On the receiving end of the connection, AAL5 reassembles incoming cells into a packet, checks the CRC to ensure that all pieces arrived correctly, and passes the resulting block of data to the host software.
The process of dividing a block of data into cells and regrouping them is known as ATM segmentation and reassembly (SAR).
By separating the functions of segmentation and reassembly from cell transport, AAL5 follows the layering principle.
ATM standards use the term "convergence" to describe mechanisms that recognize the end of a packet.
The former scheme, in which the hosts agree on the high-level protocol for a given circuit, is referred to in RFC 2684 as "VC Multiplexing".
The latter scheme, in which the hosts use a single virtual circuit for multiple protocols, is referred to in RFC 2684 as "LLC Encapsulation".
This scheme has the advantage of allowing all traffic over the same circuit, but the disadvantage of requiring each packet to contain octets that identify the protocol type, which adds overhead.
At the receiving end, AAL5 reassembles the cells, checks the CRC to verify that no bits were lost or corrupted, extracts the datagram, and passes it to the IP layer.