MPLS (Multi-Protocol Label Switching)

CCIE Jan 9, 2011

OK, so having known about MPLS for a few years and actually get a provided service in my work environment as well as the fact it is on the CCIE R&S blueprint I thought I should get a much better understanding of how it works and the various terminology’s. My notes so far;

The benifits of MPLS;

  • The use of one unified network infrastructure
  • Better IP over ATM integration
  • Border Gateway Protocol (BGP)-free core
  • The peer-to-peer model for MPLS VPN
  • Optimal traffic flow
  • Traffic engineering
Some MPLS applications;
- Traffic engineering (MPLS TE) - MPLS VPN - AToM (Any Transport over MPLS) - VPLS - Unicast IP Routing - Multicast IP routing - QoS
What are the advantages of the MPLS VPN solution for the service provider over all the other
VPN solutions?
- MPLS VPN allows for easy provisioning of sites and allows for optimal traffic flow in the backbone network at all times.
Four technologies that can be used to carry IP over ATM are as follows:
- RFC 1483 - LANE - MPOA - MPLS
Two pre-MPLS protocols that use label switching.
- ATM - Frame Relay
The ATM switches need an IP routing protocol and a label distribution protocol to operate MPLS.
To ensure optimal traffic flow between all the customer sites in an ATM or Frame Relay overlay network the connectivity between the customer sites needs to be a full mesh of virtual circuits.
FEC = Forwarding Equlivalance Class
MPLS VPNs are highly scaleable and support  IP Services such as;
- Multicast - Quality of QoS - Telephany support within a VPN - Centrilised services including content and web hosting VPN
AToM transports Layer-2  traffic over an IP or MPLS backbone

AT0M – accommodates many Layer-2 frames including Ethernet, Frame Relay, ATM, PPP and HDLC

Examples of AToM;

  • Ethernet over MPLS (EoMPS) – Applications include TLS and VPLS
  • ATM over MPLS – supports 2 types of transport mechanisms of ATM frames across an MPLS core: AAL5-over-MPLS & Cell-relay modes.
  • Frame Relay over MPLS


Rob Edwards

Northern (UK) chap focusing on platforms, automation, cloud and cloud native applications. Recovering network engineer, although it turns out networking is as important, if not more, now than before!