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Ethernet length restrictions

The permissible network extension of an Ethernet depends on the Ethernet variant and thus on the transmission speed on the network. In general, the expansion decreases with increasing transmission speed.

If we consider the classic Ethernet with 10 Mbit/s transmission speed, the permissible network expansion is determined from the round-trip delay on the transmission medium. This is determined by the propagation time between the two most distant stations. With a cable-specific signal propagation delay of 0.77c, this results in a propagation delay of 2.165 µs for a 500 m segment.

Based on the minimum packet length of a standard Ethernet frame of 64 bytes, or 512 bits, and the transmission rate of 10 Mbit/s, the round trip time between the two most distant stations is 51.2 µs, so the simple propagation delay is 25.6 µs. This round trip delay corresponds to an extension of about 5 km. Taking into account the signal propagation times in the transceiver cables and the delay times of the active components, Ethernet extensions of about 3,000 m are thus possible.

Maximum Ethernet extension with three coaxial segments

Maximum Ethernet extension with three coaxial segments

This limit can be exceeded by using bridges, as these do not forward the collisions but segment the network into LAN segments and thus divide it into collision domains.

Signal propagation time in 10 Mbit/s Ethernet

Signal propagation time in 10 Mbit/s Ethernet

Since the network extension is reduced with a higher transmission rate, the process for Fast Ethernet in the 100Base-T version results in a length limitation reduced by a factor of 10 to approx. 210 m with a tenfold higher transmission rate of 100 Mbit/s.

In order to avoid further restrictions for Gigabit Ethernet( GbE), an extension of 200 m has been specified in the standard for all transmission media for a collision domain.

Englisch: Ethernet length restrictions
Updated at: 08.05.2012
#Words: 277
Links: network, extension (EXTN), Ethernet, transmission speed, indium (In)
Translations: DE

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