Electrical computers and digital data processing systems: input/ – Input/output data processing – Peripheral configuration
Reexamination Certificate
2001-03-15
2004-09-14
Myers, Paul R. (Department: 2112)
Electrical computers and digital data processing systems: input/
Input/output data processing
Peripheral configuration
C710S302000, C713S100000
Reexamination Certificate
active
06792479
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates in general to a method and system for using a Fibre Channel. More particularly, the present invention relates to a system and method for obtaining a unique identifier from a remote device in a known configuration.
2. Description of the Related Art
Computer systems in general and International Business Machines (IBM) compatible personal computer systems in particular have attained widespread use for providing computer power to many segments of today's modern society. Computer systems typically include a system processor and associated volatile and non-volatile memory, a display area, input means, and often interfaces, such as a network interface or modem, to other computing devices.
One of the distinguishing characteristics of these systems is the use of a system board to electrically connect these components together. These computing devices are information handling systems which are designed primarily to give independent computing power to a single user, or a group of users in the case of networked computing devices. Personal computing devices are often inexpensively priced for purchase by individuals or businesses. Nonvolatile storage devices such as hard disks, CD-ROM drives and magneto-optical drives are considered to be peripheral devices. Computing devices are often linked to one another using a network, such as a local area network (LAN), wide area network (WAN), or other type of network. Computer systems can also be interconnected using a Fibre Channel network. By linking to other computer systems, a computing device can use resources owned by another computing device. These resources can include files stored on nonvolatile storage devices and resources such as printers and storage area networks (SANs).
Data Storage has become an increasingly important issue for business people and IT professionals. Organizations store records in databases regarding customers, products, competitors, and other records. This storage space becomes expensive when more data is stored. These expenses can be potentially prohibitive for small businesses who must employ people to manage the data, purchase storage equipment and software, and ensure that the data is properly protected from disaster or storage device failure. A solution to this problem comes in the form of an emerging technology called Fibre Channel. Fibre Channel can be used to connect devices to each other, including connecting computer systems to storage devices such as SAN devices.
Fibre Channel is a high speed (100 to 1000 Mbps currently, with speeds increasing quickly over time) medium used for data transfer and storage. It is essentially a serial data channel preferably created over fiber optic cabling. Fibre Channel provides a logical bi-directional, point-to-point connection between a host and a device. Similar to networking technologies using local area network (LAN) or wide area network (WAN) configurations, Fibre Channel also is used to connect PCs, servers, printers, and storage devices. Because Fibre Channel allows the use of fiber optic cabling, connections along a Fibre Channel network makes it possible to transfer data at greater distances. In addition, Fibre Channel makes high-speed data transfers possible. Fibre Channel also provides increased bandwidth over communication channels.
Channels and networks are the two primary ways that data is transferred between devices. Such devices include processors and peripherals such as printers and storage devices. Channels transfer data through switched or direct point to point connections. Channels work by creating a fixed connection between the source and destination devices until the transfer is complete. Channels transfer data at high speeds and are very economical. Networks (i.e., LAN or WAN), on the other hand are collections of nodes such as processors, print devices, and workstations. Connections on networks are typically slower than those made via channels. Also, because networks are software intensive, they are much more expensive due to upgrade and compatibility issues. Channels work best among few devices and connect via predefined addresses. Networks, on the other hand, can handle multiple requests among multiple connections.
Fibre Channel is hybrid of both network and channel methods. Consequently, Fibre Channel is often considered a new I/O (input/output) interface that combines the best of networks and channels. In addition, Fibre Channel systems can be configured in different ways depending on needs of the user, thus providing flexibility in an ever changing systems environment.
Although the ideal medium for Fibre Channel is fiber optic cabling, Fibre Channel can also be used with a variety of cable types such as copper, coaxial cables or Unshielded twisted pair (UTP) wires. Fiber optic cabling is generally preferred on a Fibre Channel system for purposes of increased speed and reliability. Fiber optic cabling works by using photons to transmit digital signals. A laser light connected to a device pulses in binary format (0's and 1's). A light emitting diode (LED) codes and transmits the signal from one end of the cable. This signal is subsequently decoded at the other end of the cable by a photo-detector connected to the receiving device. Fiber optic cables do not have the same challenges that are associated with copper cabling. These challenges include attenuation (loss of signal strength) and noise. Fiber optic cables are also more secure than copper cables because crosstalk does not occur with Fiber Optic cables (crosstalk is interference caused by a signal transferring from one circuit to another, as on a telephone line). This insures that data being transferred across a network gets to its destination intact which makes the stored data more reliable for the user.
Fibre Channel technology makes use of classes of service to define messaging types (communication between devices). According to the ANSI standard, a Fibre Channel system's classes of service can be 1, 2, 3, 4 or 6. These classes make it possible to configure Fibre Channel systems according to the needs of the users.
In a class 1 configuration, there is a dedicated channel between two connection devices. In this configuration, if a host and a device are connected, no other host uses the connection. The advantage of using service class 1 is speed and reliability which is an excellent combination for mass storage use such as in a data library. Class 2 is known as a “connectionless” service. Class 2 provides a frame-switched link that guarantees delivery of packets from device to device. It also provides packet receipt acknowledgments. In this configuration, bandwidth is shared among several devices, as there is no dedicated link. The third Fibre Channel service class (Class 3) is called “unacknowledged connectionless service” and is often used for messages that do not need to be acknowledged, as there is no acknowledgement with a Class 3 configuration. Class 4 is called “fraction bandwidth connection oriented” and allows a device to reserve a portion of the overall bandwidth and use the reserved portion to create a dedicated channel between devices (similar to Class 1, except only part of the available bandwidth is used for the dedicated channel). Class 6 is called “multicast” and is used for one-to-many broadcast communications over the Fibre Channel network. There is an additional Fibre Channel service class called “intermix,” which creates a dedicated connection like that of class one, but it also allows class 2 traffic to access the link. This method is efficient and allows for greater bandwidth because more than one connection can access the system at any time.
The Fibre Channel Structure, or architecture, is set forth in the table below. The layers in the table represent a different function that exists within a Fibre channel system.
Layer
Function
FC-0
Physical characteristic specifications
FC-1
Encoding/Decoding
FC-2
Data Transfer Sequence Management/Data Framing
FC-3
Bandwidth Management
F
Allen James P.
Grande Marcus Bryan
Iyengar Madhuranath Narasipur Krishna
Kovacs Robert George
Neemidge John Leslie
Gerhardt Diana Roberts
Leeuwen Joseph T. Van
Myers Paul R.
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