 protocol, see ITU-T X.226. This procedure also requires some extra opera- tions in the interface between the ENC and its user, operations that in OSI are called P-CONNECT, P-ALTER-CONTEXT and P-RELEASE, see ITU-T X.216. Following its tradition of regarding every layer as a connection-handling layer, OSI regards an established set of presentation contexts (for a session between ENC users) as a "presentation layer connection". SM&AML recognizes the ENC function as a function that, in some form, must exist in every logical node. The OSI view of presentation layer connections is therefore not shared. By definition, SM&AML regards a connection as a channel for transferring bits or octets over SAPs, i.e. between logical nodes that belong to different logical networks. An encoding function use such a connection, but does not itself create or handle connections. An AML-ENC can therefore be neither a logical node nor a layer, in the OSI presentation layer sense. AML also defines the relation between abstract syntaxes and transfer syntaxes in a way that does not require a negotiation procedure in the ENC-protocol, see Sect. 5.7. This method is less flexible than the OSI presentation layer protocol, but far more acceptable to implementers. The OSI suggestion to separate abstract syntaxes from presentation syntaxes is shared by SM&AML. A common misunderstanding over the years has been that ASN.1, as a notation for operation specifications, message specifications and abstract syntaxes, can only be used in combination with BER. Since BER is rather complicated and creates considerable overhead in bits, it cannot be used over low- capacity channels, or by protocol elements with restricted computing power (con- ditions that apply to service access protocols, link-level protocols etc.). Conse- quently, ASN.1 has never been used to describe these kinds of protocols. As a result, the behaviour of most protocols is described on the bit-level, as e.g. "if bit 6 in octet 11 of the message is 0, the message receiver shall interpret the