1. Multiplexing Rick Graziani graziani@cabrillo.edu

2. Multiplexing Multiplexing and WAN (Wide Area Networks)
The ability to establish, maintain and terminate multiple wide area system-to-system connections over a single wide area link.
Data/Voice systems to Data/Voice systems
LAN to LAN
Terminal to Host
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3. Multiplexing Adtran TSU (T1) Multiplexer
Multiplexer (mux) = A device which allows several devices to share the same communications circuit (cable, airwaves, etc.).
Common Types of Multiplexing
Time Division Multiplexing (TDM)
Statistical Time Division Multiplexing (STDM)
Frequency Division Multiplexing (FDM)
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4. Multiplexing Adtran T3SU 300 (T3) Multiplexer http://www.adtran.com
Blackbox Multiplexer
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5. Time Division Multiplexing
Time Division Multiplexing = A multiplexer which allows devices to transmit information (data/voice) over the circuit by quickly interleaving information.
Train Example:
Five Accordion Manufacturers with 20 box cars of accordions needed to get to their destination ASAP
SF to New York
Three solutions
1. Build 5 sets of tracks
2. Build 1 set of tracks and have 5 separate trains
3. Build 1 set of tracks and share a single train (multiplexing)
Rick Graziani,

6. Time Division Multiplexing
3. Build 1 set of tracks and share a single train with the box cars lined up as:
Company Box Car A B C D E A B
etc.
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7. Time Division Multiplexing
Each source connected to the TDM mux has the entire bandwidth for a portion of time.
TDM constructs a “frame” consisting of one or more time slots for each input source.
TDM scans each input source for data during its designated time slot. If the source has no data to transmit, TDM mux inserts null data and the time slot is wasted.
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8. Time Division Multiplexing
The TDM channel or circuit must be able to handle the sum of the data rates of all its input sources plus overhead (later).
TDM can handle input sources with different data rates.
A slower device may be assigned one time slot, where a faster device may be assigned two or more time slots.
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9. Frequency Division Multiplexing
Multiplexing where input devices share the bandwidth of the circuit by dividing the link into many separate frequencies.
Involves modulating the signal from digital to analog and any other modulation techniques such as TCM.
Each user has the full bandwidth of the circuit at all times.
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10. LAN Topology Rick Graziani graziani@cabrillo.edu

11. Direct Point-to-Point Communications
Nodes Connections
,016
,128
The total number of connections grows more rapidly than the total number of connections.
Full mesh formula: Connections = (N2-N)/2
Could you imagine 8,128 separate connections for 128 PC LAN!
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12. Direct Point-to-Point Communications
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13. Shared Communication Channels
LAN networks allow multiple computers to share a communcations medium, used for local communications.
Point-to-point connections are used for long-distance and a few other special cases.
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14. Shared Communication Channels
Why are shared networks used only for LANs?
Technically: Shared networks require coordination and having timing restrictions (later).
Economically: Much more expensive over long distances.
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15. Shared Communication Channels
LANs operate under the principle of locality of reference.
Locality of Reference: Computer communication follows two distinct patterns:
First, a computer is more likely to communicate with computers that are physically nearby than with computers that are far away.
We will see this later with Ethernet frame sizes and cable distances.
Second, a computer is more likely to communicate with the same set of computers repeatedly. (Temporal Locality of Reference)
We will see this later with ARP tables.
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16. Topologies
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17. Topologies
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18. Topologies
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19. History of Ethernet Bob Metcalfe Volume 2
Developed at Xerox PARC (Palo Alto Research Center) in early 1970’s.
One of three technologies Steve Jobs saw before developing the MacIntosh (Ethernet, OOP, and GUI),
Bob Metcalfe, founder of 3Com, was one of the developers
Digitial Equipment Corporation, Intel and Xerox later produced the DIX standard.
IEEE now controls Ethernet standards, IEEE 802.3
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20. Ethernet Transmissions and Manchester Encoding
Ethernet frames are sent out using Manchester Encoding.
Note: Token Ring uses Differential Manchester Encoding.
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21. Ethernet Transmissions and Manchester Encoding
A digital encoding technique in which each bit period is divided into two complementary halves to provide timing information.
A negative-to-positive voltage (0-to-1) transition in the middle of the bit period designates a binary “1” while a positive-to-negative transition represents a “0.” (Newton)
The data is included in the direction of the transition.
Rick Graziani,

22. Ethernet Transmissions and Manchester Encoding
Rick’s Coding method (no standard – can go other direction)
draw lines in the middle of the bit cell
make a up arrow for a one bit
make an down arrow for a zero bit
connect the lines and make transition when necessary (i.e. consecutive 1’s or 0’s)
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23. Sharing on an Ethernet
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24. 6.2.1 Media Access Control (MAC)
Non-Deterministic
(1st come 1st served)
Deterministic
(taking turns)
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25. 6.2.2 MAC rules and collision detection/backoff
(JAM) When a collision occurs, each node that is transmitting will continue to transmit for a short time to ensure that all devices see the collision.
The devices that were involved in the collision do not have priority to transmit data.
Transmitting and receiving data packets
Decoding data packets and checking them for valid addresses before passing them to the upper layers of the OSI model
Detecting errors within data packets or on the network
Rick Graziani

26. 6.1.2 IEEE Ethernet naming rules
In BASE band signaling, the data signal is transmitted directly over the transmission medium.
In BROADband signaling, not used by Ethernet, a carrier signal is modulated by the data signal and the modulated carrier signal is transmitted.
Rick Graziani

27. DIX Ethernet is essentially the same as 802.3
Introduction to Ethernet
DIX Ethernet is essentially the same as 802.3
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28. Designation Description Rick Graziani graziani@cabrillo.edu
10Base-2
10 Mbps baseband Ethernet over coaxial cable with a maximum distance of 185 meters. Also referred to as Thin Ethernet or Thinnet or Thinwire.
10Base-5
10 Mbps baseband Ethernet over coaxial cable with a maximum distance of 500 meters. Also referred to as Thick Ethernet or Thicknet or Thickwire.
10Base-36
10 Mbps baseband Ethernet over multi-channel coaxial cable with a maximum distance of 3,600 meters.
10Base-F
10 Mbps baseband Ethernet over optical fiber.
10Base-FB
10 Mbps baseband Ethernet over two multi-mode optical fibers using a synchronous active hub.
10Base-FL
10 Mbps baseband Ethernet over two optical fibers and can include an optional asynchronous hub.
10Base-FP
10 Mbps baseband Ethernet over two optical fibers using a passive hub to connect communication devices.
10Base-T
10 Mbps baseband Ethernet over twisted pair cables with a maximum length of 100 meters.
10Broad-36
10 Mbps baseband Ethernet over three channels of a cable television system with a maximum cable length of 3,600 meters.
10Gigabit Ethernet
Ethernet at 10 billion bits per second over optical fiber. Multimode fiber supports distances up to 300 meters; single mode fiber supports distances up to 40 kilometers.
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29. Designation Description Rick Graziani graziani@cabrillo.edu
100Base-FX
100 Mbps baseband Ethernet over two multimode optical fibers.
100Base-T
100 Mbps baseband Ethernet over twisted pair cable.
100Base-T2
100 Mbps baseband Ethernet over two pairs of Category 3 or higher unshielded twisted pair cable.
100Base-T4
100 Mbps baseband Ethernet over four pairs of Category 3 or higher unshielded twisted pair cable.
100Base-TX
100 Mbps baseband Ethernet over two pairs of shielded twisted pair or Category 4 twisted pair cable.
100Base-X
A generic name for 100 Mbps Ethernet systems.
1000Base-CX
1000 Mbps baseband Ethernet over two pairs of 150 shielded twisted pair cable.
1000Base-LX
1000 Mbps baseband Ethernet over two multimode or single-mode optical fibers using longwave laser optics.
1000Base-SX
1000 Mbps baseband Ethernet over two multimode optical fibers using shortwave laser optics.
1000Base-T
1000 Mbps baseband Ethernet over four pairs of Category 5 unshielded twisted pair cable.
1000Base-X
A generic name for 1000 Mbps Ethernet systems.
Rick Graziani

30. 6.1.3 Ethernet and the OSI model
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31. 6.1.3 Ethernet and the OSI model
All other stations in the same collision domain see traffic that passes through a repeater.
Stations separated by bridges or routers are in different collision domains.
Rick Graziani

32. The 5-4-3 rule. 7.1.2 10BASE5 Not more than five segments.
no more than 5 segments separated by more than 4 repeaters, and no more than three populated segments
Not more than five segments.
No more than four repeaters may be connected in series between any two distant stations.
No more than three populated segments.
Rick Graziani

33. Thin Net 7.1.3 10BASE2 Rick Graziani graziani@cabrillo.edu

34. 7.1.4 10BASE-T Rick Graziani graziani@cabrillo.edu

35. BASE-T
Signal leaves the cable and enters the NIC on the SPLIT Green pair. White-Green is +ve, solid Green is negative.
568B
Signal leaves the NIC and enters the cable on the Orange pair. White-Orange is +ve, solid Orange is negative.
Rick Graziani

36. The 5-4-3 rule still applies.
BASE-T wiring and architecture
The rule still applies.
10BASE-T links can have unrepeated distances up to 100 m.
Hubs can solve the distance issue but will allow collisions to propagate.
The 100 m distance starts over at a Switch.
Rick Graziani

37. Cat 5e cable can reliably carry up to 125 Mbps of traffic.
Because Gigabit Ethernet is inherently full-duplex, the Media Access Control method views it as a point-to-point link.
Cat 5e cable can reliably carry up to 125 Mbps of traffic.
1000BASE-T uses all four pairs of wires.
This is done using complex circuitry called a Hybrid to allow full duplex transmissions on the same wire pair.
This provides 250 Mbps per pair.
With all four-wire pairs, this provides the desired 1000 Mbps.
Since the information travels simultaneously across the four paths, the circuitry has to divide frames at the transmitter and reassemble them at the receiver.
1st Frame
2nd Frame
3rd Frame
4th Frame
Rick Graziani

38. BASE-FX
200 Mbps transmission is possible because of the separate Transmit and Receive paths in 100BASE-FX optical fiber.
The main application for which 100BASE-FX was designed was inter-building backbone connectivity
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, and general infrastructure needs.
Rick Graziani

39. 7.1.8 100BASE-FX Rick Graziani graziani@cabrillo.edu

40. 7.1.8 100BASE-FX Rick Graziani graziani@cabrillo.edu

41. 7.1.8 100BASE-FX Rick Graziani graziani@cabrillo.edu

42. L=Long Wave Length 1300nm S=Short Wave Length 850 nm error multimode
5000
550
S=Short Wave Length 850 nm
550
error
multimode
550
275
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.
100 25
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43. Rick Graziani

44. Broadcast Domain vs Collision Domain
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45. 7.2.7 Future of Ethernet Copper (up to 1000 Mbps, perhaps more)
Wireless (approaching 100 Mbps, perhaps more)
Optical fiber (currently at 10,000 Mbps and soon to be more)
Rick Graziani