Transition Networks, Inc.
S4224 Web User Guide
33595 Rev. C
Page 641 of 669
The authenticator acts like a ‘security guard’ to a protected network. The supplicant (client device) is not allowed
access through the authenticator to the protected side of the network until the supplicant’s identity has been
validated and authorized. The commonly used EtherType for EAPOL is 0x888E.
ECS
Emergency Call Service (e.g. E911 and others), such as defined by TIA or NENA.
ECEs
(EVC Control Entries) The ECE ID identifies the ECE. Unique ECE IDs are automatically assigned to ECEs
added. The possible range is from 1 through 128. See also “EVC”.
EEE
EEE is an abbreviation for Energy Efficient Ethernet defined in IEEE 802.3az.
ELIN
Emergency Location Identification Number, a valid North America Numbering Plan format telephone number,
supplied to the PSAP for ECS purposes.
ENNI
(External Network-to-Network Interface) External Network to Network Interface; a reference point representing
the boundary between two Operator MENs that are operated as separate administrative domains per MEF 26,
30. Previously “E-NNI”.
Epoch
The origin of a PTP timescale.
EPS / ELPS
EPS is an abbreviation for Ethernet Protection Switching defined in ITU/T G.8031 (Ethernet (Linear) Protection
Switch). Rec. ITU-T G.8031/Y.1342 (11/2009) defines the automatic protection switching APS protocol and
linear protection switching mechanisms for point-to-point VLAN-based ETH SNC (Subnetwork Connection) in
Ethernet transport networks. Protection switching occurs based on detection of certain defects on the transport
entities (working and protection) within the protected domain. These defects are discussed in ITU-T G.8021.
The G.8031 Recommendation specifies linear protection switching mechanisms to be applied to VLAN-based
Ethernet networks as described in G.8010. Protection switching is a fully allocated survivability mechanism
(‘fully allocated’ in that the route and bandwidth of the protection entity is reserved for a selected working entity).
EPS provides a fast and simple survivability mechanism. It is easier for a network operator to understand the
network status (e.g., active network topology) with EPS than with other survivability mechanisms such as RSTP.
G.8031 specifies linear 1+1 protection switching architecture and linear 1:1 protection switching architecture.
The ETH-APS defined in Y.1731 is used as a signaling channel.
G.8031 (2006) Amd. 1renamed EPS to ELPS.
ERP instance
An entity that is responsible for the protection of a subset of the VLANs that transport traffic over the physical
Ethernet ring. Each ERP instance is independent of other ERP instances that may be configured on the physical
Ethernet ring. Per ITU-T Rec.G.8032/Y.1344 (03/2010).
ERPS
ERPS is an abbreviation for Ethernet ring protection switching. Recommendation ITU-T G.8032/Y.1344 defines
the automatic protection switching (APS) protocol and protection switching mechanisms for ETH layer Ethernet
ring topologies. Included are details on Ethernet ring protection characteristics and architectures, and the Ring
APS (R-APS) protocol. The protection protocol defined in this Recommendation enables protected point-to-
point, point-to-multipoint and multipoint-to-multipoint connectivity within a ring or interconnected rings, called
"multi-ring/ladder network" topology. The ETH layer ring maps to the physical layer ring structure.
The ERPS effort at ITU-T under G.8032 is to provide sub-50ms protection and recovery switching for Ethernet
traffic in a ring topology and at the same time ensuring that there are no loops formed at the Ethernet layer.
G.8032v1 supported a single ring topology and G.8032v2 supports multiple rings/ladder topology.
ERPS specifies protection switching mechanisms and a protocol for Ethernet layer network (ETH) rings.
Ethernet Rings can provide wide-area multipoint connectivity more economically due to their reduced number of
