Explanation/Reference:
Section: Enterprise Network Design Explanation
Explanation:
Time division multiplexing (TDM) is a leased-line WAN technology that divides a link's bandwidth into equal-sized segments based on clock rate. TDM enables several data streams to share a single physical connection. Each data stream is then allotted a fixed number of segments that can be used to transmit data. Because the number of segments dedicated to each data stream is static, unused bandwidth from one data stream cannot be dynamically reallocated to another data stream that has exceeded its available bandwidth. By contrast, statistical multiplexing dynamically allocates bandwidth to data streams based on their traffic flow. For example, if a particular data stream does not have any traffic to send, its bandwidth is reallocated to other data streams that need it.
Metro Ethernet does not divide a link's bandwidth into equal-sized segments based on clock rate. Metro Ethernet is a WAN technology that is commonly used to connect networks in the same metropolitan area.
For example, if a company has multiple branch offices within the same city, the company can use Metro Ethernet to connect the branch offices to the corporate headquarters. Metro Ethernet providers typically provide up to 1,000 Mbps of bandwidth.
Wavelength division multiplexing (WDM) does not divide a link's bandwidth into equal-sized segments based on clock rate. WDM is a leased-line WAN technology used to increase the amount of data signals that a single fiber strand can carry. To accomplish this, WDM can transfer data of varying light wavelengths on up to 16 channels per single fiber strand. Whereas TDM divides the bandwidth in order to carry multiple data streams simultaneously, WDM aggregates the data signals being carried within the fiber strand.
Dense WDM (DWDM) does not divide a link's bandwidth into equal-sized segments based on clock rate.
DWDM is a leased-line WAN technology that improves on WDM by carrying up to 160 channels on a single fiber strand. The spacing of DWDM channels is highly compressed, requiring a more complex transceiver design and therefore making the technology very expensive to implement.
Asynchronous Transfer Mode (ATM) uses statistical multiplexing and does not divide a link's bandwidth into equal-sized segments based on clock rate. ATM is a shared WAN technology that transports its payload in a series of 53byte cells. ATM has the unique ability to transport different types of traffic- including IP packets, traditional circuit-switched voice, and video-while still maintaining a high quality of service for delay-sensitive traffic, such as voice and video services. Although ATM could be categorized as a packet-switched WAN technology, it is often listed in its own category as a cell-switched WAN technology.
Multiprotocol Label Switching (MPLS) does not divide a link's bandwidth into equal-sized segments based on clock rate. MPLS is a shared WAN technology that makes routing decisions based on information contained in a fixed-length label. In an MPLS virtual private network (VPN), each customer site is provided with its own label by the service provider. This enables the customer site to use its existing IP addressing scheme internally while allowing the service provider to manage multiple sites that might have conflicting IP address ranges. The service provider then forwards traffic over shared lines between the sites in the VPN according to the routing information that is passed to each provider edge router.
Reference:
CCDA 200-310 Official Cert Guide, Chapter 6, TimeDivision Multiplexing, p. 225 Cisco: ISDN Voice, Video and Data Call Switching with Router TDM Switching Features