LCP packets are classified into three types, according to their function:
#Ppp frame flag code
The actual format of the Data field is set by the Code field value. Zero or more octets (indicated by the Length field) used for data or configuration options. Any additional information (data or configuration options) follows the Length field. Two-octet field indicating the length of the entire LCP packet. Any packet sent in response to a request must contain the same Identifier value as the request. One-octet field consisting of an incremented number, starting with zero, used to associate requests and replies. One-octet field identifying the type of packet (Configure-Request, Echo-Request, and so on), as shown in the Packet and Code Type column of Table 5-8. Table 5-7 provides a description of each LCP packet field.
#Ppp frame flag serial
Automates the configuration and establishment of serial links for bridges and routers over WANs.Provides procedures for establishing, configuring, testing, and terminating the operation of data-link connections.Sixteen bits containing the remainder from a cyclic redundancy check (CRC) to detect bit errors.įor PPP to be versatile and flexible enough to support a wide variety of environments, the LCP is provided. The default maximum size is 1,500 octets however, through negotiation, other values for the maximum Data field length can be used. Zero or more octets containing a datagram from the protocol identified in the Protocol field. Values in the 0 xxx to 3 xxx range identify Network-layer protocols values in the 4 xxx to 7 xxx range are used for those protocols with low-volume traffic and no associated NCP values in the 8 xxx to B xxx range identify the associated NCP values in the c xxx to f xxx range identify the Link Control Protocol (LCP). Two octets specific to PPP identifying the protocol encapsulated in the Information field of the frame. Frames with the Control field containing any other values are discarded. Single octet containing the Unnumbered Information (UI) command with the p/f bit set to zero. Frames with unrecognized addresses are discarded. NetWare Link/PPP does not assign individual station addresses the use of other address lengths and values might be defined at a later time. Single octet containing the binary sequence 11111111, the All-Stations address. Used as a frame separator, only one Flag field is required between two frames two consecutive Flag fields constitute an empty frame, which is ignored. Single octet indicating the beginning or end of a frame. Table 5-6 explains each field of the frame format. The figure does not include start/stop bits for asynchronous links or any bits/octets for transparency. NetWare Link/PPP supports the use of both types of links and operates across most modems and DTE/DCE interfaces (for example, EIA RS-232, EIA RS-422, EIA RS-423, X.21, and ITU V.35).įigure 5-5 shows the NetWare Link/PPP frame format. Error detection is included using the ITU CRC-16 FCS for error detection, but not error recovery, and is compatible with most hardware.Īt the Physical layer, PPP works over any asynchronous or synchronous, dedicated or dial-up, full-duplex bit-serial circuit. The protocol is characterized by a low-overhead, high-throughput orientation. PPP uses a variant of HDLC that provides a basic level of transport services for the delivery of data packets.
The links must be full-duplex and can be either dedicated or switched. The NetWare Link/PPP implementation of the PPP specification uses encapsulation methods supporting bit-synchronous and character-asynchronous serial communications links.
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