Figure 3 shows the network architecture, which includes many components, interfaces, and protocols. The following sections discuss tuning guidelines for some of the components involved in server workloads.
WMS
HTTP.SYS
TCP/IP
DNS
IIS
AFD.SYS
Network Driver
User-Mode Applications
System Drivers
Protocol Stack
NDIS
Network Interface
UDP/IP
VPN
NDIS
Figure 3. Network stack components
The network architecture is layered, and the layers can be broadly divided into the following sections:
The network driver and Network Driver Interface Specification (NDIS)
These are the lowest layers. NDIS exposes interfaces for the driver below it and for the layers above it, such as TCP/IP.
The protocol stack
This implements protocols such as TCP/IP and UDP/IP. These layers expose the transport layer interface for layers above them.
System drivers
These are typically clients that use a transport data extension (TDX) or Winsock Kernel (WSK) interface to expose interfaces to user-mode applications. The WSK interface was introduced in Windows Server 2008 and Windows Vista, and it is exposed by AFD.sys. The interface improves performance by eliminating the switching between user mode and kernel mode.
User-mode applications
These are typically Microsoft solutions or custom applications.
Tuning for network-intensive workloads can involve each layer. The following sections describe some tuning recommendations.
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