It is more likely to be the result of an implementation error. Implementation Note: Although the Configure-Nak and Configure-Reject cause the same state transition in the automaton, these packets have significantly different effects on the Configuration Options sent in the resulting Configure-Request packet.
Implementation Note: This event is not identical to the Close event see above , and does not override the Open commands of the local network administrator. The Terminate-Ack packet is usually a response to a Terminate-Request packet. The Terminate-Ack packet may also indicate that the peer is in Closed or Stopped states, and serves to re-synchronize the link configuration.
A Code-Reject packet is sent in response. These are within the scope of normal operation. The implementation MUST stop sending the offending packet type. This event communicates an unrecoverable error that terminates the connection. The Echo-Reply packet is a response to an Echo-Request packet. There is no reply to an Echo-Reply or Discard-Request packet. Illegal-Event - This indicates an event that cannot occur in a properly implemented automaton.
The implementation has an internal error, which should be reported and logged. This-Layer-Up tlu This action indicates to the upper layers that the automaton is entering the Opened state. This-Layer-Down tld This action indicates to the upper layers that the automaton is leaving the Opened state. This-Layer-Started tls This action indicates to the lower layers that the automaton is entering the Starting state, and the lower layer is needed for the link. This results of this action are highly implementation dependent.
This-Layer-Finished tlf This action indicates to the lower layers that the automaton is entering the Initial, Closed or Stopped states, and the lower layer is no longer needed for the link. The counter is decremented for each transmission, including the first.
Implementation Note: In addition to setting the Restart counter, the implementation MUST set the timeout period to the initial value when Restart timer backoff is used. Zero-Restart-Count zrc This action sets the Restart counter to zero. Implementation Note: This action enables the FSA to pause before proceeding to the desired final state, allowing traffic to be processed by the peer.
In addition to zeroing the Restart counter, the implementation MUST set the timeout period to an appropriate value. This indicates the desire to open a connection with a specified set of Configuration Options.
The Restart timer is started when the Configure-Request packet is transmitted, to guard against packet loss. The Restart counter is decremented each time a Configure-Request is sent. This acknowledges the reception of a Configure-Request packet with an acceptable set of Configuration Options. Configure-Nak packets are used to refuse a Configuration Option value, and to suggest a new, acceptable value.
Configure-Reject packets are used to refuse all negotiation about a Configuration Option, typically because it is not recognized or implemented. This indicates the desire to close a connection. The Restart timer is started when the Terminate-Request packet is transmitted, to guard against packet loss.
The Restart counter is decremented each time a Terminate-Request is sent. This acknowledges the reception of a Terminate-Request packet or otherwise serves to synchronize the automatons. This indicates the reception of an unknown type of packet. This acknowledges the reception of an Echo-Request packet. Loop Avoidance The protocol makes a reasonable attempt at avoiding Configuration Option negotiation loops. However, the protocol does NOT guarantee that loops will not happen. As with any negotiation, it is possible to configure two PPP implementations with conflicting policies that will never converge.
It is also possible to configure policies which do converge, but which take significant time to do so. Counters and Timers Restart Timer There is one special timer used by the automaton.
Expiration of the Restart timer causes a Timeout event, and retransmission of the corresponding Configure-Request or Terminate-Request packet. The default value is designed for low speed 2, to 9, bps , high switching latency links typical telephone lines.
Instead of a constant value, the Restart timer MAY begin at an initial small value and increase to the configured final value. The initial value SHOULD be large enough to account for the size of the packets, twice the round trip time for transmission at the link speed, and at least an additional milliseconds to allow the peer to process the packets before responding.
Some circuits add another milliseconds of satellite delay. Round trip times for modems operating at 14, bps have been measured in the range of to more than milliseconds. Max-Terminate There is one required restart counter for Terminate-Requests.
Max-Terminate indicates the number of Terminate-Request packets sent without receiving a Terminate-Ack before assuming that the peer is unable to respond. Max-Configure A similar counter is recommended for Configure-Requests. Max- Configure indicates the number of Configure-Request packets sent without receiving a valid Configure-Ack, Configure-Nak or Configure-Reject before assuming that the peer is unable to respond.
Max-Failure indicates the number of Configure-Nak packets sent without sending a Configure-Ack before assuming that configuration is not converging. Any further Configure-Nak packets for peer requested options are converted to Configure-Reject packets, and locally desired options are no longer appended.
In the interest of simplicity, there is no version field in the LCP packet. A correctly functioning LCP implementation will always respond to unknown Protocols and Codes with an easily recognizable LCP packet, thus providing a deterministic fallback mechanism for implementations of other versions.
In particular, each Configuration Option specifies a default value. This ensures that such LCP packets are always recognizable, even when one end of the link mistakenly believes the link to be open.
A summary of the Link Control Protocol packet format is shown below. When a packet is received with an unknown Code field, a Code-Reject packet is transmitted. When a packet is received with an invalid Identifier field, the packet is silently discarded without affecting the automaton. Octets outside the range of the Length field are treated as padding and are ignored on reception.
When a packet is received with an invalid Length field, the packet is silently discarded without affecting the automaton. Data The Data field is zero or more octets, as indicated by the Length field.
The format of the Data field is determined by the Code field. The Options field is filled with any desired changes to the link defaults. A summary of the Configure-Request packet format is shown below. Identifier The Identifier field MUST be changed whenever the contents of the Options field changes, and whenever a valid reply has been received for a previous request. For retransmissions, the Identifier MAY remain unchanged. Options The options field is variable in length, and contains the list of zero or more Configuration Options that the sender desires to negotiate.
All Configuration Options are always negotiated simultaneously. The format of Configuration Options is further described in a later chapter.
Invalid packets are silently discarded. A summary of the Configure-Ack packet format is shown below. Options The Options field is variable in length, and contains the list of zero or more Configuration Options that the sender is acknowledging. All Configuration Options are always acknowledged simultaneously. The Options field is filled with only the unacceptable Configuration Options from the Configure-Request. The default value MAY be used, when this differs from the requested value.
When a particular type of Configuration Option can be listed more than once with different values, the Configure-Nak MUST include a list of all values for that option which are acceptable to the Configure-Nak sender. This includes acceptable values that were present in the Configure-Request.
Finally, an implementation may be configured to request the negotiation of a specific Configuration Option. If that option is not listed, then that option MAY be appended to the list of Nak'd Configuration Options, in order to prompt the peer to include that option in its next Configure-Request packet. Some Configuration Options have a variable length. A summary of the Configure-Nak packet format is shown below.
Options The Options field is variable in length, and contains the list of zero or more Configuration Options that the sender is Nak'ing. All Configuration Options are always Nak'd simultaneously. Configure-Reject Description If some Configuration Options received in a Configure-Request are not recognizable or are not acceptable for negotiation as configured by a network administrator , then the implementation MUST transmit a Configure-Reject.
A summary of the Configure-Reject packet format is shown below. Options The Options field is variable in length, and contains the list of zero or more Configuration Options that the sender is rejecting. All Configuration Options are always rejected simultaneously. Terminate-Request packets SHOULD continue to be sent until Terminate-Ack is received, the lower layer indicates that it has gone down, or a sufficiently large number have been transmitted such that the peer is down with reasonable certainty.
Reception of an unelicited Terminate-Ack indicates that the peer is in the Closed or Stopped states, or is otherwise in need of re-negotiation. A summary of the Terminate-Request and Terminate-Ack packet formats is shown below. Identifier On transmission, the Identifier field MUST be changed whenever the content of the Data field changes, and whenever a valid reply has been received for a previous request. On reception, the Identifier field of the Terminate-Request is copied into the Identifier field of the Terminate-Ack packet.
The data may consist of any binary value. The end of the field is indicated by the Length. Upon reception of the Code-Reject of a code which is fundamental to this version of the protocol, the implementation SHOULD report the problem and drop the connection, since it is unlikely that the situation can be rectified automatically.
A summary of the Code-Reject packet format is shown below. Protocol-Reject Description Reception of a PPP packet with an unknown Protocol field indicates that the peer is attempting to use a protocol which is unsupported.
This usually occurs when the peer attempts to configure a new protocol. Upon reception of a Protocol-Reject, the implementation MUST stop sending packets of the indicated protocol at the earliest opportunity. A summary of the Protocol-Reject packet format is shown below. This is useful as an aid in debugging, link quality determination, performance testing, and for numerous other functions.
A summary of the Echo-Request and Echo-Reply packet formats is shown below. Magic-Number The Magic-Number field is four octets, and aids in detecting links which are in the looped-back condition.
See the Magic-Number Configuration Option for further explanation. Data The Data field is zero or more octets, and contains uninterpreted data for use by the sender. This is useful as an aid in debugging, performance testing, and for numerous other functions. If a Configuration Option is not included in a Configure-Request packet, the default value for that Configuration Option is assumed. The effect of this is Configuration Option specific, and is specified by each such Configuration Option description.
None of the Configuration Options in this specification can be listed more than once. Unless otherwise specified, all Configuration Options apply in a half-duplex fashion; typically, in the receive direction of the link from the point of view of the Configure-Request sender. Design Philosophy The options indicate additional capabilities or requirements of the implementation that is requesting the option. A default is specified for each option which allows the link to correctly function without negotiation of the option, although perhaps with less than optimal performance.
Except where explicitly specified, acknowledgement of an option does not require the peer to take any additional action other than the default. It is not necessary to send the default values for the options in a Configure-Request. Caractersticas PPP Un mtodo de entramado que delinea sin ambigedades el final de una trama y el inicio de la siguiente. El formato de trama tambin maneja la deteccin de errores. Caractersticas PPP 2 Un protocolo de control de enlace para activar lneas, probarlas, negociar opciones y desactivarlas ordenadamente cuando ya no son necesarias.
Admite circuitos sncronos y asncronos y codificaciones orientadas a bits y a caracteres. Caractersticas PPP 3 Un mecanismo para negociar opciones de capa de red con independencia del protocolo de red usado. El mtodo escogido consiste en tener un NCP Protocolo de Control de Red distinto para cada protocolo de capa de red soportado.
Campo de Direccin, que siempre se establece al valor binario para indicar que todas las estaciones deben aceptar la trama. Este valor indica una trama no numerada.
En otras palabras, PPP no proporciona de manera predeterminada transmisin confiable usando nmeros de secuencia y confirmaciones de recepcin. Su tarea es indicar la clase de paquete que est en el campo de Carga til. Los que comienzan con un bit 1 se utilizan para negociar otros protocolos. El tamao predeterminado del campo de protocolo es de 2 bytes, pero puede negociarse a 1 byte usando LCP. Si la longitud no se negocia con LCP durante el establecimiento de la lnea, se usa una longitud predeterminada de bytes.
De ser necesario se puede incluir un relleno despus de la carga. Campos de Trama PPP Campo de Suma de verificacin, que normalmente es de 2 bytes, pero puede negociarse una suma de verificacin de 4 bytes. Soporta deteccin de errores, negociacin de opciones, compresin de encabezados y, opcionalmente, transmisin confiable con formato de tramas similar al de HDLC.
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Denunciar este documento. Marcar por contenido inapropiado. Dificultad Principiante Intermedio Avanzado. Explora Documentos. Compartir este documento Compartir o incrustar documentos Opciones para compartir Compartir en Facebook, abre una nueva ventana Facebook. Denunciar este documento. Marcar por contenido inapropiado. Descargar ahora. Carrusel anterior Carrusel siguiente. Buscar dentro del documento. Paso 2: Borrar todas las configuraciones de los routers.
Use el comando router ospf con un ID de proceso de 1. Use los comandos show ip route y ping para verificar la conectividad. El enlace se activa y se restablece la adyacencia OSPF.
Verifique esto mediante el comando show ip interface brief. R1 R1 show running-config Building configuration Current configuration : bytes version ZeCi1 username R1 password 0 cisco!
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