PDF of this tutorialHaving exhausted trunk-side solutions in attempts to relieve the entire network, exploration of line-side solutions is in order. Line-side off-loading serves to relieve the PSTN by keeping data traffic away from Class-5 and tandem switches entirely.
The key component in line-side off-loading is the access gateway (AGW), which separates data calls from voice calls before they hit the ingress switch. The AGW dynamically determines call type using dialed number via intelligent network (IN)/local number portability (LNP) or local database, and routes the traffic accordingly.
Figure 9. Access Gateway Preswitch Off-Load in Detail
In this approach, baseband voice calls are sent to the ingress PSTN Class-5 switch as always, while dial-up ISP calls are routed around it. Fully compatible with trunk-side off-load, COBRAS, and RAS, Internet off-load prior to the ingress switch provides for parsed time division multiplexing (TDM) modem data transport to the egress central office TGW via DS–1 or IMT/PRI, affording total network off-load.
Figure 10. Preswitch Off-Load: Hot Spot Elimination through Redirecting Dial-Up Internet Calls before the Class-5 Switch
Ultimately, preswitch off-load solutions allow carriers to save tremendous switch resources by redirecting various access technologies to the Internet or other data networks without involving any Class-5 switch. By utilizing a preswitch off-load solution, carriers can lessen their investment in costly, inefficient circuit-switched technology and invest in the future.
