2. Network Power Management for Windows 7
Bob Combs Lead Program Manager Core Networking

3. Agenda Power Management Background Wake on LAN / Wake on Wireless LAN
Power Management Offloads
Capability Advertisement
Wireless Offload
Wake Patterns
Wake on Media Connect
Keywords and Windows Management Instrumentation (WMI)

4. WoL Today Today Wake on LAN (WoL) -
Wake up on magic packet
Wake up on patterns
Off by default
When WoL is enabled, it wakes too often
Wakes due to frequent Address Resolution Protocol (ARP) requests
Wakes due to directed packet
From

5. Network Power Management Goals
Sleep when idle, by default
Reduce runtime idle power consumption by reducing power consumed by network devices when idle
PC that sleeps for 14 hours a day saves between 598 and 760 kWh/yr (~1/10 automobile)
Average savings of $63,500 per year for an organization with 1,000 PCs
Environmental impact: saves between 420 kg and 534 kg of carbon dioxide generated with energy production

6. Windows 7 Power Management Features
Power management offloads
Address Resolution Protocol (ARP)
Neighbor Solicitation (NS)
Wake-on-LAN (WoL)
On by default
Revised set of wake pattern bitmaps
Wake patterns include packet types
Wake-on-Wireless LAN (WoWLAN)
Same as WoL plus …
Offload Robust Security Network (RSN) rekey
Wake on Media Connect (a.k.a. D3 on Disconnect)

7. Capability Advertisement
Miniport driver reports capabilities to NDIS during initialization
WoL pattern type packets supported
Total number of patterns supported (pattern type & bitmap patterns)
Protocols that can be offloaded to the NIC
Number of ARP supported
Number of NS supported

8. New Power Management OIDs
OID to query the hardware capabilities of the NIC
Returns the supported capabilities of the NIC
OID to query/set the miniport driver capabilities
Query the capabilities of the NIC that are currently enabled
Enable/disable the capabilities of the NIC
OIDs to manage WoL patterns
Add/remove bitmap patterns
List the current set of patterns in the NIC
OIDs to manage protocol offloads (ARP, NS)
Add/remove/list protocol offloads

9. Wake Patterns Magic packet Bitmap pattern
Wake Packet Type (new for Windows 7)
Can be used in place of bitmap pattern
NDIS_PM_WOL_PACKET specifies packet type WoL patterns
IPv4 TCP SYN packet
IPv6 TCP SYN packet
802.1x EAPOL request identity message
Same as previous NDIS

10. Address Resolution Protocol Offloads
ARP request processing in the NIC
Takes a Host IPv4 address and a Host MAC address
NIC should support multiple IPv4-MAC address tuples
NS processing in the NIC
Takes a Solicitation IPv6 address, a MAC address, and a list of up to 2 Target IPv6 addresses
Typically need at least two NS sets

11. Wireless Offload 802.11 RSN rekey processing on NIC 802.11 waking
Offload Group Temporal Key (GTK) rekeying (WPA2) while system is asleep
OS initiates offload of Pairwise Master Key (PMK) and Temporal Key (TK)
waking
Wake reloads PMK & TK
OS initiates reload
Wake events are the same as wired, plus
Association with current Access Point (AP) is lost
802.1x EAP request/identity packet received
4-way handshake request received / TK unicast expires

12. Windows Wake Patterns OFFLOAD SUPPORTED ENTERPRISE HOME
ARP & NS OFFLOAD
Magic Packet
NETBIOS name query
TCP SYN v4
TCP SYN v6
LLMNR v6
LLMNR v4
ARP OFFLOAD only NS
NO OFFLOADs
Magic packet
ARP

13. Wake on Media Connect While machine is in system working state (S0)
On LAN cable disconnect
Miniport driver is notified
NIC is placed in device sleep (D3)
On reconnect
NIC asserts WAKE#
NDIS puts the device into working state (D0)
If the system goes to sleep while the cable is disconnected, wake on media connect is canceled

14. Media Disconnect Sequence

15. Media Reconnect Sequence

16. Standard Keywords for Power Management
SubkeyName
ParamDesc
Value
EnumDesc
*WakeOnPattern
Wake on pattern match
Disabled
1 (Default)
Enabled
*WakeOnMagicPacket
Wake on Magic Packet
*DeviceSleepOnDisconnect
Device sleep on disconnect
*PMARPOffload
ARP offload
*PMNSOffload
NS offload
*PMWiFiRekeyOffload
WiFi rekeying offload

17. WMI Interfaces WMI interfaces to query and set configuration settings
WMI interfaces to query current and hardware capabilities
Diagnostics - nicstats
Display power management capabilities and enable status

18. NDIS 6.20 Power Management Logo Requirements
NDIS 6.20 WoL logo
Support at least 6 WoL patterns
Support at least 8 WoL patterns required by 2010
Network presence offloads
Support ARP and NS optionally
ARP and NS offloads required by 2010

19. Call to Action
Update hardware and drivers to NDIS 6.20 to take advantage of new Windows 7 functionality
Provide support for at least 8 wake patterns
Implement ARP and NS power management offloads on NIC
Support new packet type patterns
Implement RSN Rekey offload for wireless NICs

20. Resources Windows 7 WDK will be available as of WinHEC
Windows Logo Program Web site:
NDIS 6 Feedback alias:

21. Related Sessions Session Day / Time NDIS 6.20 Overview
Mon. 9:45-10:45 and
Tues. 9:45-10:45
Windows Logo Program Tests for NDIS
Mon and
Wed. 9:45-10:45
Discussion: Porting Drivers to NDIS 6.20
Wed. 8:30-9:30
Lab: How to Debug an NDIS 6.20 Driver
Mon. 2:45-3:45 and
Mobile Broadband Driver Development for Windows 7
Mon. 1:30-2:30
Virtual Machine Queue Architecture Review
Tues. 2:45-3:45
Virtual Machine Queue Driver Development
Tues. 4-5
Developing TCP Chimney Drivers for Windows 7
Tues

22. Questions?