Resources

PICMG Master Glossary

Last Update 26^th August 2007
Copyright PICMG 2007

The following Glossary was developed by PICMG^® to provide the reader with an informative generalized reference of terms and definitions used throughout the PICMG^® family of hardware specifications.

PICMG^® reserves the right to update this document without prior notice. Readers are encouraged to periodically visit this website for the latest version.

This document is Copyright PICMG and shall not be reproduced in whole or in part without permission.

Term	Definition
10 GbE	Ten gigabit per second Ethernet, e.g., 10GBASE-BX4.
10/100/1000BASE-T	A four pair point to point interconnect capable of supporting the 1000BASE-T baseband medium and 100BASE-TX and 10BASE-T subject to auto-negotiation as specified in Clause 28 of IEEE 802.3-2002.
1000BASE-BX	The common name of the standard of a one gigabit-per-second Ethernet data link over two pairs of copper: One pair for transmit and one for receive. See the PICMG® 3.1 specification for electrical specification.
1000BASE-T	Twisted-pair baseband medium per Clause 40, IEEE 802.3-2002.
100BASE-TX	Twisted-pair baseband medium per Clause 25, IEEE 802.3-2002.
10BASE-T	Twisted-pair baseband medium per Clause 14, IEEE 802.3-2002.
10GBASE-BX4	The common name of the standard that defines 10 gigabit-per-second Ethernet data link over eight pairs of copper: Four pairs for transmit and four pairs for received. See the PICMG® 3.1 specification for electrical specification.
–48 Volts (or –48 VDC)	The nominal supply voltage for AdvancedTCA Shelves, normally supplied by batteries ranging from –36 to –72 Volts DC under normal operating conditions.
A	Ampere(s). The unit of electric current, i.e., electric charge per second.
A+B+ Connector	The AMC Connector style A+B+ is a Connector used in Cutaway Bays. A+B+ Connectors have two Slots to accommodate up to two Compact Modules. The “+” indicates this connector is an Extended Connector meaning each Slot has 170 connections to the AMC Module.
AB Connector	The AMC Connector style AB is used in Cutaway Bays. AB Connectors have two Slots to accommodate up to two Compact Modules. AB is a Basic Connector meaning each Slot has 85 connections to the AMC Module.
Active ShMC	The ShMC (Shelf Management Controller) currently in use by the Shelf Manager, and responding at IPMB address 20h.
ADF connector	Advanced Differential Fabric connector. The Zone 2 connector used in AdvancedTCA Boards and Shelves.
AdvancedMC Slot, AMC Slot	The environment providing connectivity for an AMC Module to a Carrier or Backplane.
AdvancedTCA® or ATCA	Advanced Telecommunications Computing Architecture. A registered trademark of the PCI Industrial Computer Manufacturers Group® referring to the PICMG 3.0 architecture.
ATCA Base specification	PICMG 3.0 AdvancedTCA specification.
Aggressor	A signal inductively and/or capacitively coupled to a Victim signal and considered to be source of noise that distorts the Victim signal being transferred between transmitter and receiver.
AdvancedMC® or AMC	Advanced Mezzanine Card. When the term is used on its own, it can refer to the AMC.0 specification or it can generically refer to the family of AMC specifications, depending on the context.
AMC Bay or Bay	A single mounting location (or site) on an AMC Carrier that provides an AMC module interface for AMC Modules, as defined by AMC.0. An AMC Bay provides the mechanical housing and structural support necessary to properly align, install and secure an AMC Module onto an AMC Carrier. There are two kinds of AMC Bays: Cutaway Bays and Conventional Bays.
AMC Carrier AdvancedTCA Board or AMC Carrier or Carrier or Carrier Board	A purpose-built AdvancedTCA Board that provides AMC Bays, serving as a target environment for AMC Modules utilized in AdvancedTCA deployments. An AMC Carrier supports all of the design elements necessary to house and activate one or more AMC Modules; including AMC Bays, IPMC support, power distribution and signal routing to/from the AMC Module.
AMC Connector	Used to refer to any of the connector styles B, B+, AB, A+B+ as defined in the AMC.0 specification, mounted on a Carrier for the insertion of AMC Modules.
AMC Connector Slot	The B and B+ Connectors support one Slot (Slot B) to accept an AMC Module. The AB and the A+B+ Connectors support two Slots (lower Slot A and upper Slot B).
AMC Module or Module	An AMC Module is a mezzanine or modular add-on card that extends the functionality of a Carrier Board. The term is also used to generically refer to the different varieties of Multi-Width and Multi-Height Modules.
AMC Slot ID	An AMC Slot ID identifies the physical location of each Slot in all AMC Bays on a Carrier into which AMC Modules can be installed.
AMC.1 Link	A PCI Express Link or an Advanced Switching Link established in the Fat Pipe Region of the AMC Connector.
ANSI	American National Standards Institute. A private nonprofit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States .
ASIC	Application Specific Integrated Circuit.
ATCA board	In the AMC context, refers to the combination of an AMC Carrier and AMC Modules as a complete assembly.
ATCA interface	In the AMC context, refers to the ATCA board interface to the backplane base and fabric connections, as distinguished from the AMC.0 module interfaces.
B Connector	The AMC Connector style B is a Basic Connector which supports one AMC Module. The style B connector is used in Conventional Bays or Single Slot Cutaway Bays.
B+ Connector	The AMC Connector style B+ is an Extended Connector which supports one AMC Module. The style B+ Connector is used in Conventional Bays or Single Slot Cutaway Bays.
Backend Power	Backend Power includes all the power supplies on the Module derived from Payload Power.
Backplane	A passive circuit Board providing the Zone 1 and Zone 2 connectors for Front Board Slots. Link Ports of the Slots are connected via high speed signal pairs. Power distribution, management, and auxiliary signal connections are supported.
Backup ShMC	Any ShMC capable of assuming support for the Shelf Manager function.
Base Channel	A physical connection within the Base Interface composed of 4 differential signal pairs (1 row) along the Zone 2 Advanced Differential Fabric (ADF) connector. Base Channels are numbered 1 through 16.  Two Base Hub Slots support a dual star topology to the Base Node Slots/Boards.
Base Hub Board	Indicates a Hub Board that supports the Base Interface. A Base Hub Board provides 10/100/1000BASE-T packet switching services to all Node Boards installed in the Shelf. Base Hub Boards are installed into Logical Slots 1 and 2. Hub Boards that support the Fabric Interface and the Base Interface are also referred to as Hub Boards.
Base Hub Slot	Logical Slots 1 and 2 are the Base Hub Slots, providing 15 radial Base Channel connections via the Zone 2 connector. Base Hub Slots also support an ShMC Port connection.
Base Node Board	A Node Board which supports a redundant pair of Base Channel connections via Base Channels 1 and 2.
Base Node Slot	Logical Slots 3 and higher are supported via Base Channel 1 by a radial connection to the Base Hub Board in Logical Slot 1 and via Base Channel 2 by a radial connection to the Base Hub Board in Logical Slot 2.
Base Interface	A Zone 2 interface that is used to support 10/100 or 1000BASE-T connections between Front Boards in a Shelf. Backplanes are required to support the Base Interface by routing 4 differential signal pairs between all Node Slots and each Hub Slot (Logical Slots 1 and 2). Front Board support of the Base Interface is optional. If the Fabric Interface does not support IP, it is expected that the Base Interface will be used for carrying IP management data between Front Boards within a Shelf.
Basic Carrier/ Reconfigurable Carrier	Basic and Reconfigurable Carriers provide function-agnostic connections between AMC bays. Reconfigurable Carriers allow any AMC bay to serve as a Storage Server or Storage Client; Basic Carriers define specific AMC bays as storage bays, and may further define specific bays as Storage Server or Storage Client.
Basic Connector	Provides conductive contacts on only one side of each AMC Connector Slot and supports all the indispensable connectivity including power and management, and yields 8 Ports. Basic Connector contains 85 contacts per Slot. Conventional and Cutaway Connectors can be Basic Connectors.
Basic Side	Refers to the side of the AMC Connector that supports the defined connections via Pins 1 to 85.
Battery Plant	A collection of battery cells connected in series and parallel to yield the nominal voltage and current required. A central office is presumed to have two such plants, designated “A” and “B” providing redundant power more or less independent of the AC Mains.
BGA	Ball Grid Array. A type of surface-mount packaging used for integrated circuits.
BI_D[A,B,C,D]	Balanced Interface Data (see IEEE 802.3).
BITS	Building Integrated Timing Supply.
BLVDS	A variant of LVDS. The output current was boosted threefold to drive heavily loaded buses driven at any point and with the buses terminated at both ends.
Board	An AdvancedTCA-compliant Front Board or Rear Board and interfaces with the Backplane.
Bottom	When used in reference to an AdvancedTCA® Board, the end which would be on the bottom side in a vertically oriented Subrack.
Branch	A particular pair of conductors providing power from one of the Feeds. It is filtered and circuit protected consistent with its capacity.
Cabinet	A Cabinet is an enclosed Frame to provide for cooling, EMC, and/or security.
Card Guide	See Module Card Guide or Card Guide.
Card-edge Interface	The conductive fingers used on AMC Modules that interface to the AMC Connector.
Carrier Face Plate	Face Plate of the AMC Carrier AdvancedTCA Board.
Carrier Handle	The Handle of the AMC Carrier AdvancedTCA Board.
Carrier IPMC	IPM Controller on the Carrier. This is the required intelligent controller on the Carrier that interfaces with the Module's MMC over the IPMB-L.
Carrier SDRR	Sensor Data Record Repository that resides on the Carrier Board.
Carrier switch	Refers to a switch on the AMC Carrier that connects two or more Ports (including AMC Modules) to allow packets to be routed from one Port to another. This term is used consistently in the AMC.0 E-Keying definition and is used in the AMC.1 Management definition for consistency.
Carrier switch/ On-Carrier Switch	Refers to a switch on the AMC Carrier that connects two or more Ports (including AMC Modules) to allow signals to be logically routed from one Port to another.
CAT 5 / CAT 5e	CATegory 5 cable, as defined in ANSI/TIA/EIA-568-A, is a twisted pair cable type designed for high signal integrity. Cat 5e cable is an enhanced version of Cat 5 that adds specifications for far end crosstalk. It was formally defined in 2001 in the TIA/EIA-568-B standard, which no longer recognizes the original Cat 5 specification.
CFM	Cubic Feet per Minute. A unit of volumetric airflow. One CFM is approximately equivalent to 472 cubic centimeters per second, or 0.000472 cubic meters per second.
Channel	A group of differential signal pairs that are physically routed together on the Backplane to provide an interconnect trunk between two Slots (or between two Front Boards). The Base Channel consists of four differential signal pairs. A Fabric Channel consists of eight differential signal pairs. The Update Channel consists of ten differential signal pairs.
CJTPAT	Continuous Jitter Test PATtern. A specific 2640-bit long 8b/10b encoded test pattern in the form of a valid Fibre Channel frame. The sequence is defined in Fibre Channel document #03-042v3.
Clearance	The shortest distance between two conductive parts, measured through air.
Clock Link	A connection between two clocks, together with the associated protocol.
CMC	Common Mezzanine Card per IEEE 1386-2001.
Common Options Region	A region on the Basic Connector (Ports 0-3) used to define essential interfaces that are common across diverse assignments in the Fat Pipes Region. Ideal candidates for this region include storage (e.g., SAS, SATA and FC) and Control Path interfaces.
Compact Module	Compact Modules are the smallest size Module. The Face Plate and component height on Component Side 1 are defined to allow for two Compact Modules to be installed into a Dual Slot Cutaway Bay. Compact Modules can also be installed into Compact Conventional Bays. Previously termed Half-height AMCs in AMC.0 R1.0.
Compliant Portion	Only those specific portions of products (hardware, software or combinations thereof) that: (i) implement and are compliant with all relevant portions of a Specification, and (ii) are within the bounds of the Statement of Work under which such Specification was created.
Component Envelope Depth	Maximum length for placing components between the Face Plate and rear connector.
Component Envelope Height	Maximum height allowed for components.
Component Side 1	1.  When used in reference to an AdvancedTCA® Board, it is the side on which the highest electronic components would be mounted. Identical with the Right side as defined below. 2.  When used in reference to an AdvancedMC module, it is the side that supports the greater Component Envelope Height and faces the Carrier Board when the Module is installed into a Bay. Component Side 1 height definition varies between Compact, Mid-size and Full-size Modules.
Component Side 1 Cover and Component Side 2 Cover	Board Covers provide mechanical rigidity for the Carrier Boards as well as a place to mount the Module Card Guides and the AMC Connector body. Board covers are required on both sides of all AMC Carrier Board configurations.
Component Side 2	1.  When used in reference to an AdvancedTCA® Board, the side normally reserved for making solder connections with through-hole components on Component Side 1 but on which low height electronic components can also be mounted. Identical with the Left side as defined below. 2.  When used in reference to an AdvancedMC module, it is the side that supports the lesser Component Envelope Height and does not face the Carrier Board when the Module is installed into a Bay. Component Side 2 height definition is the same for Compact, Mid-size and Full-size Modules.
Connector Brace	A counter-pressure plate needed in conjunction with compression mount connectors that is mounted on Component Side 2 of the Carrier Board, opposite the AMC Connector and required to guarantee uniform contact conditions between Connector and Carrier by preventing the Carrier Board from bending.
Contact List	Defines the use of each connector contact. Directed signals appear in the lists differently, as applies to the respective viewpoint of the Module and the Carrier.
Conventional Bay	A Conventional Bay utilizes the B or B+ style AMC Connector and is characterized by the presence of the Carrier PCB and components under the AMC Bay. A Compact Conventional Bay supports a Compact Module, while a Mid-size Conventional Bay supports a Mid-size Module.
Conventional Carrier	A Conventional Carrier exclusively supports one or more Conventional Bays. Conventional Carrier AdvancedTCA Boards can support up to four Conventional Bays.
CPU	Central Processing Unit. The central processing functional element of a Computer.
Creepage	The shortest path between two conductive parts, measured along the surface of the insulation.
Cutaway Bay	A Cutaway Bay is characterized by cutaway of the Carrier PCB between the AMC Connector and the Face Plate. A Cutaway Bay may be a Dual Slot Cutaway Bay or a Single Slot Cutaway Bay. The Dual Slot Cutaway Bay is equipped with the AB or the A+B+ style connector and supports two Compact Modules or one Full-size Module. The Single Slot Cutaway Bay is equipped with a B or B+ style Connector and supports one Full-Size Module.
Cutaway Carrier	A Cutaway Carrier exclusively supports one or more Cutaway Bays. Cutaway Carrier AdvancedTCA Boards can support up to four Cutaway Bays.
Data Transport Interface	Interconnect channels providing a means of data transport for the Payload implemented on the ATCA Front Boards. In the ATCA Base specification the Data Transport Interfaces are the Base Interface, the Fabric Interface, and the Update Channel Interface.
Dedicated Shelf Management Controller	An IPM Controller residing in a FRU location in the Shelf other than a Board location that is reserved for hosting a Shelf Management Controller. Dedicating an ShMC location could be due to hardware considerations (e.g., the Shelf designer wishes to include special hardware on the ShMC for setting the Shelf Address) or IPMB topology considerations (e.g., the IPMBs are routed in a Star topology).
Depth	Edge-to-edge distance from the leading edge of the Face Plate to the trailing edge of the connector.
Device	An integrated circuit implementing one end of an AMC.1 Link.
Double Bay	Mounting location on an AMC Carrier for Double Modules. Double Bays can be Conventional or Cutaway Bays.
Double Module	An AdvancedMC Module that is roughly twice the width of a Single Module and requires a Double Bay. Compact, Mid-size and Full-size Modules can be Double Module configurations. Previously termed Double-width AMCs in AMC.0 R1.0.
Double Port Channel	A Fabric Channel connection that only uses or supports AdvancedMC Port 1 and Port 2.
Downstream	A direction of information flow through a PCI Express hierarchy where the information is flowing away from the Root Complex.
Downstream switch	A generally defined PCI Express switch. A Downstream switch is required to support peer-to-peer transfers.
DSP	Digital Signal Processor.
Dual Star Topology	An interconnect fabric topology in which two switch resources provide redundant connections to all end points within the network. A pair of Hub Boards provides redundant interconnects between Node Boards.
Dual-Dual Star Topology	An interconnect fabric topology in which four switch resources provide redundant connections to all end points within the network. Two pairs of Hub Boards provide redundant interconnects between Node Boards via two independent networks in parallel.
EIA	Electronic Industries Alliance. A trade organization comprised of an alliance of trade associations for electronics manufacturers in the United States .
E-Keying	Electronic Keying. The protocol used to describe the compatibility between the Base Interface, Fabric Interface, Update Channel Interface, and Synchronization Clocks connections of ATCA Front Boards. Electronic Keying defines the process in which a Carrier determines a matching configuration of the Channel and clock connections to an AMC Module. Information supplied by an AMC module or Carrier that describes the electrical protocol of a port. E-keying information from the connection endpoints is compared to determine if the module/ Carrier ports are compatible.
EMC	Electromagnetic Compatibility. The condition that prevails when telecommunications (communication-electronic) equipment is collectively performing its individual designed functions in a common electromagnetic environment without causing or suffering unacceptable degradation due to electromagnetic interference to or from other equipments/systems in the same environment.
EMC Gasket	An electrically conductive elastic strip mounted to defined edges of the ATCA Board Face Plate, of the Carrier, and of the Shelf, providing EMC closure around the ATCA Boards and AMC Modules.
EMI	Electromagnetic Interference. Electromagnetic radiation created by rapid switching in electronic circuits that causes unwanted signals to be induced in other circuits.
End Node	A PCI Express node that is not the Root Complex.
Entity	An IPMI construct that identifies a FRU or a component of a FRU, so that, for instance, a sensor can be associated with the physical component it monitors. Within a given scope (say, Shelf level or IPM Controller level) an Entity consists of an Entity ID and an Entity Instance.
Entity ID	The part of an Entity that describes the type of component identified.
Entity Instance	The part of an Entity that identifies a particular component among those of a given type.
Envelope 1, Envelope 2, Envelope 3	Envelope 1, 2 and 3 define the amount of space available on a Mid-size AMC Module or Conventional Carrier in the defined step segments. Envelope 1 is closest to the Face Plate with Envelopes 2 and 3 going successively towards the rear of the Module or Carrier.
ESD	Electrostatic Discharge. Momentary unwanted currents that may cause damage to electronic equipment.
ESD Contact	1.  Conductive element integral to the ATCA Subrack card guide that provides a low-impedance path to Shelf Ground. The ESD Contact touches the ATCA Board ESD Strip during Board insertion/removal and provides a path for controlled discharge of electrostatic energy from the ATCA Board PCB to Shelf Ground. 2.  Conductive element in the Carrier's Strut that provides a low-impedance path to Shelf Ground in the Carrier. The ESD Contact touches the Module ESD Strip during Module insertion/removal and provides a path for controlled discharge of electrostatic energy from the AMC Module PCB to Shelf Ground.
ESD Segment	ESD Segment 1, ESD Segment 2, and ESD Segment 3 constitute the AMC Module or ATCA Board ESD Strip. The ESD Segments are the contact areas on the Board/Module which the ESD Contact wipes along during the Board/Module insertion providing discharge phases for the Shelf Ground and Logic Ground domains and granting a low impedance connection of the Board/Module Face Plate to Shelf Ground for the installed Board/Module.
Ethernet	A large, diverse family of frame-based computer networking technologies that operates at many speeds for local area networks. Ethernet has been standardized as IEEE 802.3, which defines a number of wiring and signaling standards for the physical layer, through means of network access at the Media Access Control (MAC)/Data Link Layer, and a common addressing format.
ETSI	European Telecommunications Standards Institute. An independent, non-profit, standardization organization of the telecommunications industry (equipment makers and network operators) in Europe.
ETTE	Environmental Testing for Telecommunication Equipment.
Eurocard	A tradename given to the original 100x160mm PCB size, hence the “Eurocard System.” The Eurocard mechanical architecture was defined originally under IEC-60297-3.
Extended Connector	Provides conductive traces on both sides of the AMC Connector and is an extension of the Basic Connector definition. Extended Connectors contain 170 contacts per Slot and are identified with the “+” designation (i.e., B+ and A+B+).
Extended Options Region	The Extended Options Region of the AMC Connector is loosely defined but recommend for use for RTM (Rear Transition Module) support. It is also recommended for use as an extension of both the Common Options and Fat Pipes Regions, when additional Ports are needed.
Extended Side	Refers to the side of the AMC Connector associated with the additional connectivity provided by an Extended Connector.
Fabric Channel	Each Slot in the Backplane supports at least Fabric Channels 1 and 2. Slots 1 and 2, which are Hub Slots, support Channel connections to all other Slots in the Backplane. Each Fabric Channel connection of a Front Board is the endpoint of a Slot-to-Slot connection so that a Slot/Board with 2 Channels supports connections to two other system Slots/Boards. Fabric Channels are numbered 1 through 15 on each Front Board/Slot. Fabric Channels are sub-divided into four 2-pair Ports and can be Single Port (2-pair), Double Port (4-pair), or Full Channel (8-pair) implementations.
Fabric Interface	A Zone 2 interface that provides 15 connections per Board/Slot each comprised of up to 8 differential signal pairs (Channel) supporting connections with up to 15 other Slots/Boards. Backplanes could support the Fabric Interface in a variety of configurations including Full Mesh and Dual Star topologies. Boards that support the Fabric Interface can be configured as Fabric Node Boards, Fabric Hub Boards, or Mesh Enabled Boards. Board implementations of the Fabric Interface are defined by the PICMG® 3.x subsidiary specifications.
Face Plate	The front-most element of an ATCA Board or AMC Module, perpendicular to the PCB, that serves to mount connectors, indicators, controls and mezzanines, and also seals the front of the Subrack for airflow and EMC.
Fat Pipes Region	Ports 4 though 11 of the AMC Connector constitute the Fat Pipes Region. This Region of Ports is intended for the assignment of multiple Lane interfaces, also called “fat pipes”.
FC-PI	Fibre Channel-Physical Interface.
Feed	The complex of paired copper conductors by which power is distributed a Battery Plant.
FIC	Fabric Interface Component.
FRU	Field Replaceable Unit. Any entity that can be replaced by a user in the field. Not all FRUs are hot­ swappable. At its most basic, the FRU does not have an IPM Controller on the assembly and, hence, is not directly controllable through the IPMI infrastructure. Basic product inventory data for the FRU could be maintained at a proxy IPM Controller elsewhere in the Shelf. Examples of this type of FRU might include: backpanel (the Shelf housing, for all practical purposes), Power Entry Module, fan module, PMC, and RTMs.
FRU Information	Data that describes a FRU with an emphasis on data that characterizes the FRU. Format for this data is described in IPMI Platform Management FRU Information Storage Definition, and is further extended in the ATCA implementation.
Filler Module	A unit with no or very limited functionality used for filling up the empty AMC Bays and Slots that often has air baffle included.
Frame	A physical or logical entity that might contain one or more Shelves. Also called a rack, or, if enclosed, a Cabinet.
Front Board	A Board that conforms to AdvancedTCA mechanicals (8U x 280 mm), including a PCB and a Panel. Further, a Board connects with the Zone 1 and Zone 2 Backplane connectors and, optionally, connects with a Zone 3 Midplane Connector or directly to an RTM connector. A Board is installed into the front portion of a Shelf.
Full Channel	An ATCA Fabric Channel connection that uses all eight differential signal pairs between end­points.
Full Mesh Backplane	A Backplane that implements the Full Mesh Topology to interconnect the Fabric Interface Channels of the supported Slots.
Full Mesh Topology	Full Mesh configurations could be supported within the Fabric Interface to provide one dedicated Channel of connectivity between each pair of Slots within a Shelf. Full Mesh configured Backplanes are capable of supporting Mesh Enabled Boards or Hub and Node Boards installed in a Dual Star arrangement (a.k.a. Full Mesh Backplane).
Full-size Module	Full-size Modules utilize the maximum size Module Face Plate and component area on Component Side 1. Full-size Modules can be installed into Cutaway Bays only. Previously termed Full-height AMCs in AMC.0 R1.0.
g	Grams. A unit of mass. One gram is equivalent to 0.001 kilogram.
Gbd	Gigabaud. A measure of signaling rate that includes encoding overhead.  For example, a link delivering data at 1 Gigabit per second using an 8B/10B coding scheme is operating at 1.25 Gbd.
GbE	Gigabit Ethernet.
Gbps	Gigabits (= 1,000,000,000 bits) per second.
GBps	Gigabytes (= 1,000,000,000 bytes) per second.
Gen1	Refers to the first generation of PCI Express which operates @ 2.5 Gbps in each direction.
Gen2	Refers to the second generation (after Gen1) of PCI Express which is expected to support a raw signaling rate of 5.0-6.4Gbps in each direction (at the time this spec was published).
Geographic Address	Geographic Address identifies the physical location of the AMC Slots in the AMC Bays on a Carrier via three, three-state signals. Each valid GA combination of the three signals maps to a specific AMC Slot ID in which the A and B layers of the AMC Bays that are implemented on a Carrier are numbered sequentially in their order of occurrence starting with 1 and from the top of the Carrier.
GPDU	General Power Distribution Unit.
GPS	Global Positioning System. A satellite-based global navigation system that consists of (a) a constellation of 24 satellites in orbit 11,000 nautical miles above the Earth, (b) several on-station (i.e., in-orbit) spares, and (c) a ground-based control segment. The satellites transmit signals that are used for extremely accurate three-dimensional (latitude, longitude, and elevation) global navigation (position determination), and for the dissemination of precise time. GPS-derived position determination is based on the arrival times, at an appropriate receiver, of precisely timed signals from the satellites that are above the user's radio horizon.
GUID	Globally Unique Identifier. A GUID is 128 bits long, and if generated in a compliant manner, is either guaranteed to be different from all other GUIDs generated until 3400 A.D. or extremely likely to be different (depending on the mechanism chosen). An AdvancedTCA OEM GUID is constructed and processed as specified in Chapter 17.8 of the IPMI v1.5 specification.
Guide Rail	Provides for the Front Board and RTM guidance feature in a Slot. Also see Module Card Guide or Card Guide.
HA	High Availability. A system design protocol and implementation that ensures operational continuity during a given measurement period. In the telecommunications industry, a minimum of 99.999% uptime is required for a highly available system.
Handle	An item or part used to insert or extract AMC Modules, and ATCA Boards and RTMs in and out of Subracks.
Handle Switch	A switch that is activated by the lower Handle on an ATCA Board or AMC Module and indicates whether the Handle is open or closed. The Handle Switch is considered closed when it is activated and the Handle is closed; it is considered open otherwise.
Hardware Address	An address assigned with hardware signals from the ATCA Shelf to a Front Board. The term Hardware Address is used rather than geographic address since the latter implies an association between a set of numbers and a set of locations within a Shelf that are consistent across all Shelves.
Hertz, Hz	The base unit of the measurement of frequency. One Hertz is equal to one cycle per second.
Host Switch	A PCI Express switch optionally closest to the root complex. A Host Switch is not required to support peer-to-peer transfers.
Hot Swap	To remove a component (e.g., an ATCA Board or AMC Module) from a system (e.g., an AMC Carrier AdvancedTCA Board) and plug in a new one while the power is still on and the system is still operating.
Hot Swap FRU	Managed FRU that also implements all of the hot-swap protection mechanisms during FRU insertion and extraction.
Hot Swap Switch	A switch that is integrated with the AMC Module Latch Mechanism so that its state reflects the state of the Module Handle. The Hot Swap Switch is activated when the Module Handle is fully inserted.
HP	Horizontal Pitch (5.08 mm or 0.2 inches). Subrack aperture width for Panels (1 Horizontal Pitch (HP)=5.08 mm; max 84 HP internal aperture for 19” Subracks).
Hub Board	An ATCA Board intended for use in a Star topology Backplane that provides connectivity to a number of Node Boards within the Backplane. Hub Boards support either or both the Base Interface and Fabric Interface. Boards utilizing the Fabric Interface will typically provide switching resources to all 15 available Fabric Channels. Hub Boards supporting the Base Interface are installed into Logical Slots 1 and 2 and utilize all 16 Base Channels to provide 10/100/1000BASE-T Ethernet switching resources to up to 14 Node Boards and the other Hub Board. One Base Channel is assigned to support a connection to the Shelf Management Controller.
Hub Slot	An ATCA Slot in a Backplane that is capable of supporting Hub Boards, Mesh Enabled Boards, or Node Boards. In a Star topology Backplane, Hub Slots must reside in Logicial Slots 1 and 2, and possibly Logical Slots 3 and 4. All Slots in a Full Mesh Backplane are considered Hub Slots. Hub Slots support both the Base Interface and Fabric Interface. Hub Slots located in Logical Slots 1 and 2 are capable of supporting both Base Interface and Fabric Interface Hub Boards. Logical Slots 1 and 2 are always Hub Slots regardless of the Fabric Topology. These Slots support up to 16 Base Channels and up to 15 Fabric Channels each. Hub Slots located in Logical Slots 3-16 support 2 Base Channels and up to 15 Fabric Channels.
Hybrid Carrier	An AMC Carrier that has both Conventional and Cutaway Bays.
I/F	Interface.
I/O or IO	Input / Output.
I2C	Inter-integrated Circuit bus. A multi-master, two-wire serial bus used as the basis for IPMBs.
ICMB	Intelligent Chassis Management Bus. A character-level transport for inter-chassis communications between intelligent chassis.
IEC	International Electrotechnical Commission.
IEEE	Institute of Electrical and Electronics Engineers.
IETF	Internet Engineering Task Force. An SDO that develops and promotes Internet standards, cooperating closely with the W3C and ISO/IEC standard bodies; and dealing in particular with standards of the TCP/IP and Internet protocol suite.
Intelligent FRU	A FRU containing an IPM Controller. Intelligent FRUs include the Node and Hub Boards, and they could also include other FRUs such as the Fan Tray, Power Supplies, Alarm Boards, etc.
IPM Controller or IPMC	Intelligent Platform Management Controller. The portion of a FRU that interfaces to the AdvancedTCA® IPMB-0 and represents that FRU and any device subsidiary to it. The function that provides the IPMB-0 interface, message handling and routing, device SDR, device FRU, and other required services on behalf of an Intelligent FRU. It could include interfaces to its Payload, and to the Base Interface.
IP-Based Services	Higher level services based on the TCP/IP Protocol Suite such as remote booting, SNMP, WBEM, etc. These services are principally accessed by Payload through a 10/100/1000BASE-T Ethernet or other IP-compliant fabric connection.
IPMB	Intelligent Platform Management Bus. The lowest level hardware management bus as described in Intelligent Platform Management Bus Communications Protocol Specification.
IPMB-0	Intelligent Platform Management Bus Channel 0 as defined in the IPMI v1.5 specification. This is the logical aggregation of ATCA IPMB-A and IPMB-B, as defined in the PICMG 3.0 specification.
IPMB-0 Hub	A hub device that provides multiple radial IPMB-0 Links to various FRUs in the system. For example, an IPMB-0 Hub is present in an ShMC that has radial IPMB-0 Links.
IPMB-0 Link	With radial topology, this is the Physical IPMB-0 segment between an IPMB-0 Hub and a single FRU. Each IPMB-0 Link on an IPMB-0 Hub is usually associated with a separate IPMB-0 Sensor. An IPMB-0 Link can also connect in a bused topology to multiple FRUs.
IPMB-0 Link Number	Identifier for a particular IPMB-0 Link. There can be up to 95 Links in a Shelf (1 to 95). IPMB-0 Link Number 0 is reserved as an indicator for a fully bused IPMB-0 topology, and to maintain backward compatibility with legacy systems. IPMB-0 Link Number 127 is reserved to maintain compatibility with legacy systems.
IPMB-A IPMB-B	Intelligent Platform Management Buses A and B, respectively. Refers to the two redundant IPMBs that aggregate into IPMB-0.
IPMB-L or Local IPMB	The IPMB located on the AMC Carrier interconnecting the Module’s MMC with the Carrier IPMC. This bus is electrically separate and occupies a separate address space from the Carrier's IPMB (IPMB-0).
IPMI	Intelligent Platform Management Interface. A specification and mechanism for providing inventory management, monitoring, logging, and control for elements of a computer system. As defined in Intelligent Platform Management Interface Specification.
IPMI Messaging	IPMI Messages as defined in the IPMI v1.5 specification and extended herein used to communicate across an AdvancedTCA® defined IPMI medium.
ISO	International Standards Organization.
Isolation	A method of reducing the inductive and/or capacitive coupling (i.e., crosstalk) between an Aggressor and Victim.
ITU	International Telecommunication Union (ITU): A civil international organization established to promote standardized telecommunications on a worldwide basis. Note: The ITU-R and ITU-T are committees under the ITU. The ITU headquarters is located in Geneva, Switzerland . While older than the United Nations, it is recognized by the U.N. as the specialized agency for telecommunications.
JTAG	Joint Test Action Group (test bus, IEEE 1149.1).
kg	Kilogram. A unit of mass. One kilogram is equivalent to 1,000 g, and is approximately equal to 2.205 pounds.
kHz	Kilohertz. A unit of frequency. One kHz is equal to 1,000 Hertz.
LAN	Local Area Network.
Landlord	The entity providing the shared resources of the facility, power, cooling, connectivity, and a management domain for the allocation of these resources. A service provider owner/operator of an AdvancedTCA® Shelf that hosts Boards either owned or leased by one or more third parties (Tenants). The Landlord provides the hardware platform management, power, and cooling infrastructure.
Lane	1.  [PCI Express] A set of differential signal pairs, one pair for transmission and one pair for reception. One or more Lanes operate together to form a PCI Express Link. Same as Port. 2.  E-Keying definition of a differential pair associated with a specific Fabric Link (e.g., a Link generally consists of Lanes[x:y]).
LED	Light Emitting Diode. A semiconductor device that emits incoherent narrow-spectrum light when electrically biased in the forward direction of the p-n junction.
Left	When used in reference to an AdvancedTCA® Board, the side that would be on the leftmost side when viewed from the front of a vertically oriented Subrack.
LFM	Linear Feet per Minute. A unit of air velocity. One LFM is equivalent to 0.508 centimeters per second, or 0.005,08 meters per second.
Link	1.  One or more Ports aggregated under a common protocol. Links are groups of Ports that are enabled and disabled by Electronic Keying operations. A xN Link (pronounced “by-N Link”) is composed of N Ports. 2.  A group of Lanes which operates together to connect two devices; the number of Lanes used is negotiated.
Link Negotiation	The process whereby two PCI Express Ports negotiate a common number of PCI Express Lanes, Lane polarity, Lane ordering, and Link speed that will be used to interconnect the two PCI Express Ports and form a single Link.
Logic Ground, Ground, or GND	Shelf-wide electrical net used on Boards and Backplanes as a reference and return path for logic-level signals that are carried between Boards. It also serves as the reference potential for logic signaling and local power distribution on the Carrier and on the Module.
Logical Slot	A Slot within an ATCA Shelf defined by the Zone 1 Hardware Address. Every Slot has a unique Logical Slot # (maximum of 16 Logical Slots per Shelf). Logical Slot numbers are used to determine Channel mapping between Slots. PICMG® 3.0 defines a direct correlation between Channel numbers and Logical Slot numbers. For example, Channel 1 (Base and/or Fabric Channels) of every Slot establishes a direct connection to Logical Slot 1. Logical Slots 1 and 2 are always designated as Hub Slots.
LUN	Logical Unit Number as defined by IPMI.
LVDS	Low Voltage Differential Signaling. A point to point electrical interface defined in ANSI/EIA-644-A.
m	Meter(s). A unit of linear measurement. One meter is approximately equal to 39.37 inches.
MAC	Media Access Control. A part of the data link layer specified in the seven-layer OSI model (layer 2). It provides addressing and channel access control mechanisms that makes it possible for several terminals or network nodes to communicate within a multipoint network.
Managed FRU	Either an Intelligent FRU or a FRU that is represented by an Intelligent FRU via a FRU Device ID. The basic operational states of Managed FRUs are visible to and controlled through the IPMI infrastructure, including distinct FRU Information for each of them. Examples of this type of FRU might include ATCA Boards or Fan Trays. ATCA Boards are Intelligent FRUs and, therefore, Managed FRUs by definition. Fan Tray FRUs could be Intelligent FRUs or Managed FRUs but are not necessarily either.
MP	Management Power. The 3.3V power for a Module's Management function, individually provided to each Slot by the Carrier.
Mbps	Megabits (1,000,000 bits) per second.
MBps	Megabytes (1,000,000 bytes) per second.
Mesh	A fabric topology in which all network end-points have a direct connection to all other end-points.
Mesh-Enabled Board	An ATCA Board intended for use in a Mesh topology Backplane that provides connectivity to all other Boards within the Backplane. Mesh Enabled Boards support the Fabric Interface and could also support the Base Interface. Mesh Enabled Boards utilize 2 to 15 Fabric Interface Channels (typically all 15 Channels) to support direct connections to all other Boards in the Shelf. The number of Channels supported dictates the maximum number of Boards that can be connected to within a Shelf.
MHz	Megahertz. A unit of frequency equal to one million Hertz.
MicroTCA	A PICMG specification in which AMC Modules plug directly into a backplane.
Mid-size Module	Mid-size AMC Modules are optimized for installation into Conventional Bays. Each Conventional Bay can accept one Mid-size Module. Mid-size Modules can also be installed into Cutaway Bays if converted to a Full-size Module with a different Face Plate.
Mixed Channel	A Fabric Interface Channel that uses arbitrary combinations of up to four Ports to support dissimilar Link technologies as defined by a PICMG® 3.x subsidiary specification.
MLVDS	Multipoint Low Voltage Differential Signaling. A later development of LVDS defined in TIA/EIA-644. It is specifically designed for multi drop and multi sourced signaling.
mm	Millimeter(s). A unit of linear measurement. One millimeter = 10-3 meters, and is equal to 0.03937 inches, rounded to five significant figures.
MMC	Module Management Controller. The MMC is the required intelligent controller that manages the Module and is interfaced to the Carrier via IPMB-L.
Module	An assembly that may be inserted into an AMC bay. Modules are not limited to storage devices, but may include processing functions as well.
Module and On- Carrier device	When used in a requirement this phrase specifically means that the requirement applies equally to a PICMG® AMC.1 Module and to a PICMG® AMC.1 On-Carrier device.
Module Card Guide or Card Guide	Card Guide utilized by ATCA Boards to facilitate insertion into the ATCA Subrack, and utilized by AMC Modules to facilitate insertion into the AMC Bay. Card Guides also facilitate Hot Swap of ATCA Boards and AMC Modules.
Module ESD Strip	Plated region on the AMC Module PCB that provides a path for controlled discharge of electrostatic energy. The Module ESD Strip includes all three ESD Segments found on an AdvancedMC Module.
Module Handle	Hand grip that is connected to the AMC Module Latch Mechanism, provides user interface that initiates Hot Swap sequence and Module removal.
Module Latch Mechanism	Mechanism to hold the Module locked in the AMC Bay with the Module in contact with the bottom of the AMC Connector Slot. The Module Latch Mechanism also provides coupling to the Hot Swap Switch.
Module LEDs	The collective name for the following LEDs available at the AMC Module Face Plate: BLUE LED, LED 1, and LED 2.
Multi-Tenant Shelf	A Shelf that is owned and operated by a service provider. The Shelf is populated with blades either owned or leased by multiple third parties. The third parties are allowed unlimited provisioning and configuration of elements to which they hold title. However, they are prevented from sourcing or observing provisioning and control of elements to which they do not hold title.
NEBS	Network Equipment Building System. The most common set of safety, spatial and environmental design guidelines applied to telecommunications equipment installed in Central Office environments throughout the United States .
Necessary Claims	Those claims under patents and/or patent applications, other than design patents and design registrations, anywhere in the world, that would be Necessarily Infringed by the implementation of the required or recommended (i.e., “shall" and "should") elements of a PICMG Specification. Notwithstanding the foregoing sentence, Necessary Claims do not include any claims other than those set forth above even if contained in the same patent or patent application as the Necessary Claims.
Node Board	An ATCA Board intended for use in a Star topology Backplane that has connectivity to a Hub Board within the Backplane. Node Boards can support either or both the Base Interface and Fabric Interface. Boards supporting the Fabric Interface utilize Fabric Channels 1 and 2 (and possibly 3 and 4). Boards supporting the Base Interface utilize Base Channels 1 and 2 only to support 10/100/1000BASE-T Ethernet.
Node Slot	An ATCA Slot in a Backplane that supports Node Boards only. A Node Slot is not capable of supporting a Hub Board, thus never occupy Logical Slots 1 or 2. Node Slots apply only to Backplanes designed to support Star topologies. Node Slots support both the Base Interface and Fabric Interface. Typically, a Node Slot supports two or four Fabric Channels and Base Channels 1 and 2. Each two Channel Node Slot establishes connections to Logical Slots 1 and 2, respectively and four Channel Node Slots establish connections to Logical Slots 1, 2, 3, and 4, respectively.
Non-AMC Carrier AdvancedTCA Board	An AMC Carrier that is not an AdvancedTCA Board.
OC-3	Optical Carrier level 3. OC-3 is a network line with transmission speeds of up to 155.52 Mbit/s (payload: 148.608 Mbit/s; overhead: 6.912 Mbit/s, including path overhead) using fiber optics. OC-3 is also known as STS-3 (electrical level) and STM-1 (SDH).
Octet	A normally contiguous group of eight bits not necessarily byte aligned.
On-Carrier Device	An On-Carrier device is a device located on an AMC Carrier which provides a Link to a Bay. This term is used consistently in the AMC.0 E-Keying definition and is used in the AMC.1 Management definition for consistency.
Operational State	The management state of an AdvancedTCA FRU, defined as one of eight specified states which indicates the status of that FRU.  The eight Operational States are designated “M0” through “M7.”
OSI (Reference) Model	Open Systems Interconnection Model. A layered, abstract description for communications and computer network protocol design, developed as part of Open Systems Interconnection (OSI) initiative. It is also called the OSI seven layer model. The layers, from top to bottom, are: Application, Presentation, Session, Transport, Network, Data Link and Physical.
Payload	The primary function that a FRU provides. This includes all the hardware on the FRU except that associated with management. It might also include the firmware, operating system and application software running on the Payload hardware.
Payload Interface	The interface, usually local to the ATCA Board, between an IPM Controller and its Payload.
Payload Power or PWR	The nominal 12V supply power, individually provided to each Slot by the AMC Carrier for the payload function of the AMC Module.
PBA	Printed Board Assembly. A PCB with all electronic components attached.
PCB	The Printed Circuit Board (PCB) definition used for the ATCA Front Board, RTM, and AdvancedMC Module.
PCI	Peripheral Component Interconnect. A parallel data bus for attaching peripheral devices to a computer motherboard. The PCI specification was developed by the PCI SIG.
PCIe	PCI Express. A high speed point-to-point serial computer data interface developed by the PCI SIG.
PCI SIG	PCI Special Interest Group. An electronics industry consortium responsible for developing the Peripheral Component Interconnect (PCI), PCI-X, and PCI Express (PCIe) computer buses.
PDH	Plesiochronous Digital Hierarchy. Refers to the DS1/DS2/DS3 family of signals that were developed as an asynchronously multiplexed hierarchy for transmission systems, which are now more frequently encountered as payload in a SONET system.
PDU	Power Distribution Unit.
Peer-to-Peer	A transfer initiated by an End Node and targeting another End Node. Does not require Root Complex intervention.
PEM	Power Entry Module.
PHY	IEEE 802.3 compatible Physical Interface situated in Layer 1 of the OSI Model.
Physical Address	An address that defines the physical location of a FRU; consists of Site Type and Site Number.
Physical Slot Number	Designates the physical location of a Slot within a Shelf. Physical Slot Numbers start with 1, designating the left-most (or bottom-most) physical Slot, and incrementing sequentially toward the right (or top for horizontally oriented Slots). The Physical Slot Number of a Slot is not necessarily the same as its Logical Slot designation. The Address Table in the Shelf FRU Information provides a mapping between the Physical Slot Number and Logical Slot designation for each Slot in the Shelf. Site Number fields for Slot entries in that table contain the Physical Slot Number.
PICMG®	PCI Industrial Computer Manufacturers Group. PICMG is a globally recognized consortium comprised of hundreds of companies that collaboratively develops open specifications for high performance telecommunications and industrial computing applications.
Pin	The elementary connectivity provided by the Connector.
Pitch Line	Horizontal Pitch Line between Slots, also called “inter-Board separation plane.”
PMA	Physical Medium Attachment.
PMC	PCI Mezzanine Card per IEEE 1386.1-2001.
Port	1. ATCA: The minimum number of Backplane differential conductor pairs that can be allocated by E-Keying in support of an LVDS signaling technology. In the case of the Base Interface, a Port consists of four pairs. In the case of a Fabric Channel it is two differential pairs. In the case of the Update Channel Interface, it is ten pairs. 2. AMC: A set of differential signal pairs, one pair for transmission and one pair for reception. One or more Ports operate together to form a Link. A Port refers to the location of a specific such pair on the AMC Connector and the associated traces on the Carrier and Module.     PCI Express calls a Port a ‘Lane’, and uses the word Port to denote the interface at one end of a Link. AMC.1 uses the AMC.0 sense of ‘Port’ unless specifically referring to as a “PCI Express Port”. AMC.1 E-Keying defines the binding of Lanes to Ports.
ps	Pico second. One pico second = 10-12 second.
PRBS	Pseudo Random Bit Sequence. An algorithmically generated sequence of bits used as an approximation of random bits.
PRS	Primary Reference Source. Equipment that provides a timing signal whose long-term accuracy is maintained at 1 x 10-11 or better with verification to Coordinated Universal Time (UTC), and whose timing signal may be used as the basis of reference for the control of other clocks within a network. The primary reference source may generate a timing signal completely autonomous of other references, in which case cesium beam technology is suitable. Alternatively, the primary reference source may not be a completely autonomous implementation, in which case it may employ direct control from normal UTC-derived frequency and time services.
RAID	Redundant Array of Independent Disks. Provides data storage schemes that divide and/or replicate data among multiple hard drives, thus providing increased data reliability or increased I/O performance.
RAS	Reliability, Availability, Serviceability.
RTM	Rear Transition Module. An 8U x 70 mm x 6 HP assembly installed into the rear portion of a Shelf and mated with a Front Board through Zone 3 connectors to provide I/O connectivity. Also called Rear Board.
RMCP	Remote Management Control Protocol. Protocol to encapsulate IPMI messages across an Ethernet interface as defined in the Alert Standard Format (ASF) Specification from the DMTF, and extended in the IPMI v1.5 specification.
Replicated Mesh Topology	Replicated Mesh configurations provide multiple Channels of Fabric Interface connectivity among the Slots within a Shelf. The number of Channels provided between any two Slots is dependent on the Slot count.
Right	When used in reference to an AdvancedTCA® Front Board, the side that would be on the rightmost side when viewed from the front of a vertically oriented Subrack.
RJ-45	Registered Jack-45, an eight-wire connector used commonly to connect computers onto a local-area network (LAN), especially Ethernet.
RoHS	Restriction of Hazardous Substances directive, as defined in 2002/95/EC. This directive restricts the use of six hazardous materials in the manufacture of various types of electronic and electrical equipment deployed throughout the European Union. It is closely linked with the Waste Electrical and Electronic Equipment Directive (WEEE).
RC	Root Complex. Location of the host for a PCI Express hierarchy.
s	Second(s). A unit of time.
SBC	Single Board Computer.
SDH	Synchronous Digital Hierarchy. A synchronous optical networking standard developed by the International Telecommunication Union (ITU), documented in standard G.707 and its extension G.708.
SDR	Sensor Data Record. A data record that provides platform management sensor type, locations, event generation, and access information.
SDR Device	An SDR maintained by an individual IP Controller to describe local sensors.
SDR Repository	A single, centralized non-volatile storage area maintained by the Shelf Manager.
SDO	Standards Development Organization. An entity whose primary activities are developing, coordinating, promulgating, revising, amending, reissuing, interpreting, or otherwise maintaining standards that address the interests of a wide base of users outside the standards development organization.
SELV	Safety Extra-Low Voltage. A designation defined in IEC 60950-1 and related documents for circuits with a voltage that remains below 60 V.
SerDes	Serializer-Deserializer.
SFP	Small Form-factor Pluggable. An industry standard definition for a pluggable Module and cage typically used for fiber optic connections.
Shelf	The ATCA Shelf consists of the Subrack, Backplane, Front Boards, cooling devices, RTMs, power supplies, etc. Also historically known as a chassis.
Shelf Address	A variable length, variable format descriptor of up to 20 bytes in length providing a unique identifier for each Shelf within a management domain.
Shelf FRU Info Device	Any IPM Controller which hosts Shelf FRU Information.
Shelf FRU Information	A collection of data records describing Shelf power, cooling, and interconnect capabilities at a minimum.
Shelf Ground	A safety ground and earth return that is connected to the Frame, Subrack metal, and available to all Boards, Carriers and AMC Modules.
Shelf Manager	The entity responsible for managing the power, cooling, and interconnects (with Electronic Keying) in an AdvancedTCA® Shelf. The Shelf Manager also: routes messages between the System Manager Interface and IPMB-0, provides interfaces to System repositories, and responds to event messages. The Shelf Manager can be partially or wholly deployed on the ShMC and/or System Manager Hardware.
Shelf Manager IP Address	An RFC790 compliant Internet Protocol version 4 (IP) address unique to a single Shelf that provides Ethernet based management systems a contact point in addressing the Shelf. This IP address can be transferred at any time between redundant Shelf Manager instances that have 802.3 interfaces, under the direction of the Shelf Manager. At any point in time this IP address can only be associated with a single media access control (MAC) address.
ShMC	Shelf Management Controller. An IPMC that is also capable of supporting the functions required of the Shelf Manager. An ShMC is a mandatory component part of an AdvancedTCA Shelf.
ShMC Cross-Connect	A redundant two-port 10/100BASE-TX connection between a Base Hub Board's ShMC Ports and two Dedicated ShMCs.
ShMC Cross-connect A, ShMC Cross-connect B	An individual ShMC Cross-connect port implemented on two differential signal pairs of a Base Hub Slot ShMC Port, providing a Backplane connection to one Dedicated ShMC site.
Single Bay	Mounting location on an AMC Carrier for Single Modules. Single Bays can be Conventional or Cutaway Bays.
Single Module	AMC Module with a width of approximately 74 mm which fits into a Single Bay. Previously termed Single-width AMCs in AMC.0 R1.0.
Single Port	A Fabric Channel connection that only uses 2 differential signal pairs (of a possible 8-pair) between end-points.
Site	See AMC Bay or Bay.
Site Number	The part of a Physical Address that identifies a particular instance of a given FRU site type. Architecture-independent abstraction of the AMC Slot identification for the purposes of System Management. Site Number would distinguish among multiple Fan Trays or Power Entry Modules, for instance. The Site Number for a Slot is equivalent to its Physical Slot Number.
Site Type	The part of a Physical Address that identifies the type of FRU site, distinguishing for instance, a Front Board site (a Slot) from a Fan Tray site.
Slot	A Slot defines the position of one Front Board and or one RTM. Front Boards and RTMs are inline. See also AdvancedMC Slot, AMC Slot, or Slot.
Slot A	The lower Slot of an AB or an A+B+ Connector. It is located in the cutout section of a Cutaway Bay and is utilized by Compact-Modules only.
Slot B	The upper Slot of and AB or A+B+ Connector or the Slot position of a B or B+ Connector.
SMC	SONET minimum clock.
SMT	Surface Mount Technology.
SNMP	Simple Network Management Protocol. Part of the Internet protocol suite as defined by the Internet Engineering Task Force (IETF). SNMP is used by network management systems to monitor network-attached devices for conditions that warrant administrative attention.
SONET	Synchronous Optical NETworking. An interface standard for synchronous optical-fiber transmission as defined by Telcordia GR-253-CORE, applicable to the Physical Layer of the OSI Reference Model.
SPR	Single-Point Return
SRT	Synchronous Receiver/Transmitter. A hardware interface capable of transmitting and receiving byte wide data on the I2C bus on behalf of a micro-controller.
Stacked Modules	Used to describe two Compact Modules installed into a Cutaway Bay.
Standard Air	This term is used in this specification to provide a consistent and repeatable definition of a complex substance suitable for electronic cooling. For high power cooling the use of standard air ensures that pressures and flow rates are consistently defined by all vendors. Simple scaling can be used by system implementers for temperature, atmospheric pressure and altitude differences.
Standard Atmosphere	A term introduced by the aeronautic community to provide a consistent and repeatable definition of a complex substance.
Star	A Backplane topology having one of more Hub Slots providing connectivity among the supported Node Slots.
STM-1	Synchronous Transport Module level 1.The basic rate of transmission of the SDH ITU-T fiber optic network transmission standard. It has a bit rate of 155.52 Mbit/s and is the SDH equivalent of an STS-3c (SONET).
Storage	A device that stores information for subsequent use or retrieval.
Storage Client	An AMC compliant device that uses a Storage Server.
Storage Server	An AMC.3 module that accepts data to be stored or presents stored data, to or from a Storage Client. The module may provide a storage function explicitly, or may act as a storage (RAID) controller for other Storage Servers.
Storage-client Carrier/ Storage-client	Carriers implement a carrier -dependent function that utilizes Storage Server modules. Some or all of the AMC bays are usually Storage Server bays exclusively.
Strut	A mechanical feature used to align the Module Card-edge within the AMC Bay.
Subrack	The Subrack provides the interface to AdvancedTCA Boards and consists of the Guide Rails, ESD discharge, alignment/keying, Handle interface, Face Plate mounting hardware, EMC gasketing, and Backplane interface. The Subrack is a subset of the Shelf.
Synchronization Clock Interface	A Zone 2 interface that provides Synchronization Clocks between all Slots. There are 3 distinct, redundant clock pairs that are bused between all Slots. Backplanes must support the Synchronization Clock Interface, Boards can support any or all of the clock interfaces.
System	A managed entity that could include one or more Node and Hub Boards, and/or one or more Shelves, and/or one or more Frames.
System Manager	A level of management functionality above the Shelf Manager charged with the management of an entire System, whatever that means in a specific implementation. The System Manager can, nevertheless, be partially or wholly deployed on the ShMC and/or System Manager Hardwa