Module 7Module 7Chapter 6Chapter 6

Ethernet Technologies Ethernet Technologies

10-Mbps Ethernet10-Mbps Ethernet

• Legacy Ethernet– 10BASE5, 10BASE2, and 10BASE-T

• Four common features of Legacy Ethernet – Timing parameters– Frame format– Transmission process– Basic design rule

10-Mbps Ethernet10-Mbps Ethernet10BASE5

Single thick coaxial cable bus Cable is large and heavy

Primary benefit was length (500m) Only in half-duplex

Inexpensive Sensitive to signal reflection

No configuration Not for new installations

Components are difficult to find Difficult to install

10-Mbps Ethernet10-Mbps Ethernet10BASE2

Uses half-duplex Compared to 10Base5

Components are difficult to find Low cost

No need for hubs Smaller size, lighter weight

Not for new installationsGreater flexibility

Thin netInstallation easier

10-Mbps Ethernet10-Mbps Ethernet10BASE-T

Cheaper and easier to install Extended Star

Category 3 Originally half-duplex protocol

Category 5 Full-duplex features added later

Category 5e New installations Cat5e or better

Uses a hub10 Mbps in half-duplex mode

Star topology 20 Mbps in full-duplex mode   

Wiring and ArchitectureWiring and Architecture

• 5-4-3 rule– No more than five segments – Separated by no more than four repeaters.

– No more than three populated segments between any two

distant stations

• Hubs or repeaters merely extend the length of a network segment within a single collision domain

• Bridges and switches divide a segment into separate collision domains

Manchester Encoding

• Manchester encoding is used in 10 Mbps systems • The direction of the edge transition in the middle of the timing

window determines the binary value

100-Mbps Ethernet

• 100-Mbps Ethernet is also known as Fast Ethernet– 100BASE-TX is copper UTP

– 100BASE-FX is multimode optical fiber

• Three common characteristics:– Timing parameters

– Frame format

– Parts of the transmission process

100-Mbps Ethernet

• Timing parameters– One bit time in 100-Mbps Ethernet is 10nsec

• Frame format– 100-Mbps frame format is the same as the 10-

Mbps frame

• Parts of the transmission process– Two separate encoding steps are used

• The first part of the encoding uses a technique called 4B/5B

• The second part of the encoding is the actual line encoding specific to copper or fiber

100-Mbps Ethernet

• 100BASE-TX uses 4B/5B encoding which is then scrambled • Converted to multi-level transmit-3 levels or MLT-3.• Half-duplex = 100 Mbps • Full-duplex = 200 Mbps

Fast Ethernet Architecture

• Fast Ethernet links consist of a connection between a station and a hub or switch

– Hubs are considered multi-port repeaters

– Switches are considered multi-port bridges

– These are subject to the 100 m UTP distance limitation

Fast Ethernet Architecture

• Class I repeater – Any repeater that changes between one Ethernet

implementation and another

– 140 bit-times of latency

• Class II repeater

– 92 bit-times latency

– Cable between Class II repeaters may not exceed 5 meters

Fast Ethernet Architecture

• Signaling scheme is inherently full duplex– Half duplex are not uncommon – Half duplex is undesirable

• Switches have made the 100m limitation less important

• Workstations are located within 100m of the switch

• 100 m distance starts over at the switch

1000-Mbps Ethernet

• 1000-Mbps Ethernet or Gigabit Ethernet Transmission – Fiber and copper media  

• The 1000BASE-X IEEE 802.3z– Specifies 1 Gbps full duplex over optical fiber

• 1000BASE-TX, 1000BASE-SX, and 1000BASE-LX

– Timing parameters• 1 nanosecond or 1 billionth of a second bit time.

– Frame Format • Same format used for 10 and 100-Mbps Ethernet

– Transmission • Depending on the implementation

1000-Mbps Ethernet

• 1000BASE-T (IEEE 802.3ab) was developed to provide additional bandwidth for:

– Intra-building backbones– Inter-switch links– Server farms– Connections for high-end workstations – Supports both half-duplex and full-duplex

• Fiber-based Gigabit Ethernet (1000BASE-X)

– Uses 8B/10B encoding (similar to 4B/5B) – This is followed by Non-Return to Zero (NRZ) line encoding

1000Base-LX/SX• Common to all versions of 1000 Mbps

– Timing– Frame format– Transmission

• NRZ signals are pulsed into the fiber– Short-wavelength (1000BASE-SX )– Long-wavelength (1000BASE-LX)

• Media Access Control – Link as point-to-point

• Separate fibers – Transmitting (Tx) – Receiving (Rx) – Inherently full duplex

Gigabit Ethernet

• Gigabit Ethernet is the dominant technology for:

– Backbone installations,

– High-speed cross-connects

– General infrastructure

10 Gigabit Ethernet• IEEE 802.3ae, governs the 10GbE family

• Provide increased bandwidth

• Interoperable with existing infrastructure

• Implementations being considered:

– 10GBASE-SR

– 10GBASE-LX4

– 10GBASE-LR and 10GBASE-ER

– 10GBASE-SW, 10GBASE-LW, and 10GBASE-EW

10 Gigabit Ethernet• 10GBASE-SR –

– short distances, supports a range between 26 m to 82 m

• 10GBASE-LX4 – – Uses wide wavelength division multiplexing (WWDM)– 240 m to 300 m over multimode fiber – 10 km over single-mode fiber

• 10GBASE-LR and 10GBASE-ER – – Support 10 km and 40 km over single-mode fiber

• 10GBASE-SW, 10GBASE-LW, and 10GBASE-EW – – Known collectively as 10GBASE-W – Works with OC-192 synchronous transport module

Future of EthernetFuture of Ethernet• The future of networking media is three-fold:

1. Copper (up to 1000 Mbps, perhaps more) 2. Wireless (approaching 100 Mbps, perhaps more)

3. Optical fiber (currently at 10,000 Mbps and soon to be more)

• Copper and wireless media have certain physical and practical limitations

• Limitations on optical fiber are:

– Electronics technology • emitters and detectors

– Fiber manufacturing processes

• Developments in Ethernet – Heavily weighted towards Laser light sources– Single-mode optical fiber

OK Lab Time.Then……..have a good

week !