The services provided on the network must be viewed independently of the divisional network structure. The integrated-network model groups the computers by the services they provide to the company rather than by division. The services can be grouped into four categories, called layers: Enterprise, Division, Department, and Desktop.
Table 4.1 Layers of the Services-based Network Model
Network Level | Services provided | Users | |
Enterprise | Support for the global network (such as centralized user accounts and network services) and providing master copies of common information across the organization | 40,000 | |
Division | Centralized file, print, and application services, focusing on business operations | 100 to 1,000 | |
Department | Local file, print, and application services | 25 to 100 | |
Desktop | Local file and application services | 1 to 25 | |
The new model also enables productive change in the following other areas.
The next sections describe the network services at each level and show how these will help create an efficient network at Terra Flora.
Servers at this level focus on supporting the global network (such as centralized user accounts and administration) and providing the master copy of common information across the organization. Enterprise servers are directly connected to the corporate or remote backbone, are kept in protected environments in the work area of the network administrators, and usually operate at 100 MB per second (such as by FDDI, CDDI, or Fast Ethernet). An Enterprise server might provide networking services for up to 40,000 users.
Local availability of the servers can affect which services exist at which level. When remote distances separate the servers and the users, backbone traffic can make timely access to these services difficult. Communications across WANs can be slow and costly. This makes direct, corporate-wide access to Enterprise services impractical. It makes sense to set up the servers at this top (Enterprise) level to maintain and update information, which users would access at lower levels.
For example, a server can be the master distribution point for site- or corporate-licensed software, standard corporate applications, and employee information. The master source servers would store the master copy, which would be used to replicate sources and download to servers on the Division level. This ensures that they are synchronized with the master corporate copy. Since Division-level servers are local to the users in the division, this replication and synchronization reduces both the network traffic on the corporate backbone and the cost of WAN communications.
Enterprise servers can also host the master copy of the distribution packages deployed by Microsoft Systems Management Servers.
The services typically offered at this level include the following items.
This service ensures that users can log on to the network and perform the tasks for which they have permission. NetLogon is the Windows NT service that performs this function.
This service allows a copy of the Directory Database (formerly called SAM) to be replicated on other servers, effectively distributing the logon authentication process. Under Windows NT Server, NetLogon performs this function.
These services allow an administrator to configure network services that affect the entire network and to make any administrative changes from one site.
For example, a Dynamic Host Configuration Protocol (DHCP) server can be added to the network and configured to allow centrally defined global and subnet TCP/IP parameters for the entire internetwork. When a workstation computer moves between subnets, it is automatically reconfigured for TCP/IP at system startup.
This service centralizes the resolution of the unique user names and TCP/IP addresses that allow access to computer resources on the network.
For example, a server running the Windows Internet Name Service (WINS) server software would perform this function. WINS servers maintain a database that maps computer names to IP addresses, allowing users to communicate with other computers and gain all the benefits of using TCP/IP.
As another example, a DNS server also provides dynamic mapping of domain names to IP addresses and is the commonly used name-resolution service in environments running a UNIX operating system.
Servers at any level typically provide backup services for the next lower level of servers. Enterprise servers perform this function for the servers on the Division level, which, in turn, perform backups for the Department-level servers. Enterprise servers do not usually back up for the Department level.
To reduce network traffic across the Enterprise backbone, servers at this level might support only one or two networking protocols. Frequently, the choice is the TCP/IP protocol.
These servers can be used to create web sites that the public can access for corporate information and customer-focused marketing.
These servers store information that is to be available to all employees on the internal corporate network, but not to users outside of the company or organization. This might include corporate standards, employee benefits, corporate events, and other information, such as job listings. These Enterprise-level servers typically host references to the Division-level servers. For example, an Enterprise server might refer to a Division web site for the company's retail operations.
These services affect organization sites but are hidden to the users. For example, the Enterprise servers can act as storage and master source for distribution of organization-supported software. The replicator service distributes the software to the Division level for distribution to the lower levels.
This level typically contains the centralized file and print application, focusing on business operations. Division-level servers often provide networking services for up to 1,000 users, although they can be scaled to support larger numbers of users.
If the location of the division or region requires connecting over slower WAN links, then Enterprise services may be supplied at this level.
The Division level usually include the following services.
These interfaces allow interoperability with other servers including UNIX, NetWare, LAN Server, and Banyan VINES.
This level may provide heterogeneous protocols, such as TCP/IP, IPX/SPX, SNA, and VINES IP, which allow integration with services offered on UNIX, NetWare, or mainframe Enterprise servers.
These servers provide corporate information that focuses on the division or region. For example, project plans, schedules, reviews, presentations, and background information for the division are stored here. Data sheets, product reviews, product comparisons, and product specification sheets may also be stored here for easy access and distribution to field sales and marketing personnel.
Servers at any level typically provide backup services for the next lower level of servers. For example, Division servers perform this function for servers on the Department level.
Servers at this level focus on the business tasks. These servers provide local file, print, and application services. They also provide temporary file storage for workgroup projects, home directories, and scheduled-backup directories. In a typical scenario for this level, servers are organized by workgroups or departments to provide networking services for 25 to 100 users.
At the Enterprise level, a limited number of high-cost, high-performance servers address the centralized needs of the entire organization. At the Division level, less expensive servers provide adequate performance to a smaller group. At the Department level, a server may be a workstation-class machine, such as a 486 computer with 16 MB RAM running Windows NT Server.
Department-level servers typically provide the following services.
Information is stored about the department tasks and workgroup projects. Enterprise and Division servers can access this information to compile reports.
This information is specific to the Department. Status reports and the supporting information may be posted here for everyone to browse through at their convenience.
At this level, project web sites may be created and posted to the Internet.
Servers at any level typically provide backup services for servers or computers on the next lower level. Department servers perform this function for Desktop computers.
In most corporations, the desktop computer is the productivity platform, running either Windows 95 or Windows NT Workstation with various applications, such as Microsoft Office and custom programs for specific business needs. The focus here is to provide services to remote, mobile-networking, and desktop clients. The logical grouping of the desktop groups may include small departments of 5 to 20 people, or may include thousands of desktop computers. The services offered include the following functions.
The Desktop provides local storage for personal files and application data for business applications.
For productivity desktops, the local applications might include Microsoft Office Professional. For developer-class desktops, this might include Microsoft Visual C++® compilers and debug versions of the operation systems. For Internet Information Server service (IIS) developers, this might include IIS and SQL applications.