The X.25 Recommendations

X.25 is defined in a series of documents issued by the International Telecommunication Union--Telecommunication Standardization Sector. These documents are called the X.25 Recommendations and specify the following:

• X.25 Physical Layer

• X.25 Datalink Layer - LAP, LAPB and MLP

• X.25 Packet Layer Protocol

The component layers of X.25 fit together as shown in Figure 2-3:

Figure 2-3 X.25 Protocol Layers Overview