ATM

• fixed-sized packets over broadband and baseband LANs or WANs
• 155 Mbps to 622 Mbps or more
• ATM can accommodate voice, data, fax, realtime video, CD-quality audio, imaging, and multimegabit data transmission.
• ATM is like frame relay because it assumes noise-free lines and leaves error checking to devices at either end of a connection. Also, ATM creates a PVC between two points across an ATM network as part of setting up a communication session.
• ATM Technology
• broadband cell relay method that transmit data in 53-byte cells rather than in variable-length frames. This uniform cell size is a big factor for speed => uniformity is easier to switch, route and buffer.
• cell consists of 48 bytes of application info and 5 bytes of ATM header data => a consistent uniform package
• in theory, up to 1.2 Gigabits per second, but can transmit normally at 155 Mbps
• can be used in LANs and WANs
• hardware like routers, bridges have to be ATM compatible
• switches are multiport hubs
• Any media type is OK
• media recommended
• T3 (45 Mbps)
• FDDI (100 Mbps)
• fiber channel (155 Mbps)
• OC3 SONET (155 Mbps)
• ATM can even interface with frame relay and X.25.

About Optical Carrier Levels, T-Carrier Rates, And More
The Optical Carrier rating level for standard ATM technologies is cus-tomarily abbreviated as OC-n, where n is a multiplier applied to the basic OC level 1 rate (OC-1) of 51.84 Mbps. OC-1 describes the basic transmission rate for SONET communications. Table 10.1 (seen later in this chapter) summarizes most of the WAN service types that we cover in this chapter, along with their common abbreviations, basic characteristics, maximum throughput rates, and associated transmission technologies. - Exam Cram p. 197