Voice Services & Packet Data

Voice Services
IXC voice service is the providing of audio communication circuits that can pass analog frequencies below 3.3 kHz between switches. IXC voice services must automatically compensate for differences in digital signal formats between countries.

IXCs often use tiered (multi-level) voice service rate plans that depend on regions or countries where the call is connected. In the United States, the average per minute revenue for regional calls has dropped over 80% between 1990 through 2000.

Figure 1 compares the cost of regional and international telephone service in various countries around the world. This table shows that that the costs are based on a recurring charge with unlimited usage. The customer may also pay additional recurring fees for advanced services.


Figure 1: Comparison of Regional and International Telephone Service Cost.
Source: Federal Communications Commission (FCC) and LAN Times.

Figure 2 shows several long distance cost plans. This table shows that the average per minute charge in the United States in 2001 was approximately 7 cents per minute.


Figure 2: Cost of Long Distance Voice Services.


Packet Data
Packet data service is the sending of data through a network in small packets (typically under 100 bytes of information at a time). A packet data system divides large quantities of data into small packets for transmission through a switching network that uses the addresses of the packets to dynamically route these packets through a switching network to their ultimate destination. When a data block is divided, the packets are given sequence numbers so that a packet assembler/disassembler (PAD) device can recombine the packets to the original data block after they have been transmitted through the network. Examples of IXC packet data services include X.25, frame relay, and ATM packet data.

X.25 packet data services are being replaced in developed countries by frame relay and ATM services. However, X.25 systems are expanding in developing countries that have poor (low quality) communication lines.

Frame relay (often known as only “frame”) is a variable bandwidth packet data service. It was designed in the 1980’s primarily for data traffic and resulted from improved digital network transmission quality that reduced the need for error protection. It provides for dynamic bandwidth assignment governed by two transport speeds: committed information rate (CIR) and burst information rate (BIR). This is accomplished by varying frame sizes.

Frame relay access is available from IXC’s and requires each site to be connected to the IXC’s frame network by an access line (e.g., T-1 or fractional T-1) circuits.

Figure 3 shows the typical cost of frame relay service is based on the level of access, the CIR, and the BIR. This diagram shows that the end-user must own or lease an access line to the IXC carrier to enter into the frame relay network. The customer pays a port charge for each entry point into the frame relay network. The IXC service provider charges the customer a monthly fee based on a minimum CIR. The end customer may exceed the CIR if the network is not busy (congested).


Figure 7.14: Cost of Frame Relay Services

ATM packet switching service is a connection based high-speed packet data transmission service. To connect to the ATM network, the customer pays for an access line (leased line) and pays a port charge for each ATM entry and exit point. The cost of ATM service can vary based on the guaranteed data transmission rate and level of quality of service (QoS).

Figure 4 shows the typical cost for connecting to an ATM system. This table shows that the cost per megabyte of data dramatically drops from $500 per megabyte for a DS1 connection ($750/1.5 Mbps) to under $50 per megabyte ($7000/148 Mbps) as higher capacity connections are used.


Figure 4: Cost of ATM Services. Source: Pacific Bell, 2001