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English
10 Gbps
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Thick coaxial cable, 500m
10Base2
Thin coaxial cable, 185m
10BaseT
Two pairs of category 3+ UTP
10Base-F
10 Mb/s over optical fiber
100Base-Tx
Category 5 UTP or STP, 100 m maximum
100Base-FX
Two multi-mode optical fiber, 2 km maximum
1000Base-CX
Two pairs shielded twisted pair, 25m maximum
1000Base-SX
Two multi-mode or single mode optical fibers with lasers
10 Gbps
Optical fiber but also Category 6 UTP
40-100 Gbps
Optical fiber (experiences are performed with copper)
Footnotes
Additional information about the history of the Ethernet technology may be found at http://ethernethistory.typepad.com/
Initially, the OUIs were allocated by Xerox [DP1981]_. However, once Ethernet became an IEEE and later an ISO standard, the allocation of the OUIs moved to IEEE. The list of all OUI allocations may be found at http://standards.ieee.org/regauth/oui/index.shtml
The official list of all assigned Ethernet type values is available from http://standards.ieee.org/regauth/ethertype/eth.txt
The attentive reader may question the need for different `EtherTypes` for IPv4 and IPv6 while the IP header already contains a version field that can be used to distinguish between IPv4 and IPv6 packets. Theoretically, IPv4 and IPv6 could have used the same `EtherType`. Unfortunately, developers of the early IPv6 implementations found that some devices did not check the version field of the IPv4 packets that they received and parsed frames whose `EtherType` was set to `0x0800` as IPv4 packets. Sending IPv6 packets to such devices would have caused disruptions. To avoid this problem, the IETF decided to apply for a distinct `EtherType` value for IPv6. Such a choice is now mandated by :rfc:`6274` (section 3.1), although we can find a funny counter-example in :rfc:`6214`.
These network interfaces compute the TCP checksum while a segment is transferred from the host memory to the network interface [SH2004]_.
Fortunately, IEEE was able to define the [IEEE802.3]_ frame format while maintaining backward compatibility with the Ethernet [DIX]_ frame format. The trick was to only assign values above 1500 as `EtherType` values. When a host receives a frame, it can determine whether the frame's format by checking its `EtherType/Length` field. A value lower smaller than `1501` is clearly a length indicator and thus an [IEEE802.3]_ frame. A value larger than `1501` can only be type and thus a [DIX]_ frame.
Ethernet Switches
Increasing the physical layer bandwidth as in `Fast Ethernet` was only one of the solutions to improve the performance of Ethernet LANs. A second solution was to replace the hubs with more intelligent devices. As `Ethernet hubs` operate in the physical layer, they can only regenerate the electrical signal to extend the geographical reach of the network. From a performance perspective, it would be more interesting to have devices that operate in the datalink layer and can analyze the destination address of each frame and forward the frames selectively on the link that leads to the destination. Such devices are usually called `Ethernet switches` [#fbridges]_. An `Ethernet switch` is a relay that operates in the datalink layer as is illustrated in the figure below.
An `Ethernet switch` understands the format of the Ethernet frames and can selectively forward frames over each interface. For this, each `Ethernet switch` maintains a `MAC address table`. This table contains, for each MAC address known by the switch, the identifier of the switch's port over which a frame sent towards this address must be forwarded to reach its destination. This is illustrated below with the `MAC address table` of the bottom switch. When the switch receives a frame destined to address `B`, it forwards the frame on its South port. If it receives a frame destined to address `D`, it forwards it only on its North port.
Operation of Ethernet switches
One of the selling points of Ethernet networks is that, thanks to the utilization of 48 bits MAC addresses, an Ethernet LAN is plug and play at the datalink layer. When two hosts are attached to the same Ethernet segment or hub, they can immediately exchange Ethernet frames without requiring any configuration. It is important to retain this plug and play capability for Ethernet switches as well. This implies that Ethernet switches must be able to build their MAC address table automatically without requiring any manual configuration. This automatic configuration is performed by the `MAC address learning` algorithm that runs on each Ethernet switch. This algorithm extracts the source address of the received frames and remembers the port over which a frame from each source Ethernet address has been received. This information is inserted into the MAC address table that the switch uses to forward frames. This allows the switch to automatically learn the ports that it can use to reach each destination address, provided that this host has previously sent at least one frame. This is not a problem since most upper layer protocols use acknowledgments at some layer and thus even an Ethernet printer sends Ethernet frames as well.
Component Translation Difference to current string
This translation Propagated Empty cnp3-ebook/protocols/ethernet
The following string has the same context and source.
Propagated Empty cnp3-ebook/protocols/lan

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cnp3-ebook / protocols/ethernet — French

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String information

Source string location
../../protocols/ethernet.rst:179 • ../../protocols/ethernet.rst:358
String age
2 years ago
Source string age
2 years ago
Translation file
locale/fr/LC_MESSAGES/protocols/ethernet.po, string 44