- A PPP FRAME INCLUDES FCS SERIAL
- A PPP FRAME INCLUDES FCS SOFTWARE
- A PPP FRAME INCLUDES FCS SIMULATOR
If anyone wants, I can add a sample of the data output I am getting to the serial modem. Can someone come up with a simple way (preferably in Python) of calculating an FCS that matches the one that the kernel produces? It seems quite difficult to implement, as I have no experience in kernel hacking. I have been looking into the source of pppd and the linux kernel itself, and I can see that both of them have a method of adding an FCS to the data.
A PPP FRAME INCLUDES FCS SOFTWARE
I have found several pieces of software that will calculate this checksum, but none of them produce what is coming out the serial line (I have a serial line "sniffer" that shows me everything the modem is being sent). From what I can tell, the cell modem I am using has a 2 byte FCS using the CRC16-CCITT method. I am having trouble with the FCS that goes after the data.
A PPP FRAME INCLUDES FCS SIMULATOR
I would like this simulator to take outgoing packets, strip off the ethernet header, insert the PPP flags (7E, FF, 03, 00, and 21) and place the IP layer information in the PPP packet. The flag field consists of the binary sequence 01111110.I am trying to create a software simulation on an Ubuntu GNU/Linux machine which will work like PPPoE. Flag - A single byte that indicates the end of a frame. By prior agreement, consenting PPP implementations can use a 32-bit (4-byte) FCS for improved error detection. Frame check sequence (FCS) - Normally 16 bits (2 bytes).
By prior agreement, consenting PPP implementations can use other values for the maximum information field length. The default maximum length of the information field is 1,500 bytes. The end of the information field is found by locating the closing flag sequence and allowing 2 bytes for the FCS field. Data - Zero or more bytes that contain the datagram for the protocol specified in the protocol field. The most up-to-date values of the protocol field are specified in the most recent Assigned Numbers Request For Comments (RFC). Protocol - Two bytes that identify the protocol encapsulated in the information field of the frame. A connectionless link service similar to that of Logical Link Control (LLC) Type 1 is provided. Control - A single byte that contains the binary sequence 00000011, which calls for transmission of user data in an unsequenced frame. PPP does not assign individual station addresses. Address - A single byte that contains the binary sequence 11111111, the standard broadcast address. The flag field consists of the binary sequence 01111110. Flag - A single byte that indicates the beginning or end of a frame. The following descriptions summarize the PPP frame fields illustrated in Figure 3.6 The PPP frame format appears in the Figure Shown below: A family of NCPs for establishing and configuring different network layer protocols An extensible LCP to establish, configure, and test the connection Nor is there any escaping of control characters, nor are there any FCS or framing characters included. The frame does not include the 0xff address byte or the 0x03 control byte that are optionally used in async PPP. A method for encapsulating datagrams over serial links At the interface to the PPP generic layer, PPP frames are stored in skbuff structures and start with the two-byte PPP protocol number. PPP provides a method for transmitting datagrams over serial point-to-point links, which include the following three components: PPP supports these functions by providing an extensible Link Control Protocol (LCP) and a family of Network Control Protocols (NCPs) to negotiate optional configuration parameters and facilities.PPP also established a standard for the assignment and management of IP addresses, asynchronous (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.The Point-to-Point Protocol (PPP) originally emerged as an encapsulation protocol for transporting IP traffic over point-to-point links.