Appendix B: ATM Overview
B.3 THE ATM NETWORK
ATM is a connection-oriented transmission technology. This means that no information transfers prior to establishing connection between devices. When preparing information, ATM uses Virtual Channels and Virtual Paths as cell addresses and places this channel data into the cell header. When transferring information, ATM combines these Virtual Channels and Virtual Paths into bundles, or “pipes” before sending them out over an ATM physical link segment.
B.3.1 VIRTUAL CHANNELS AND VIRTUAL PATHS
Rather than addressing cells to a specific destination, as in a LAN, ATM addresses cells to Virtual Channels (VCs) and/or Virtual Paths (VPs). This addressing takes place in the header field of the ATM cell.
VCs and VPs are bi-directional (i.e., they transfer information in both directions on a single channel or path) and are “set-up” between devices on the ATM network prior to transmission. Similar to WAN transmission, ATM technology provides the ability of sending several VCs together over a VP, and several VPs over an ATM link segment (Figure B-3).
VP 1
VC 1
VC 2
VC 3
VC 1
Figure B-3 Virtual Channels and Virtual Paths
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