ENVS 1200 Lecture Notes - Lecture 12: Wide Area Network, Frame Relay
13 May 2018
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ENVS 1200 Tutorial 12 Notes – SONET/SDH
Introduction
• SONET (Synchronous Optical Network) and SDH (Synchronous Digital Hierarchy) are
related protocols and architectures that are designed to take advantage of fiber optic
technology.
• The intention of both standards was to create wide area networks capable of extremely
high bit rates over long distances.
• The differences between the two standards are minor.
• We shall refer to both as SONET for the remainder of this discussion.
• SONET is based on networks that are synchronized globally to a single clock.
• Electrical signals from different sources are converted to light, then synchronously
multiplexed and added and removed from nodes by add/drop multiplexers as required
to optimize the speed of each packet.
• To extend the distance, regenerators are built into the network.
• These recreate the signal as it is attenuated within the fiber, to extend its range.
• SONET networks are constructed as meshes, or rings, or point-to-point links.
• SONET is frequently employed as a physical layer carrier, supporting other higher-level
protocols.
• The technology, frame formats, and details of operation of SONET are complex.
• Further information is beyond the scope.
• Frame Relay is a relatively slow, wide area network standard.
• It is included because it is still in common use as an inexpensive on-ramp to wide area
networks and to the Internet through service providers, especially large telephone
companies.
• Like the other protocols discussed here, Frame Relay relies on edge connections to
convert data between other protocols and frame relay frames for transmission over the
network.
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