Origins and Evolution
Ethernet started off life as 3 Mbit/s over coaxial cable (coax) bus in 1973. Bob Metcalfe at the Xerox Palo Alto Research Center, PARC wrote a memo which the Ethernet network system he had invented for both sending data between advanced computer workstations and to high-speed laser printers. Basically he had developed a new protocol CSMA/CD (Carrier sense multiple access with collision detection ) that enabled higher link utilization than previously acheivable. However it took another 7 years of research and improvements for the first standard to be released this was created by the DEC-Intel-Xerox vendor consortium and was known as the DIX standard and was largely concerned with the implementation of Ethernet over co-axial cable. This working group fundamentally was governing what was a Xerox owned technology and it took until 1985 for them to relinquish control of the technology and allow the IEEE to formulate what is considered the first standard specification for Ethernet known as 802.3 this standard has now had over 50 amendments or additional standards defined under the 802.3 umbrella of protocols. Some of these describe speed specifications like 802.3i (10M) , 802.3u(100M) and 802.3z(1G) but many other describe associated technology which have expanded the capabilities of Ethernet which in turn has secured Ethernet as one of the leading standards for inter-networking.
However the 802.3 standard for Ethernet over gone through numerous changes and advancements that almost typify the state of network technology, from 802.3a (Ethernet on thin Coax) to today’s 1000BASE-T (802.3ab) switched networks, the Ethernet standard has led the way in both providing a working model for all network manufactures and the vision to continually improve technology.
Looking at the key applications spaces which Ethernet is both a leading player and the working basis for many other technologies,
LAN : The original deployment model for Ethernet was the LAN infrastructure and has proven its value for over 30 years of active development. Originally developed for shared broadcast domains using the CSMA/CD protocol as speeds became higher devices such as hub and repeaters were phased out in favor of dedicated switches with only two devices per broadcast domain, this allowed significant speed enhancements and was the foundation for current Gigabit LAN environments. With low-cost network implementations and extensive topological flexibility for network installation, there is no end in sight for Ethernet in the LAN as it has no significant valid competition and only future speed enhancements to come. Additional standards such as :
- 802.3ac extended the maximum packet size to 1522 bytes allowing the Q-tag to be inserted to support both vLAN (802.1q) and priority (802.1p) information, which allowed segmentation of switched networks and integrated support for QoS in switched networks.
- PoE (Power over Ethernet) initially a Cisco propriety protocol this was quickly standardized into 802.3af when its utility was realized for powering devices especially IP phones. Several amendments have been made to the original specification increasing the power delivered both to 30W with 802.3at
EFM(Ethernet in the first mile) : First specified in the 802.3ah amendment the success of Ethernet in the LAN is broadened to be used over new media types
- Voice-grade copper. These new EFM copper (EFMCu), or Ethernet over copper, interfaces allow optional multi-pair aggregation
- Long wavelength single optical fiber (as well as long wavelength dual-strand fiber)
- Point-to-multipoint (P2MP) fiber. These new interfaces are known under the collective name of Ethernet over passive optical networks (EPON).
This extension of Ethernet beyond the typical LAN/WAN boundary has simplified the provision of symmetrical leased lines providing low contention and highly reliable service that also has increased support for OA&M. Due to it being available for both copper and fiber with higher link speeds than traditional DSL technologies and less signal degradation it is becoming a significant player in this market.
Backplane: Often overlooked but important deployment case for Ethernet is in internal circuitry of network equipment, the development of the 802.3ap standard also know as 10G/40G/100GBaseK this has allowed the development of dedicated off-the-shelf chips for interconnects in servers/storage and high capacity switches. This has reduced the cost of developing such backplanes and adds functionality such as speed auto-negotiation.
Higher Speeds 25G/40G/100G/400G
The road-map set out by the Ethernet Alliance specifies that the development of new 25 Gbps serial technology has enabled single 25 Gbps Ethernet lanes where previously 10 Gbps was the maximum possible. This theoretically opens up significant speed improvements with the
New Interfaces :
With the proliferation of data-centers the need for much fatter connections between sites than the current Ethernet service definitions can provide. So the Optical Internetworking Forum is stepping up with a new project to define more flexible Ethernet options for using the entire capacity of a given optical link.
Power over Ethernet Enhancements
- 4 Pair Power over Ethernet (PoE)
- Power over Data Line (PoDL)
802.3bp 1000BASE-T1 – Gigabit Ethernet over a single twisted pair, automotive & industrial environments
802.3bq 25G/40GBASE-T for 4-pair balanced twisted-pair cabling with 2 connectors over 30 m distances
802.3bs 400 Gbit/s Ethernet over optical fiber using multiple 25G/50G lanes
802.3bt Power over Ethernet enhancements up to 100 W using all 4 pairs balanced twisted-pair cabling, lower standby power and specific enhancements to support IoT applications (e.g. Lighting, sensors, building automation).
802.3bw 100BASE-T1 – 100 Mbit/s Ethernet over a single twisted pair for automotive applications
802.3by Optical fiber, twinax and backplane 25 Gigabit Ethernet
802.3bz 2.5GBASE-T and 5GBASE-T – 2.5 Gigabit and 5 Gigabit Ethernet over Cat-5/Cat-6 twisted pair
802.3ca 100G-EPON – 25 Gb/s, 50 Gb/s, and 100 Gb/s over Ethernet Passive Optical Networks
802.3cc 25 Gb/s over Single Mode Fiber
802.3cd Media Access Control Parameters for 50 Gb/s and Physical Layers and Management Parameters for 50 Gb/s, 100 Gb/s, and 200 Gb/s Operation