Appendix A
xPON Definitions
Activation
: A set of distributed procedures executed by the OLT and the ONUs that allows an
inactive ONU to join or resume operations on the PON. The activation process includes three phases:
parameter learning, serial number acquisition, and ranging.
Bandwidth allocation
: An upstream transmission opportunity granted by the OLT for the duration of the specified time interval to
the specified traffic-bearing entity within an ONU.
C/M-plane
: A plane of the xPON protocol suite that handles control and management information in a xPON system. Data on OMCI
is transferred through this plane.
Dynamic bandwidth assignment
(
DBA)
: A process by which the optical line terminal (OLT) distributes the upstream PON capacity
between the traffic-bearing entities within optical network units (ONUs), based on the dynamic indication of their activity status and
their configured traffic contracts.
Embedded OAM
: An operation and management channel between the OLT and the ONUs that utilize the structured overhead fields
of the downstream GTC frame and upstream GTC burst, and supports the time sensitive functions, including bandwidth allocation,
key synchronization, and DBA reporting.
Equalization delay (EqD)
: The requisite delay assigned by the OLT to an individual ONU as a result of ranging.
G-PON encapsulation method (GEM)
: A data frame transport scheme used in xPON systems that is connection-oriented and that
supports fragmentation of the user data frames into variable-sized transmission fragments.
G-PON transmission convergence (GTC) layer
: A protocol layer of the xPON protocol suite that is positioned between the
physical media dependent (PMD) layer and the xPON clients. The GTC layer is composed of GTC framing sublayer and GTC
adaptation sublayer.
GEM port
: An abstraction on the GTC adaptation sublayer representing a logical connection associated with a specific client packet
flow.
Gigabit-capable passive optical network (G-PON)
: A variant of the passive optical network (PON) access technology supporting
transmission rates in excess of 1 Gbit/s and based on the G.984-series of ITU-T Recommendations.
GTC adaptation sublayer
: A sublayer of the G-PON transmission convergence layer that supports the functions of user data
fragmentation and de-fragmentation, GEM encapsulation, GEM frame delineation and GEM Port-ID filtering.
GTC framing sublayer
: A sublayer of the G-PON transmission convergence layer that supports the functions of GTC frame/burst
encapsulation and delineation, embedded OAM processing and Alloc- ID filtering.
Optical access network (OAN)
: A set of access links sharing the same network-side interfaces and supported by optical access
transmission systems. The OAN may include a number of ODNs connected to the same OLT.
Optical distribution network (ODN)
: In the PON context, a tree of optical fibers in the access network, supplemented with power or
wavelength splitters, filters or other passive optical devices.
Optical line termination (OLT)
: A device that terminates the common (root) endpoint of an ODN, implements a PON protocol, such
as that defined by [ITU-T G.984.1] and adapts PON PDUs for uplink communications over the provider service interface. The OLT
provides management and maintenance functions for the subtended ODN and ONUs.
Optical network termination (ONT)
: A single-subscriber device that terminates any one of the distributed (leaf) endpoints of an
ODN, implements a PON protocol and adapts PON PDUs to subscriber service interfaces. An ONT is a special case of an ONU.
Optical network unit (ONU)
: A generic term denoting a device that terminates any one of the distributed (leaf) endpoints of an
ODN, implements a PON protocol and adapts PON PDUs to subscriber service interfaces. In some contexts, an ONU implies a
multiple subscriber device.
Physical layer OAM (PLOAM)
: A message-based operation and management channel between the OLT and the ONUs that
supports the PON TC-layer management functions, including ONU activation, OMCC establishment, encryption configuration, key
management and alarm signaling.
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