Chapter 4: Network Design Fundamentals - Avaya 8800 Planning And Engineering

Chapter 4: Network design fundamentals

To efficiently and cost-effectively use your Avaya 8000 Series routing switch, you must properly design
your network. Use the information in this section to help you properly design your network. When you
design networks, you must consider the following:
• reliability and availability
• platform redundancy
• desired level of redundancy
A robust network depends on the interaction between system hardware and software. System software
can be divided into different functions as shown in the following figure.
Figure 1: Hardware and software interaction
These levels are based on the software function. A driver is the lowest level of software that actually
performs a function. Drivers reside on a single module and do not interact with other modules or external
devices. Drivers are very stable.
MultiLink Trunking (MLT) is a prime example of Local Software because it interacts with several modules
within the same device. No external interaction is needed, so you can easily test its function.
Interacting Software is the most complex level of software because it depends on interaction with external
devices. The Open Shortest Path First (OSPF) protocol is a good example of this software level. Interaction
can occur between devices of the same type or with devices of other vendors than run a completely
different implementation.
Based on network problem-tracking statistics, the following is a stability estimation model of a system
using these components:
• Hardware and drivers represent a small portion of network problems.
• Local Software represents a more significant share.
• Interacting Software represents the vast majority of the reported issues.
Planning and Engineering — Network Design November 2010 17