he hosting network. Such channels are normally called timeslot (such as the 32 timeslots in an E1 transmission system, or the eight timeslots of an GSM car- rier). Since such channels are available to a hosting node in precise, recurrent time intervals, no identifier other than a synchronization signal is needed in sending and receiving. In asynchronous routes, channels must be identified by some type of channel identifier (CHi), both by the using hosted network and in the protocol that the hosting network uses. The OSI RM (which calls channels "connections") sug- gests that different identifiers should be used at the endpoints of a channel (con- nection-endpoint identifier, CEi) and in the protocol (connection identifier, Ci) in order to allow local references to be used inside hosting nodes. As usual, however, each standard tends to use its own terminology: the connection-ori- ented X.25 network calls its channels channel; ATM calls its channels virtual circuit and virtual path; LAPD calls its channels connection. Some standards do separate CEi from Ci, others don't. Identifiers are normally named in accordance with how channels are named (e.g., VCi for "virtual circuit identifier" in ATM), with the exception of LAPD that calls its Ci terminal identifier (TEI). Criterion 5: The route structure is modeled as shown in Fig. 3.20. Point-to-point Point-to-multipoint, i.e., multipoints cannot send to each other Broadcast, i.e., every point sends to all other point Fig. 3.20 Route symbols for route structures It is obvious that a much greater number of route symbols could be created by combining these criteria with other properties of connectivity services. This would make network models more expressive but less intelligible. In general, therefore, AMLn recommends only the basic route symbols that were discussed. However, an AMLn user must be allowed to define route symbols that can express the specific characteristics of the network system being modelled. The only requirement from the AMLn point of view is therefore 