The idea on which is based MPLS is to route IP packets based on a label, which represents the name of a virtual circuit (circuit switching).
The switching circuit is very fast packet switching-based IP longest prefix match (can be handled in hardware).
Thanks to the switching circuit is also possible to route the packet according to the preferred policy, as it is possible to impose the path.
To realize this technology will need different devices:
-LSR (Label Switch Router) have no connection to external devices to the MPLS network. They have a table (for each port) that indicates the routing (given a label on a port x x1, x2 where the door is indicated route the packet and the new label y).
Label-edge routers, which are designed to add / remove the label to the incoming IP packets according to a table (for a destination I have to put a label of x).
Label-Switched Path (LSP) are virtual paths (tunnels) that leave dall'Ingress the Egress router to router.
There are different versions:
-Allows you to label MPlambaS able to route packets on wavelength switched paths.
-G-MPLS allows a packet / cell / circuit / lambda switching. These additional features are implemented by configuring the switches manually.
-Ability to manage flows at different levels of granularity (in terms of machine / application or subnets). This means that it can take different paths depending on the type of packet (WEB / VOIP), or depending on the destination.
-Independence of the level 2/3. Although it is normally used with IP.
-Interfaces with existing protocols.
Is-fold in other MPLS packets, so as to ensure virtual circuits between different operators.
-If you use ATM or frame relay in tandem with the MPLS label is derived by ATM or Frame Relay.
Each package consists of:
3ben-class of service (priority).
1bit-flag indicates whether the last MPLS header.
-8 Bit TTL indicates the time to live.