Bridging Your World with L2

11th May 2021
Network communications and automotive transportation often share terminology. A term used frequently in both is ‘bridges’. With road traffic, bridges are structures that allow traffic to move from one area to another. As the networking world moves forward in preparation for 5G, nearly every piece of the network is important. Bridging Layer-2 networks efficiently together is key to end-to-end success.

In networking, the device used to connect multiple networks together at layer 2 (L2) is called a bridge. Layer 2 refers to the data link layer of the OSI model, where data is encoded into units (frames), checked, and transmitted. The bridge has interfaces to several LAN segments which it connects (or bridges) together. Ethernet bridges have been around since the mid-1980s. Operation of a bridge was first standardized in IEEE Std 802.1D in 1990. Since 2000 (roughly) most bridges have been based on IEEE Std 802.1Q, which introduced support for virtual LANs (VLANs) through a method of tagging frames with additional information.

Often the term “switch” is used instead of “bridge”. In reality, an Ethernet Bridge and an Ethernet Switch are the same thing (the only term used in the standards is “bridge”), but “switch” came into vogue to describe a bridge with more than two ports. But the term “switch” is frequently used for technology that is not bridging (e.g., an MPLS switch) so “bridge” is still the preferred term.