Multiprotocol Label Switching (MPLS) was designed to provide a unified data-carrying service for both circuit-switched and packet-switched networks which provide a datagram service model.
Why do we care?
MPLS is an architecture for fast packet switching and routing, and has become an important protocol of the core network for the next generation networking (NGN).
Functionality
MPLS controls the flow of packet traffic through networks by specifying information used for packet designation, routing, forwarding and switching.
Explanatory example required here.
These traffic flows can be managed at various granularity levels.
Explanatory example required here.
MPLS is independent of the layer 2 and layer 3 protocols, such as ATM and IP.
MPLS
Diagram required showing where MPLS would be deployed in such a network.
MPLS Features
highly scalable,
protocol agnostic,
packet-switched networking mechanism.
End-to-end transfer can be performed across
Label refers to the fact that in MPLS, labels are assigned to data packets for the purpose of determining packet forwarding. Due to the presence of these labels, packet contents do not need to be inspected in order to make packet-forwarding decisions.
Example:
Details of the Labels in MPLS
Benefits of MPLS
Main benefits of using Labels, to eliminate :-
(1) dependence on a particular technology, such as
ATM,
frame relay,
SONET or Ethernet.
(2) the need for multiple Layer 2 networks to satisfy different types of traffic.
OSI Layer where operation of MPLS is defined:
MPLS operates at an OSI Model layer that is generally considered to lie between traditional definitions of Layer 2 (Data Link Layer) and Layer 3 (Network Layer).
So, MPLS is often referred to with the jargon term, “Layer 2.5” protocol. For networkers, what does this actually refer to?
What Layer 2 functions are incorporated in the MPLS architecture?
What Layer 3 functions are incorporated in the MPLS architecture?
Types of packets carried:
MPLS can be used to carry many different kinds of traffic, including IP packets, native ATM frames, Synchronous Optical Network (SONET), and Ethernet frames.
Previous technologies with the same goal:
A number of different technologies were previously deployed with essentially identical goals, such as frame relay an ATM.
ATM
Strengths & weaknesses of ATM informed the development of MPLS technology.
Many network engineers agree that ATM should be replaced with a protocol that requires less overhead, while providing connection-oriented services for variable-length frames.
MPLS technologies have evolved with the strengths and weaknesses of ATM in mind.
Frame Relay
Will MPLS completely replace these technologies in the future?
In particular, MPLS dispenses with the cell-switching and signaling-protocol baggage of ATM.
The small size of ATM cells has become less of an advantage since the advent of optical fibre networks, which provide such high speed (greater than 40Gbit/sec., so full-length 1500 byte packets do not incur significant real-time queuing delays (the need to reduce such delays — e.g., to support voice traffic — which was the motivation for the cell nature of ATM).
At the same time, MPLS attempts to preserve the traffic engineering and out-of-band control that made frame relay and ATM attractive for deploying large-scale networks.
While the traffic management benefits (increased reliability, better performance) of migrating to MPLS are valuable advantages, there is a significant loss of visibility and access into the MPLS cloud for IT departments.