Application Transport Group Application protocols are the ultimate producers and consumers in a computer network. They exist above the transport protocol. There are many different kinds of applications. The size of the packets and their intergeneration time are very regular. In general, the event engine tries to determine as early as possible whether the user has defined a particular handler, and, if not, avoids undertaking the work associated with generating the corresponding event.
Backdoors are, by design, difficult to detect.
Some FTP requests are sent in response to user activity, and accordingly have interactive like timing. Each FTP session opens two network connections, a control channel, used to send commands from client to server, and a data channel, used for transferring files from machine to machine. RFC 959, October, 1985. 90.7 Table 1. There may be several file transfers 3 in a single FTP session 4 .