Packet switching

The packet switching, or more generally the commutation of labels is one of the switching techniques. The great switching techniques correspond to commutation:

of circuits (Circuit switching):

physical
temporal (time-division Switching)

of labels

The characteristic of the commutation of labels that the decision of commutation is based on one of the fields of PDU (Protocol Data Links, generic term of ISO origin for a screen, a cell, a package, a Datagramme, a segment, etc), is called “label”, to convey: the switch which receives a PDU extracted the label and will seek in its Table of commutation the entry which corresponds to the interface on which it received the PDU and with the value of the label: in this table it thus finds the number of the interface on which it will transmit the PDU and, possibly, the new value of the label:

in a Router, the label in question is to address contained in the heading IP, and it does not change in the course of road of course. The same applies in a Commutateur Ethernet where the label is the Adresse MAC of destination

in a switch X25, FR, ATM, MPLS, it acts of Mode connected and the label corresponds to a Connection, but its value changes with each crossing of switch

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