses a DFS root or
link, the Windows 2003 DFS Server will return a list of root targets or link
targets arranged in the following order:

1.. Link or root targets in the same site as that of the client. Within
this set, the DFS lists the targets randomly.
2.. Link or root targets in the next closest site from the client's site.
Within this set, the DFS lists the targets randomly. And so on .
3.. Lastly, the link or root targets without site information configured.
Within this set, the DFS lists the targets randomly.
Effectively, the client will connect to a target in its first site if
available. If all the targets in its site are unavailable, it will connect
to targets in the site closest from its own site and so on.

This functionality is called closest site selection and it exists in all DFS
flavors of Windows Server 2003. This requires ISTGs (inter-site topology
generator) running on Windows Server 2003 in each site where a DFS server
exists. Please refer to Active Directory documentation for details on ISTG.
This functionality is not enabled by default.

To enable closest site selection do the following:

In Windows Serve 2003, this functionality can be enabled using command line
tool Dfsutil.exe version shipped in Windows Server 2003 Support tools:

Dfsutil /Root:<DfsName> /SiteCosting /Enable

The closest site selection mode can be enabled for SYSVOL share too by
creating a registry key described below on all the DCs and then restarting
the DFS service on each DC.

Key:
HKLM\System\CurrentControlSet\Services\Dfs\Parameters\SiteCostedReferrals
Value: DWORD 1 or 0

Note:

v In Windows 2000 DFS, if a target server is moved to a new site, the
Windows 2000 DFS server will not automatically refresh its site information.
This can be solved by removing it as a root target and then re-add it as a
root target.

v Windows Server 2003 can migrate from one site to another site without
the problem in the note above. Windows Server 2003 can discover the site
information dynamically.

v DFS client feature stickiness overrides site awareness and closest
site selection mode.

v After enabling the closest site selection, this mode will come into
effect within 45 minutes on Windows 2000 and 60 minutes on Windows Server
2003 by default.

-------------

"gobi" <gobi...@hotmail.com> wrote in message
news:047901c2e4d2$6d921330$3301...@phx.gbl...

[Mukul Gupta [MSFT]]

In W2K DFS, DFS used to get site information of its target servers using
DsGetSiteName (which makes RPC call to target machine). For getting client's
site, it used its IP and used it to get site from AD.

--
Thanks
Mukul [MSFT]

PS: Please post DFS related queries in newsgroup
microsoft.public.win2000.file_system. Please use "DFS" in subject to make it
immediately noticeable.

Disclaimer: This posting is provided "AS IS" with no warranties, and confers
no rights

"gobi" <gobi...@hotmail.com> wrote in message
news:047901c2e4d2$6d921330$3301...@phx.gbl...

[gobi]

Thanks for the reponse. Mukul, do you know at what point
DFS stopped using DsGetSiteName to get site info? Was it
with Windows 2003 or with a W2K service pack?

Also, what happens if DsGetSiteName calls on a non-W2K
machine -- does it return an error code? Would DFS be able
to determine the site?

>.
>

[Mukul Gupta [MSFT]]

Windows 2003 DFS started using IP address to site mapping for determining
site of target servers as well.
The RPC call (DsGetSiteName) should fail against any non-windows machine (it
fails against NT4.0 machines also as they didn't have the concept of AD
sites).
--
Thanks
Mukul [MSFT]

PS: Please post DFS related queries in newsgroup
microsoft.public.win2000.file_system. Please use "DFS" in subject to make it
immediately noticeable.

Disclaimer: This posting is provided "AS IS" with no warranties, and confers
no rights

"gobi" <gobi...@hotmail.com> wrote in message

news:01d301c2e58e$63d5fc00$a001...@phx.gbl...