Notes on IT (mainly Microsoft)

Archive for the ‘Windows 8’ Category

TCP Loopback Fast Path in Windows Server 2012 and Windows 8

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“The default behavior of the TCP loopback interface is to move local TCP traffic through most of the network stack, including AFD (which is essentially the kernel mode representation of a user mode TCP socket),  as well as the layers corresponding to TCP and IP protocol layers.

Windows Server 2012 and Windows 8 introduce a new optional fast path…


TCP Loopback fast path is just one of the Low Latency Workload support features in Windows Server 2012.

Written by adamsync

January 26, 2013 at 00:35

Windows Azure Active Directory update

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In an earlier post I explained that AD DS on Windows Azure Virtual Machines is not Windows Azure Active Directory and later last year Microsoft announced that two key features of Windows Azure Active Directory are available at no charge.

There is now a whitepaper available that covers Active Directory from on premises to the cloud; here’s a snip of the content.


UPDATE: Microsoft have added an additional paper at the same link:

‘The technical article “Leveraging Windows Azure AD from Windows 8 based Line Of Business (LOB) applications” that comes along with the whitepaper further illustrates how a mobile LOB application built on top of the Windows Store app model can be “connected” to the organization’s Windows Azure AD directory tenant, and how to federate a cloud REST API built with .NET with that directory tenant and consume this API from a Windows Store app. Step-by-step instructions are provided to easily reproduce the configuration.’

Written by adamsync

January 26, 2013 at 00:04

Microsoft Windows 8 and Cisco Wireless LAN Controller incompatibility

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During the Windows 8 beta and preview program, a colleague and I did some detailed testing of new features in Windows 8 wireless networking particularly around the new EAP-TTLS support. We found some issues which Microsoft fixed, however  one problem we found, unrelated to EAP-TTLS, was with certain Broadcom wireless NICs failing to connect to our Cisco wireless network (Lightweight APs with central wireless LAN controllers CUWN). We filed a bug and provided detailed debugging but were disappointed to find the issue still present in Windows 8 RTM. It now seems to be the case that the issue was not with the Broadcom wireless NICs per se, but with the fact that the Broadcom drivers in Windows 8 are Windows 8 logo certified and implement 802.11w (Management Frame Protection) and that it transpires that Cisco wireless LAN controller software has problems in this area, an 802.11w-capable client cannot connect to an SSID on Cisco (controller-based) CUWN using WPA or WPA2 key management with AES encryption, see here for an explanation from Cisco and their official announcement here.

See this //Build conference presentation for Windows 8 wireless networking and particularly the Appendix of the slide deck for more 802.11w in Windows 8 logo certification.

UPDATE: There are now versions of the 7.0, 7.2 and (new) 7.3 cisco software trains that have fixes for the bug (CSCua29504).

UPDATE: A KB article from Microsoft covering this problem is here.

UPDATE: Having now seen a number of Windows 8 clients connected to Cisco wireless networks running controller software that fixes the 802.11w issue, we have found some clients running Broadcom wireless NICs that have very degraded performance. One such example was a Samsung netbook that had been upgraded to Windows 8 and was using the BCMWL63.SYS driver dated 13/03/2012 version; downgrading the driver to the Windows 7 version (BCMWL664.SYS version greatly improved performance. The downlevel driver was obtained from the Samsung support page for the netbook.

Written by adamsync

September 5, 2012 at 23:28

Early reflections on Windows Server 2012 (Was: “Offloaded Data Transfer (ODX) in Windows 8 and Windows Server 2012”)

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I have always felt a little disappointed by the “SANs” that I have encountered, possibly because I have never gotten to use a top of the range product but also because those that I have encountered seem unable to avoid accumulating data from standard applications like file and print. It often seems that once you have spent a big chunk of money on a centralised storage system it becomes inevitable that all storage moves there due to the reluctance to buy any more direct attached storage and “ease of management” and “integration with backup”. However JBODs just keep falling in price; my experience (just mine no general reflection intended here) with Exchange had the following storage profile:

Exchange 5 /Exchange 2000 – DAS array

Exchange 2003 combined roles – SAN based : split database and logs, performance hampered by not being able to afford enough spindles, surprisingly unlucky with 1018 corruptions

Exchange 2007 clustered mailbox roles – DAS array : storage group best practice for LUN allocation etc, just worked but ESE improvements (single bit error correction) make comparison with my Exchange 2003 on SAN experience difficult. Mailboxes became very large due to business needs this started hurting performance.

Exchange 2010 combined roles – DAS : DAG, the application handles the replication/availability. Excellent support for large mailboxes.

The reason for writing about this, which has nothing to do with Exchange, is that watching recent TechEd presentations on Windows 8 and Windows Server 2012 I saw some of the demos on Offloaded Data Transfer (ODX) and I guess this is the sort of heavy-lifting handoff that I always hoped for when having paid for a storage array. For the detail see:

Offloaded Data Transfer (ODX) with Intelligent Storage Arrays

I wanted to give this feature a dedicated post as, in a way, for me it is singular in that it relates to a “high end” hardware capability whereas, as I learn more about Windows Server 2012 the truly remarkable thing to me is amount of IT infrastructure capability it delivers as standard, in the areas of storage and filesystem alone any vendor delivering just those components as present in Windows Server 2012 would be a major player. Microsoft server releases since Windows 2000 have felt to me like continuous evolution; Windows Server 2012 feels like punctuated evolution, a step change brought about it seems from Microsoft’s learning from the demands of running infrastructure at large scale with virtualization as an integrated part of that. As Novell and a need for scalability were a spur that drove innovation in Windows Server 2000, so VMware in the enterprise and Amazon AWS in the cloud, and again the need for scalability, seem to be a spur to Windows Server 2012.

Written by adamsync

July 12, 2012 at 23:00

EAP-TTLS on Windows 8 (Build 8250)

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In Windows 8 Microsoft has invested in EAP-TTLS (RFC 5281) as an outer tunnel for wireless 802.1x connections in addition to the PEAP outer more familiar in Windows clients:

The available non-EAP (inner) methods are:

See RFC5281 Section 15.1 for the message sequences in an example that shows CHAP as non-EAP inner.

Looking at Section 11.2, in particular 11.2.3 (MS-CHAP) and 11.2.3 (MS-CHAP v2) it can be seen that based on the use of “ttls challenge” material (Section 11.1) the client generates the Challenge and the Response based on the corresponding MS-CHAP (v2) algorithm.

The EAP methods for the inner are:

More details on the settings are on TechNet and on Wireless Connection Processes with Windows 8 Release Preview

Written by adamsync

May 8, 2012 at 23:11