amatically increasing the velocity of propagation. Of course, this is patently not true. If bandwidth permits, 3 bit rate can be increased. That certainly will speed things up. One way to get around the bandwidth crunch is to employ some other, less constraining transmission medium such as optical fiber or very-wide-bandwidth EHF radio. Probably the greatest impetus to speed up the network came from LAN users that wished to extend LAN connectivity to distant destinations. Ostensibly this traffic, as described in Chapter 11, has local transmission rates from 4 Mbps to > 1 Gbps. A packet-switched network base on ITU-T Rec. X.25 was an intermediate expedient. On one hand, it was robust with excellent error correction capabilities. On the other hand, it was slow and tedious. It was designed for circuits where error performance was mediocre by today's standards, as poor as 1 X 10-4. Since X.25's inception, error performance has improved greatly. Today, for example, Telcordia requires 5 X 10-10 (Ref. 21) and Sprint requires 1 X 10-12. Such excellent error performance begs the question of removing the responsibility of error recovery from the service provider. If statistically errors occur in about 1 in 100 million bit and better, there is a strong argument for removing error recovery, at least in the data-link layer. As a result, frame relay was conceived. Its salient points are: There is no process for error recovery by the frame relay service provider. The service provider does not guarantee delivery nor are there any sort of acknowl- edgments provided. It only uses the first two OSI layers (physical and data-link layer), thus removing layer 3 and its intensive processing requirements. Frame overhead is kept to a minimum, to minimize processing time and to increase useful throughput. There is no control field, and no sequence numbering. Frames are discarded without notifying originator for such reasons as congestion and having encountered an error. It operates on a statmultiplex concept. In sum, the service that the 