DIT

Dar es Salaam institute of Technology (DIT)

ETU 07420

Switching Systems

Ally, J

jumannea@gmail.com

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MPLS Fundamentals

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MPLS Contents Data networking and need for MPLS

Basic concepts and working of MPLS

Label - Allocation and Distribution

MPLS Forwarding

Traditional Data Networks

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Data Network Concept A data network is a set of nodes connected by

links. Nodes could be Routers, Switches, Multiplexers

connected by links from 64 kbps till 10 gigabit ethernet.

Fundamental property of data networks is multiplexing.

Two main types of multiplexing are - Time Division Multiplexing ( TDM ) Statistical Multiplexing ( StatMux)

Others are FDM , WDM etc.

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Data Network Concept TDM is practice of allocating certain amount of

time on a physical circuit for a particular connection. This translates to bandwidth allocation as the circuits are fixed rate.

Examples for TDM being E1 (2Mbps circuit) , SDH

Bandwidth permanently allocated for a connection whether connection used ( carrying traffic) or not.

No traffic congestion issues, bandwidth guaranteed

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Data Network Concept Statmux - is the practice of sharing available

bandwidth between all users. Examples are : IP , Frame Relay, ATM & now

MPLS. It works by way of dividing traffic (data) into

discrete units which are handled separately. IP units are Packets, ATM units are Cells, Frame Relay units are Frames.

Better utilisation of bandwidth, allows oversubscription.

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Data Network Concept Introduces resource contention. Therefore statmux technologies have to deal with

Buffering of data units Queuing of data units Dropping of data units

Running one statmux technology over other eg. IP over ATM . Mechanisms available in one technology to deal with contention does not translate properly into another.

Requirement of translating Layer 3 contention controls mechanisms to Layer 2.

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Data Network Concept

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Traditional IP Forwarding

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Traditional IP Forwarding

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Virtual Connection

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Virtual Connection

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ATM Switching Process

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MPLS Origin

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MPLS Origin To bring advantages of connection oriented

protocols to packet switched networks.

Faster switching - Replace IP header with short and fixed-length labels as forwarding basis.

To substitute ATM & Frame Relay & provide Integrated services with QoS without the overhead of call segmentation.

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MPLS Origin Technology combining the advantages of ATM

and IP

Layer 3 routing – Scalable and Flexible Layer 2 switching – Reliable and Traffic Engineering capability MPLS - Multi-Protocol Label Switching

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Multiple Protocol Support

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MPLS MPLS is the binding of the control plane at the bottom

of the network layer with the data forwarding plane at the top of data link layer.

MPLS is a hybrid of a traditional network layer-3 routing protocols and layer-2 switching technologies

MPLS is not a new network layer protocol because it does not have its own routing capabilities and addressing schemes

MPLS is designed to work over many of the data layer technologies that provides requisite layer-2 addressing and functionality

MPLS is a “Layer 2.5 Technology”

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MPLS Data Encapsulation

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Label Position in Packet

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Basic Working Process of MPLS

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MPLS Label

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MPLS Devices

MPLS uses Label Switched Path (LSP) for layer-2 forwarding.

The path is setup using signaling protocols like Label Distribution Protocol (LDP) and routing protocols.

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MPLS Terminology LER -Label Edge Router

Examines inbound IP packets and assigns them to an FEC Generates MPLS header and assigns initial label i.e Ingress

& Egress LSR - Label Switch Router

Forwards MPLS packets using Label swapping Table lookup in Label Information Base (LIB)

LSP - Label Switch Path Path thro’ MPLS network setup by signaling protocol (LDP) LSP’s are unidirectional , roughly equivalent to VC LSP setup is based on FEC criteria LSP may be different from IGP path

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MPLS Terminology Forwarding Equivalence Class (FEC) is a stream of

IP packets that are forwarded over the same path, treated in the same manner and mapped to the same label. ( Same QoS ; Same Next Hop; Same Path)

LDP ( Label Distribution Protocol) associates a set of destinations with each LSP

Packets could be assigned to a LSP based on Combination of destination address and application

type Combination of destination address and source

address

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Label Processing Push

Add a new label to the top of the packet The TTL, stack and CoS fields are derived from the IP packet

header Can be performed on an existing MPLS packet-Label

Stacking Pop

Remove the label TTL is copied from the label to the IP header IP packet is forwarded as a native IP packet

Swap Replace the label at the top of the label stack with a new label The TTL, stack and CoS fields are copied from the previous label

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MTNL MPLS Network - Mumbai

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Thanks!

Technology changes but communication lasts.