Managed Leased Line Network

Managed Leased Line Network

Introduction

Leased Line & MLLN

A leased line is a telecommunications path between two points that is available for 24 hours a day for use by a designated user (Individual or company).

In the traditional leased line which can be a physical path owned by the user or rented from BSNL there is no active monitoring of the faults and downtime.

MLLN is able to provide roundthe- clock network monitoring by the introduction of the following network elements.

Network Termination Unit NTU) : These are customer premises equipment.

Versatile MUX : These equipments multiplexes all ports coming from other devices.

Digital Cross Connect: Equipment that cross connects similar capacity of ports specified by the network operator.

Network Management System: Management functions of the network.

These elements are explained in the subsequent chapters.

Functional Requirement of MLLN:

1. Speedy end-to-end service provisioning

2. Round the clock performance monitoring

3. Auto re-routing in the case of failure in the circuit

4. Automated alarm/fault management

5. Accounting and security management

6. On-demand bandwidth availability up to 2 Mbps

7. Centrally manage all elements of the network

8. Network Partitioning

9. Auto Recovery

10. Virtual private Networking.

Advantages of MLLN:

1. Voice, Data & Video transmission over the same media

2. Fast and simple implementation of new application by adding /plugging the units

3. Transparent, protocol-independent connections

4. Modular system

5. Optimization of transmission bandwidth with grooming and compression

6. Centralized control and network management

7. SDH & PDH solution

MLLN Structure of BSNL

MLLN is planned as 3 tier structure consisting of aggregation and connectivity at different levels.

1. Central Node: is responsible for the operation of NMS, Connectivity to second stage and aggregation of leased lines.

2. 2nd Stage : Located in major cities where demand for leased line is high , connectivity to 3rd stages and Aggregation of leased lines.

3. 3rd Stage: Located at smaller cities, where demand for leased line is low and aggregation of leased line.

Solutions Provided By MLLN

Features of BSNL MLLN Network:

The following features of BSNL MLLN make it possible to provide powerful solutions to telecommunication requirements.

1. Mesh connectivity between SR DXCs of the same region.

2. All SR-DXCs connected to RDXCs.

3. Major SSAs have been provided with SS DXCs.

4. Remote Operator Terminal (ROT) planned for every station having more than 30 leased circuits.

Business Service Solution:

Business Organizations that want to change and upgrade the way they function by implementing Wide Area Network (WAN) in their organization can use MLLN to achieve the same. The following features of MLLN facilitate the same.

1. MLLN integrates all transmission protocol to support voice, data & video

2. LAN of one City can be connected to LAN of another City.

3. PABX of one city can be connected to PABX of another city.

4. 64 kbps DTE can be managed from any of the DTE in the network.

5. All networks are manageable from NMS.

Mobile Transport Solution:

MLLN can provide mobile transport solutions, which are compatible with radio base stations of all sizes.

1. Radio station can be connected using ring, star or chain network architectures, according to capacity.

2. Voice compression, grooming and consolidation is possible to use available band width.

3. At the Mobile Switching Center (MSC), the use of switch ports is optimized using high-capacity, non-blocking cross connection nodes.

Key Elements of MLLN

Digital Cross Connect (DXC):

A DXC or DACC device is equipped with several trunk interfaces. This equipment cross connects similar capacity of ports specified by the network operator. Setting up and releasing a connection is provided by the operator and not by the subscriber.

Features of Digital Cross Connects (DXC)

DXC Capacity:

DXC (64 ports up gradable to 128 ports)

DXC (96 ports up gradable to 128 ports)

DXC (128 ports up gradable to 256 ports)

DXC (256 ports)

1/0 cross-connect capability.

Non-Blocking architecture

Redundancy

Power supply

Switch Matrix

Cross connect memory

Expansion to be made possible by addition of cards only.

Fully managed from centralized NMS.

Port capacity of different systems:

ElementsCapacity

Micro Node (DXC)Small capacity cross-connection devices.

Mini Node (DXC)Access multiplexers or small capacity cross connection equipment (slot limited)

Midi Node (DXC)Flexible Mul

Digital Multiplexer (Versatile MUX):

This network element multiplexes that all tributaries (ports ) coming from other devices and forms a higher hierarchy level output at the specified port.

The basic node of the MartisDXX is offered to meet the VMUX requirements.

Expansion to be made possible on the same chassis by the addition of cards.

3 Types of VMUX

Type I

Type II

Type III

Hotline circuits can be extended from VMUX

Point to Point & Point to Multipoint circuit possible.

HDSL driving distance:

3.5 km at 2Mbps

5 km at 1 Mbps

7 km for 64/128 kbps (at 0.5 mm dia copper cable)

Key Requirement of VMUX

VMUx Type -1., Type 2, Type 3 with the configurations given below.

TypeInitial RequirementsExpansion Requirement (Incremental)

64 kbpsNx 64 kbsHotlineE164 kbpsNx 64 kbsHotlineE1

VMUX Type 1328101646

VMUX Type 216441646

VMUX Type 384448444

Network Termination Unit (NTU)

Base band modems (Network Terminating Units = NTUs) are usually customer premises equipment (CPE)

NTUs can also be used for standalone point-to-point connections without the Tellabs 8100 point to point network.

NTUs also allow use of the existing copper cables (twisted pair) to carry digital traffic over medium distances (~5km) and high speeds capacity. Different type of NTU are

64/128 kbps NTU with V.35

64/128 kbps NTU with G.703

Nx64 kbps NTU with V.35

Nx64 kbps NTU with G.703

Nx64 kbps NTU with 10/100 Ethernet Interface.

Base Band NTUs (SDSL Modems) are CPE of the networks

Allows use of existing telecom copper cables for digital traffic.

STU-160 & STU-2304 base band table top modems are used in our network.

STU-160, 64 Kbps NTU can be connected up to the distance of 8.5 kms

STU-2304, N*64 Kbps NTU can be connected up to the distance of kms

CTU-S,CTU-R modems with V.35/G.703/etherne interfaces available.

NTUs are configured from ROT

NTUs are working on 230 V , 50 Hz-AC power supply.

Architecture of MLLN:

Connection Diagram:

Description:

The figure shows the network configuration of the MLLN network.

The Network Terminating Unit (NTU) is the subscriber premises equipment of the MLLN. The NTU supports G.703/ V.35/Ethernet interfaces.

The NTU can be configured to have any bandwidth from 64kbps to N x 64 kbps fashion.

The NTU is connected to the Versatile MUX (V-MUX) that provides concentration of the data coming from several NTUs placed at different customer premises.

Digital Cross Connect (DXC) is the highest level equipment that provides circuit switching of the data between different stations. The V-MUXs are connected to the DXC. The DXCs are also connected to one another. The DXC is in a 3 Layer Architecture with

R-DXC : Regional DXC are connected in Mesh architecture

SR-DXC : Sub Regional DXC

SS-DXC : Secondary Switching Area DXC

The Network Management System (NMS), is located at Bangalore with backup at Pune for disaster management.

The Remote Operating Terminal (ROT) can be connected to any VMUX in the system and is used to fault monitoring, configuration and service provisioning.

Network Elements:

A node can be described as a digital multiplexer equipped with several trunk interfaces and a digital cross-connect device equipped with several channel interfaces.

The following are different types of nodes

NodeApplication

Cluster NodeHigh Capacity Cross Connect

Basic NodeAccess to the Network requires lot of tributary port capacity. Can also used as as a cross connect device.

Midi NodeAccess multiplexer or low capacity cross-connect equipment.

Micro NodeVery small capacity cross-connection especially in mobile networks.

NTUCustomer premises equipment

Mini NodeCan be used as a separate cross connect device controlled and supervised locally.

Accelerator NodeOperated with network manager.

Switch NodeIt is an NE with ADM , LTM & SDXC

Network Management:

General:

Tellabs 8100 Network Management System (NMS) is a tool for a network operator to build up and maintain a Tellabs_8100 managed access system network.

The operator can create and test connections , monitor faults, monitor performance statistics and manage customer accounting.

There are also automatic fault recovery for faulty connections in the Tellabs 8100 system network. A large network can be divided into small regional sub networks to make managing easier.

The tellabs 8100 manager applications are implemented as a set of interactive and non interactive application components using client-server architecture.

The interactive components (clients) make up the graphical user interface of the network management system. The non-interactive components (servers) perform background tasks and provide services to the interactive components. The management data is stored in a relational database.

Network Editor:

Network Editor is a database tool providing facilities to define the topology and configuration of the network. It also allows the user to run other network management tools which provides facilities for editing the individual nodes, interface binding and editing the control network.

Network editor displays network objects graphically and it has text-based dialogs to set and change parameters of the objects.

The network configuration is determined by placing nodes and modems to the network, equipping nodes with units, equipping units with interface modules and adding trunks to connect nodes.

Navigator consists of three view windows, toolbar, window menu and a number of utility dialogs. View windows are:

Tree View window for easy navigation in the network.

List view window for reporting all or selected elements of the network

List View window for displaying the elements graphically.

The network editor is shown in the next tab.

Network Editor (Views) :

Node Manager:

Node Manager is a tool that provides facilities to manage the network elements: nodes, units, interfaces & NTUs . The element management facilities include parameter setting, fault and error monitoring, testing and performance monitoring.

Node Manager is the only application that can also be used in service computer.

In node manager it is also possible to make preplanning before real hardware exists. It means that the network configuration and parameter values read from the database and the changed parameters are updated to database only.

Functioning of MLLN:

Functional Areas & Tools:

Functional AreaTellabs 8100 Manager Tool or Server

Performance ManagementPerformance Management

Node Management

DXX Server

Web Server

Fault ManagementFault Management

Trouble Ticket

Recovery Management

Recovery Simulator (with simulation DB)

Circuit loop Tests

Node Management

Fault Simulator (with simulator DB)

Circuit Fault Monitoring

DXX Server

Recovery Server

Communication Server

Fault Server

Web Reporter

Configuration ManagementNetwork Editor

Router

Circuit Loop Tests

Node Management

VLAN Manager

Unit Software Manager

Network Capacity Calculator

Circuit Simulator (with simulation DB)

Security Management

DXX server

Communication Server

Accounting ManagerSecurity Management

Router

Recovery Manager

Accounting Management

VPN Trunk Accounting

Circuit Lop Tests

Recovery Server

DXX Server

Communication Server

Security ManagementSecurity Management

VPN Authentication.

Fault Management:

General:

The Fault Management Systems (FMS) of the Telllabs 8100 manager is used for monitoring and reporting faults in the Tellabs 8100 system elements. The network element faults are mapped into the respective trunks and circuits so that the operator can easily see how the services are affected by the faults. The Fault Management System offers an operator a real-time view, since the fault monitoring is based on continuous network polling.. In the normal state, the network does not have any faults. However when a fault occurs, it has to be acknowledged

The following points are noteworthy in fault management

The status of the network element is faulty until the reason for the fault is removed or the fault is removed.

The severity of a fault is indicated with color coding.

All the faults are network element specific.

Faults are read from the network elements and stored to the database.

The workstations having FMS check the database once every 6 seconds for faults.

There are two numbers assigned to each fault

General Problem Type (GPT) : assigns a fault to one of the general problem classes

Specific Problem Type (SPT) : is unit specific and identifies the fault in detail.

Fault Status:

Every Fault has two fault status fields:

1. Fault Maintenance Status

PMA = Prompt Maintenance Alarm Red

DMA = Deferred Maintenance Alarm Yellow

MEI = Maintenance Event Information Green

2. Service Status of a fault (S-Alarm, nonS-Aalarm)

S-alarm = service affecting fault (starts for example recovering)

Non S-alarm = non-service affecting fault (starts for example recovering)

Prompt Maintenance alarms are often caused by faulty Tellabs 8100 elements, parameters, cables or connectors. Replacing the faulty object at the site can solve PMAs. PMA faults are colored red by default and they should be taken care of as soon as possible.

Deferred Maintenance alarms is a quality alarm detected by the element causing the alarm. A DMA alarm related to a trunk is often detected as a PMA on the other end if a a faulty device causes the DMA. In other cases the alarm is caused by a fault in the carrier network. DMA faults are nor as severe as PMAs.

Most Maintenance Event information alarms are considered as non-service affecting. However frequency difference for instance might have a major impact on service quality.

Alarms are considered service affecting if they break the circuits or have a major impact on their quality.

Faults in Hardware:

The faults are stored in units volatile flash memories. Every time the unit is reset, the faults disappear from memory. There is room for 50 faults. Once there are 50 faults, the next one will erase the first one.

The Faults of a unit from the hardware can be checked in the Unit Fault Window (UFLT).

There are five different report types in the Unit Fault Window.

1. Fault History Report - reports all faults after last fault history reset

2. Active Fault Report - all active faults in the unit

3. All Monitored Faults - all faults that can occur in the unit

4. Changed Fault report - displays all faults that can occur in the unit.

5. Options menu - refresh of fault information

The Customer Circuit Fault Report displays circuit fault monitoring information for a customer (or all customers). The circuit fault report shows the list of faulty circuits having selected faults. For each circuit, the following information is played.

FieldDescription

NrRow Number

Customer NameCustomer Name

Circuit IDCircuit ID

Circuit NameCircuit Name

Mal StatMaintenance status (PMA, DMA , MEI)

ServiceService status : S if the fault is service affecting, in other cases

StateFault State (ON, OFF)

AckAcknowledgement status (X = fault acknowledgement)

Fault Acknowledgement:

Each fault event must be acknowledged. That means informing the Fault Management that the operator is aware of the alarm. The fault acknowledging is either performed by the operator or by the system automatically. When the fault is acknowledged, the alert indication (blinking stops). Alerting is thus active for an unacknowledged fault even if the fault itself has disappeared.

The corresponding object turns into normal state only after the fault is fixed and the acknowledgement is performed. The fault can be turned into the fault history only after this. The acknowledgement can be made from several windows in the fault report window in the FMS.

The acknowledgement time of the fault and the user name of the operator who acknowledged the fault is stored in the database.

Circuit Fault Monitoring:

The circuit fault monitoring in the Tellabs 8100 network manager enables the operator to get real-time information about the faults of the pre selected groups of circuits called service categories. It includes the continuous supervision of all the circuits that are assigned to a certain service category.

In addition to the pre-defined service categories, can select dynamically customers to be taken under monitoring. All circuits belonging to these customers are supervised automatically from that point.

CFM means rapid end-customer response. For example, in a trunk failure situation, the operator will now be able to rapidly identify the customers and services affected by such a fault.

When the faults are stored in the database, Fault Management processes then in such a way that detected fault events are attached to the circuits which are affected by the fault event, If these circuits belong to a circuit category or a customer, the appearance of corresponding object symbols in the CFM windows directly indicates the severity of the faults by colors and blinking.

CFM monitors only active and unacknowledged faults. Only circuits that are in IN Use state are included.

Conclusion

MLLN in BSNL is implemented by Tellabs equipment at the nodes. The nodes are classified as Cluster, Midi, Mini, Basic Node, Accelerator Node, Switch node depending on their size.

The important network elements of MLLN are NTU, V-MUX, DXC, NMS & ROT.

With these network elements, the MLLN is able to provide the following functions

F Fault Management

C Configuration Mangement

A Accounting Management

P Performance Management

S Security Management

NTU

NTU

VMUX

VMUX

NTU

VMUX

VMUX

NTU

NTU

NTU

DXC

DXC

NMS

NMS

ROT

ROT