SPP packets also contain two 16-bit connection identifiers . One connection identifier is specified by each end of the connection. Together, the two connection identifiers uniquely identify a logical connection between client processes. SPP packets cannot be longer than 576 bytes. Client processes can negotiate use of a different packet size during connection establishment, but SPP does not define the nature of this negotiation.
PEP is single-packet based, providing retransmissions but no duplicate packet detection.
As such, it is useful in applications where request-response transactions can be repeated without damaging data, or where reliable transfer is executed at another layer. This protocol is used, for example, in situations where an SPP implementation has identified a duplicate packet. The Printing Protocol provides print services. The Filing Protocol provides file-access services. The Clearinghouse Protocol provides name services.