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Multiprotocol Label Switching (MPLS)

What is

Wikipedia defines MPLS as
MPLS (Multiprotocol Label Switching acronym) is a data transport mechanism standard created by the IETF and defined in RFC 3031. Operates between the data link layer and network layer of the OSI model. It was designed to unify the data transport service for circuit-based networks and packet based. Can be used to carry different types of traffic, including voice traffic and IP packets.

MPLS was originally proposed by a group of Cisco engineers, with the name of "Tag Switching", was submitted to the IETF standardization process then changed its name.


How

is noteworthy that IP switching is performed at Layer 3 and is based on the destination IP address (in some cases also the source ip), if we look at a routing table only see partnership "destination network" - "next hop".
For example: 192.168.0.0/24 via 10.10.2.1

192.168.1.0/24 via 10.10.2.2

192.168.2.0/24 via 10.10.2.3 0.0.0.0 / 0 via 10.10.2.254

routing itself, imposes restrictions and some care in our networks, such as that in the allocation of IP addresses there are no collisions ( two network segments can not have the same addresses).
interesting thing about MPLS is that packet switching is based on labels and is between the layer 2 and layer 3 (IP header does not depend on), these tags are added before entering the MPLS network and are removed when packages out of it.
MPLS works by adding a bale a MPLS header, containing one or more labels, this is called "label stack."

Each label contains 4 fields:
* 20 bits - value of the label.
* 3 bits - Experimental field reserved for future use.
* 1 bit - End of the stack. If set to 1 then the last label stack.
* 8 \u200b\u200bbits - Country TTL (time to live)

MPLS network architecture

Note: this image was generated with the simulator "Open SimMpls."

• LER (Label Edge Router): an element starts or ends the tunnel (add and remove labels). Is the point of entry / exit to the MPLS network. A router is called Ingress entrance and one exit Router and Egress Router. Both are often called Edge Label Switch Router, as found at the ends of the MPLS network.

• LSR (Label Switching Router): An element that switches labels.

• LSP (Label Switched Path): generic name of a MPLS path (for some traffic or FEC), ie MPLS tunnel established between the ends. Keep in mind that a LSP is unidirectional.

• LDP (Label Distribution Protocol): a protocol for the MPLS label distribution.

• FEC (Forwarding Equivalence Class): The name given traffic is routed on a label. Subset of packets treated equally by the switch. Possible uses

The sectors that benefit most from MPLS are service providers (carriers), large enterprises and government institutions (ie, grids). Some medium-sized companies can hire a VPN service based on MPLS of a service provider, but the fun is done by the supplier.
The most important uses are:

MPLS-VPN
With MPLS VPNs can be made robust, more scalable and less expensive than alternatives such as IPSec, ATM or frame relay, and also adds QoS.

Traffic Engineering / QoS / congestion
traditional IP routing overload often leads to shorter paths (sometimes longer paths may have less congestion and less delay). Regarding this issue
MPLS can be used to:
- Maximize the use of links and nodes
- Ensure the level of delay (respect SLAs)
- Minimize the impact of major fallasLos protocols for traffic engineering with MPLS are CR-LDP and RSVP-TE.

various network integration: ATM, Frame relay, IP, Ethernet and optical
Maintaining a network is cheaper to keep many. With MPLS you can build a universal transport network.

Some considerations
thought

• When switching based on labels, it was believed that it could be much faster than that based on IP headers, as it requires less processing and can be implemented in hardware, but the development of some technologies such as ASICs or TCAM-based switching and CAM, have made it possible for IP-based switching can be as fast as the tag-based.

• MPLS-based VPNs tend to be confined to a single service provider.

• An alternative MPLS is L2TPv3, although still in draft. References

• RFC - http://www.ietf.org/rfc/rfc3031.txt
• MPLS Network Simulator, written in java and English - http://gitaca.unex.es/
OpenSimMPLS
• An interactive tutorial is instructive to Nortel - http://www.nortel.com/products/announcements/mpls/tooldemo.html
• BGP / MPLS VPNs - http://www.ietf.org/rfc/rfc2547 . txt - http://www.netcraftsmen.net/welcher/papers/mplsvpn.html
• Several articles about MPLS - MPLS
http://www.convergedigest.com/tutorials/ #
• Wikipedia - http:// en.wikipedia.org / wiki / Multiprotocol_Label_Switching
• MPLS on Linux - http://mpls-linux.sourceforge.net/
  

Author: Sebastian Serrano