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MATHEMATICAL EVOLUTIONS FOR RISK MANAGEMENT: THETARAY ANOMALY DETECTION ALGORITHMS ARE A GAME CHANGER

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MPLS-TP FOR MISSION-CRITICAL

NETWORKS

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MAINTAINING TDM PERFORMANCE OVER PACKET NETWORKS

Mission-critical communication networks serve strategic national assets. Energy (electricity, Gas & Oil, nuclear),

transportation, water, government agencies and military organizations are all considered critical infrastructures. The key

attributes for their communication networks are reliability, resiliency, and security. Therefore, it is not surprising that they

would try to avoid any change from the highly-trusted TDM-based infrastructure to a new packet-based one. However,

this shift is inevitable, since TDM-based communication equipment is reaching its end-of-life state and is becoming too

expensive to maintain.

The inevitable move to packet poses new challenges to strategic industries. These include increased security threats,

higher network complexity, and above all, maintaining TDM-predictable and deterministic performance over the packet

infrastructure.

MPLS-TP (MPLS Transport Profile) is the most widely accepted

technology as the successor for maintaining TDM transport

attributes. In this paper, we will outline the key differences between

MPLS-TP and IP/MPLS, with special focus on the implications for

mission-critical networks. We will present the features that are

common to the two technologies that make them interoperable.

The paper will also indicate which features were discarded and

which functionalities were added to maintain TDM performance

attributes over the packet infrastructure. Ultimately, we can see that

MPLS-TP and IP/MPLS are complementarynot competing

technologies.

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RELIABILITY enables end-user services to run on transport

layers that comply with stringent resiliency and

recovery constraints.

SCALABILITY enables the coordination of subscribers, service

providers, and operators to achieve Carrier-Ethernet

based data connectivity between multiple subscriber

sites across multiple operator networks.

Ethernet has been the standard packet technology in the LAN. Therefore, it was the natural choice for service

providers who want to expand packet technology to the WAN. However, native Ethernet has a number of weaknesses

that disqualify it from maintaining carrier-grade quality. Many of them are rooted in the connectionless nature of the

technology, which does not support deterministic behavior. As a result, native Ethernet performs restoration relatively

slowly, has limited scalability, cannot guarantee performance parameters, and does not support service management. To

address these issues, MEF (Metro Ethernet Forum) defined a new class of Ethernet Carrier Ethernetwhich features

five key attributes:

FROM NATIVE ETHERNET TO CARRIER ETHERNET

STANDARDIZED SERVICES enables the coordination of subscribers, service providers,

and operators to achieve Carrier-Ethernet based data

connectivity between multiple subscriber sites across

multiple operator networks.

SERVICE MANAGEMENT enables service providers to roll out, maintain, and

troubleshoot data-connectivity services in a

cost-effective and timely manner.

QUALITY OF SERVICE enables a single network to run multiple services to

multiple end-users, running a wide variety of applications

with different bandwidth and latency requirements. It

also provides the required tools to ensure that services

maintain performance requirements according to Service

Level Specifications (SLS).

CARRIER

ETHERNET

When MEF defined the attributes for Carrier Ethernet compliance,

it did not define the implementation method.

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MPLS (MULTI-PROTOCOL LABEL SWITCHING)

MPLS-TP (MPLS TRANSPORT PROFILE)

MPLS-TP AND IP/MPLS COMPARISON

Standardized by the IETF, MPLS is a scalable protocol-agnostic mechanism designed to carry circuit and packet traffic

over virtual circuits, known as Label Switched Paths (LSPs). MPLS makes packet-forwarding decisions, based on the

contents of the label, without examining the packet payload and is considered as a layer between the traditional definitions

of Layer 2 and Layer 3.

MPLS (also known as IP/MPLS) was originally developed to facilitate packet forwarding by using label switching. It also

has additional attributes, like connection establishment, improved network resiliency, and OAM functions. These all

help overcome some of native Ethernet transport shortcomings. However, MPLS has several major deficiencies when

implemented in transport networks. These deficiencies became the drive for the development of the MPLS Transport

Profile (MPLS-TP).

MPLS-TP is the result of a joint effort by IETF and ITU-T. The drive behind it is to overcome the drawbacks of IP/MPLS

when used for metro transport networks.

MPLS-TP is a simplified version of IP/MPLS that is optimized for transport networks. MPLS-TP is both a subset and an

extension of IP/MPLS. The basic label-based packet forwarding is retained. However, some of the complex

IP/MPLS functionalities that do not support deterministic performance or that are not connection-oriented were

removed. Also, other transport features to facilitate operation and visibility were added. As a result,

MPLS-TP is strictly connection-oriented and does not rely on IP forwarding or routing. Nevertheless, MPLS-TP and IP/

MPLS are interoperable, enabling their use within the same network.

MPLS-TP key objectives are:

To enable MPLS deployment in a transport network and

to operate in a similar manner to existing TDM transport

technologies (SDH/SONET)

To enable MPLS support of packet transport services with a

similar degree of predictability, reliability, and OAM to that of

existing transport networks.

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COMMON FEATURES

MPLS-TP and IP/MPLS share some key functionality.

MULTI-PROTOCOL

MPLS is L2-protocol independent and, therefore, is agnostic to the underlying transport protocols. In addition, using a

mechanism called pseudowire (PW), it is also agnostic to services running on top of it. MPLS PW is a mechanism that

emulates the essential attributes of a native service, while transporting over a packet switched network. With MPLS PW,

native services like ATM, Frame Relay, PDH, SONET/SDH, Ethernet, and others, are tunneled through the packet

network. Multi-protocol support is well suited to the mixed-technology environment of mission-critical networks (like

TDM-based SCADA and packet-based SCADA) and allows gradual and controlled transition.

LABEL SWITCHING

In traditional IP routing, each router makes independent routing decisions and determines the next hop, based on its

routing table. With MPLS, on the other hand, a path (LSP) from the source to the final destination is predetermined and

a label is applied to it.

The first device in the path adds the MPLS label. Subsequent devices along the path use this label to route the traffic,

without any additional IP lookups. The label switching process is considered faster and simpler to implement than routing.

The final destination device removes the label and the packet is delivered via normal IP routing, in the case of IP service.

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ADDED FEATURES

In order to maintain TDM-like deterministic performance, visibility and control, several features

that do not exist in IP/MPLS were added in MPLS-TP.

These additional features or modifications of existing IP/MPLS features are divided into four responsibilities:

CONTROL PLANE

for label distribution and LSP setup

OAM

for monitoring and

troubleshooting

information

PROTECTION AND

RESILIENCY

for maintaining undisrupted

service

DATA PLANE

for packet forwarding

DATA PLANE

Bidirectional LSPs

A key difference bet