Networks have grown and become increasingly complex. In the past, all network users sat at office workstations, and servers lived in a data center. Now organizations have more users, with some in the office while many others are at home or on the road. Additionally some data and applications now reside in the cloud.
A valuable way to gain control of this complexity is to organize devices by function and design a standard module for each type of network subdivision.
What are the benefits of modular network design?
Understanding the operation of the whole network may be overwhelming. But understanding the operation of each type of module one at a time is much easier. If a problem can be traced back to a single module or type of module, then finding the problem should be easier than looking at the entire network.
Network maintenance is simplified by module use. If a new higher-performance workstation or server is introduced, a new module design with higher bandwidth interconnects can be designed. Importantly, modules can be systematically replaced with the new design with the installation of each improved workstation or server.
Modules can also be replicated as many times as necessary. For example, each time more end users are added, additional modules containing workstations and interconnects can be added. Additional server modules can be added as new applications and associated data are added, with each type of module containing different types of interconnects. A module containing servers requires higher bandwidth than a workstation module, and switches and routers in each may reflect different types and capabilities.
Since each module of a type is identical to others of the same type, a problem in one module may not have shown up yet in others of that type but may in the future. A schedule for making the fix in other identical modules can be planned before a problem shows up. Similarly, configuration changes or software upgrades for all modules of a type can be scheduled.
Some of the common benefits of modular network design include the following:
- Easier troubleshooting.
- Improved network maintenance.
- Streamlined network changes.
The three-layer concept and modules
The module concept can be integrated with the widely adopted hierarchical network design principles. Specifically, the network is divided into three layers known as access, distribution and core:
- Access layer. This provides connection points to devices.
- Distribution layer. This is primarily made up of switches and routers that connect devices in the access layer to the core.
- Core layer. This ties the overall network together. It contains the high-capacity switches that link the network to those located nearby or are distant.
The three-level network model does not constrain how elements of each layer are combined into modules, which are commonly defined to combine access and distribution for each type of input. The interconnect switches in each module connect the access layer input devices to the interconnect switches in other modules and to the core.
Different modules include interconnects appropriate to the requirements of the device. For example, a low-bandwidth workstation access module provides connections for relatively low-bandwidth links for workstations and printers used in the accounting department as well as the switches in the distribution layer.
A data module provides connections for servers and storage and higher capacity switches in the distribution layer. A set of internet access modules would be used to support different types of access. One module could support the organization's website and include web servers, a firewall, security devices, load-distribution devices and possibly storage.
A different type of internet access module could be designed to support remote access users. It could support different types of security than the module supporting the web and would support data rates appropriate to its uses.
Yet a different internet access module could support connections to remote offices with different bandwidth and security requirements than the other internet access modules. Other modules would be designed for any other types of access device required by the network.
Network designers are free to design modules for each type of device in their network to suit the requirements of that network. The design of a workstation access module for one network will not necessarily be appropriate for another network. At the same time, adhering to the three-layer concept has proven value for many organizations.
How do enterprises design modular networks?
The modular approach can be expanded beyond modules for individual functions. A set of modules of modules can define an entire network designed for a particular purpose.
For example, an organization may have several remote sales offices. Each of them would have the same requirements: several low-bandwidth workstation modules, a relatively simple core and an internet access module for connecting to the central office. Depending on how the workstation access module is designed, the number of these modules in a sales office network may vary. A module of modules for manufacturing facilities would likely differ from the sales office modules but simplify network design efforts when a new factory is added.
The flexibility of the module concept is its strength. Don't start from scratch for each remote office or factory network. Start by taking modules off the shelf. Define a new module type when necessary. When possible, try to make them as similar as possible so each may differ by bandwidth, but don't violate the layering concept. Don't connect individual workstations to the core. Don't combine workstations with internet access devices.
Use of modules can both speed up network design and simplify maintenance since operation of an individual module is easier to understand than understanding the entire network.