Large NEs

The trend is towards the deployment of much bigger devices, and as with any engineering proposition, this has advantages and disadvantages. The advantages of bigger (denser) routers and switches are:

• They reduce the number of devices required, saving central office (CO) space and reducing cooling and power requirements.

• They may help to reduce cabling by aggregating links.

• They offer a richer feature set.

Reduced inventory is important because less maintenance is needed, and a richer feature set provides for greater control and functional diversity. (Minimizing inventory also reduces operational and capital expenditure and helps retain cash. It also reduces the risk of holding obsolescent stock.) The disadvantages of such devices are:

• They are harder to manage.

• They potentially generate vast amounts of management data.

• They are a possible single point of failure if not backed up.

Compressing so much functionality into devices makes them harder to manage. Correlating faults with services and their users becomes problematic because of the sheer weight of connections. Also, the management system must support more interaction in all of the FCAPS functional areas. This adds up to more I/O and computation.

A related problem is that of SNMP agents timing out during periods of heavy traffic. The SNMP software process on a given NE may have been given a lower priority than the other service implementation modules, with the result that management operations may not be processed quickly enough. In other words, heavily loaded devices may temporarily starve the onboard management software. It is precisely at the time of heavy loading that the management function is most needed in order to control the network, and this may not be possible because of:

• Process priority clashes

• SNMP message queue sizes that are too small

• Excessive I/O interrupts

Management system availability is increasingly important on large networks, and it is also more at risk precisely because of the growing dimensions of the network. Management system capabilities have to be extended beyond what is currently available. The skills required to create these systems seem to be in short supply in the industry. This shortage of skills is examined in the next section.