E-NNI support for single node ASON domains

Overview

An automatically switched optical network (ASON) consists of a transport plane for the transport of customer traffic, and a control plane for network administration and configuration. The basic functions of a control plane for an ASON are signaling and routing. Signaling is used to establish, teardown and maintain end-to-end connections. Routing is used to select the most appropriate path between and within network domains. These functions take place over the singaling communications network (SCN)

SCN description

Network elements support a data communications network for transport of management messages between NEs and OSs, termed the Management Communications Network (MCN). However, optical control plane capable NEs require a data communications network for transport of control plane signaling and routing messages between NEs. This is termed the Signaling Communications Network (SCN).

The SCN is an IP-based network with communication channels called (IP) control channels. Control channel connections can be over DCC or LAN via the external IP network.

Interfaces

The logical interfaces of an SCN are defined by ITU-T G.807 as:

• User-Network Interface (UNI) - An interface for communication between a user (client) and a service provider (transport network).

• External Network-to-Network Interface (ENNI) - An interface for communication between control domains.

• Network-to-Network Interface (I-NNI) - An interface for communication within a control domain.

ASON access domain connections

An ASON access domain may consist of a single node or multiple nodes. Within a multi-node access domain, SCN links between the nodes are interconnected via I-NNI. SCN links between domains are interconnected via E-NNI. Alcatel-Lucent 1665 DMXtend and Alcatel-Lucent 1665 DMX support E-NNI to provide control plane connections over the inter-domain links between single-node access domains and a core domain, as shown in Figure 3-23, Single-node access domain E-NNI control plane connections to a core domain. I-NNI links within multi-node domains are not supported.

Control channel physical interface support

Alcatel-Lucent 1665 DMXtend and Alcatel-Lucent 1665 DMX support both LAN (LAN-3) and DCC (Line DCC) as the physical interfaces of SCN control channels. The following illustration shows the basic IP stack diagram for SCN. Note that this SCN IP stack is a separate stack instance from the current IP stack used for the management communications network (MCN). By default, both LAN (LAN-3) and line DCC are disabled.

E-NNI control plane connection

Figure 3-23, Single-node access domain E-NNI control plane connections to a core domain illustrates an example of a Alcatel-Lucent 1665 DMXtend E-NNI single-node access domain control plane connection to an I-NNI capable edge node of a core domain. In this example, Alcatel-Lucent 1665 DMXtend NEs serve as edge nodes and Alcatel-Lucent 1675 LambdaUnite MSS or other vendors’ NEs serve as core nodes. The core domain nodes support I-NNI within the domain and E-NNI between the domains. The transport topology for the E-NNI is SONET linear, supporting 0x1 unprotected and line 1+1 protection schemes. For I-NNI the topology is mesh.

As depicted in Figure 3-23, Single-node access domain E-NNI control plane connections to a core domain, an end-to-end connection between edge ports consists of three connection segments - two E-NNI segments and one I-NNI segment. E-NNI signaling is responsible for establishing the E-NNI portion of the end-to-end connection, as well as providing additional information that conveys the end-to-end request to the border nodes in the core for establishing the I-NNI portion of the end-to-end connection.

Figure 3-23: Single-node access domain E-NNI control plane connections to a core domain

In the context of the E-NNI, the SCN provides control channels between the E-NNI interface on the upstream signaling router (eNNI-U) and the E-NNI interface on the downstream signaling router (eNNI-D) over DCC or a LAN using an external IP network.

This capability is supported on Alcatel-Lucent 1665 DMXtends equipped with LNW84 and LNW141 VLF circuit packs. It is also supported on the low-speed interfaces of the LNW62 and LNW55 OLIUs, when installed in shelves equipped with VLF Main circuit packs.

Service application

The primary service offered by such an ASON is the ability to create and delete end-to-end SONET TDM soft permanent connections (SPCs) by creating or deleting the link between an ingress and an egress client-facing edge port. The connection setup and release are invoked by TL1 commands sent to the source edge node from the OS, and carried out by the control plane (E-NNI and I-NNI). The connection can be either unidirectional or bi-directional. The signal rates for connections are restricted to STS-1, STS-3c, STS-12c and STS-48c.