Label switching

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As Label Switching a method for optimizing data transport in one designated computer networks . It enables the effort for forwarding data from conventional routing (layer 3 of the OSI layer model ) to be reduced to pure switching (layer 2). This significantly reduces the processing effort for the routers involved, which enables significantly less processing time and thus packet transit time. Costs can also be saved in this way.

Path building

In large computer networks, such as B. the Internet, the data is usually routed from sender to recipient. This means that the devices involved in the transport, the so-called routers, have to determine again how to proceed with each data packet. Routers often have many different communication partners (other routers) and manage a list in which certain target addresses are assigned to certain remote stations. Routers therefore examine the destination and often also the sender address of each data packet and use this data to determine the next destination. This procedure is complex.

With label switching, a logical path is established with the aid of a signaling protocol before the actual data transmission . All network components involved in this path are programmed to transport a specific label. This process can be compared to dialing a telephone number that precedes a conversation. The path can then no longer change. It is cleared after the connection is terminated.

Switching the labels

During the actual data transmission, the labeled frames are only switched. A label can be thought of as the coloring of a data packet. The network devices only forward the data packets to the next device in the path based on their label. Delay times in the power supply units are short compared to routing. There is also no need to burden the hardware with maintaining the routing tables. As a result, networks with label switching are predestined for high-speed tasks. Because of the special devices, the complex configuration and the low distribution, this technology is still expensive at the beginning of 2006. Another disadvantage is the high susceptibility to failure. If a line or a device fails on the path, the fault is not even noticed in the worst case. Routed networks react more flexibly to interruptions.

realization

In most cases, is between the header of the link layer and the header of the network layer a label inserted, which is a short connection identifier of fixed length, like the VPI / VCI identifiers in ATM .

As part of the VIOLA project, label switching is being examined with other network technologies for their suitability in the high-speed range.

An example of an implementation of label switching is the multiprotocol label switching .

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