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1.5 Operation of Ethernet

Best Effort Data Delivery

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This brings up an interesting point, which is that the Ethernet system, in common with other LAN technologies, operates as a best effort" data delivery system. To keep the complexity and cost of a LAN to a reasonable level, no guarantee of reliable data delivery is made. While the bit error rate of a LAN channel is carefully engineered to produce a system that normally delivers data extremely well, errors can still occur.

A burst of electrical noise may occur somewhere in a cabling system, for example, corrupting the data in a frame and causing it to be dropped. Or a LAN channel may become overloaded for some period of time, which in the case of Ethernet can cause 16 collisions to occur on a transmission attempt, leading to a dropped frame. No matter what technology is used, no LAN system is perfect, which is why higher protocol layers of network software are designed to recover from errors.

It is up to the high-level protocol that is sending data over the network to make sure that the data is correctly received at the destination computer. High-level network protocols can do this by establishing a reliable data transport service using sequence numbers and acknowledgment mechanisms in the packets that they send over the LAN.

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Quick Reference Guide to the Ethernet System - 04 SEP 95

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