Windows® Internals, Sixth Edition, Part 1

For example, the Workstation service (redirector) automatically binds to the TCP/IP protocol. The order of the binding, which you can examine on the Adapters And Bindings tab in the Advanced Settings dialog box (shown in Figure 7-46), determines the priority of the binding. (See the section Multiple Redirector Support earlier in this chapter for instructions on how to launch the Advanced Settings dialog box.) When the redirector receives a request to access a remote file, it submits the request to both protocol drivers simultaneously. When the response comes, the redirector waits until it has also received responses from any higher-priority protocol drivers. Only then will the redirector return the result to the caller. Thus, it can be advantageous to reorder bindings so that bindings of high priority are also the most performance efficient or applicable to most of the computers in your network. You can also manually remove bindings with the Advanced Settings dialog box.

Figure 7-46. Editing bindings with the Advanced Settings dialog box

The Bind value, in the Linkage subkey of a network component’s registry configuration key, stores binding information for that component. For example, if you examine HKLM\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\Linkage\Bind, you’ll see the binding information for the Workstation service.

Layered Network Services

Windows includes network services that build on the APIs and components we’ve presented in this chapter. Describing the capabilities and detailed internal implementation of all these services is outside the scope of this book, but this section provides a brief overview of remote access, Active Directory, Network Load Balancing, and Distributed File System (DFS), including DFS Replication (DFSR).

Remote Access

Remote access, which is available with Windows Server with the Routing and Remote Access service, allows remote access clients to connect to remote access servers and access network resources such as files, printers, and network services as if the client were physically connected to the remote access server’s network. Windows provides two types of remote access:

Dial-up remote access is used by clients that connect to a remote access server via a telephone or other telecommunications infrastructure. The telecommunications medium is used to create a temporary physical or virtual connection between the client and the server.

Virtual private network (VPN) remote access lets a VPN client establish a virtual point-to-point connection to the server over an IP network such as the Internet. Windows also supports the Secure Socket Transmission Protocol (SSTP), which is a newer tunneling protocol for VPN connections that has the ability to pass through most firewalls and routers that block PPTP or L2TP/IPsec traffic. It does so by packaging PPP data over the SSL channel of the HTTPS protocol. Because the latter operates on port 443 and is usually part of typical Web browsing behavior, it is much more likely to be available than traditional VPN tunneling protocols.

Remote access differs from remote control solutions because remote access acts as a proxy connection to a Windows network, whereas remote control software executes applications on a server, presenting a user interface to the client.

Active Directory

Active Directory is the Windows implementation of Lightweight Directory Access Protocol (LDAP) directory services (RFC 4510). Fundamentally, Active Directory is a database that stores objects representing resources defined by applications in a Windows network. For example, the structure and membership of a Windows domain, including user accounts and password information, are stored in Active Directory.

Object classes and the attributes that define properties of objects are specified by a schema. The objects in the Active Directory are hierarchically arranged, much like the registry’s logical organization, where container objects can store other objects, including other container objects. (See Chapter 6 for more information on container objects.)

Active Directory supports a number of APIs that clients can use to access objects within an Active Directory database:

The LDAP C API is a C language API that uses the LDAP networking protocol. Applications written in C or C++ can use this API directly, and applications written in other languages can access the APIs through translation layers.

Active Directory Service Interfaces (ADSI) is a COM interface to Active Directory implemented on top of LDAP that abstracts the details of LDAP programming. ADSI supports multiple languages, including Microsoft Visual Basic, C, and Microsoft Visual C++. ADSI can also be used by Microsoft Windows Script Host (WSH) applications.

Messaging API (MAPI) is supported for compatibility with Microsoft Exchange client and Outlook Address Book client applications.