Chapter 17. Monitoring WAN TechnologiesISDN and Dial

Chapter 17. Monitoring WAN Technologies ISDN and Dial

The use of network access servers (NAS) transcends the division between service providers and enterprise networks. Service providers tend to supply public and private dial-in services for businesses or individual home users. Enterprises tend to provide private dial-in access for employees dialing in from remote LANs (a remote office) or individual remote nodes (a telecommuter). Additionally, there are hybrid forms of dial access virtual private dial networks (VPDNs) that are jointly owned, operated, and set up by service providers and enterprises.

Both service providers and enterprise network managers have to find ways to manage the modems, lines, and calls that are being made through the remote access part of the network. Often, the user's perception of the network is driven by their ability to have "remote" access. If your remote access users have consistently poor connectivity to the network, they will perceive that the entire network is poor. Therefore, the success of your remote access strategy becomes a key customer-satisfaction issue.

Now for some bad news: Very few organizations can manage their network access solely through SNMP. There appear to be a few reasons for this:

• Not all information needed is accessible through MIBs.

• There are few commercial access management applications.

• The polling of modem variables can have an adverse effect on the router CPU.

There are no definitive performance guidelines relating a level of SNMP polling to the respective level of CPU utilization. Polling the modem variables is analogous to polling hundreds of interfaces on a router. Therefore, if another CPU-intensive process such as OSPF recalculation occurs at the same time as the SNMP polls, the CPU utilization can increase to nearly 100 percent and the router might even start dropping packets.

Therefore, most customers are using a combination of SNMP, Cisco IOS show commands, and logs (syslog and AAA) to gather the data needed to manage remote access.

This chapter covers the following topics:

• An overview of dial networking

• Performance data for ISDN and dial

• Correlating different variables and performance issues

• Error/fault data for dial and ISDN