repeater

Definition of repeater in The Network Encyclopedia.

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What is Repeater?

A networking component that extends a network by boosting the signal so that it can travel farther along the cabling.

How It Works

Digital signals traveling on cables weaken with distance - a phenomenon known as attenuation. A repeater is a form of digital amplifier that works at the physical layer (layer 1) of the Open Systems Interconnection (OSI) reference model for networking to regenerate (amplify) the signal so that it can travel farther. Repeaters also perform other functions such as filtering out noise caused by electromagnetic interference (EMI), reshaping the signal, and correcting timing to remove signal jitter so that the signal can travel farther. Repeaters can also be used to join dissimilar media such as unshielded twisted-pair (UTP) cabling and thinnet, but they cannot be used to join dissimilar network architectures such as Ethernet and Token Ring. Repeaters are an inexpensive way to extend a network.

Repeaters can be used in Ethernet and Token Ring local area networks (LANs) to extend signal transmission to remote nodes and over long fiber-optic cabling runs to connect LANs. Repeaters can also be used in mainframe environments for boosting signals for serial transmission to remote terminals.

Other uses for repeaters include the following:

  • Joining two 16-Mbps Token Ring networks in different buildings over distances up to 3000 meters over multimode fiber-optic cabling or up to 20 kilometers over single-mode fiber
  • Increasing the lobe length between a Token Ring main ring and a remote node
  • Joining dissimilar 10Base2 and 10Base5 segments to form a single Ethernet LAN
  • Boosting signals from mainframe controllers to 3270 terminals over coaxial or UTP cabling to support distances up to 2500 meters
  • Extending the operating distance of T1 lines by placing G.703 repeaters at 2.2-kilometer intervals
  • Extending backbone fiber-optic cable runs in campuswide LANs or metropolitan area networks (MANs)

Repeaters are also used in fiber-optic networks to amplify and regenerate light signals for long-distance cable runs. Repeaters come in various types for different network architectures and data communication technologies.

NOTE

Up to two Class II Ethernet repeaters can be cascaded together to connect remote nodes that are up to 205 meters apart.

TIP

Other than increasing signal strength, repeaters do not filter network traffic in any way. In particular, they do not block broadcasts, so if you connect two Ethernet segments using a repeater, you increase the size of the collision domain, which degrades overall network performance. For this reason, bridges and routers are often preferable to repeaters.

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