Classes of service are available in Fibre Channel Class-1: Dedicated connection between two communicators with acknowledgement of frame delivery. In class 1 service, a dedicated connection source and destination is established through the fabric for the duration of the transmission. It provides acknowledged service. This class of service ensures that the frames are received by the destination device in the same order in which they are sent, and reserves full bandwidth for the connection between the two devices. It does not provide for a good utilization of the available bandwidth, since it is blocking another possible contender for the same device. Because of this blocking and necessary dedicated connection, class 1 is rarely used. Class-2: connection less but provides acknowledgement Class 2 is a connectionless, acknowledged service. Class 2 makes better use of available bandwidth since it allows the fabric to multiplex several messages on a frame-by-frame basis. As frames travel through the fabric they can take different routes, so class 2 service does not guarantee in-order delivery. Class 2 relies on upper layer protocols to take care of frame sequence. The use of acknowledgments reduces available bandwidth, which needs to be considered in large-scale busy networks. Class-3: connection less and provides no notification of delivery There is no dedicated connection in class 3 and the received frames are not acknowledged. Class 3 is also called datagram connectionless service. It optimizes the use of fabric resources, but it is now upper layer protocol to ensure that all frames are received in the proper order, and to request to the source device the retransmission of missing frames. Class 3 is a commonly used class of service in Fibre Channel networks. Class-4: allows fractional bandwidth for virtual circuits Class 4 is a connection-oriented service like class 1, but the main difference is that it allocates only a fraction of available bandwidth of path through the fabric that connects two N_Ports. Virtual Circuits (VCs) are established between two N_Ports with guaranteed Quality of Service (QoS), including bandwidth and latency. Like class 1, class 4 guarantees in-order delivery frame delivery and provides acknowledgment of delivered frames, but now the fabric is responsible for multiplexing frames of different VCs. Class 4 service is mainly intended for multimedia applications such as video and for applications that allocate an established bandwidth by department within the enterprise. Class 4 was added in the FC-PH-2 standard. Class -5: Class 5 is called isochronous service, and it is intended for applications that require immediate delivery of the data as it arrives, with no buffering. It is not clearly defined yet. It is not included in the FC-PH documents. Class-6: Provides multicast, dedicated connection with acknowledgment Class 6 is a variant of class 1, known as multicast class of service. It provides dedicated connections for a reliable multicast. An N_Port may request a class 6 connection for one or more destinations. A multicast server in the fabric will establish the connections and get acknowledgment from the destination ports, and send it back to the originator. Once a connection is established, it should be retained and guaranteed by the fabric until the initiator ends the connection. Class 6 was designed for applications like audio and video requiring multicast functionality. It appears in the FC-PH-3 standard. Class-F: used for switch to switch communication in the fabric. Class F service is defined in the FC-SW and FC-SW-2 standard for use by switches communicating through ISLs. It is a connectionless service with notification of non-delivery between E_Ports used for control, coordination, and configuration of the fabric. Class F is similar to class 2; the main difference is that Class 2 deals with N_Ports sending data frames, while Class F is used by E_ports for control and management of the fabric. a)Fabric Login b)SNS c)Fabric Address Notification d)Registered state change notification e)Broadcast Servers 51.What are the layers of Fibre Channel Protocol? a)FC Physical Media b)FC Encoder and Decoder c)FC Framing and Flow control d)FC Common Services e)FC Upper Level Protocol Mapping 57.How does FC Switch maintain the addresses? FC Switch uses simple name server (SNS) to maintain the mapping table What is the smallest unit of information transfer in FC? Frame 66.How is the capacity of the HDD calculated? Number of Heads X Number of Cylinders X Sectors per track X Sector Size 68.What are two types of recording techniques on the tapes? a)Linear Recording b)Helical Scan Recording. Types of login Port Login: To exchange service parameters between N_Ports and N_Ports Process Login: To establish the SCSI operating environment between two N_PORTS Fabric Login: Similar to port login, FLOGI is an extended link service command that sets up a session between two participants. With FLOGI a session is created between an N_Port or NL_Port and the switch. 90.What is BER/Bit error rate? Probability that a transmitted bit will be erroneously received is the measure of number of bits (erroneous) at the output of the receiver and dividing by the total number of bits in transmission. 93.What is burst Length? The burst length is the number of bytes that the SCSI initiator sends to the SCSI target in the FCP_DATA sequence.