network protocols handbook.pdf

98Protocols GuideTCP/IP - Data Link Layer ProtocolsProtocol NameIPCP and IPv6CP: IP ControlProtocol and IPv6 ControlProtocolProtocol DescriptionIP Control Protocol (IPCP) and IPv6 Control Protocol (IPv6CP)define the Network Control Protocol for establishing and configuringthe Internet Protocol or IPv6 over PPP, and a method tonegotiate and use Van Jacobson TCP/IP header compressionwith PPP.IPCP is responsible for configuring, enabling, and disablingthe IP protocol modules on both ends of the point-to-point link.IPCP uses the same packet exchange mechanism as the LinkControl Protocol (LCP). IPCP packets may not be exchangeduntil PPP has reached the Network-Layer Protocol phase. IPCPpackets received before this phase is reached should be silentlydiscarded.Before any IP packets may be communicated, PPP must reachthe Network-Layer Protocol phase, and the IP Control Protocolmust reach the Opened state.Van Jacobson TCP/IP header compression reduces the size ofthe TCP/IP headers to as few as three bytes. This can be asignificant improvement on slow serial lines, particularly for interactivetraffic.The IP Compression Protocol Configuration Option is used toindicate the ability to receive compressed packets. Each end ofthe link must separately request this option if bidirectional compressionis desired.IPv6CP is responsible for configuring, enabling, and disablingthe IPv6 protocol modules on both ends of the point-to-pointlink. IPv6CP uses the same packet exchange mechanism asthe Link Control Protocol (LCP). IPv6CP packets may not beexchanged until PPP has reached the Network-Layer Protocolphase. IPv6CP packets received before this phase is reachedshould be silently discarded.Protocol StructureIPCP and IPv6CP configuration option packet header:For IPCP:Type 1: IP-AddressesType 2: IP-Compression ProtocolType 3: IP-Address.For IPv6CP:Type 1: Interface – IdentifierType 2: IPv6-Compression ProtocolIPCP and IPv6CP header structure:8 16 32bitCode Identifier LengthData (variable)• Code - Specifies the function to be performed.• Identifier - Used to match requests and replies.• Length - Size of the packet including the header.• Data -Zero or more bytes of data as indicated by theLength. This field may contain one or more Options.Related protocolsIP, IPv6, PPP, TCP, Van JacobsonSponsor SourceIPCP is defined by IETF (http://www.ietf.org) in RFC 1332 andIPv6CP is defined in RFC 2472.Referencehttp://www.javvin.com/protocol/rfc1332.pdfThe PPP Internet Protocol Control Protocol (IPCP).http://www.javvin.com/protocol/rfc2472.pdfIP Version 6 over PPPhttp://www.javvin.com/protocol/rfc3241.pdfRobust Header Compression (ROHC) over PPP.http://www.javvin.com/protocol/rfc3544.pdfIP Header Compression over PPP.8 16 32bitType Length Configuration Option• Type – 1 for IP-Address, 2 for IP-Compression Protocol,and 3 for IP-Address• Length >= 4• Configuration Option - The field is two octets and indicatesone of the following options: