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)
3
|
IP
|
2.5
|
MPLS
|
2
|
Ethernet, PPP, atm etc
|
1
|
physical layer
|