. Why did the designers of the Synchronous Digital Hierarchy choose unusual values for data rates instead of the exact powers of ten? 2. Why would a service provider choose Hybrid Fiber Coax instead of Fibe

the designer choose because it has many basic and advance feature and it is Synchronous digital hierarchy (SDH) and synchronous optical network (SONET)

refer to a group of fiber-optic transmission rates that can transport digital signals

with different capacities. And it feature is Almost all new fiber-transmission systems now being installed in public networks

use SDH or SONET. They are expected to dominate transmission for decades to

come, just as their predecessor PDH has dominated transmission for more than

20 years (and still does in terms of total systems installed). Bit rates in long-haul

systems are expected to rise to 40 Gbps soon after the year 2000, at the same

time as systems of 155 Mbps and below penetrate more deeply into access

networks.

2 they choose Because of these problems, the big cable networks use hybrid fiber-coax networks. The use of fiber increases the upstream bandwidth and reduces noise, making it easier for upstream data to reach its destination. But upgrading to hybrid fiber-coax is hugely expensive.