Examples include EIA/TIA 232 C (formerly RS 232 C), EIA/TIA 422 (formerly RS 422), EIA/TIA 423 (formerly RS 423 (formerly RS 423) and International Telecommunication Union Telecommunication Standardization Sector (ITU-T) (formerly CCITT) V.35. PPP is capable of operating across any DTE/DCE interface. Link will remain configured for communication till plain LCP or NCP frames closed and some external events occurred like inactivity timer expires or user intervenes. After configuring each network layer protocol packets of each network layer could be transferred and link will remain configured and packets could be sent over those links. After establishing link and negotiating optional facilities using LCP the original PPP will send NCP frames to choose and configure one or more network layer protocols. To establish communications over a point-to-point link, the originating PPP first sends LCP frames to configure and test the data-link. PPP is designed to permit the simultaneous utilize of numerous network layer protocols. A suite of Network Control Protocols (NCPs) for establishing and configuring different network-layer protocols.A Link Control Protocol (LCP) for establishing, configuring, and testing the data-link connection.PPP uses the High Level Data Link Control (HDLC) protocol as a basis for encapsulating datagram over point-to-point links.
A PPP FRAME INCLUDES FCS SERIAL
A method for encapsulating datagram over serial links. PPP provides a method for transmitting datagram over serial point-to-point links. In addition to IP, PPP supports other protocols, including Novell’s Internetwork Packet Exchange (IPX) and DECnet. PPP supports these functions by providing an extensible Link Control Program (LCP) and a family of Network Control Program (NCP) to negotiate optional configuration parameters and facilities. PPP also established a standard for the assignment and management of IP address, synchronous (start/stop) and bit-oriented synchronous encapsulation, network protocol multiplexing, link configuration, link quality testing, error detection, and option negotiation for such capabilities as network layer address negotiation and data compression negotiation. Encapsulation is the process of storing packets from the foreign protocol inside PPP frames. PPP was designed to enable the transmission of different protocols over one point-to-point link by utilizing encapsulation. Although PPP is primarily used over dialup lines, variants such as PPoE (PPP over Ethernet) and PPoA (PPP over ATM) extend PPP to new data-link layer protocols. Protocols of the Internet protocol suite tend to use checksums.PPP (Point-to-Point Protocol) is the most widely used method for transporting IP packets over a serial link between the user and the Internet Service Provider (ISP). Refer to Ethernet frame § Frame check sequence for more information.īy far the most popular FCS algorithm is a cyclic redundancy check (CRC), used in Ethernet and other IEEE 802 protocols with 32 bits, in X.25 with 16 or 32 bits, in HDLC with 16 or 32 bits, in Frame Relay with 16 bits, in Point-to-Point Protocol (PPP) with 16 or 32 bits, and in other data link layer protocols. An alternative approach is to generate the bit reversal of the FCS so that the reversed FCS can be also sent least significant bit (bit 0) first. 
For Ethernet and other IEEE 802 protocols, the standard states that data is sent least significant bit first, while the FCS is sent most significant bit (bit 31) first.
The FCS is often transmitted in such a way that the receiver can compute a running sum over the entire frame, together with the trailing FCS, expecting to see a fixed result (such as zero) when it is correct.
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