PPP Internet Protocol Control Protocol (IPCP) 1. Introducing PPP has three main components:
Denual reports are encrypted on the serial line; the connection control protocol (LCP) for establishing, configuring, and detecting a data link connection. Network Control Protocol (NCP) protocols for establishing and configuring different network layer protocols. In order to establish communication on point-to-point connections, each PPP side must first send an LCP package to configure and detect data links. After the connection is established and optional options have been completed by the LCP settings, the PPP must have to send an NCP package to select and configure one or more network layer protocols. Once the protocol of each layer is configured, it can be communicated on the chain. Connection is open before the LCP or NCP is explicitly closed. 2. The IP PPP Network Control Protocol IP Control Protocol (IPCP) is responsible for establishing, enabling and abort the IP module. IPCP and LCP protocol use the same package switching mechanism. The IPCP package cannot be exchanged before the PPP does not meet the network layer protocol phase. If there is an IPCP package to arrive before reaching this phase will be abandoned. IPCP and LCP are basically the same, except for the following: Data Link Layer Protocol Domain. An IPCP package is included in the information field of the PPP data link layer frame, and the protocol domain in the frame will indicate the value of 8021. The coding domain is only available from 1 to 7. Other codes are considered to be unrecognizable and abandoned. Timeout. The IPCP package cannot be exchanged before the PPP does not reach the network layer protocol. In implementations, you should prepare a confirmation or other response before you have not received a completion of authentication and link quality. Implementation should be guaranteed to be interrupted without interruption in other cases of user interference or superior. Configuration option type. IPCP has different configuration options, which will be specifically talked below. 2.1. Send IP Datasters Before the IP packet communication, PPP must reach the network layer protocol phase, and IPCP must reach the open state. An IP packet includes an IP packet in the information field of the PPP data link layer frame, and the protocol domain in the frame indicates the type value 0021. The maximum length of the IP package is transmitted on the PPP connection is consistent with the maximum length of the information field of the PPP data chain layer frame. Excessive IP datagram must be resigned. If the system does not want the segmentation restructuring, you must use the TCP maximum segment size option and the MTU discovery. 3. IPCP Configuration Option IPCP Configuration Options You can select the desired IP parameters. IPCP uses the same configuration option format as LCP. The value of the IPCP option type is as follows: 1 IP address 1 2 IP Compression Protocol 3 IP Address 2 3.1. IP Address 1 Using the Configuration Option IP address is not good, this has been proven in the implementation. The IP address configuration option can replace this domain and you should use the IP address configuration option. This option should not be included in the configuration request if the IP address or IP address option is included in the received configuration request. This option is sent if the IP address option is received as an additional option because the IP address option is received, or the IP address option is included as an additional option. 3.2. Compression Protocol This configuration option can use the system to use a specific compression protocol, default, no need to compress it. The IP Compressed Protocol Configuration Options format is as follows, the transfer order is from left to right. Type 2 Length> = 4 IP Compression Protocol The domain consists of two bytes, indicating the desired compression protocol, the value of this domain, and the compression protocol indicated by the PPP data link layer protocol domain. The currently available compression protocol is as follows: 002D represents Van Jacobson Compressed TCP / IP. The data field is 0 or more bytes, and some parameters of a specific compression protocol are stored. 3.3. IP address 2 This domain provides a method for determining an IP address for a local connection. It allows the sender of the configuration request to request the IP address you want, or ask the other party to provide the corresponding information. The other party can provide information on this aspect by returning NAKING options and legitimate IP addresses. If it is necessary to determine the remote IP address, the other party is not available in its configuration request option, this option should be added to the configuration rejection option. The IP address value is either a legitimate remote IP address, or the other party provides information. The IP address is not specified by default. Below is the IP address configuration option format, and the transfer order is from left to right.
Type 3 length 6 four bytes of IP addresses are configuration request senders want local addresses. If the four digits are all zero, the other party is required to provide IP address information. 4. Van Jacobson TCP / IP Baotou Compressed VAN Jacobson TCP / IP Package Compression reduces the size of the TCP / IP header to approximately 3 bytes, which is a big increase in slow serial lines. The IP Compression Protocol Configuration option is used to indicate the ability to receive the compression package. If you need two directions, it is required to apply for both parties. The PPP protocol domain is set to the following value: 0021 type IP when transmitting the IP package. The IP protocol is not TCP, or a package is a data segment, or has not been compressed. 002d compressed TCP. The TCP / IP header is replaced by the compressed header. 002F Uncompressed TCP. The IP protocol domain is replaced by the slot (Slot) tag. 4.1. Configuration Options Format IP Compression Protocol Configuration Options Format As shown below, the transfer order from left to right: Type 2 length 6 IP compression protocol 002d Indicates the VAN Jacobson Compressed TCP / IP Package. Max-slot-id domain one byte indicates the maximum slot mark, which is less than the actual number of slots, and the groove is marked from 0 to the max-slot-ID. In practice, if MAX-SLOT-ID = 0, there may be problems. The CoMP-SLOT-ID domain one byte indicates whether the groove log domain is compressed. 0 tank marks must not be compressed. All compressed TCP packets must be set in each change mask (Change Mask) and include groove marks. 1 Compressible tank tag.
