Technical data

Release 5.0.x Turin Networks Page 6-1
6.1 Introduction
This section describes the functionality of the Local Equipment Interconnects (LEIs) and how they affect
the bandwidth and equipment capacity within a node.
6.2 LEI (Local Equipment Interconnect)
The LEI is a redundant, protected, bidirectional STS-48 facility that connects the TE-2020 Main Shelf to
the OTS2 , ETS1, or the ETS2 tributary shelves. A single LEI connection is made up of two fully redun-
dant cables. The TE-2020 Main Shelf supports four LEI connections (8 cables). The OTS2 is capable of
supporting up to 48 STS-1s worth of bandwidth using a single LEI connection or up to 192 STS-1s worth
of bandwidth using up to 4 LEI connections. The ETS1 and ETS2 shelves are equipped with only one LEI
with a maximum drop capacity of 48 STS-1s.
6.3 LEI Protection
Both the working and protect STS-48 signals within an LEI carry identical traffic. LEI protection switch-
ing is performed at the destination element on a per STS-48 basis. Both the upper and lower CCT cards
within the shelf select traffic from the same LEI, either active or protect. The protection switching is unidi-
rectional and non-revertive.
6.4 Hairpinning within a Node
Hairpinning is a term used to describe traffic that enters on a tributary interface within a node (TE-2020
Main Shelf, OTS2, ETS1, or ETS2) and leaves the same node on a second tributary interface (i.e., not
being used on the transport facility). For example, a signal may enter on a OC-3 PLM in one OTS2 in the
form of an STS-1 and exit the node on another OC-3 PLM or any other interface within the shelf in the
same OTS2. When utilizing a hairpin connection, the LEI bandwidth is not affected. Hairpinning can be
performed on DS1 connections from an ETS2 shelf if VT grooming is not performed. VT grooming is per-
formed on the TE-2020 Main Shelf so LEI bandwidth is affected.
6.5 Bandwidth Allocation
The bandwidth allocation between the tributary shelves and the TE-2020 Main Shelf is assigned according
to the bandwidth specified in a connection. If an OTS2 receives a request for an STS-1 connection on a 4-
port OC-12 PLM (capable of supporting a full 2.488Gbps, i.e., 4 x OC-12), only one STS-1 capacity on the
LEI is used.
With this flexability, an OTS2 shelf can be equipped with four 4-port OC12 PLMs (capable of passing 192
STS-1s) interconnecting multiple ring systems and only utilize one LEI as long as a maximum of 48 STS-
1s are not exceeded between the OTS2 and the Main Shelf. A mix of OC-12, OC-3, and OC-48 PLMs can
be used in the same example, interconnecting multiple optical wavelength rings within the OTS2 without
affecting the bandwidth between it and the Main Shelf. If more bandwidth or connections are required
between the Main Shelf and an OTS2, additional LEIs will need to be connected.