 | This article provides insufficient context for those unfamiliar with the subject.(July 2015) |
Remote error indication (REI) or formerly far end block error (FEBE) is an alarm signal used in synchronous optical networking (SONET). It indicates to the transmitting node that the receiver has detected a block error. [1]
REI or FEBE errors are mostly seen on DS3 circuits, however they are known to be present on other types (SONET/T1s etc.).
Each terminating device (router or otherwise) monitors the incoming signal for CP-bit path errors. If an error is detected on the incoming DS3, the terminating elements transmit a FEBE bit on the outgoing direction of the DS3. Network monitoring equipment located anywhere along the path then measures these FEBEs in each direction to gauge the quality of the circuit while in service.
If you have a DS3 running from New York to Atlanta, and there's a problem within one of the central offices in Virginia. The errors are being generated by a device in the central office, and being detected by the terminating device (a NID, M13 Mux or router). The terminating device then sends the 'FEBE' error signal outbound to alert further devices there were problems.
So, errors are generated on the incoming side of the loop, the device terminating that end picks up the errors, and transmits a 'FEBE errors' message on the outgoing side. This specific setup of error reporting is what causes the confusion between many technicians trying to perform repairs.
Technical jargon: An error detected by extracting the 4-bit FEBE field from the path status byte (G1). The legal range for the 4-bit field is between 0000 and 1000, representing zero to eight errors. Any other value is interpreted as zero errors.
The DS-3 M-frame uses P bits to check the line parity. The M-subframe uses C bits in a format called C-bit parity, which copies the result of the P bits at the source and checks the result at the destination. An ATM interface reports detected C-bit parity errors back to the source via a far-end block error (FEBE). ( Cisco.com all rights reserved)
An indication sent to a transmitting node that a flawed block has been detected at the receiving node. (DS3) A FEBE in C-bit parity is a parity violation detected at the far-end terminal and transmitted back to the near-end terminal.
A maintenance cell indicates that an error occurred with a data block at the far end of the link. This cell then sends a message back to the near end.
Frame Relay is a standardized wide area network (WAN) technology that specifies the physical and data link layers of digital telecommunications channels using a packet switching methodology. Originally designed for transport across Integrated Services Digital Network (ISDN) infrastructure, it may be used today in the context of many other network interfaces.
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The T-carrier is a member of the series of carrier systems developed by AT&T Bell Laboratories for digital transmission of multiplexed telephone calls.
In computer networking, Fast Ethernet physical layers carry traffic at the nominal rate of 100 Mbit/s. The prior Ethernet speed was 10 Mbit/s. Of the Fast Ethernet physical layers, 100BASE-TX is by far the most common.
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In fiber-optic communications, wavelength-division multiplexing (WDM) is a technology which multiplexes a number of optical carrier signals onto a single optical fiber by using different wavelengths of laser light. This technique enables bidirectional communications over a single strand of fiber as well as multiplication of capacity.
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A controller area network (CAN) is a vehicle bus standard designed to enable efficient communication primarily between electronic control units (ECUs). Originally developed to reduce the complexity and cost of electrical wiring in automobiles through multiplexing, the CAN bus protocol has since been adopted in various other contexts. This broadcast-based, message-oriented protocol ensures data integrity and prioritization through a process called arbitration, allowing the highest priority device to continue transmitting if multiple devices attempt to send data simultaneously, while others back off. Its reliability is enhanced by differential signaling, which mitigates electrical noise. Common versions of the CAN protocol include CAN 2.0, CAN FD, and CAN XL which vary in their data rate capabilities and maximum data payload sizes.
In computer networking, cut-through switching, also called cut-through forwarding is a method for packet switching systems, wherein the switch starts forwarding a frame before the whole frame has been received, normally as soon as the destination address and outgoing interface is determined. Compared to store and forward, this technique reduces latency through the switch and relies on the destination devices for error handling. Pure cut-through switching is only possible when the speed of the outgoing interface is at least equal or higher than the incoming interface speed.
Spatial Reuse Protocol is a networking protocol developed by Cisco. It is a link layer protocol for ring-based packet internetworking that is commonly used in optical fiber ring networks. Ideas from the protocol are reflected in parts of the IEEE 802.17 Resilient Packet Ring (RPR) standard.
The STM-1 is the SDH ITU-T fiber optic network transmission standard. It has a bit rate of 155.52 Mbit/s. Higher levels go up by a factor of 4 at a time: the other currently supported levels are STM-4, STM-16, STM-64 and STM-256. Above STM-256 wavelength-division multiplexing (WDM) is commonly used in submarine cabling.
Signalling System R2 is a signalling protocol for telecommunications that was in use from the 1960s mostly in Europe, and later also in Latin America, Asia, and Australia, to convey exchange information between two telephone switching systems for establishing a telephone call via a telephone trunk. It is suitable for signaling on analog as well as digital circuits.
Alarm indication signal (AIS) is a signal transmitted by an intermediate element of a multi-node transport circuit that is part of a concatenated communications system to alert the receiving end of the circuit that a segment of the end-to-end link has failed at a logical or physical level, even if the system it is directly connected to is still working. The AIS replaces the failed data, allowing the higher order system in the concatenation to maintain its transmission framing integrity. Downstream intermediate elements of the transport circuit propagate the AIS onwards to the destination element.
IEEE Standard 1355-1995, IEC 14575, or ISO 14575 is a data communications standard for Heterogeneous Interconnect (HIC).
A digital cross-connect system is a piece of circuit-switched network equipment, used in telecommunications networks, that allows lower-level TDM bit streams, such as DS0 bit streams, to be rearranged and interconnected among higher-level TDM signals, such as DS1 bit streams. DCS units are available that operate on both older T-carrier/E-carrier bit streams, as well as newer SONET/SDH bit streams.
Dynamic Packet Transport (DPT) is a Cisco transport protocol designed for use in optical fiber ring networks. In overview, it is quite similar to POS and DTM. It was one of the major influences on the Resilient Packet Ring/802.17 standard.
In telecommunications, subnetwork connection protection (SNCP), is a type of protection mechanism associated with synchronous optical networks such as synchronous digital hierarchy (SDH).
An optical mesh network is a type of optical telecommunications network employing wired fiber-optic communication or wireless free-space optical communication in a mesh network architecture.
Path protection in telecommunications is an end-to-end protection scheme used in connection oriented circuits in different network architectures to protect against inevitable failures on service providers’ network that might affect the services offered to end customers. Any failure occurred at any point along the path of a circuit will cause the end nodes to move/pick the traffic to/from a new route. Finding paths with protection, especially in elastic optical networks, was considered a difficult problem, but an efficient and optimal algorithm was proposed.
Fast automatic restoration (FASTAR) is an automated fast response system developed and deployed by American Telephone & Telegraph (AT&T) in 1992 for the centralized restoration of its digital transport network. FASTAR automatically reroutes circuits over a spare protection capacity when a fiber-optic cable failure is detected, hence increasing service availability and reducing the impact of the outages in the network. Similar in operation is real-time restoration (RTR), developed and deployed by MCI and used in the MCI network to minimize the effects of a fiber cut.