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Operating System

Notes contiguous DNS naming hierarchy. For example, bell-labs.com might be the root of the tree, with
research.bell-labs.com and pez.bell-labs.com as children -(domains research and pez). A forest is
a set of non-contiguous names. An example would be the trees bell-labs.com and/or lucent.com.
A forest may be comprised of only one domain tree, however.
Trust relationships may be set up between domains in three ways: one-way, transitive, and cross-
link. Versions of NT through version 4.0 allowed only one-way trusts to be set up. A one-way
trust is exactly what its name implies: Domain A is told it can trust domain B. However, B would
not trust A unless another relationship is configured. Under a transitive trust, if A trusts B and

B trusts C, then A, B, and C all trust each other since transitive trusts are two-way by default.
Transitive trusts are enabled by default for new domains in a tree and can only be confi gured
among domains within a forest. The third type, a cross-link trust, is useful to cut down on

authentication traffic. Suppose that domains A and B are leaf nodes, and that users in A often use
resources in B. If a standard transitive trust is used, authentication requests must traverse up to
the common ancestor of the two leaf nodes; but if A and B have a cross-linking trust established,
the authentications would be sent directly to the other node.

14.5.5 Name Resolution in TCP/IP Networks

On an IP network, name resolution is the process of converting a computer name to an IP address,
such as resolving www.bell-labs.com to 135.104.1.14.
Windows 2000 provides several methods of name resolution, including Windows Internet Name

Service (WINS), broadcast name resolution, domain name system (DNS), a hosts file, and an
LMHOSTS file. Most of these methods are used by many operating systems, so we describe only

WINS here.
Under WINS, two or more WINS servers maintain a dynamic database of name-to-IP address
bindings, and client software to query the servers. At least two servers are used, so that the WINS
service can survive a server failure, and so that the name-resolution workload can be spread over
multiple machines.

WINS uses the dynamic host-configuration protocol (DHCP). DHCP updates address

configurations automatically in the WINS database, without user or administrator intervention,
as follows. When a DHCP client starts up, it broadcasts a discover message. Each DHCP
server that receives the message replies with an offer message that contains an IP address and

configuration information for the client. The client then chooses one of the confi gurations and
sends a request message to the selected DHCP server. The DHCP server responds with the IP

address and configuration information it gave previously, and with a lease for that address. The
lease gives the client the right to use that IP address for a specified period of time. When the lease

time is half expired, the client will attempt to renew the lease for that address. If the lease is not
renewed, the client must get a new one.
14.6 Programmer Interface

The Win32 API is the fundamental interface to the capabilities of Windows 2000. This section

describes five main aspects of the Win32 API: access to kernel objects, sharing of objects between
processes, process management, interprocess communication, and memory management.

14.6.1 Access to Kernel Objects

The Windows 2000 kernel provides many services that application programs can use. Application
programs obtain these services by manipulating kernel objects. A process gains access to a kernel
object named XXX by calling the CreateXXX function to open a handle to XXX. This handle is
unique to that process. Depending on which object is being opened, if the create function fails, it

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