Electrosmart.Net

Multi Protocol Layered Switching [MPLS]

Multi Protocol Layered Switching [MPLS] was to developed to overcome the inherent problems of IP over ATM, this is:

Two independently different network technologies that do not mesh together well
Complex algorithms required to determine and find the next hop
Does not support Multi-Level Servies - providing differentiated QoS products
Congestion and failure are common - causing excessive error messages

MPLS

MPLS solution delivered the advantages of connection oriented protocols to packet switched networks, providing an integrated QoS service without the overhead of cell segmentation and switching.

The switching in MPLS is significantly less complex, and significantly faster.

The MPLS Header consists of one or more lables added to the IP Datagram between Layer 2 [Ethernet or ATM] and the IP Layer. The added labels are known as the Label Stack.

Components of MPLS

Label Value - the identifier by which the Label Switch Router determines the next hop
QoS - determines class of service
Flag - whether the label is the bottom one of the stack
TTL - works as in IP

Label Switched Path [LSP]

The LSP starts in the network at an Label Edge Router [LER] and following along the path via Label Switch Routers [LSR] to terminates at the exit LER.

A data packet enters the network at the entry LER
The LER determines the Forwarding Equivalence Class [FEC] and defines the LSP it must take to reach its destination either via:
1. Hop By Hop Path - LER attaches one label and forwards to next LSR, which swaps out the label for the next LSR.
2. Explicit Route - the LER attaches a stack of labels identifying the full path, each LSR 'pops' the top label and forwards it on to the next hop.
The FEC is determined by the IP Address:

FEC_1 = VoIP and will travel along the most optimal LSP
Other packets will travel along the standard LSP

Benefits of MPLS

Advantages for Network Managers

Supports uniform and convenient traffic engineering
More efficient routing – single protocol and more efficient routing tables
Administrators do not need to have proficiency in ATM networks and underlying Layer 2 protocols
Removes complex algorithmic calculations and complexity from network
Futureproof - Works independently of Layer 2 Protocol – making it easier to accommodate future technologies and adjusting to Layer 3 Protocols [such as IPv6] requires only minor changes in LER’s

Advantages for Users

Easy creation of VPNs [ Virtual Private Networks]
Improved quality - native support for QoS and constant bandwidth assurance.

Next: Converged IP/MPLS