Multiplexing Rick Graziani graziani@cabrillo.edu Rick_Graziani@csumb.edu

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 Rick Graziani, graziani@cabrillo.edu

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) Rick Graziani, graziani@cabrillo.edu

Multiplexing Adtran T3SU 300 (T3) Multiplexer http://www.adtran.com Blackbox Multiplexer http://www.blackbox.com Rick Graziani, graziani@cabrillo.edu

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, graziani@cabrillo.edu

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 1 B 2 C 3 D 4 E 5 A 6 B 7 etc. Rick Graziani, graziani@cabrillo.edu

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. Rick Graziani, graziani@cabrillo.edu

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. Rick Graziani, graziani@cabrillo.edu

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. Rick Graziani, graziani@cabrillo.edu

LAN Topology Rick Graziani graziani@cabrillo.edu Rick_Graziani@csumb.edu

Direct Point-to-Point Communications Nodes Connections 2 1 4 6 8 28 16 120 32 496 64 2,016 128 8,128 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! Rick Graziani, graziani@cabrillo.edu

Direct Point-to-Point Communications Rick Graziani, graziani@cabrillo.edu

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. Rick Graziani, graziani@cabrillo.edu

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. Rick Graziani, graziani@cabrillo.edu

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. Rick Graziani, graziani@cabrillo.edu

Topologies Rick Graziani, graziani@cabrillo.edu

Topologies Rick Graziani, graziani@cabrillo.edu

Topologies Rick Graziani, graziani@cabrillo.edu

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 Rick Graziani, graziani@cabrillo.edu

Ethernet Transmissions and Manchester Encoding Ethernet frames are sent out using Manchester Encoding. Note: Token Ring uses Differential Manchester Encoding. Rick Graziani, graziani@cabrillo.edu

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, graziani@cabrillo.edu

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) Rick Graziani, graziani@cabrillo.edu

Sharing on an Ethernet Rick Graziani, graziani@cabrillo.edu

6.2.1 Media Access Control (MAC) Non-Deterministic (1st come 1st served) Deterministic (taking turns) Rick Graziani graziani@cabrillo.edu Rick_Graziani@csumb.edu

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 graziani@cabrillo.edu Rick_Graziani@csumb.edu

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 graziani@cabrillo.edu Rick_Graziani@csumb.edu

DIX Ethernet is essentially the same as 802.3 6.1.1 Introduction to Ethernet DIX Ethernet is essentially the same as 802.3 Rick Graziani graziani@cabrillo.edu Rick_Graziani@csumb.edu

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. Rick Graziani graziani@cabrillo.edu Rick_Graziani@csumb.edu

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 graziani@cabrillo.edu Rick_Graziani@csumb.edu

6.1.3 Ethernet and the OSI model Rick Graziani graziani@cabrillo.edu Rick_Graziani@csumb.edu

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 graziani@cabrillo.edu Rick_Graziani@csumb.edu

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 graziani@cabrillo.edu Rick_Graziani@csumb.edu

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

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

7.1.4 10BASE-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 graziani@cabrillo.edu Rick_Graziani@csumb.edu

The 5-4-3 rule still applies. 7.1.5 10BASE-T wiring and architecture The 5-4-3 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 graziani@cabrillo.edu Rick_Graziani@csumb.edu

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 graziani@cabrillo.edu Rick_Graziani@csumb.edu

7.1.8 100BASE-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 graziani@cabrillo.edu Rick_Graziani@csumb.edu

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

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

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

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 Rick Graziani graziani@cabrillo.edu Rick_Graziani@csumb.edu

Rick Graziani graziani@cabrillo.edu Rick_Graziani@csumb.edu

Broadcast Domain vs Collision Domain Rick Graziani, graziani@cabrillo.edu

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 graziani@cabrillo.edu Rick_Graziani@csumb.edu