Connecting Multiple Site Locations - Frequently Asked Questions
1. What do the terms Fully Meshed, Connectivity and MPLS mean?
Full Mesh - Term describing a network in which devices are organized in a mesh topology, with each network node having either a physical circuit or a virtual circuit connecting it to every other network node. A full mesh provides a great deal of redundancy.
Connectivity - A domain of connected components that adhere to a defined set of connection rules. The set of rules is termed Connectivity Architecture. Connectivity is the property of a network that allows dissimilar devices to communicate with each other.
MPLS - A family of IETF standards in which Internet Protocol networks can make forwarding decisions based on a pre-allocated label to setup a Label Switched Path (LSP). MPLS has faster forwarding performance than IPv4 networks due to its ability to make decisions based on the pre-allocation of a 20-bit label through the IPv4 routing protocols.
MPLS works like this: As an IP data stream enters the edge of the network, the ingress Label Edge Router (LER) reads the destination address of the first data packet and attaches a 32-bit shim header "label" in between the layer 2 and layer 3 headers of the packet. The label is mapped to a Forwarding Equivalency Class (FEC) based on the destination network and the MPLS EXP value which signifies the QoS level.
The Label Switch Router (LSR) in the core of the network examines the 20-bit label, and switches the packet with greater speed than if the device had to interrogate the IP routing table of the device. The router swaps the label with the new label that the next router needs to assist in the completion of the LSP.
There are two flavors of MPLS available: Frame-based and cell-based. Cell-based MPLS is used in ATM networks, while frame-based MPLS is used in packet-based networks like Ethernet and Frame-Relay. Although MPLS offers slight performance increases, the richness of MPLS comes from the MPLS applications. The two MPLS applications most widely deployed are MPLS VPNs and MPLS Traffic Engineering.
Source: Newton's Telecom Dictionary. 23rd ed. New York: Flatiron, 2007.
