Page 919 - (ISC)² CISSP Certified Information Systems Security Professional Official Study Guide

as-you-go fee. ATM is a connection-oriented packet-switching
technology. However, ATM is now an older technology that is being

phased out in favor of faster fiber solutions.

SMDS

Switched Multimegabit Data Service (SMDS) is a connectionless
packet-switching technology. Often, SMDS is used to connect multiple
LANs to form a metropolitan area network (MAN) or a WAN. SMDS
was often a preferred connection mechanism for linking remote LANs
that communicate infrequently. SMDS supports high-speed bursty

traffic and bandwidth on demand. It fragments data into small
transmission cells.

Synchronous Digital Hierarchy and Synchronous Optical Network

Synchronous Digital Hierarchy (SDH) and Synchronous Optical
Network (SONET) are fiber-optic high-speed networking standards.
SDH was standardized by the International Telecommunications
Union (ITU) and SONET by the American National Standards
Institute (ANSI). SDH and SONET are mostly hardware or physical

layer standards defining infrastructure and line speed requirements.
SDH and SONET use synchronous time-division multiplexing (TDM)
to high-speed duplex communications with minimal need for control
and management overhead.

These two standards have only slight variations and use the same
hierarchy of bandwidth levels. The transmission service supports a
foundational level of speed of 51.48 Mbps, which supports the

Synchronous Transport Signals (STS) of SDH and/or the Synchronous
Transport Modules (STM) of SONET. The term Optical Carrier (OC)
can also be substituted for STS. The main bandwidth levels of SDH
and SONET are shown in Table 12.4.

TABLE 12.4 Bandwidth levels of SDH and SONET

SONET SDH Data Rate

STS-1 / OC-1 STM-0 51.84 Mbps

STS-3 / OC-3 STM-1 155.52 Mbps