The ICA packet composition has preambles that are established during the connection. These preambles control the transmission of the packet. The type of medium used for transmission (VPN, WAN, LAN etc.) will influence the composition of the preamble just like user defined parameters like compression. It is comprised of a Frame Head, Reliable, Encryption, Compression, Command, Command Data, and Frame Trail. IP specifies the format of the datagrams and the addressing scheme. It has to be coupled with TCP in order to be connected to a destination and a source. IPX is a datagram protocol that is used for connectionless communications. It must be coupled with SPX to add connection oriented services to two nodes of a network.

Reference: MetaFrame Administration Module 3