Ethernet Types Includes some material from Forouzan ‘Data Communications’

Abbreviated designation The abbreviated description consists of: A number indicating the number of Mbps transmitted (10, 100, 1000, 10G) The word base, indicating that baseband signaling is used (base) One or more numbers and/or letters indicating the type of medium used: (2, 5, T, TX, CX, FX, SX, LX) 2 / 5 = thin / thick Coax T = unshielded twisted pair C = shielded twisted pair F = fiber optical cable S = fiber optical cable – with shorter light wavelengths L = fiber optical cable – with longer light wavelengths Also SR, LX4, LR, ER, SW, LW, EW - 10Gigabit Ethernet only - see later. Examples include: 10base2 10base5 10base-T 100base-TX 100base-FX 1000base-TX 1000base-SX 1000base-LX

Types of Ethernet – Legacy Ethernet 10BASE5, 10BASE2, and 10BASE-T Four common features: timing parameters, frame format, transmission process basic design rule. 1 bit time at 10 Mbps = 100 nSec All use Manchester line encoding: A self-clocking data signal in which there is a transition in the middle of each bit. A high to low transition in middle of bit represents a 0 A low to high transition in middle of bit represents a 1

Types of Ethernet – Fast Ethernet (100Mb/S) 100BASE-TX uses UTP. Half duplex 100BASE-TX represents a 10-fold increase in speed over 10BASE-T. Full-duplex 100BASE-TX can exchange data at 200 MbpS. 100BASE-FX uses Multimode optical fiber. Not successfully adopted due to the introduction of Gigabit Ethernet standards. Three common features: timing parameters, frame format (the 100-MbpS frame format is the same as the 10-MbpS frame), parts of the transmission process. Bit time at 100Mb/S is 10nSec. Higher frequency signals → more susceptible to noise. (Bits are shorter in duration and occur more frequently) Two separate encoding steps are used: The first part of the encoding uses a technique called 4B/5B. The second part is the actual line encoding specific to copper or fiber.

Types of Ethernet – Gigabit Ethernet (1000Mb/S) 1000BASE-TX Uses 4D-PAM5 line encoding over Cat 5e UTP or Cat 6 UTP Uses all four pairs in full duplex simultaneously. 1000BASE-SX Short-wavelength, uses 850nm laser or LED source in Multimode fiber Lower-cost but shorter distances. 1000BASE-LX Long-wavelength 1310nm laser source uses Single mode / Multimode optical fiber. Distances of up to 5000 meters. Common features: timing parameters frame format (1GbpS frame format is the same as the 10 and 100MbpS frame) Bit time at 1Gb/S is 1nSec High-speed transmission, close to copper medium bandwidth limitations → Susceptible to noise (more than 100Mb/S Ethernet) especially on copper. Gigabit Ethernet may use different processes to convert frames to bits on the cable. Differences between Gigabit Ethernet and slower Ethernets occur at the physical layer. Fiber-based Gigabit Ethernet (1000BASE-X) uses 8B/10B encoding.

Types of Ethernet – 10 Gigabit Ethernet, also termed 10GbE 10GBASE-SR – short distances (26 - 82m) over already-installed multimode fiber. 10GBASE-LX4 – uses wavelength division multiplexing (WDM), distances 240 - 300m over multimode fiber, 10 km over single-mode. 10GBASE-LR –10 km over single-mode fiber. 10GBASE-ER – 40 km over single-mode fiber. 10GBASE-SW, 10GBASE-LW, and 10GBASE-EW – collectively termed 10GBASE-W use OC-192 synchronous transport module (9.584640 Gbps) (STM) SONET/SDH WAN equipment. Ethernet is traditionally thought of as a LAN technology. Operation at 40 km distance makes 10GbE a viable MAN technology. Frame format is the same as other varieties of Ethernet, allowing interoperability. Bit time at 10Gb/S is 0.1nSec Only full-duplex fiber connections are used so CSMA/CD is not necessary. An IEEE 802.3 supplement, 802.3ae, governs 10GbE.

Auto negotiation There is a requirement that the various Ethernet technologies interoperate → different speed interfaces can be directly connected via appropriate hubs or switches. Devices must be able to determine the fastest speed at which they can all function. Example: a 10Mb/S NIC connected to a 10/100 hub; the hub must operate at 10 Mb/S. Devices must also be able to determine automatically whether to operate in full-duplex of half-duplex mode. Auto-Negotiation uses a special message transmitted approx every 16mS (±8mS). This pulse communicates the capabilities of the transmitting station to its link partner. Each node switches to the highest performance configuration that both can support. Transmission Priority Rank (the order attempted): 1000 Base-TX Full Duplex 1000 Base-TX Half Duplex 100 Base-TX Full Duplex 100 Base-TX Half Duplex 10 Base-T Full Duplex 10 Base-T Half Duplex

Three generations of Ethernet