TCP/IP Explained
An easy to understand, comprehensive, and high-level introduction to TCP/IP.
TABLE OF CONTENTS TCP/IP Explained
Section 22.7: The Internet Protocol Control Protocol (IPCP)
22.7 The Internet Protocol Control Protocol (IPCP)
PPP defines a number of Network Control Protocols (NCPs) designed to configure a link for operation with those specific Network Layer protocols. While other NCPs are beyond the scope of this book, the Internet Protocol Control Protocol (IPCP) standardized by RFC 1332 - is described here since it is this that is responsible for the configuration of PPP links to carry IP datagrams.
IPCP uses the same exchange mechanisms as LCP, except that no NCPs are exchanged before the link has reached the Network phase. Once entered, IPCP packets are then encapsulated in PPP Data Link frames using a Protocol field containing the value 8021 16, and Code field values of 1 to 7 ( Configure Request, Configure Ack, Configure Nak, Configure Reject, Terminate Request, Terminate Ack, and Code Reject). Once successfully negotiated, IP datagrams are then encapsulated in the Information field of PPP Data Link layer frames that have a Protocol field of 0021 16 to represent IP.
22.7.1 IPCP Configuration Options
Three IPCP configuration options exist, of which one is now deprecated and is only used in older implementations to assure backward compatibility. The three options are:
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IP-Addresses
Broadly, this option allows for the configuration of IP Addresses on dial up links. Now deprecated, this option has been superseded by the IP-Address option. As such, this option is only sent as a Configuration Request where a Configure Reject has been received in...
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