2.- Ethernet system www.redes.upv.es/ralir/en/  Other technologies

2.- Ethernet system http://www.redes.upv.es/ralir/en/ Other technologies The physical layer: a reminder general aspects MAC Full-duplex auto-negotiation Ethernet Fast Ethernet Gigabit Ethernet thanks to: thanks to: Igor Radovanović, [email protected] Igor Radovanović, [email protected] Technische Universiteit Eindhoven Technische Universiteit Eindhoven Local Area Networks/School of Engineering in Computer Science/2009-2010

http://www.redes.upv.es/ralir/en/ Other LAN technologies Token Ring Token Bus FDDI Local Area Networks/School of Engineering in Computer Science/2009-2010

Local Area Networks (RALIR) /School of Engineering in Computer Science 3 What is a Token Ring LAN? A token ring network (IEEE 802.5) is a LAN technology based on a token-passing protocol for media access control. (No collisions) Data frames are transmitted from node to node, in either a clockwise or counter-clockwise direction, over a pointto-point link. A Token Ring LAN is implemented either: Logical ring using a physical ring topology Logical ring using a physical star topology (uses Token Ring Hubs that incorporate logical rings) http://www.redes.upv.es/ralir/en/

Ends here when Station A: Station A: Grabs 24 bit token and sets Tbit from 1 to 0 (free to busy) Puts data frame on network. Sets destination: Station D is in transmit mode. F RAME T A C DATA SD 0 0 0 10010101 A Station B: Receives frame and reads its destination address Sees destination is Station D and copies the rec eived frame to the output link is in listen mode. 4 F RAME T A C DATA SD 0 1 1 10010101 A http://www.redes.upv.es/ralir/en/ DA D Station D: F RA M E T A C D ATA S D D A 0 0 0 10 01 0 10 1A D Starts here Receives originally sent frame Examines frame status flags to find: A 1: address recognized C 1: f rame c opied suc ces sfully Does NOT retransmit frame Sets T-bit in token to 1 (free) Releas es token F RAM E T A C D ATA S D D A 0 0 0 10 01 0 10 1A D Local Area Networks (RALIR) /School of Engineering in Computer Science Token-Passing Access Methodology Receives frame and identifies itself as the destination address Moves data from f rame into memory Changes f rame status flags to confirm delivery DA D Station C: is powered off so network traffic flows through unproc essed. is in bypas s mode. ABBREVIATED FR AME LEGEND T busy status A address recognized C copied suc cessfully DATA transmit ted data SD sourc e address DA destination address

5 Local Area Networks (RALIR) /School of Engineering in Computer Science Token Ring Topologies http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science Terminology Token Ring hubs are called Multistation Access Units (MAUs). Nodes connected to a Token Ring network are called lobes; The distance between MAUs is called the main ring length. The distance between an MAU and its lobes is called lobe length. IEEE 802.5 defined the specifications of Token Ring LANs, which is based in part on IBM’s set of token ring specifications. (IBM is the primary vendor of this technology) 6 http://www.redes.upv.es/ralir/en/

7 Local Area Networks (RALIR) /School of Engineering in Computer Science Illustrative Example of MAUs http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science Token Ring vs. Token Bus (1) A Token Bus is a logical ring on a physical bus topology. It uses a token passing protocol (defined in IEEE 802.4). The network is physically a bus topology and logically arranged as a ring with respect to passing the token from lobe to lobe. Token Bus is based on broadcasting (similar to Ethernet/802.3), even thought token passing is point-topoint. The Medium Access Control is similar to Token Ring (802.5). At the physical layer, IEEE 802.4 uses coaxial cable or fiber-optic cable. 8 http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 9 Token Ring vs. Token Bus (2) Token Bus priority scheduling supports up to four priority modes (0 (lowest), 2, 4, and 6 (highest)). Token Bus is not a popular LAN protocol, primarily used for control of industrial and factory automation processes. http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 1 Advantages and Disadvantages Advantages: its ability to run on many different media types its efficient use of bandwidth its stable behavior during high load times its deterministic nature its priority scheme, which enables nodes with high-priority data to reserve the network Disadvantages: need special recovery procedures when network fails difficulty in configuring new hosts to an established LAN in priority scheduling, the susceptibility of low priority nodes to increased delays in accessing the network. http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 1 FDDI: General aspects Fiber Distributed Data Interface MAC: Token Passing Logical topology: Sequential Physical topology: Dual counter-rotating rings. Uses cable types: Fiber optic cable Data rate/speed 100 Mbps Each cable length 2 Km Max # of cables 100; Max # of repeaters 100 Max total Network length 200 Km Max # of nodes/segment 10 Max # of nodes/network 1000 http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 1 FDDI: Architecture basics Primary ring---is the outer ring. Secondary ring---is the inner ring. Uses 2-types of Computers: DAS and SAS SAS Single attachment station Connected to the outer/primary ring DAS Dual attachment station Connected to both the primary/secondary rings. If SAS/Primary ring fails, DAS takes over. Each of these DASs/SASs must use FDDI-NIC. http://www.redes.upv.es/ralir/en/

1 Local Area Networks (RALIR) /School of Engineering in Computer Science FDDI-Topology http://www.redes.upv.es/ralir/en/

2.- Ethernet http://www.redes.upv.es/ralir/en/ The physical layer: a reminder general aspects MAC Full-duplex auto-negotiation Ethernet Fast Ethernet Gigabit Ethernet Local Area Networks/School of Engineering in Computer Science/2009-2010

Local Area Networks (RALIR) /School of Engineering in Computer Science Physical layer reminder: Terminology Guided (wired) vs. Unguided (wireless) examples of guided transmission media: Twisted Pair Coaxial cable Optical fiber point-to-point vs. multipoint simplex, half-duplex and full-duplex links 1 http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science Physical layer reminder: Twisted Pair pair short connections ( 50m) data rates 19.2 kbps Problems: crosstalk noise twisted pair often “bundled” into cables and usually installed in buildings during constructions better than pair but still susceptible to interference and noise Pros and Cons: 1 Cheap Easy to work with Limited data rate (100MHz) Limited bandwidth (1MHz) Limited distance repeater every 2km or 3km http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science Physical layer reminder: Unshielded and Shielded Twisted Pair Unshielded Twisted Pair (UTP) Cheapest Easiest to install Suffers from external EM interference Categories: Cat 3 up to 16MHz Voice grade found in most offices Twist length of 7.5 cm to 10 cm Cat 4 up to 20 MHz Cat 5 up to 100MHz Commonly pre-installed in new office buildings Twist length 0.6 cm to 0.85 cm Shielded Twisted Pair (STP) Metal braid or sheathing that reduces interference More expensive Harder to handle (thick, heavy) 1 http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 1 Physical layer reminder: Coaxial Cable Most versatile medium two types: 50-ohm and 75-ohm Long distance telephone transmission Can carry 10,000 voice calls simultaneously Being replaced by fiber optic Short distance computer systems links Local area networks http://www.redes.upv.es/ralir/en/ Analog Amplifiers every few km Closer if higher frequency up to 500MHz Digital Repeater every 1km Closer for higher data rates up to 350 MHz (500 Mbps)

Local Area Networks (RALIR) /School of Engineering in Computer Science Physical layer reminder: Optical Fiber Greater capacity Data rates of hundreds of Gbps Smaller size & weight Lower attenuation Electromagnetic isolation Greater repeater spacing 10s of km at least problems with junctions Applications: 1 http://www.redes.upv.es/ralir/en/ Long-haul trunks Metropolitan trunks Rural exchange trunks Subscriber loops LANs

Local Area Networks (RALIR) /School of Engineering in Computer Science Physical layer reminder: Optical Fiber Transmission Characteristics Act as wave guide for 1014 to 1015 Hz Portions of infrared and visible spectrum Light Emitting Diode (LED) Cheaper Wider operating temp range Last longer Injection Laser Diode (ILD) More efficient Greater data rate Wavelength Division Multiplexing: WDM and DWDM 2 http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science Physical layer reminder: Encoding and modulation techniques g(t) [digital or analog] x(t) [digital] coder decoder m(t) [digital or analog] s(t) [analog] modulator fc 2 http://www.redes.upv.es/ralir/en/ g(t) m(t) demodulator

Local Area Networks (RALIR) /School of Engineering in Computer Science 2 Physical layer reminder: Nonreturn to ZeroLevel NRZ-L: two different voltages for 0 and 1 bits Voltage constant during bit interval no transition, i.e., no return to zero voltage Example: absence of voltage for zero, constant positive voltage for one More often, negative voltage for one value and positive for the other http://www.redes.upv.es/ralir/en/ NRZ-I: Nonreturn to zero inverted on ones Constant voltage pulse for duration of bit Data encoded as presence or absence of signal transition at beginning of bit time Transition (low to high or high to low) denotes a binary 1; no transition denotes binary 0

Local Area Networks (RALIR) /School of Engineering in Computer Science 2 Physical layer reminder: Self-clocking line encoding http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science Physical layer reminder: Multilevel Binary mBnL codes: a sequence of m bits is represented by n pulses, each of L levels (n m and L 2) 2 http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science Ethernet: some historical notes. 1972: Robert Metcalfe designs the first prototype at the Xerox PARC 1980: the first standard appears, by DEC-Intel-Xerox 1985: IEEE802.3 standard is released. The complete name is: “Carrier Sense Multiple Access with Collision Detection (CSMA/CD) Access Method and Physical Layer Specifications” IEEE supplements 2 802.3d-1987: FOIRL fiber link 802.3i-1990: 10BASE-T twisted pair 802.3z-1998: Gigabit Ethernet 802.3ab-1999: 1000BASE-T Gigabit Ethernet over twisted pair 802.3ae-2002: 10Gb/s Ethernet http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science The Ethernet “family tree” 10Mbps 10Base2 10Base5 10Base-T FOIRL 10Base-F 10Base-FB 10Base-FP 10Base-FL 22 thin thincoaxial; coaxial; 55 thick thickcoaxial; coaxial; TT twisted twistedpair; pair; FF fiber fiberoptics; optics; 100 Mbps (100Base-T) 100Base-X 100Base-TX 100Base-FX 100Base-T4 1000 Mbps 1000Base-X 1000Base-SX 1000Base-LX 1000Base-CX 1000Base-T 2 http://www.redes.upv.es/ralir/en/ SS short shortwavelength; wavelength; LL long longwavelength; wavelength; CC short shortcopper copper cable; cable;

2 Local Area Networks (RALIR) /School of Engineering in Computer Science Devices Hubs Switches Adaptors http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 2 Connection media Different connection types are used by each physical layer implementation. The registered jack (RJ-45) connector and jack are the most common. In some cases the type of connector on a NIC does not match the media that it needs to connect to. The AUI connector allows different media to connect when used with the appropriate transceiver. http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 2 Connection media EIA/TIA specifies an RJ-45 connector for UTP cable. The letters RJ stand for registered jack, and the number 45 refers to a specific wiring sequence. The RJ-45 connector is the male component, crimped on the end of the cable. http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 3 Connection media The jack is the female component in a network device, wall outlet, or patch panel. http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 3 Cable Standards For electricity to run between the connector and the jack, the order of the wires must follow EIA/TIA-T568-A or T568-B standards. Identify the correct EIA/TIA category of cable to use for a connecting device by determining what standard is being used by the jack on the network device. http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 3 Straight-through Cable The 10BASE-T and 100BASE-TX Ethernet standards use one wire pair for transmission in each direction. This requires that the transmit pair of each device be connected to the receive pair of the device on the other end. If the two RJ-45 connectors of a cable are held side by side in the same orientation, the colored wires will be seen in each. If the order of the colored wires is the same at each end, then the cable is straight-through. http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science Straight-through Cable Use straight-through cables for the following cabling: Switch to Host (PC or server) Hub to Host (PC or server) Switch to router Rule of thumb: Connect devices of the same OSI Layer with CROSSOVER cable. Connect devices of different OSI Layers with STRAIGHT cables. 3 http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 3 Crossover cables One terminal device may be connected directly to another without the use of a switch or hub, but in that case the crossover must be done externally in the cable. Since 10BASE-T and 100BASE-TX use pairs 2 and 3, these two pairs must be swapped in the cable. This is a crossover cable. When a terminal device is connected to a switch or hub, this crossover is done internally in the switch or hub. Automatic crossover Automatic MDI/MDI-X Configuration is specified as an optional feature in the 1000BASE-T standard meaning that straight-through cables will usually work between Gigabit capable interfaces. This feature eliminates the need for crossover cables, obsoletes the uplink/normal ports and manual selector switches found on many older hubs and switches, greatly reducing installation errors. Note that although Automatic MDI/MDI-X is generally implemented, a crossover cable would still be required in the occasional situation that neither of the connected devices has the feature implemented and enabled. Even for legacy 10/100 devices, many NICs, switches and hubs automatically apply an internal crossover when necessary. This feature may also be referred to by various vendor-specific terms including: Auto uplink and trade, Universal Cable Recognition and Auto Sensing. http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 3 Crossover Cable With crossover, the RJ-45 connectors on both ends show that some of the wires on one side of the cable are crossed to a different pin on the other side of the cable. Pins 1 and 2 on one connector connect respectively to pins 3 and 6 on the other. http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science Crossover Cable Use crossover cables typically between like devices, for example: Switch to switch Hub to hub Router to router PC to PC Rule of thumb: Connect devices of the same OSI Layer with CROSSOVER cable. Connect devices of different OSI Layers with STRAIGHT cables. 3 http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science Frame format in traditional Ethernet MAC frame Preamble 7 bytes of alternating 0s and 1s – receiver sync Not necessary in high-speed Ethernet systems (FastEth, GigE) Start of Frame Delimiter 10101011 – unique sequence - last chance to synchronize Source Address, Destination Address 48 bit unique address Length/Type Value up to 1518: length; value larger than 1536 – type of PDU encaps Data Frame Check Sequence (CRC); Preamble and SFD excluded 3 http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science Min & Max Ethernet frame length Minimum length - used for CSMA/CD Every end station senses the frame within the correct time limits Historical requirement derived for bus topology with a coax cable and a network with a 2 byte field Maximum length – to assure fair access A station should not occupy the medium too long 3 http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 48-Bit Universal LAN MAC Addresses Described in IEEE Std802-1990, pg. 25 48 bits burned into ROM on adaptor Octet: 0 1 2 3 4 5 0011 0101 0111 1011 0001 0010 0000 0000 0000 0000 0000 0001 First bit transmitted on the LAN medium. (Also the I/G Address Bit: 0 Individual; 1 Group) Second bit, the Universally or Locally Administered, U/L Address Bit, indicates whether the address has been assigned by a local ( 1) or universal administrator ( 0). The hexadecimal representation is: AC:DE:48:00:00:80 Organizationally Unique Identifier as assigned by the IEEE 3 Unicast address: destined for individual receiver Broadcast address: all 1’s in address- for every node Multicast address: leading 1 in address– subset of nodes http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 4 Random Access MAC protocols CSMA/CD (Collision Detection) CSMA/CD: carrier sensing, deferral as in CSMA collisions detected within short time colliding transmissions aborted, reducing channel wastage persistent or non-persistent retransmission collision detection: easy in wired LANs: measure signal strengths, compare transmitted, received signals difficult in wireless LANs: receiver shut off while transmitting human analogy: the polite conversationalist http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 4 Random Access MAC protocols CSMA/CD collision detection http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science The CSMA with Collision Detection protocol while while there there are are frames frames to to be be sent sent while while (channel (channel is is busy)loop; busy)loop; /* /* the the channel channel is is available available (idle) (idle) */ */ wait wait IFG IFG sending sending if if aa collision collision is is detected detected then then send send jam jam signal signal abort abort the the transmission transmission wait wait aa random random amount amount of of time time whend whend 4 http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science Binary Exponential Backoff th - - iith collision collision if if ii 10 10 then then i choose choose aa number number nn between between 00 and and (2 (2i-1) -1) wait wait nn time-slots time-slots try try sending sending again again else else if if ii 16 16 then then 10 choose choose aa number number nn between between 00 and and (2 (210-1) -1) wait wait nn time-slots time-slots try try sending sending again again else else if if ii 16 16 then then error error fi fi 4 http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science CSMA/CD: a few details A B C time data interframe gap (IFG): 96 bits (9.6msec at 10Mbps) collision enforcement jam signal: 32 bits collision backOff time: multiples of the slot time: 512 bits 4 http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science Collisions and minimum frame size A B A t t-e t 0 A B A t t 1km coax cable, Tprop d/Vprop 5msec; 2,5 km with 4 repeaters, measured 2t 51.2msec s vt 10Mbps·51.2msec 512 bits 64bytes 4 http://www.redes.upv.es/ralir/en/ B B t 2t

Local Area Networks (RALIR) /School of Engineering in Computer Science Media System Timing Depends on: physical layer roud-trip propagation time collision enforcement procedure 512 bit time for 10 and 100 Mbps sytems networks diameter in 10 Mbps systems: approx. 2800meters networks diameter in 100 Mbps systems: approx. 205meters In half-duplex Gigabit ethernet networks diameter would be approx. 20 meters The solution: carrier extension; it allows not to modify the frame structure i.e., 4096 bits 4 http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 4 Frame bursting Carrier extension is very inefficient for the short packets for example for 64 byte packet we have 448 bytes of padding low throughput Solution: introduce Frame bursting The maximum burst size is 65536 bit (8192 bytes) plus the final frame transmission http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science Definition of a collision domain “defined as all the Ethernet segments between a pair of bridges or other layer 2 devices” “a single CSMA/CD network in which there will be a collision if two computers attached to the system both transmit at the same time” 4 http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 4 Segmentation Segmentation is the process of splitting a single collision domain into two or more collision domains. Layer 2 bridges or switches can be used to segment a logical bus topology and create separate collision domains. However the entire bus topology still represents a single broadcast domain because, bridges and switches forward broadcast packets. http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 5 An example of a collision domain A collision domain is also known as a bandwidth domain http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 5 Bridged Ethernet: creating separate collision domains Bridges: rise the bandwidth and separate collision domains http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 5 Switched Ethernet: micro-segmentation Each end station uses a separate path to the port in the switch (no sharing medium) Used to add bandwidth without replacing NICs http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 5 Full-duplex Ethernet “Ethernet is CSMA/CD” Dedicated media (structured wiring) and microsegmentation (provided by switches) have evolved to enable full-duplex capability in Ethernet Disable carrier-sense, collision detect! Eliminate the link length restrictions Increase the aggregate channel capacity Gigabit Ethernet basically works in full-duplex mode http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science Limitations of Full-duplex Operation Requirements for full duplex as stated in the 802.3x standard: 1. The underlying physical channel must be capable of supporting simultaneous, bi-directional communications without interference 2. Exactly two devices on the LAN segment. 3. The interfaces in both devices must be capable of and configured to use full-duplex mode. If all of these conditions are met, then full-duplex mode not only can be used, it should be used. 5 http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 5 Ethernet Flow Control Need for flow control Loss of a frame due to buffer unavailability has the same effect as a frame lost due to a bit error Effect of frame loss can be devastating on throughput if flow control is implemented by a higher layer protocol Backpressure in half duplex networks will not work; a full duplex Ethernet requires an explicit flow control MAC Control Client (higher layers) Network Data Link Physical MAC Control MAC – Media Access Control MAC Control client (such as a switch desiring to prevent buffer overflow) uses the added capabilities of the MAC control sub layer. It can request the MAC at the other end of a full-duplex link to cease further data transmissions, thereby preventing the impending overflow (PAUSE function) http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 5 PAUSE Function Implement flow control on a single full-duplex Ethernet link Simple “stop-start” form of flow-control A device (end station or switch) wishing to temporarily inhibit incoming data sends a PAUSE frame (along with the time to wait) When a device receives a PAUSE frame, it stops sending data frames for the period specified Flow control policy http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 5 PAUSE Packet The only packet defined by the MAC control sublayer A station starts a timer set to the specified pause time after it receives a PAUSE packet and resumes sending data frames when the timer expires A station can still send PAUSE packet after it receives a PAUSE frame to ask the other device to stop sending data A device may send several PAUSE packets. The more recent PAUSE packet can cancel the effect of the previous one http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 5 Auto negotiation The auto-negotiation algorithm (known as NWay) allows two devices at either end of a 10 Mbps, 100 Mbps, or 1000 Mbps link to advertise and negotiate the link operational mode—such as the speed of the link and the duplex configuration of half or full duplex—to the highest common denominator. Auto-negotiation addresses the following goals: Provide easy, plug-and-play upgrades from 10 Mbps, 100 Mbps, and 1000 Mbps as the network infrastructure is upgraded Prevent network disruptions when connecting mixed technologies such as 10BaseT, 100BaseTX, and 1000BaseT Accommodate future PHY (transceiver) solutions Support backward compatibility with 10BaseT The negotiation covers only the link (between a station and a hub or between two hubs), not the whole network Negotiation can only occur during link initialization Negotiation uses a separate frame format and signaling system Each device advertises its capabilities to the other http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 5 Auto negotiation The Auto-Negotiation specification includes reception, arbitration, and transmission of normal link pulses (NLPs). It also defines a receive LIT function for backward compatibility with 10BaseT devices. All of these functions are implemented as part of the physical layer transceiver. The exchange of link information occurs between the PHY and the Medium Dependent Interface (MDI) or RJ-45 connector. All auto-negotiation functions are implemented as part of the transceiver integrated circuit, which is part of a network interface card or integrated on the motherboard of a computer. http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 6 Auto negotiation: link test 10BaseT link test pulses The 10BaseT standard includes a link test mechanism to ensure network integrity. In the absence of network traffic, a 100 nanosecond (ns) heartbeat unipolar (positive only) pulse is sent every 16 milliseconds (ms) within a range of /- 8 ms. The link test pulse is sent by the transmitters of all 10BaseT media attachment units (MAUs) between the data terminal equipment (DTE) and the repeater. A link fail condition is entered if the receiver does not receive a packet or a link test pulse within 50-150 ms. The link fail condition disables the data transmit, data receive, and loopback functions. The link test pulses continue to be transmitted and received during the link failure. The link is reestablished when two consecutive link test pulses or a single data packet have been http://www.redes.upv.es/ralir/en/ received. 100BaseT/1000BaseT fast link pulses The link information is encoded in a special pulse train known as the fast link pulse (FLP) burst. The FLP builds on the LIT pulse used by 10BaseT devices as a heartbeat pulse to the link partner at the opposite end of the link. The LIT was redefined as the normal link pulse (NLP). The NLP is the 10BaseT link integrity test pulse, and the FLP is a group of NLPs. Each pulse is 100 ns in width. Auto-negotiation replaces the single 10BaseT link pulse with the FLP burst. Auto-negotiation stops the transmission of FLP bursts once the link configuration is established. The FLP burst looks the same as a single link test pulse from the perspective of 10BaseT devices. Consequently, a device that uses NWay must recognize the NLP sequence from a 10BaseT link partner, cease transmission of FLP bursts, and enable the 10BaseT physical medium attachment

Local Area Networks (RALIR) /School of Engineering in Computer Science 6 FLP bursts FLP bursts Each FLP burst consists of 33 pulse positions that provide clock and data information. The 17 oddnumbered pulses are designated as clock pulses, while the 16 evennumbered pulse positions represent data information. A logic one is represented by the presence of a pulse, while the absence of a pulse is represented by a logic zero. FLP burst encoding The data pulses in the FLP burst encode a 16-bit link code word (LCW). A device capable of autonegotiation transmits and receives the FLP. The receiver must identify three identical LCWs before the information is authenticated and used in the arbitration process. The devices decode the base LCW and select capabilities of the highest common denominator supported by both devices. Once the LCWs are properly received, each device transmits a FLP burst with an acknowledge bit. At this point, both devices enable the http://www.redes.upv.es/ralir/en/ mode that is the highest common

6 Local Area Networks (RALIR) /School of Engineering in Computer Science Three generations of Ethernet http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science Ethernet- Physical layer If PLS to be connected to a different MAU PLS the same Medium Attachment Unit Medium dependant MDI External: tap or a tee connector Internal: jack 6 http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science Ethernet 10Base5 MDI (MAU) 10Base5 transceiver 6 http://www.redes.upv.es/ralir/en/

6 Local Area Networks (RALIR) /School of Engineering in Computer Science Ethernet 10Base2 http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science Physical layer implementation sTYPE-t(l) s – speed in Mbps TYPE – broadband or baseband signaling l – cable distance in multiple of 100 m t – media type used 6 http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 6 10BASE-T uses a physical star topology end stations connected to a hub using external or internal transceiver maximum distance 100 m using UTP cable maximum number of hubs is 4 (total span 2500 m) http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 6 10BaseT: the RJ45 jack Pin#1: TX Pin#2: TXPin#3: RX Pin#6: RX“cross-over” connection http://www.redes.upv.es/ralir/en/

6 Local Area Networks (RALIR) /School of Engineering in Computer Science 10BaseT: twisted pair HUB http://www.redes.upv.es/ralir/en/ HUB

7 Local Area Networks (RALIR) /School of Engineering in Computer Science Three generations of Ethernet http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 7 Fast Ethernet Keep MAC layer untouched Increase the speed 10 times while keeping the compatibility with the Ethernet Quick deployment Autonegotiation negotiate the mode (full- or half-duplex) or data rate of operation (10 Mbps, 100 Mbps) Different encoding technique to transfer the high data rate signal Physical layer Reconciliation: pass data in 4-bit format (nibble) to the MII interface MII: operates at both 10 Mbps and 100 Mbps; features a parallel data path (4 bits) between PHY and reconciliation sublayer; defines 5 types of signals: transmit, receive, control (carrier sense & collision detect), management, and power; not needed for internal PHY (see page 242) PHY: transceiver, also responsible for encoding/decoding http://www.redes.upv.es/ralir/en/ MDI: medium dependent interface to connect to the medium

7 Local Area Networks (RALIR) /School of Engineering in Computer Science Fast Ethernet implementations http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 100BASE-TX uses two pairs of twisted-pair cable (Cat5 UTP or STP) in the physical star topology (up to 500 m) encoding 7 http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science MLT-3 Uses 3 levels of signals ( 1,0,-1) Transition at the beginning of bit 1 Used to decrease transmission frequency Q: Why? 7 http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science Physical layer reminder: 4B5B coding Used by 100Base-TX Based on NRZI at 125 Mbaud/s. 4 bits are represented with 5 bits symbols using a table. The remaining sequences are used for signaling 1 0 1 1 1 0 0 0 1 0 0 7 1 8 ns. 125Mbaud/s http://www.redes.upv.es/ralir/en/ 1 1 1 1 0 1 1 0

Local Area Networks (RALIR) /School of Engineering in Computer Science 100BASE-FX Two pairs of fiber-optic cables in a physical star topology Can support larger distances (up to 2km); unrepeated 412 m single-mode fiber Long-wavelength lasers in NICs Problem: not compatible with previous fiber standards 7 http://www.redes.upv.es/ralir/en/

7 Local Area Networks (RALIR) /School of Engineering in Computer Science 100BASE-FX - encoding http://www.redes.upv.es/ralir/en/

7 Local Area Networks (RALIR) /School of Engineering in Computer Science Three generations of Ethernet http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 7 Gigabit Ethernet Once more 10 times faster Ethernet wanted to keep MAC layer unaltered 802.3z (z indicates the end of the road) Design goals: backwards compatibility offer unacknowledged datagram services same 48 bit address scheme All configurations are point-to-point Defined for both half- & full-duplex Half-duplex supports CSMA/CD All implementations today are full-duplex http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 8 Gigabit Ethernet Physical Layer Reconciliation: pass data in 8-bit format to the PHY sublayer via a GMII interface GMII: operates at 1000 Mbps; with chips supporting both 10 Mbps and 100 Mbps; features a parallel data path (8 bits) between PHY and reconciliation sublayer; a logical, rather than a physical interface PHY: transceiver, also responsible for encoding/ decoding MDI: medium dependent interface to connect to the medium http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science Gigabit Ethernet implementations based on optical fiber short wavelengths 260 m - MM fiber 550 m - SM fiber 8 http://www.redes.upv.es/ralir/en/ based on STP; never implemented long wavelengths 550 m - MM fiber 3 km - SM fiber 25 m Cat5 UTP 100 m

Local Area Networks (RALIR) /School of Engineering in Computer Science 8 1000BaseSX & LX The NRZ signals are then pulsed into the fiber using either short-wavelength or long-wavelength light sources. The short-wavelength uses an 850 nm laser or LED source in multimode optical fiber (1000BASE-SX). It is the lower-cost of the options but has shorter distances. The long-wavelength 1310 nm laser source uses either single-mode or multimode optical fiber (1000BASE-LX). Laser sources used with singlemode fiber can achieve distances of up to 5000 meters. Because of the length of time to completely turn the LED or laser on and off each time, the light is pulsed using low and high power. A logic zero is represented by low power, and a logic one by high power. The Media Access Control method treats the link as pointto-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. http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 8 1000 Mbps on Cat5e? How? Because Cat 5e cable can reliably carry up to 125 Mbps of traffic, getting 1000 Mbps (Gigabit) of bandwidth was a design challenge. The first step to accomplish 1000BASE-T is to use all four pairs of wires instead of the traditional two pairs of wires used by 10BASE-T and 100BASE-TX. This is done using complex circuitry 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. http://www.redes.upv.es/ralir/en/

8 Local Area Networks (RALIR) /School of Engineering in Computer Science 1000Base-T http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 8 10-Gigabit Ethernet - 2002 IEEE 802.3ae was adapted to include 10 Gbps full-duplex transmission over fiber optic cable. This 10-Gigabit Ethernet (10GbE) is evolving for not only LANs, but also MANs, and WANs. 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. Ethernet is traditionally thought of as a LAN technology, but 10GbE physical layer standards allow both an extension in distance to 40 km over single-mode fiber and compatibility with synchronous optical network (SONET) and synchronous digital hierarchy (SDH) networks. Compatibility with SONET/SDH networks operating up to OC-192 speeds (9.584640 Gbps) make 10GbE a viable WAN technology. 10GbE may also compete with ATM for http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 8 10-Gigabit Ethernet Architecture As with the development of Gigabit Ethernet, the increase in speed comes with extra requirements. The shorter bit time duration because of increased speed requires special considerations. Because of the short duration of the 10 GbE data bit, it is often difficult to separate a data bit from noise. 10 GbE data transmissions rely on exact bit timing to separate the data from the effects of noise on the physical layer. This is the purpose of synchronization. By using codes to represent the user data, transmission is made more efficient. The encoded data provides synchronization, efficient usage of bandwidth, and improved Signal-to-Noise Ratio characteristics. 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. http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science 10-Gigabit Ethernet Variety As is typical for new technologies, a variety of implementations are being considered, including: 10GBASE-SR Intended for short distances over already-installed multimode fiber supports a range between 26 m to 82 m 10GBASE-LX4 Uses wavelength division multiplexing (WDM) supports 240 m to 300 m over already-installed multimode fiber and 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 are intended to work with OC192 synchronous transport module (STM) SONET/SDH WAN equipment. 8 http://www.redes.upv.es/ralir/en/

Local Area Networks (RALIR) /School of Engineering in Computer Science The Future of Ethernet Ethernet has gone through an evolution from Legacy Fast Gigabit MultiGigabit technologies. While other LAN technologies are still in place (legacy installations), Ethernet dominates new LAN installations. While 1-Gigabit Ethernet is now widely available and 10Gigabit products becoming more available, the IEEE and the 10-Gigabit Ethernet Alliance are working on 40, 100, or even 160 Gbps standards. The problem of collisions with physical bus topologies of 10BASE5 and 10BASE2 and 10BASE-T and 100BASE-TX hubs is no longer common. Using UTP and optical fiber with separate Tx and Rx paths, and the decreasing costs of switches make single shared media, half-duplex media connections much less important. The future of networking media is three-fold: 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) 8 http://www.redes.upv.es/ralir/en/