The Interexchange Carriers (IXCs)

There are four main long-distance players in the United States: AT&T, MCI, Verizon, and Sprint. These carriers face a number of seemingly insurmountable problems including rapidly increasing customer counts, growing minutes of use (MoU) per subscriber, and a rapidly declining dollars-per-transported-bit-per-mile figure, the combination of which is deadly. Needless to say, this explains their compelling argument for accelerated local service and broadband entry.

One bone of contention for the IXCs is that more than 40 percent of all IXC revenues are paid to ILECs as access charges. Access charges are the fees paid to ILECs by long-distance carriers for the right to use local exchange facilities for the origination or termination of traffic transported to or from one exchange to another by an interexchange carrier. And while some access charges are billed directly to the end user, most of them are paid by interexchange carriers—not an insignificant amount of money. IXCs hope that future regulatory decisions will address the magnitude of this fee. In fact, one reason that VoIP has become so popular among those deploying the service is that it is currently classified by the FCC as an information service rather than as a telecom service, which means that VoIP carriers are exempt from many of the regulatory tethers that bind traditional service providers.

Inter Exchange Networks

Inter-exchange networks (IXCs) are telecommunications networks that connect local exchange carriers (LECs), competitive local exchange carriers (CLECs), local post, or telephone and telegraph (PTT) with each other. IXCs provide long distance bearer service communication and may provide other value-added teleservices. IXC’s are regulated by governmental commissions but are not usually government-owned. In other parts of the world the government may own and operate LECs and PTTs.

Some IXC’s provide interconnection for the Internet through their high-speed links and switching nodes. IXC networks use meshes of microwave, fiber, copper, coaxial cable, and satellite links to interconnect their switching systems.

Figure 1 shows a diagram of an inter-exchange carrier network. This diagram shows that the IXC interconnects LECs and CLECs with teach other through POP switching points. Access lines connect the IXC POP switching centers with LEC and CLEC tandem switching systems. These interconnection lines are typically dedicated high-speed carrier transmission lines such as DS3 or OC3 lines.


Figure 7.1: Inter-Exchange Carrier Network

Overview
IXC networks use high-speed switching systems to interconnect high-capacity transmission lines. End users connect to IXC networks either through local telephone systems or through direct connection using customer provided equipment (CPE). Network interconnections are the points where IXCs connect to other networks. Transmission lines transport signals through the IXC network. High-speed switching systems provide interconnections between transmission lines and individual channels on those transmission lines. IXCs have multiple types of international interconnection issues to adapt telecommunication formats between different types of systems.

The overall operation of services, switches, and transmission lines in an IXC is coordinated by network operations centers (NOCs). NOC’s continuously monitor the status and performance of all network nodes and links. If a network transmission or equipment fails, most networks will automatically reconfigure to (reroute) communication lines or automatically switch to backup systems. Practically all network components have redundant assemblies that will automatic switch into service on detection of equipment failure. Multiple routes are required between all switching facilities. These facilities are hardened with all support systems such as power, water, local emergency access, security redundant, and sabotage-proof.

NOC’s management systems are usually distributed to multiple locations. These management centers contain information related to addressing, routing, and reroute scenarios. These regional centers are capable of distributing the network configuring information to remote switching nodes through communication links. Through this application of decentralized control and operations combined with an extensive data base maintenance and support activity, the utilization, efficiency, and security of network capacity can be maximized.

The actual placement of circuits and switching equipment is confidential information when viewed as an operational system. This is because of the critical nature of this type information to all countries. Major damage to a country’s telecommunications infrastructure could easily cripple an area or even a whole country. Telecommunications is considered a vital part of national security and special requirements exist to the protection and reliability of telecommunications networks.

Network Interconnection Points
IXCs connect to LECs, CLECs, PTTs, and other networks through access lines and network interconnection points. Network interconnection points link networks to an IXC through the IXC’s point of presence (POP). POPs are the switching points in an IXC network that are located on the edge of the network (end switching points). A POP can be a switching location (like an end office (EO) where direct access to the IXC’s high-speed infrastructure is available. POP’s can also be simply access nodes (multiplexers) that are co-located with the LEC/CLEC for convenience and logistics.

Some IXCs connect directly with end users to provide high-speed communication services. When an end user directly connects to an IXC, facilities such as T-1’s may be installed directly tying the customer to the IXC’s POP without connecting through the LEC, CLEC or PTT. This is often the case when a business contractually receives discounts for the amount of long distance the IXC can bill to the customer business per month.

Inter-Exchange Carriers (IXC)

Inter-Exchange Carrier (IXC) networks are used to link telephone networks within geographical service area to each other. AT&T, Sprint, MCI, and Qwest are examples of well-known IXCs.

In order to provide the bandwidth necessary to carry the volume of long-distance voice and data traffic at reasonable cost, most IXCs have deployed large bundles of fiber-optic cables that interconnect their switching systems. Burying thousands of miles of fiber cable is costly. However, each pair of fibers is capable of providing many Gbps of bandwidth.

The explosion of the Internet and the demand for advanced multi-media services continues to drive the demand for increased bandwidth at low cost. To increase the capacity of fiber cables, new fiber optic technology has emerged. By utilizing a technology known as dense wavelength division multiplexing, DWDM, each fiber can carry 80 or more separate light-waves. As of 2001, some DWDM technologies were capable of providing over 1 Tbps (1,000 Gbps) of bandwidth, enough to transmit in one second the contents of 150,000 encyclopedias. Advances in optical networking equipment and light-wave amplification technologies will continue to add bandwidth the fiber networks.

Picture on top shows the typical inter-exchange carriers (IXCs) connections. This diagram shows that there are many different IXCs. Each of these IXCs must interconnect to the local telephone companies at a defined point of presence(POP)...