CCNA 1: Module 7 Ethernet Technologies

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CCNA 1 Module 7 Ethernet Technologies
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Overview

• The most successful LAN technology
• Easy to install
• Has evolved to meet changing needs
• Media
• Increased bandwidth (speed)
• Backward compatibility maintained as it has
  evolved

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7.1 10-Mbps and 100-Mbps Ethernet7.1.1 10-Mbps
Ethernet

• All implementations of 10-Mbps Ethernet are
  considered Legacy Ethernet
• The four common features of Legacy Ethernet are
• timing parameters
• frame format
• transmission process
• a basic design rule.

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7.1 10-Mbps and 100-Mbps Ethernet7.1.1 10-Mbps
Ethernet Cont.

• Parameter Value
• Bit Time 100ns
• Slot Time 512 bit
  times
• Interframe Spacing 96 bit times
• Collision Attempt Limit 16
• Collision Backoff Limit 10
• Collision Jam Size 32
• Max. Untagged Frame Size 1518
• Minimum Frame size 512 Bits (64 octets)

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7.1 10-Mbps and 100-Mbps Ethernet 7.1.1 10-Mbps
Ethernet Cont.

• The Legacy Ethernet transmission process
• The Layer 2 frame data is converted from hex to
  binary.
• As the frame passes from the MAC sublayer to the
  physical layer, further processes occur prior to
  the bits being placed from the physical layer
  onto the medium.
• All 10 Mbps forms of Ethernet take octets
  received from the MAC sublayer and perform a
  process called line encoding.
• Line encoding describes how the bits are actually
  signaled on the wire.

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7.1 10-Mbps and 100-Mbps Ethernet 7.1.1 10-Mbps
Ethernet Cont.

• Manchester Encoding
• Up transition 1
• Down transition 0

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7.1 10-Mbps and 100-Mbps Ethernet 7.1.2 10Base5
(LEGACY ETHERNET)

• The Original Ethernet (1980)
• Coaxial cable
• Bus Topology
• 10 Mbps
• Inexpensive and no configuration is needed
• NICs difficult to find
• 500 meter segment length
• Manchester encoding
• CSMA/CD timings were developed using the
  constraints of the coaxial medium (5-4-3-2-1
  Rule).
• Only supported half-duplex

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7.1 10-Mbps and 100-Mbps Ethernet 7.1.3 10Base2
(LEGACY ETHERNET)

• The 2nd Generation Ethernet (1985)
• Original Ethernet signaling was modified to be
  used over thinner coaxial cable to make
  installation easier (Thinnet)
• Bus Topology
• 10 Mbps
• It has a low cost and a lack of need for hubs
  NICs difficult to find
• 185 meter segment length
• Manchester encoding
• Used the same timings as 10Base5 and subject to
  the 5-4-3-2-1 Rule.
• Only supported half-duplex
• 30 Stations Max. on each segment

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7.1 10-Mbps and 100-Mbps Ethernet 7.1.4 10BaseT
(LEGACY ETHERNET)

• 10BASE-T was introduced in 1990
• Used cheaper and easier to install Category 3
  unshielded twisted pair (UTP) copper cable (now
  Cat 5e is minimum)
• Star Topology with a hub (multiport repeater at
  the center)
• 100 meter length between station and hub
• Used the same timings as 10Base5 and subject to
  the 5-4-3-2-1 Rule.
• Originally 10BASE-T was a half-duplex protocol,
  but full-duplex features were added later.
• Manchester encoding

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7.1 10-Mbps and 100-Mbps Ethernet 7.1.5 10BaseT
Wiring Architecture

• 10 Base T using Hubs
• Subject to the same timing constraints as 10Base5
  and 10Base2
• Reason delay and latency
• Delay time it takes the signal to propagate
  down the wire
• Latency time it takes a NIC to put the bits on
  the wire AND a repeating device to regenerate the
  signal and place it on the wire.
• The best design is to use a hierarchical
  arrangement.

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7.1 10-Mbps and 100-Mbps Ethernet 7.1.6 100
Mbps Ethernet (FAST ETHERNET)

• Two types
• 100BaseTX (copper UTP media)
• 100BaseFX (multimode fiber optic cable media)
• Three characteristics common to 100BASE-TX and
  100BASE-FX are
• the timing parameters
• the frame format
• parts of the transmission process.
• Star or Extended Star Topology with a hub or
  switch at the center
• 100 meter length between station and hub/switch
• Uses a different timing than Legacy Ethernet
• Same Frame format as Legacy Ethernet
• Two separate encoding steps are used by 100-Mbps
  Ethernet.
• The first part of the encoding uses a technique
  called 4B/5B

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7.1 10-Mbps and 100-Mbps Ethernet7.1.6 100 Mbps
Ethernet (FAST ETHERNET) Cont.

• Parameter Value
• Bit Time 10ns
• Slot Time 512 bit
  times
• Interframe Spacing 96 bit times
• Collision Attempt Limit 16
• Collision Backoff Limit 10
• Collision Jam Size 32
• Max. Untagged Frame Size 1518
• Minimum Frame size 512 Bits (64 octets)

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7.1 10-Mbps and 100-Mbps Ethernet 7.1.7
100BaseTX

• 1995 Standard adopted
• Uses Cat5 UTP
• 1997, Ethernet was expanded to include a full
  duplex capability that allowed more than one PC
  on a network to transmit at the same time.
• 100BASE-TX uses 4B/5B encoding, which is then
  scrambled and converted to multi-level transmit-3
  levels or MLT-3.
• TX can exchange 200 Mbps of traffic in
  full-duplex mode

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7.1 10-Mbps and 100-Mbps Ethernet 7.1.7
100BaseTX Encoding

• 4B/5B encoding (Frame Encoding shorthand)
• All data is encoded prior to transmission
• Encoding uses 4 of 5 group code known as 4B/5B
• Every 4 bit group (16 different combinations) is
  mapped onto a 5 bit code (symbol)
• 5B symbols for 4B data groups are chosen such
  that a maximum of 2 successive zeros occur
• 5B symbols which are not used for data encoding
  are used as control symbols - symbols such as
  0001, 00010 ... are not used
• Multi-Level Transmit-3 levels or MLT-3 (actual
  physical transmission on the wire.
• No transition 0
• Any transition (up or down) 1

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7.1 10-Mbps and 100-Mbps Ethernet 7.1.8
100BaseFX

• Fiber was developed because it could be used in
  places that were noisy AND/OR to overcome
  distance limitations.
• 100BASE-FX was never adopted successfully. This
  was due to the timely introduction of Gigabit
  Ethernet copper and fiber standards.
• Gigabit Ethernet standards are now the dominant
  technology for
• backbone installations
• high-speed cross-connects
• general infrastructure needs.
• The timing, frame format, and transmission are
  all common to both versions of 100 Mbps Fast
  Ethernet.

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7.1 10-Mbps and 100-Mbps Ethernet 7.1.9 100Mbps
Architecture

• Fast Ethernet links generally consist of a
  connection between a station and a hub or switch.
• Design is similar to 10 Mbps Ethernet
• Unlike 10 Mbps Ethernet, No allowance for
  additional delay
• Hierarchical design is best
• Class 1 repeater
• Any repeater that changes between one Ethernet
  implementation andanother
• Introduces 140 bit times of latency

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7.2 Gigabit and 10 Gigabit Ethernet 7.2.1 1000
Mbps Ethernet

• 1000Base-X (802.3z)
• 1Gbps full-duplex over optical fiber
• 1000BASE-TX, 1000BASE-SX, and 1000BASE-LX use the
  same timing parameters
• The Gigabit Ethernet frame has the same format as
  is used for 10 and 100-Mbps Ethernet.
• The differences between standard Ethernet, Fast
  Ethernet and Gigabit Ethernet occur at the
  physical layer.
• Since the bits are introduced on the medium for a
  shorter duration and more often, timing is
  critical.
• Gigabit Ethernet to use two separate encoding
  steps.
• 8B/10B (similar to 4B/5B)
• Non-Return to Zero line encoding

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7.2 Gigabit and 10 Gigabit Ethernet 7.2.1 1000
Mbps Ethernet Cont.

• Parameter Value
• Bit Time .1ns
• Slot Time 4096 bit
  times
• Interframe Spacing 96 bit times
• Collision Attempt Limit 16
• Collision Backoff Limit 10
• Collision Jam Size 32
• Max. Untagged Frame Size 1518
• Minimum Frame size 512 Bits (64
  octets)
• Burst Limit 65,536 bits

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7.2 Gigabit and 10 Gigabit Ethernet 7.2.2
1000BaseT

• was developed to provide additional bandwidth to
  help alleviate these bottlenecks
• provided more "speed" for applications such as
• intra-building backbones
• inter-switch links
• server farms
• other wiring closet applications
• connections for high-end workstations.
• One of the most important attributes of the
  1000BASE-T standard is that it be interoperable
  with 10BASE-T and 100BASE-TX.

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7.2 Gigabit and 10 Gigabit Ethernet 7.2.2
1000BaseT Cont.

• Uses all four pairs to transmit data
• Each pair can transmit up to 125 Mbps in
  half-duplex (250 Mbps in full duplex)
• Four pair multiplied by 250 Mbps equals 1000 Mbps
• Required complex circuitry to allow full duplex
  on the same wire pair
• The data from the sending station is carefully
  divided into four parallel streams, encoded,
  transmitted and detected in parallel, and then
  reassembled into one received bit stream.
• Uses 8B/10B frame encoding
• 4D-PAM5 line encoding
• 9 voltages states in idle
• 17 voltage states during transmission

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7.2 Gigabit and 10 Gigabit Ethernet 7.2.3
1000Base-SX and -LX

• The IEEE 802.3 standard recommends that Gigabit
  Ethernet over fiber be the preferred backbone
  technology.
• The timing, frame format, and transmission are
  common to all versions of 1000 Mbps
• The 8B/ 10B scheme is used for optical fiber and
  shielded copper media
• Pulse Amplitude Modulation is used for UTP
• Both use NRZ line encoding
• 1000BaseSX
• Uses Short Wavelenth (850nm laser OR LED)
• Multimode
• Shorter distances
• Lower cost

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7.2 Gigabit and 10 Gigabit Ethernet 7.2.3
1000Base-SX and LX Cont.

• 100BaseLX
• Uses Longer Wavelenth (1310nm laser)
• Single mode OR Multimode
• Longer distances (up to 5000m)
• Higher cost
• The Media Access Control method treats the link
  as point-to-point.
• Since separate fibers are used for transmitting
  (Tx) and receiving (Rx) the connection is
  inherently full duplex.
• Gigabit Ethernet permits only a single repeater
  between two stations.

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7.2 Gigabit and 10 Gigabit Ethernet 7.2.4
Gigabit Ethernet Architecture

• The distance limitations of full-duplex links are
  only limited by the medium, and not the
  round-trip delay
• Most Gigabit Ethernet is switched
• Daisy-chaining, star, and extended star
  topologies are all allowed.
• The issue then becomes one of logical topology
  and data flow, not timing or distance
  limitations.
• Modification of the architecture rules is
  strongly discouraged for 1000BASE-T.
• At 100 meters, 1000BASE-T is operating close to
  the edge of the ability of the hardware to
  recover the transmitted signal.

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7.2 Gigabit and 10 Gigabit Ethernet 7.2.5 10
Gigabit Ethernet

• IEEE 802.3ae was adapted to include 10 Gbps
  full-duplex transmission over fiber optic cable.
• With the frame format and other Ethernet Layer 2
  specifications compatible with previous
  standards, 10GbE can provide increased bandwidth
  needs that are interoperable with existing
  network infrastructure.
• A major conceptual change for Ethernet is
  emerging with 10GbE.
• No longer is Ethernet considered a LAN technology
• Up to 40km

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7.2 Gigabit and 10 Gigabit Ethernet 7.2.5 10
Gigabit Ethernet Cont.

• How does 10GbE compare to other varieties of
  Ethernet?
• Frame format is the same, allowing
  interoperability between all varieties of legacy,
  fast, gigabit, and 10 Gigabit, with no reframing
  or protocol conversions.
• Bit time is now 0.1 nanoseconds. All other time
  variables scale accordingly.
• Since only full-duplex fiber connections are
  used, CSMA/CD is not necessary
• The IEEE 802.3 sublayers within OSI Layers 1 and
  2 are mostly preserved, with a few additions to
  accommodate 40 km fiber links and
  interoperability with SONET/SDH technologies.
• Flexible, efficient, reliable, relatively low
  cost end-to-end Ethernet networks become
  possible.
• TCP/IP can run over LANs, MANs, and WANs with one
  Layer 2 Transport method.

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7.2 Gigabit and 10 Gigabit Ethernet 7.2.6 10
Gigabit Ethernet Architecture

• The shorter bit time duration because of
  increased speed requires special considerations
• For 10 GbE transmissions, each data bit duration
  is 0.1 nanosecond.
• This means there would be 1,000 GbE data bits in
  the same bit time as one data bit in a 10-Mbps
  Ethernet data stream!
• Complex serial bit streams are used for all
  versions of 10GbE except for 10GBASE-LX4, which
  uses Wide Wavelength Division Multiplex (WWDM) to
  multiplex four bit simultaneous bit streams as
  four wavelengths of light launched into the fiber
  at one time.
• As with 10 Mbps, 100 Mbps and 1000 Mbps versions,
  it is possible to modify some of the architecture
  rules slightly.
• Possible architecture adjustments are related to
  signal loss and distortion along the medium.
• Due to dispersion of the signal and other issues
  the light pulse becomes undecipherable beyond
  certain distances.

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7.2 Gigabit and 10 Gigabit Ethernet 7.2.7
Future of Ethernet

• 40, 100, and 160 Gbps standards
• Copper and wireless media have certain physical
  and practical limitations on the highest
  frequency signals that can be transmitted.
• The bandwidth limitations on optical fiber are
  extremely large and are not yet being threatened.
  
• In fiber systems, it is the electronics
  technology (such as emitters and detectors) and
  fiber manufacturing processes that most limit the
  speed.
• Qos Quality of Service Telephony