Black Box Explains... RJ-48
An RJ-48 plug is often mistaken for RJ-45. On the outside, the two look identical—both are housed in a miniature 8-position jack. The difference is in the pairing of the... more/see it nowwires.
In RJ-48, two of the wires are for transmit, two are for receive, and two are for the drain. The last two wires are reserved for future use.
There are three subsets within RJ-48: RJ-48C, RJ-48X, and RJ-48S.
RJ-48C and RJ-48X are very similar. Both use lines 1, 2, 4, and 5 and connect T1 lines. The RJ-48C is more common. The difference is that RJ-48X connectors have shorting bars.
RJ-48S uses lines 1, 2, 7, and 8. It connects 56K DDS lines. collapse
Black Box Explains... Fibre Channel Technology.
What is Fibre Channel?
Fibre Channel is a set of communication standards designed to provide high-speed data transfer over a duplex, serial interface. Its an open standard that supports multiple protocols... more/see it nowincluding higher-level protocols, such as FDDI, SCSI, HIPPI, and IPI, to manage data transfer.
Although it operates at a range of 133 Mbps to 4 Gbps, Fibre Channel is most commonly used at speeds of 1 or 2 Gbps. A working standards group recently announced that 10-Gbps speeds are expected in soon.
Why is it called Fibre Channel?
Originally, Fibre Channel was designed to support only fiber. When copper was added, the International Standards Organization (ISO) task force changed the spelling of fiber to fibre instead of renaming the technology.
Fibre Channel history.
Fibre Channel was first developed in 1988, and the American National Standards Institute (ANSI) formed a committee in 1989. To ensure interoperability, IBM®, Hewlett-Packard®, and Sun Microsystems® formed the FCSI (Fibre Channel Systems Initiative), a temporary organization, in 1992. FCSI later dissolved, and development was handed over to the FCA (Fibre Channel Association) in 1994. ANSI accepted Fibre Channel as a standard in 1994.
The best of both worlds.
This hardware-based standard combines the best of both channel and network communication methods into one I/O interface. It takes advantage of hardware-intensive, quicker point-to-point channel links that offer low overhead, such as SCSI bus technology, as well as the broad connectivity and long-distance benefits of software-intensive network technology.
Where Fibre Channel is used.
Fibre Channel is used to transfer large amounts of data quickly between supercomputers, mainframes, workstations, desktop computers, storage devices, displays, and other peripherals.
Fibre Channel offers reliability, scalability, congestion-free data flow, Gigabit bandwidth, compatibility with multiple topologies and protocols, flow control, self management, hot pluggability, speed, cost efficiency, loop resiliency, and distance. This makes it ideal for large data operations such as Internet/intranets, data warehousing, networked storage, integrated audio/video, real-time computing, on-line services, and imaging.
The most popular application for this technology right now is Storage Area Networks (SANs). Independent methods of centralized storage management within a SAN (e.g., RAID, tape backup or library, CD-ROM library) run more efficiently with a Fibre Channel backbone.
Fibre Channel topologies.
Fibre Channel can be connected by three methods. In all cases, the topology of the network is transparent to the attached devices.
Point to point is the simplest topology, which uses simple bidirectional links between two connected devices.
Arbitrated loop is the most common topology and the most complex. It is distributed, connecting up to 126 devices across shared media, and it offers shared bandwidth. Two ports on the loop establish a point-to-point, full-duplex connection through arbitration among all ports.
The cross-point or fabric-switched topology uses 24-bit addressing to connect up to 2 (to the 24th) devices in a cross-point switched configuration. This enables many devices to communicate at the same time and does not require shared media.
Fibre Channel layers.
Fibre Channel protocol is divided into five hierarchical layers: The three bottom layers, FC-0FC-2, define the physical transmission standard. Layers FC-3 and FC-4 address interfaces with other network protocols.
FC-0: Media and interface layer that defines the physical link.
FC-1: Transmission encode/decode layer. Information is encoded 8 bits at a time into a 10-bit transmission character (8B/10B from IBM).
FC-2: Signaling protocol layer that serves as the transport mechanism performing basic signaling and framing. FC-2 includes the following classes of service:
• Class 1 provides dedicated connections. Intermix is an optional type of Class 1 service in which Class 1 frames are guaranteed a special amount of bandwidth.
• Class 2 is a frame-switched, connectionless service, also known as multiplex. It guarantees delivery and confirms receipt of traffic.
• Class 3 is a one-to-many, connectionless, frame-switched service. Its similar to Class 2 except it uses buffer-to-buffer flow control and does not confirm frame delivery.
FC-3: Common-services layer that provides common services required for advanced features such as striping, hunt groups, and multicast.
FC-4: Upper layer for protocol mapping of network and channel data transmitting concurrently over the same physical interface.
Fibre Channel media.
Fibre Channel runs at up to 1 Gbps over copper or fiber, but for higher speeds, fiber is required. Copper-wire cable can be video coax, miniature coax, or, most commonly, shielded twisted pair with a DB9 or HSSDC connector. Fiber choices include 62.5- or 50-µm multimode and 7- or 9-µm single-mode fiber, all with an SC connector.
Other Fibre Channel equipment includes disk enclosures, drivers, extenders, hubs, interface converters, host bus adapters, routers, switches, and SCSI bridges. collapse