Dial Restoral and Disaster Recovery

Today's data communications networks are complex, increasingly important corporate assets. As such, network administrators strive to reduce or eliminate network downtime. GDC's dial restoral and disaster recovery products play chief roles in maintaining network uptime.

In addition, carriers may want to create an Operations Systems Support (OSS) network connection to other carriers. This connection would allow the carrier to verify calling card numbers, validate interconnect agreements for particular subscribers, and for general wholesale use of the carrier's database.

Overview

The SpectraComm 28.8 / V.34 dial back up modem provides dial back up for the SC 521A, SC 500A DDS DSUs or SC 202 private line modems.

Applications

Figure 10 - Point-to-Point Dial Backup

Point-to-point dial backup is shown in Figure 10. The dial backup procedures for both analog and digital connections are very similar. A computer or FEP is connected to a user terminal via a leased line. To establish a backup connection, the central site modem calls the remote user's terminal modem to establish a dial line. The dial backup procedure is handled entirely by the modems, or can be manually activated, in which case the dial backup link is established with assistance of a technician.

In applications involving two-wire operation, a single telephone call is all that's required. The new communication path operates in full duplex mode - data can be transmitted and received simultaneously. In four wire dial backup procedures, two telephone calls are placed on the two dial-up telephone lines - one for transmitting and one for receiving.

Figure 11 - Multidrop Automatic Restoral

Multipoint dial backup involves special considerations not found in point-to-point environments (Figure 11). First, multidrop circuits are a bit more complicated, since several modems and conversations are operating on the same circuit. The network operator must determine the number of lines required to back up a multipoint network. When a line failure occurs at one remote site, the customer would prefer to reroute only that site, while keeping the other remote site circuits on the leased line. GDC's solution does just that by dialing the failed remote site only, and bridging that connection back to the master modem.