In a 100% reliable serial connection this would be tolerable, because length information in the IP packets could be used to separate packets from the serial data stream. The receiving side would not be able to explicitly identify the start and end of a packet. In cases where a 'naked' serial connection is used as the link layer, this creates a problem, because a simple serial connection does not provide any framing facilities. The link layer is supposed to do this, so when packets are placed in some data stream they can be properly extracted from the stream. This means, the link layer is, among other tasks, responsible for properly separating each packet and identifying an IP packet's start and end when it moves the packet over some communication link. One of the services the IP protocol expects from the link layer is the framing, deframing of IP packets. Higher layers expect particular services from their lower layers. All mentioned problems are explained as it follows.ĭifferent layers have different tasks in the TCP/IP protocol stack. Of which lack of framing is the most serious one. Transmitting IP data over a serial (RS-232) line is haunted by several problems, among them: TCP/IP The complete internet protocol suite, encompassing many more protocols than just TCP or IP.Īlso, this module uses the TCP/IP notation of protocol layers, not the OSI model, unless stated otherwise: IP The IP protocol as such, at the internetworking layer. TCP The TCP protocol as such, at the transport layer. This module uses the normal TCP/IP terminology, where the terms indicate the following: This page assumes the reader is familiar with the TCP/IP protocol suite and IP communication in general.Ī Note on Terminology

Tcp ip over serial ppp