03 tecn lan_básicas
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  • In this module, we will cover the fundamentals of LAN technologies. We’ll look at Ethernet, Token Ring, and FDDI. For each one, we’ll look at the technology as well as its operation.
  • The three LAN technologies shown here account for virtually all deployed LANs: The most popular local area networking protocol today is Ethernet. Most network administrators building a network from scratch use Ethernet as a fundamental technology. Token Ring technology is widely used in IBM networks. FDDI networks are popular for campus LANs – and are usually built to support high bandwidth needs for backbone connectivity. Let’s take a look at Ethernet in detail.
  • Ethernet was initially developed by Xerox. They were later joined by Digital Equipment Corporation (DEC) and Intel to define the Ethernet 1 specification in 1980. There have been further revisions including the Ethernet standard (IEEE Standard 802.3) which defines rules for configuring Ethernet as well as specifying how elements in an Ethernet network interact with one another. Ethernet is the most popular physical layer LAN technology because it strikes a good balance between speed, cost, and ease of installation. These strong points, combined with wide acceptance in the computer marketplace and the ability to support virtually all popular network protocols, make Ethernet an ideal networking technology for most computer users today. The Fast Ethernet standard (IEEE 802.3u) has been established for networks that need higher transmission speeds. It raises the Ethernet speed limit from 10 Mbps to 100 Mbps with only minimal changes to the existing cable structure. Incorporating Fast Ethernet into an existing configuration presents a host of decisions for the network manager. Each site in the network must determine the number of users that really need the higher throughput, decide which segments of the backbone need to be reconfigured specifically for 100BaseT and then choose the necessary hardware to connect the 100BaseT segments with existing 10BaseT segments. Gigabit Ethernet is an extension of the IEEE 802.3 Ethernet standard. It increases speed tenfold over Fast Ethernet, to 1000 Mbps, or 1 Gbps.
  • One thing to keep in mind in Ethernet is that there are several framing variations that exist for this common LAN technology. These differences do not prohibit manufacturers from developing network interface cards that support the common physical layer, and software that recognizes the differences between the two data links.
  • Ethernet protocol names follow a fixed scheme. The number at the beginning of the name indicates the wire speed. If the word “base” appears next, the protocol is for baseband applications. If the word “broad” appears, the protocol is for broadband applications. The alphanumeric code at the end of the name indicates the type of cable and, in some cases, the cable length. If a number appears alone, you can determine the maximum segment length by multiplying that number by 100 meters. For example 10Base2 is a protocol with a maximum segment length of approximately 200 meters (2 x 100 meters).
  • This chart give you an idea of the range of Ethernet protocols including their data rate, maximum segment length, and medium. Ethernet has survived as an essential media technology because of its tremendous flexibility and its relative simplicity to implement and understand. Although other technologies have been touted as likely replacements, network managers have turned to Ethernet and its derivatives as effective solutions for a range of campus implementation requirements. To resolve Ethernet’s limitations, innovators (and standards bodies) have created progressively larger Ethernet pipes. Critics might dismiss Ethernet as a technology that cannot scale, but its underlying transmission scheme continues to be one of the principal means of transporting data for contemporary campus applications. The most popular today is 10BaseT and 100BaseT… 10Mbps and 100Mbps respectively using UTP wiring. Let’s take a look at how Ethernet works.
  • Let’s say in our example here that station A is going to send information to station D. Station A will listen through its NIC card to the network. If no other users are using the network, station A will go ahead and send its message out on to the network. Stations B and C and D will all receive the communication.
  • At the data link layer it will inspect the MAC address. Upon inspection station D will see that the MAC address matches its own and then will process the information up through the rest of the layers of the seven layer model.
  • As for stations B & C, they too will pull this packet up to their data link layers and inspect the MAC addresses. Upon inspection they will see that there is no match between the data link layer MAC address for which it is intended and their own MAC address and will proceed to dump the packet.
  • Broadcasting is a powerful tool that sends a single frame to many stations at the same time. Broadcasting uses a data link destination address of all 1s. In this example, station A transmits a frame with a destination address of all 1s, stations B, C, and D all receive and pass the frame to their respective upper layers for further processing. When improperly used, however, broadcasting can seriously impact the performance of stations by interrupting them unnecessarily. For this reason, broadcasts should be used only when the MAC address of the destination is unknown or when the destination is all stations.
  • Ethernet is known as being a very reliable local area networking protocol. In this example, A is transmitting information and B also has information to transmit. Let’s say that A & B listen to the network, hear no traffic and broadcast at the same time. A collision occurs when these two packets crash into one another on the network. Both transmissions are corrupted and unusable.
  • When a collision occurs on the network, the NIC card sensing the collision, in this case, station C sends out a jam signal that jams the entire network for a designated amount of time.
  • Once the jam signal has been received and recognized by all of the stations on the network, stations A and D will both back off for different amounts of time before they try to retransmit. This type of technology is known as Carrier Sense Multiple Access With Collision Detection – CSMA/CD.
  • We’ve mentioned that Ethernet also has high speed options that are currently available. Fast Ethernet is used widely at this point and provides customers with 100 Mbps performance, a ten-fold increase. Fast EtherChannel is a Cisco value-added feature that provides bandwidth up to 800 Mbps. There is now a standard for Gigabit Ethernet as well and Cisco provides Gigabit Ethernet solutions with 1000 Mbps performance. Let’s look more closely at Fast EtherChannel and Gigabit Ethernet.
  • Fast EtherChannel provides a solution for network managers who require higher bandwidth between servers, routers, and switches than Fast Ethernet technology can currently provide. Fast EtherChannel is the grouping of multiple Fast Ethernet interfaces into one logical transmission path providing parallel bandwidth between switches, servers, and Cisco routers. Fast EtherChannel provides bandwidth aggregation by combining parallel 100-Mbps Ethernet links (200-Mbps full-duplex) to provide flexible, incremental bandwidth between network devices. For example, network managers can deploy Fast EtherChannel consisting of pairs of full-duplex Fast Ethernet to provide 400+ Mbps between the wiring closet and the data center, while in the data center bandwidths of up to 800 Mbps can be provided between servers and the network backbone to provide large amounts of scalable incremental bandwidth. Cisco’s Fast EtherChannel technology builds upon standards-based 802.3 full-duplex Fast Ethernet. It is supported by industry leaders such as Adaptec, Compaq, Hewlett-Packard, Intel, Micron, Silicon Graphics, Sun Microsystems, and Xircom and is scalable to Gigabit Ethernet in the future.
  • In some cases, Fast EtherChannel technology may not be enough. The old 80/20 rule of network traffic (80 percent of traffic was local, 20 percent was over the backbone) has been inverted by intranets and the World Wide Web. The rule of thumb today is to plan for 80 percent of the traffic going over the backbone. Gigabit networking is important to accommodate these evolving needs. Gigabit Ethernet builds on the Ethernet protocol but increases speed tenfold over Fast Ethernet, to 1000 Mbps, or 1 Gbps. It promises to be a dominant player in high-speed LAN backbones and server connectivity. Because Gigabit Ethernet significantly leverages on Ethernet, network managers will be able to leverage their existing knowledge base to manage and maintain Gigabit networks. The Gigabit Ethernet spec addresses three forms of transmission media though not all are available yet: 1000BaseLX: Long-wave (LW) laser over single-mode and multimode fiber 1000BaseSX: Short-wave (SW) laser over multimode fiber 1000BaseCX: Transmission over balanced shielded 150-ohm 2-pair STP copper cable 1000BaseT: Category 5 UTP copper wiring Gigabit Ethernet allows Ethernet to scale from 10 Mbps at the desktop, to 100 Mbps to the workgroup, to 1000 Mbps in the data center. By leveraging the current Ethernet standards as well as the installed base of Ethernet and Fast Ethernet switches and routers, network managers do not need to retrain and relearn a new technology to provide support for Gigabit Ethernet. Let’s go on now and look at Token Ring.
  • The Token Ring network was originally developed by IBM in the 1970s. It is still IBM’s primary LAN technology and is second only to Ethernet in general LAN popularity. The related IEEE 802.5 specification is almost identical to and completely compatible with IBM’s Token Ring network. Collisions cannot occur in Token Ring networks. Possession of the token grants the right to transmit. If a node receiving the token has no information to send, it passes the token to the next end station. Each station can hold the token for a maximum period of time. Token-passing networks are deterministic, which means that it is possible to calculate the maximum time that will pass before any end station will be able to transmit. This feature and several reliability features make Token Ring networks ideal for applications where delay must be predictable and robust network operation is important. Factory automation environments are examples of such applications. Token Ring is more difficult and costly to implement. However, as the number of users in a network rises, Token Ring’s performance drops very little. In contrast, Ethernet’s performance drops significantly as more users are added to the network.
  • Here are some of the speeds associated with Token Ring. Note that Token Ring runs at 4 Mbps or 16 Mbps. Today, most networks operate at 16 Mbps. If a network contains even one component with a maximum speed of 4 Mbps, the whole network must operate at that speed. When Ethernet first came out, networking professionals believed that Token Ring would die, but this has not happened. Token Ring is primarily used with IBM networks running Systems Network Architecture (SNA) networking operating systems. Token Ring has not yet left the market because of the huge installed base of IBM mainframes being used in industries such as banking. The practical difference between Ethernet and Token Ring is that Ethernet is much cheaper and simpler. However, Token Ring is more elegant and robust.
  • The logical topology of an 802.5 network is a ring in which each station receives signals from its nearest active upstream neighbor (NAUN) and repeats those signals to its downstream neighbor. Physically, however, 802.5 networks are laid out as stars, with each station connecting to a central hub called a multistation access unit or MAU. The stations connect to the central hub through shielded or unshielded twisted-pair wire. Typically, a MAU connects up to eight Token Ring stations. If a Token Ring network consists of more stations than a MAU can handle, or if stations are located in different parts of a building–for example on different floors–MAUs can be chained together to create an extended ring. When installing an extended ring, you must ensure that the MAUs themselves are oriented in a ring. Otherwise, the Token Ring will have a break in it and will not operate.
  • Station access to a Token Ring is deterministic; a station can transmit only when it receives a special frame called a token. One station on a token ring network is designated as the active monitor. The active monitor will prepare a token. A token is usually a few bits with significance to each one of the network interface cards on the network. The active monitor will pass the token into the multistation access unit. The multistation access unit then will pass the token to the first downstream neighbor. Let’s say in this example that station A has something to transmit. Station A will seize the token and append its data to the token. Station A will then send its token back to the multistation access unit. The MAU will then grab the token and push it to the next downstream neighbor. This process is followed until the token reaches the destination for which it is intended.
  • If a station receiving the token has no information to send, it simply passes the token to the next station. If a station possessing the token has information to transmit, it claims the token by altering one bit of the frame, the T bit. The station then appends the information it wishes to transmit and sends the information frame to the next station on the Token Ring.
  • The information frame circulates the ring until it reaches the destination station, where the frame is copied by the station and tagged as having been copied. The information frame continues around the ring until it returns to the station that originated it, and is removed. Because frames proceed serially around the ring, and because a station must claim the token before transmitting, collisions are not expected in a Token Ring network. Broadcasting is supported in the form of a special mechanism known as explorer packets. These are used to locate a route to a destination through one or more source route bridges.
  • So to summarize on Token Ring, it is extremely reliable and has minimized collisions. It is a token passing and token seizing protocol. It either runs at 4 or 16 megabits per second. IBM and IEEE Token Ring standards are both very popular today with IBM networks. Let’s look at FDDI next.
  • FDDI is an American National Standards Institute (ANSI) standard that defines a dual Token Ring LAN operating at 100 Mbps over an optical fiber medium. It is used primarily for corporate and carrier backbones. Token Ring and FDDI share several characteristics including token passing and a ring architecture which were explored in the previous section on Token Ring. Copper Distributed Data Interface (CDDI) is the implementation of FDDI protocols over STP and UTP cabling. CDDI transmits over relatively short distances (about 100 meters), providing data rates of 100 Mbps using a dual-ring architecture to provide redundancy. While FDDI is fast, reliable, and handles a lot of data well, its major problem is the use of expensive fiber-optic cable. CDDI addresses this problem by using UTP or STP. However, notice that the maximum segment length drops significantly. FDDI was developed in the mid-1980s to fill the needs of growing high-speed engineering workstation capacity and network reliability. Today, FDDI is frequently used as a high-speed backbone technology because of its support for high bandwidth and greater distances than copper.
  • FDDI uses a dual-ring architecture. Traffic on each ring flows in opposite directions (called counter-rotating). The dual-rings consist of a primary and a secondary ring. During normal operation, the primary ring is used for data transmissions, and the secondary ring remains idle. The primary purpose of the dual rings is to provide superior reliability and robustness. One of the unique characteristics of FDDI is that multiple ways exist to connect devices to the ring. FDDI defines three types of devices: single-attachment station (SAS) such as PCs, dual attachment station (DAS) such as routers and servers, and a concentrator.
  • An FDDI concentrator (also called a dual-attachment concentrator [DAC]) is the building block of an FDDI network. It attaches directly to both the primary and secondary rings and ensures that the failure or power-down of any single attachment station (SAS) does not bring down the ring. This is particularly useful when PCs, or similar devices that are frequently powered on and off, connect to the ring.
  • So, in summary, a FDDI network is dual ring token passing protocol. One or more stations can attach information to the token at one time. FDDI’s fiber optic medium supports secure, reliable, long-distance data transmission. It is expensive since it is usually based on fiber optic technology and for this reason, it is usually found in core and backbone environments or in high bandwidth multimedia applications. Keep in mind that there is a primary and a secondary ring -- the secondary ring is used primarily for back up. Typically, FDDI networks experience data transmission rates of 100 megabits per second or greater. Since we are passing light through the cables, not voltage, the FDDI networks are shielded against electrical disturbances.
  • So, to summarize, your LAN technologies are Ethernet, Token Ring, and FDDI. Ethernet is the most popular. It’s the least expensive and supports speeds from 10 Mbps to 1000 Mbps… but it’s distance is limited. Token Ring is used primarily in IBM environments. Most Token Ring LANs operate at 16 Mbps. And finally, FDDI. You’ll find this in corporate backbones. It’s the most expensive, but supports the longest distances. It supports speeds up to 100 Mbps.

03 tecn lan_básicas 03 tecn lan_básicas Presentation Transcript

  • UNIDAD 3 : TECNOLOGÍAS BASICAS DE REDES DE AREA LOCAL ( LAN ): 802.3 , 802.5, FDDI Prof. Arsenio Pérez ( aperez@delfos.ucla.edu.ve) Presentación Diplomado 2002
  • Agenda
    • Ethernet
    • Token Ring
    • FDDI
  • Tecnologías LAN básicas
    • Ethernet
    • Token Ring
    • FDDI
    FDDI Dual Ring Token Ring
  • Ethernet (802.3) © 1999, Cisco Systems, Inc. www.cisco.com
  • Ethernet y IEEE 802.3
    • Beneficios y background
      • Ethernet es la tecnología LAN más usada puesto que presenta el mejor balance entre velocidad, costo y facilidad de instalación.
      • Suporta virtually todos protocolos de Redes
      • Iniciado por Xerox, luego se junta DEC & Intel en 1980
    • Revisiones de las especificaciones Ethernet
      • Fast Ethernet (IEEE 802.3u) incrementa la Vt de 10 Mbps a 100 Mbps
      • Gigabit Ethernet es una extension de IEEE 802.3 el cual incrementa Vt a 1000 Mbps, ó 1 Gbps
  • Ethernet y IEEE 802.3
    • Variaciones del formato del frame existen para esta tecnología de LAN tan común
  • Formatos de Frames Ethernet y IEEE 802.3 Estándares para Redes de Área Local
  • Ethernet Protocol Names LAN speed (bps) 100BaseFX “ Base” = baseband “ Broad” = broadband Indica tipo de cable Y longitud max. Si es un numero, max. long. = # x 100 m
  • Ethernet y Fast Ethernet Protocol Max. Segment Length (m) Transmission Medium Application 10Base2 185 50-ohm coaxial A: Link user stations 10Base5 500 50-ohm coaxial A: Link user stations 10BaseF Refers to 10BaseFB, 10BaseFL, and 10Base FP 10BaseFB 2000 Fiber-optic A: Add segments 10BaseFL 1000–2000 Fiber-optic A: Operate w/ FOIRL 10BaseFP 500 Fiber-optic Star topo w/out repeaters 10BaseT 100 2-pairs TP Sends link signals 10Broad36 3600 Broadband coax A: Broadband 100BaseFX 400 2 strands of multimode fiber-optic cable 100BaseT 100 UTP 10BaseT function + more 100BaseT4 100 4 prs Cat 3-5 UTP - 100BaseTX 100 2 prs UTP or STP - 100BaseX Refers to 2 strand/pair 100BaseFX and 100BaseTX
  • Operación en Ethernet A A B B C C D D
  • Operación en Ethernet A A B B C C D D D Data Link Network Transport Session Presentation Application Physical
  • Operación en Ethernet A A B B C C D D D Data Link Network Transport Session Presentation Application Physical B and C Data Link Network Transport Session Presentation Application Physical
  • Ethernet Broadcast D Data Link Network Transport Session Presentation Application Physical C Data Link Network Transport Session Presentation Application Physical B Data Link Network Transport Session Presentation Application Physical A Data Link Network Transport Session Presentation Application Physical
  • Confiabilidad en Ethernet B C D A B C D A Figure 1 Figure 2 Collision
  • Confiabilidad en Ethernet Collision C B C D A B A D JAM JAM JAM JAM JAM JAM
  • Confiabilidad en Ethernet
    • Carrier sense multiple access with collision detection (CSMA/CD)
    B C D A Collision B C D A JAM JAM JAM JAM JAM JAM
  • Opciones Ethernet High-Speed
    • Fast Ethernet
    • Fast EtherChannel ®
    • Gigabit Ethernet
    • Gigabit EtherChannel
  • ¿Qué es Fast EtherChannel? Agrupación de múltiples interfaces Fast Ethernet dentro de un camino lógico de transmission
    • Escalabilidad de BW (bandwidth) hasta 800+ Mbps
    • Usando industry-standard Fast Ethernet
    • Balanceo de Carga a través de enlaces paralelos
    • Extensible a Gigabit Ethernet
    400 Mb 600 Mb 800 Mb 800 Mb
    • 1000-Mbps data rate
    • 802.3/Ethernet frames
    • Full duplex ó half duplex
    • Fibra ó Cobre
    • 100% compatible con la existencia:
      • Network protocols
      • Network operating systems
      • Network applications
      • Network management
    ¿Qué es Gigabit Ethernet? 20% 80% Workgroup 20% 80% Backbone
    • Coaxial tipo RG- 5 8, impedancia de 50 ohm ( grueso o "thick Ethernet”).
    • Conectores Vampire Tap + Terminadores.
    • Distancia entre dispositivos  2.5 mts.
    10BASE5 Estándares para Redes de Área Local
    • Se requiere de un transceiver para conectarse al coaxial.
    10BASE5
    • Este se conecta al NIC del computador por medio de un cable transceiver cuya longitud puede alcanzar hasta 50 mts.
    Estándares para Redes de Área Local
    • Longitud del segmento: 500mts sin repetidoras.
    10BASE5 Estándares para Redes de Área Local
  • 10BASE5
    • Número de equipos conectados directamente al cable  100
    • Número de estaciones  1024
    Estándares para Redes de Área Local
    • Regla 5-4-3 :
    • Entre cualesquiera 2 nodos en la red, solo puede haber un máximo de 5 saltos o segmentos, conectados a través de 4 repetidores o concentradores y solo tres de los 3 segmentos pueden contener conexiones de usuarios
    Estándares para Redes de Área Local 10BASE2 y 10BASE5
    • Fibra Optica Multimodo.
    • Usados para enlaces punto a punto entre dispositivos.
    • Longitud máx. del segmento: 2000 mts.
    10BASEFL Estándares para Redes de Área Local
  • Estándares para Redes de Área Local IEEE 802.3
  • Estándares para Redes de Área Local IEEE 802.3
    • Extensión del IEEE 802.3
    • Topologías: Estrella
    • Método de acceso: CSMA/CD
    • Velocidad de Transmisión: 100 Mbps
    • Especificaciones para el cableado :
      • 100BaseTX: UTP categoría 5 ó STP tipo 1 de IBM
      • 100BaseT4: UTP categoría 3, 4 ó 5
      • 100BaseFX: Fibra óptica monomodo ó multimodo
    Estándares para Redes de Área Local IEEE 802.3u ó Fast Ethernet
    • 100BaseT soporta tres tipos de medio al nivel físico del Modelo OSI
    • (Layer 1) : 100BaseTX ,100BaseFX , 100BaseT4
    100BaseT Media Types Estándares para Redes de Área Local
    • 100BaseT y 10BaseT usan el mismo acceso IEEE 802.3 MAC y el mismo método de detección de colisiones , y tienen los mismos requerimientos de formato y longitud de frame.
    • La principal diferencia entre 100BaseT y 10BaseT (otro que la diferencia de velocidad ) es el diametro de la red . El diametro máximo de la red es de 205 metros (aproximadamente 10 veces menos que Ethernet a 10-Mbps).
    Comparación 100BaseT y 10BaseT Estándares para Redes de Área Local
    • Reducir el diametro de red 100BaseT es necesario puesto que 100BaseT usa el mismo mecanismo de detección de colisiones que el 10BaseT .
  • Comparación de los tipos de medio 100BaseT Estándares para Redes de Área Local 200 400 200 Max Diámetro Red 100 400 100 Máxima Long. Segm ISO 8877 (RJ-45) Duplex SC Media Interfaz Connector ST ISO 8877 (RJ-45) Conector 4 2 2 # de Pares Cat. 3,4,5 UTP 62.5/125 micron multimodo Categoría 5 UTP o Tipo 1 y 2 STP Cable 100BaseT4 100BaseFX 100BaseTX Característica
  • Token Ring (802.5) © 1999, Cisco Systems, Inc. www.cisco.com
  • Token Ring (IEEE 802.5)
    • Historia
      • Desarrollado por IBM en los 1970s; especificación IEEE 802.5 es totalemente compatible con Token Ring
      • Segundo en popularidad después de Ethernet
    • Características
      • Token determina transmisión sin colisiones
      • Ideal para aplicationess (tal como autom. de Prod.) donde los retardos deben ser predecibles y donde la operación de una red robusta es importante.
      • Más dificil y costosa que Ethernet, pero tiene menos impacto cuando más usuarios se agregan al sistema.
    • Token Ring es un estándar para LAN que usa como método de acceso el token-passing
    • Token Ring corre a 4 /16 Mbps sobre una topología de estrella. Token Ring es usado para referirse a las redes Token Ring de IBM y redes IEEE 802.5
    • Token Ring fué desarrollado y soportado por IBM en los 1980s. Sigue siendo hoy día principalmente una tecnología de LAN, y es el segundo después de Ethernet en popularidad como tecnología LAN.
    Token Ring and IEEE 802.5 Overview
    • Diseño determinístico -- Token Ring es inherentemente determinístico, a diferencia del método de acceso Carrier Sense Multiple Access/Collision Detect (CSMA/CD) de las redes como Ethernet. Este permite calcular el tiempo máximo entre transmisiones y promociona la planificación de tráfico. El diseño determinístico permite que sea usado en ambientes donde las aplicaciones requieren una alta confiabilidad.
    Token Ring/IEEE 802.5 Diseño y Topología
  • Token Ring/IEEE 802.5 Diseño y Topología Variación de la topología en Token Ring – Las especificaciones de la topología original fué definida como Estrella . Bajo este esquema , todas las estaciones finales se conectan a un dispositivo llamado un Multistation Access Unit (MSAU). IEEE 802.5 difiere del IBM Token Ring en el sentido que no especifica una topología en particular, sin embargo la mayoría de implementaciones del IEEE 802.5 son basadas en estrella.
  • Cableado Token Ring and IEEE 802.5 El MAU posee dos puertos “Ring in” y “Ring out” que permiten conectar varios MAUS aumentando el tamaño de la red.
  • Token Ring and IEEE 802.5 Cabling
    • Velocidad de Transmisión: 4 Mbps a 16 Mbps.
    • Cable :
      • Par Trenzado sin blindaje (UTP)
      • Par Trenzado con blindaje (STP) de IBM
      • Fibra Óptica
    • Usa encodificación Manchester Diferencial :
      • 0 (cero)  Un cambio en el nivel de voltaje de la señal con respecto al voltaje final de la señal anterior.
      • 1 (uno)  Ausencia de cambio del voltaje con respeto a la señal anterior.
    Token Ring and IEEE 802.5
  • Token Ring Bandwidth IBM Token Token Ring Ring Network IEEE 802.5 Data Rates 4 or 16 Mbps 4 or 16 Mbps Stations/Seg 260 STP, 72 UTP 250 Topology Star Not specified Media Twisted-pair Not specified Signaling Baseband Baseband
  • Topología Token Ring
    • Anillo Lógico, pero físicamente una configuración de estrella al MAU
    Shielded or Unshielded Twisted-Pair MAU
  • Operación Token Ring
    • Las LANsToken Ring pasan conituamente un Token o un Frame Token Ring
    A T = 0 T
  • Operación Token Ring
    • Las LANsToken Ring pasan conituamente un Token o un Frame Token Ring
    A T = 0 T Data A T = 1 T
  • Operación Token Ring
    • Las LANsToken Ring pasan conituamente un Token o un Frame Token Ring
    A T = 0 T Data A T = 1 A T = 0 T T
  • Operaciones en Token Ring y IEEE 802.5
    • Las operaciones en Token Ring y IEEE 802.5 envuelven varios estados:
          • Ring insertion
          • Passing tokens
          • Attaching data
          • Extracting data
  • Ring Insertion
    • 6 pasos deben ser cumplidos a cabalidad antes que el controlador de la interfaz de red (NIC) alcance el anillo y participe en el paso del token y la tranmisión de la data:
    • NIC ejecuta un self-test de diagnóstico interno
    • NIC chequea el lobulo de cableado y abre los relays mecánicos en el MSAU.
    • NIC escuchan el Monitor Activo.
    • NIC chequean por direcciones duplicadas
    • NIC aprenden acerca de su vecino anterior y se identifican al mismo tiempo con su vecino posterior en el anillo.
    • NIC solicitan los parametros de inicialización del anillo.
  • Passing Tokens
    • El pase del Token es el primer paso para la transmisión de la data. La posesión del Token es usado como la garantía del derecho de transmisión. Las estaciones reenvian el Token a su próximo vecino si no tiene nada que transmitir.
    • La agregación de la data al Token por una estación envuelve cuatro pasos básicos:
    • Una estación primero determina el tamaño del Token.
    • La estación que toma el token altera un bit del token ( lo cual torna al token en una secuencia de transmsión “start-of-frame sequence”).
    • La estación agrega la información que quiere transmitir.
    • Finalmente, la estación envía esta información a la próxima estación en el anillo.
    Attaching Data
    • La extracción de la Data en Token Ring envuelve un frame de información que circula en el anillo hasta que ella alcanza una estación destino.
    • La estación destino copia la información para procesarla posteriormente, luego retorna el frame al anillo.
    • El frame de información continua circulando en el anillo hasta que sea removida por la estación emisora.
    Extracting Data
  • Monitor Activo en Token Ring y IEEE 802.5
    • El Monitor Activo puede ser cualquier estación en la red. Este actúa como una fuente central de información de tiempo para el anillo. Este ejecuta una variedad de operaciones de mantenimiento del anillo, incluyendo la remoción de frames sin destino en esa red.
    • El proceso de restauración típico de un Monitor activo envuelve una estación enviante que falla y su frame continua circulando en el anillo. El frame que se mantendrá sin destino es detectada por el Monitor Activo quien la remueve y genera un nuevo token.
  • Mecanimos de Beaconing en Token Ring
    • Si una estación detecta un problema grave en la red , envía un beacon frame. En el proceso, el beacon frame define un dominio de falla, lo cual incluye a la estación que reporta la falla, el vecino anterior y cualquiera que esté entre ellos.
    • El proceso de Beaconing inicia un proceso denominado de autoreconfiguration . Los nodos dentro del dominio de falla ejecutan un diagnostico para reconfigurar el área alrededor de la falla. Un MSAU puede cumplir un proceso de recuperación de falla aislando la estación que falló.
  • Formatos de Frame en Token Ring y IEEE 802.5 Dos tipos básicos de frame: Tokens – Tienen una longitud de 3 bytes y consiste en un delimitador de inicio, un byte de control de acceso y uno de delimitador de fin. Data/command frames -- Data/command frames varian en el tamaño, dependiendo de la longitud del campo de Información. Los frames de data transportan información para los protocolos de nivel superior. Los frames de Comandos contienen información de control y no transportan data de los protocolos de nivel superior.
  • Formatos de Frame en Token Ring y IEEE 802.5 Campos del Frame Token : Start Delimiter – Sirve para alertar cada estación de la llegada de un token o un frame de data/comando. Este campo incluye señales que permiten distinguir el byte del resto del frame por violación del esquema de codificación usado en cualquier parte del frame. Access Control Byte – Contiene Un campo de Prioridad (los 3 bits + significativos) y un campo de Reservación ( 3 bits – significativos ), como tambien Un bit de Token (usado para diferenciar un token de un frame de Data/Comando ) Y un bit de Monitor (usado por el Monitor Activo para determinar si el frame que circula es indeseada) End Delimiter – Señala el fin del the token o data/command frame. Este campo tambien contiene bits que indican si un frame está dañado o es la ultima en una secuencia lógica.
  • Token Ring and IEEE 802.5 Frame Formats Campos del Frame de Data/Comando : Start Delimiter – Sirve para alertar cada estación de la llegada de un token o un frame de data/comando. Este campo incluye señales que permiten distinguir el byte del resto del frame por violación del esquema de codificación usado en cualquier parte del frame Access Control Byte – Contiene Un campo de Prioridad (los 3 bits + significativos) y un campo de Reservación ( 3 bits – significativos ), como también Un bit de Token (usado para diferenciar un token de un frame de Data/Comando ) Y un bit de Monitor (usado por el Monitor Activo para determinar si el frame que circula es indeseada) ). Frame Control Bytes – Indica si el frame contiene data o Información de control . En un frame de control, este byte especifica el tipo de información de control.
  • Token Ring and IEEE 802.5 Frame Formats Destination and Source Addresses – Dirfección de dos 6-byte que indican Fuente/Destino. Data – Longitud del campo limitado por el tiempo de mantenimiento del anillo, el cual define el tiempo máximo que una estación puede mantener el token. Frame Check Sequence (FCS) –Llenado por la estación emisora que calcula un valor en función del contenido del frame. La estación destino recalcual este valor para determinar si el frame ´se daño en su transito por el anillo. Si el frame es erronea se descarta. End Delimiter – Señala el fin del the token o data/command frame. Este campo tambien contiene bits que indican si un frame está dañado o es la ultima en una secuencia lógica. Frame Status –campo de 1-byte que frame command/data. Incluye un indicador de dirección reconocida y un indicador de que el frame fué copiado. Campos del Frame de Data/Commando :
  • IEEE 802.5 Cable tipo 9 > 133mts 200 Distancia máxima ente MAUs 12 ó 33 Nro. máximo de MAUs por LAN (1 closet) Ver tabla Ver tabla Distancia estación-múltiples MAUs (mts) 100 100 Distancia estación-única MAU (mts) 72 260 Máximo Nro. de dispositivos por anillo Cable UTP Cable Tipo 1 ó 2 Reglas para el cableado
  • Resúmen Token Ring Resúmen
    • Transporte confiable, Colisiones minimizadas
    • Token passing/token seizing
    • 4- or 16-Mbps
    • El impacto en el rendimiento es pequeño al adicionar nuevos nodos.
    • Popular en Sites Orientados a IBM- tales como bancos y manufacturas automatizadas
  • FDDI © 1999, Cisco Systems, Inc. www.cisco.com
  • Fiber Distributed Data Interface (FDDI)
    • Fiber Distributed Data Interface (FDDI)
      • Definido por ANSI X3T9.5 spec a mediados de 1980s
      • 100-Mbps token- passing network
      • Fiber-optic cable with max. distance of 2 km
      • Arquitectura Dual-ring
      • para la reduncdancia
      • Usado en backbones corporativos
    • CDDI
      • Implementa FDDI sobre cable STP y UTP
      • Transmits a 100 Mbps sobre 100 m
    FDDI Dual Ring 100 Mbps
  • FDDI Network Architecture
    • Arquitectura Dual-ring
      • Anillo Primario para la Transmisión de Data
      • Anillo Secondario para la confiabilidad y robustez
    • Componentes
      • Single attachment station (SAS)—PCs
      • Dual attachment station (DAS)—Servers
      • Concentrator
    • Concentradores FDDI
      • Tambien llamdos dual-attached concentrator (DAC)
      • Bloques de Construcción en una red FDDI
      • Conecta directamente a ambos Anillos y asegura que cualquier falla o desconexion en una SAS no tumbe el anillo.
    • Concentrator – Un concentrador FDDI (tambien llamado dual-attachment concentrator [DAC]) es el bloque constructor de la red FDDI . Este se conecta directamente al anillo primario y secundario, y asegura que la falla o muerte de una estación SAS no haga fallar el anillo. Esto es fundamental cuando los PCS, o dispositivos similares conectados al anillo son frecuentemente encendidos y apagados
    Tipos de estaciones en FDDI
    • Dual Ring : El diseño de anillo dual introduce tolerancia a fallas en la red FDDI.
    • Optical Bypass Switch : Un conmutador de bypass provee una operación continua del anillo dual si un dispositivo conectado al anillo dual falla.
    • Dual Homing : Un mecanismo conocido como Dual homing provee una redundancia adicional y tolerancia a falla para dispositivos críticos.
    Características de tolerancias a fallas
    • Dual Ring : El diseño de doble anillo introduce la tolerancia a fallas. Si una estación del doble anillo o es apagada, o si el cable es dañado, el doble anillo es automáticamente reconstruido en si mismo (doubled back onto itself) en un solo anillo. Cuando el anillo es reconstruido la topología de dual-ring se transforma en una topología de anillo simple.
    • Múltiples fallas producen múltiples anillos independientes.
    • Las operaciones de la red continúan para todas las estaciones
    Características de tolerancias a fallas
  • Tolerancia a Fallos: Si la estación 3 falla, el doble anillo automáticamente engancha a la estación 2 y 4 para conformar un solo anillo. Características de tolerancias a fallas
    • "Recovery" después de fallas múltiples
    • Cuando dos o más fallas ocurren, el anillo FDDI se segmenta en dos o más anillos independientes.
    Características de tolerancias a fallas
  • Ejemplo Red FDDI WAN FDDI Concentrator SAS SAS DAS DAS Primary Ring Secondary Ring
  • Resúmen FDDI
    • Características
      • 100-Mbps token-passing network
      • Single-mode (100 km), double-mode (2 km)
      • CDDI transmite a 100 Mbps cerca de 100 m
      • Arquitectura de doble anilla para Tolerancia a Fallos.
    • Usado en Backbones Corporativos
  • DEMOS Métodos de Acceso
  • Sumario
    • Tecnologías LAN incluyen Ethernet, Token Ring, and FDDI
    • Ethernet
      • Más usada
      • Buen balance entre Velocidad, costo, y facilidad de installación
      • 10 Mbps a 1000 Mbps
    • Token Ring
      • Uso Primario con redes IBM
      • 4 Mbps a 16 Mbps
    • FDDI
      • Uso Primario enh Backbones Corporativos
      • Suporta largas distancias
      • 100 Mbps