LANs to WANs: The Complete Management Guide

In recognition of their customers’ need for fail-safe voice and communications, LECs offer a variety of restoration services. Unfortunately, many of these services are available on a regional basis only. This means that companies with networks spanning multiple regions must implement their own restoration mechanisms via CPE, rely on local carriers for whatever restoration services might be available at each end of the circuits, or opt for an outsourcing agreement with a long-distance carrier to handle restoration from end-to-end.

• Remote call forwarding. LECs can sharply reduce the time it takes to restore vital telecommunications services in the event of a crisis. If a customer needs to reroute voice traffic, many carriers’ customer care teams will facilitate a courtesy remote call forwarding arrangement and customize the number of paths the customer needs. This goodwill capability allows a business to continue its operations until its primary services are restored.

• Preferred call forwarding. LECs also offer customers the ability to control the rerouting of incoming calls to a predetermined backup location in case of an outage. Preferred call forwarding is a line-side feature that is often available on a presubscription basis so that rerouting takes place as soon as an outage occurs.

• Alternate serving wire center. In some cases, companies will want to split their voice traffic between carriers (e.g., inbound versus outbound trunk groups). Local loops can sometimes be provisioned to the same building from two different carriers’ wire centers, offering switch diversity. Even if only one carrier’s services are used, an additional level of protection can be achieved by bringing connections into the building at two different points of entry (see Figure 15.2), so that if the services on one route go down due to a cable cut, the services on the other route remain in operation.

  Figure 15.2: Dual points of entry for connections into a building provide protection from cable cuts.

• Dynamic rerouting. To support recovery services, many of the larger LECs have upgraded their central offices with fiber-optic lines and DCS. Normally, the cross-connect systems are used to set up semi-permanent, high-speed routes between central offices. However, when a DCS is equipped with its own processors and runs management software, it can automatically redirect network traffic to and from various central offices on demand. This dynamic rerouting capability is especially valuable in circumventing cable cuts and faulty central office switches, providing customers with highly reliable communications services.

• Self-healing fiber rings. Major LECs and some of their competitors have installed fiber rings in metropolitan areas, which provide disaster recovery. T1 and T3 connections are protected with alternative routing in the event of node failure on a fiber-optic network. Another restoration service is the self-healing capability of some fiber networks, whereby traffic traverses a redundant counter-rotating ring. If there is a failure on one ring, traffic continues in a different direction to its destination, bypassing the fault.

• Customer reconfiguration. A few LECs provide a comprehensive, real-time management service, which is used in conjunction with their portfolio of digital private-line services. The service allows customers or, if they prefer, the carrier, to reconfigure their private-line networks and perform a range of management functions, such as including DS3 hubbing and reconfiguration, automatic loop-back testing of backup circuits, time-of-day routing, load balancing, and diverse routing.

• Emergency access. Major LECs and some of their competitors have arrangements in place with state authorities to gain access to areas and buildings during declared emergencies. The carriers maintain databases of CAD drawings of equipment configurations to assist in any required service restoration efforts. In addition, the carriers participate with each other in industry discussions about ways they can assist each other to sustain communication services in the event of local disasters or national emergencies.