Module 7
Chapter 6
Ethernet Technologies
10-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 Ethernet
10BASE5
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 Ethernet
10BASE2
Uses half-duplex
Compared to 10Base5
Components are difficult to find
Low cost
No need for hubs
Smaller size, lighter weight
Not for new installations
Thin net
Greater flexibility
Installation easier
10-Mbps Ethernet
10BASE-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 hub
Star topology
10 Mbps in half-duplex mode
20 Mbps in full-duplex mode
Wiring 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 10Mbps 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 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
The End
Break Time