Late collisions vs. Local collisions

Unanswered Question
Sep 23rd, 2007

Does anyone have any links to information that will identify which of these are late collisions and which are local collisions? I can't find it in either the ICND Intro or ICND books.

caused by excessive media latency

considered abnormal network operation

occurs after the first 64 bytes of a frame are transmitted

damaged frame retransmitted

occasionally occurs in normal network operation

jam signal sent to intentionally ocrrupt frame

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scottmac Sun, 09/23/2007 - 19:50

Oiiginal Ethernet was designed so that even with the minimum frame size (64bytes / 512 bit times), if a (normal) collision occurred, anywhere on the (maximum length) wire, it would be sensed.

That's the key to figuring out "normal / local" versus "Late."

So, the first three, as you have them listed, are "Late"; the last two are "normal / local" ... the damaged frame retransmitted is a little ambiguous, but at strictly at the layer two level, I"m pretty sure they would consider it "normal."

The "JAM" signal is sent once a collision is detected in the first 64 bytes to ensure that all hosts heard the collision.

Good Luck

Scott

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