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It doesn't make any sense until it's clear there are two types of twisted-pair ethernet socket, and they are almost never labelled. …

I've certainly used PLCs, for example, which will simultaneously accept Modbus over TCP/IP and RS-232 and other networking over the ethernet. …

There are very many other schemes for framing, such as "long time without signal" (used in DMX) or "no voltage at all means not inside a frame" (used in coax ethernet). … Ethernet is akin to the mechanism described, but much more complex. Especially the faster kinds, which are very much more complex. …

The padding can have any values, decided by the network interface card, the operating system and the driver. Conservative OS might pad with zeros. Lazy OS might leave whatever was in those memory lo …

It's very easy to think that internet packets go on the wire in a very simple "serial port" kind of way. In practice there is nothing inherently serial about it. If you think about some interface de …

I've used read-only cables for similar purposes: invisible syslog sinks. My understanding is that in 100baseT only autonegotiation is done with the "fast link pulse" FLP, while link-connectivity is s …

In this context it's just an abbreviation of "ethernet". It is of course named after the classical element "ether", also spelled "aether". Wikipedia …

Ethernet frames are sometimes described as 1514 octets because the hardware usually computes/checks the FCS, and the CPU never sees it or puts it in memory: only the src, dest, type, payload. … (This usage of "packet" can be confusing, as we normally speak of IP packets inside the ethernet frame.) It's just a matter of definitions, in the end, and we thankfully can look them up. …

In addition to others' excellent answers about layering, some protocols sit right on top of the L2 ethernet frame, of which the best known are ARP, RARP, CDP etc, which relate directly to the link (also … It is very uncommon, but on occasion you'll find applications which send their data in the ethernet frame, though the only reasons I've seen for this are either a) proprietary protocols designed to be …

The obvious technique is to put the ethernet frame into a memory queue, figure out what to do, then emit it in the right way. There is therefore a measurable delay between the input and the output. …

You can't calculate it without knowing the delay between two hosts. If the other host was on the moon, it takes about 1.3 seconds for light to reach it, 1.3 seconds to come back. Round trip time wou …

Gigabit ethernet over other media behaves differently. …

It's very unusual to draw an ethernet as a cloud. Clouds suggest "unknown and immaterial amount of networking equipment", and normally these are routers. … Ethernet is not permitted to have loops, as the frames will go round and round. Whatever is the first frame out of A will go into switch 20 port 1. …

Ethernet is principally designed for local area networking, and runs at speeds of 10, 100, 1000 Mbit/sec and more, and normally is for links of up to about 100 metres, though you can go further with fibre … -- ethernet is effectively a bus connecting many-to-many (and physically a bus topology in its older incarnations such as 10base2.) …

The receiver has to look at the Ethernet frame to decide its contents, which might be DECnet, Appletalk or many other things -- Internet Protocol is only one of many protocols running on top of Ethernet … A key goal of Ethernet was ubiquity -- in order to be cheap it had to be everywhere, and so it was designed to be completely neutral about its contents. …