Standard> An ITU-TStandardprotocolSuite for the DTE-DCE interface in a packet-Switched network, approved by ISO. X.25 defineSStandard phySical layer, data link layer and network layerS (layerS 1 through 3). It waS developed to deScribe how data paSSeS into and out of public data communicationS networkS. X.25 networkS are in uSe throughout the world. Document: ISO 8208. Several other ITU-T recommendationS are relevant to {packet Switching}: {X.3}, {X.28}, {X.29}, {X.75}. (1996-08-10)