1. MPLS introduction

MPLS is a protocol that allows fast tracersal of a network by labeling the data packets. MPLS stands for Multi Protocol Label Switching. MPLS switches packets, based on a label, instead of routing data. MPLS can run IP, but also other layer 2 protocols like ATM etcetera.

Rather than trying to recreate a lab from scratch, I decided to replay an MPLS lab from Socketready (http://socketready.com/2011/03/05/mpls-configuration-guide/; link is dead) with some minor adjustments. Socketready is no longer available. Therefore, you can get the configs from the appendix.

MPLS is desribed in RFC3031. There are a number of benefits, compared to traditional WAN:

  • Low cost with maximum redundancy
  • Layer3-extension over the WAN
  • The network is owned by the ISP however, it is logically an extension to your network.
  • Packets are routed through the WAN instead of circuit switched.
  • With routing comes convergence, traffic shaping (QoS and policies), and multiple routing protocols.

Some definitions:

  • LSR - Label Switching Router
  • PE - Provider Edge
  • CE - Customer Edge

MPLS operates between layer2 and layer 3; it is sometimes called layer 2.5. Packets through the MPLS network are routed through the MPLS netwok, based on a label; a packet moving across the WAN can have multiple labels. Ethernet Type is 0x8847(for MPLS unicast)
Ethernet, PPP, atm etc
physical layer