Network Working Group D. Katz Request for Comments: Draft Merit/NSFnet July 1991 The PPP OSI Network Layer Control Protocol (OSINLCP) Status of this Memo This proposal is the product of the Point-to-Point Protocol Working Group of the Internet Engineering Task Force (IETF). Comments on this memo should be submitted to the IETF Working Group at ietf- ppp@ucdavis.edu. Distribution of this memo is unlimited. Abstract The Point-to-Point Protocol (PPP) [1] provides a standard method of encapsulating Network Layer protocol information over point-to-point links. PPP also defines an extensible Link Control Protocol, and proposes a family of Network Control Protocols (NCPs) for establishing and configuring different network-layer protocols. This document defines the NCP for establishing and configuring OSI Network Layer Protocols. Katz [Page i] RFC DRAFT PPP OSINLCP July 1991 1. Introduction PPP has three main components: 1. A method for encapsulating datagrams over serial links. PPP uses HDLC as a basis for encapsulating datagrams over point- to-point links. At this time, PPP specifies the use of asynchronous or synchronous duplex circuits, either dedicated or circuit switched. 2. A Link Control Protocol (LCP) for establishing, configuring, and testing the data-link connection. 3. A family of Network Control Protocols (NCPs) for establishing and configuring different network-layer protocols. PPP is designed to allow the simultaneous use of multiple network- layer protocols. In order to establish communications over a point-to-point link, each end of the PPP link must first send LCP packets to configure and test the data link. After the link has been established and optional facilities have been negotiated as needed by the LCP, PPP must send NCP packets to choose and configure one or more network-layer protocols. Once each of the chosen network-layer protocols has been configured, datagrams from each network-layer protocol can be sent over the link. The link will remain configured for communications until explicit LCP or NCP packets close the link down, or until some external event occurs (an inactivity timer expires or network administrator intervention). 1.1. OSI Network Layer Protocols A number of protocols have been defined for the Network Layer of OSI, including the Connectionless Network Layer Protocol (CLNP, ISO 8473) [3], the End System to Intermediate System routing protocol (ES-IS, ISO 9542) [4], the Intermediate System to Intermediate System routing protocol (IS-IS, DP 10589) [5], and the Connection- Oriented Network Protocol (X.25 packet level protocol, ISO 8208) [6]. OSI Network Layer protocols can be discriminated according to the first octet in each PDU, known as the Network Layer Protocol Identifier (NLPID), defined in ISO/TR 9577 [7]. This allows the various protocols to be run over a common data link without any discriminator below the network layer. Katz [Page 1] RFC DRAFT PPP OSINLCP July 1991 2. A PPP Network Control Protocol (NCP) for OSI The OSI Network Layer Control Protocol (OSINLCP) is responsible for configuring, enabling, and disabling the OSI protocol modules on both ends of the point-to-point link. OSINLCP uses the same packet exchange machanism as the Link Control Protocol (LCP). OSINLCP packets may not be exchanged until PPP has reached the Network-Layer Protocol phase. OSINLCP packets received before this phase is reached should be silently discarded. Likewise, OSI NPDUs may not be exchanged until OSINLCP has finished opening the connection (reached the Opened state). The OSI Network Layer Control Protocol is exactly the same as the Link Control Protocol [1] with the following exceptions: Data Link Layer Protocol Field Exactly one IPCP packet is encapsulated in the Information field of PPP Data Link Layer frames where the Protocol field indicates type hex 8023 (OSI Network Layer Control Protocol). Code field Only Codes 1 through 7 (Configure-Request, Configure-Ack, Configure-Nak, Configure-Reject, Terminate-Request, Terminate-Ack and Code-Reject) are used. Other Codes should be treated as unrecognized and should result in Code-Rejects. Timeouts OSINLCP packets may not be exchanged until PPP has reached the Network-Layer Protocol phase. An implementation should be prepared to wait for Authentication and Link Quality Determination to finish before timing out waiting for a Configure-Ack or other response. It is suggested that an implementation give up only after user intervention or a configurable amount of time. Configuration Option Types Currently, OSINLCP has no Configuration Options defined. 2.1. Sending OSI NPDUs Before any NPDUs may be communicated, PPP must reach the Network- Layer Protocol phase, and the OSI Network Layer Control Protocol must reach the Opened state. Exactly one OSI NPDU is encapsulated in the Information field of PPP Katz [Page 2] RFC DRAFT PPP OSINLCP July 1991 Data Link Layer frames where the Protocol field indicates type hex 0023 (OSI Network Layer). The maximum length of an OSI NPDU transmitted over a PPP link is the same as the maximum length of the Information field of a PPP data link layer frame. Larger NPDUs must be segmented as necessary. If a system wishes to avoid segmentation and reassembly, it should use transport layer mechanisms to discourage others from sending large PDUs. 2.2. Exchanging Network Layer Addressing Information OSINLCP does not define a separate configuration option for the exchange of OSI Network Layer address information. Instead, the ES- IS protocol, ISO 9542, should be used. This protocol provides a mechanism for determining the Network Layer address(es) of the neighbor on the link, as well as determining if the neighbor is an End System or an Intermediate System. The ES-IS protocol does not currently support Network Layer address assignment. If address assignment is viewed as being desirable, it would be preferable to add this capability to ISO 9542, rather than creating a mechanism within PPP. This matter is for further study. Katz [Page 3] RFC DRAFT PPP OSINLCP July 1991 References [1] Perkins, D., "The Point-to-Point Protocol for the Transmission of Multi-Protocol of Datagrams Over Point-to-Point Links", RFC 1171, July 1990. [3] ISO, "Information processing systems--Data communications-- Protocol for providing the connectionless-mode network service", ISO 8473, 1988. [4] ISO, "Information processing systems--Telecommunications and information exchange between systems--End system to Intermediate system Routeing exchange protocol for use in conjunction with the protocol for providing the connectionless- mode network service (ISO 8473)", ISO 9542, 1988. [5] ISO, "Information processing systems--Telecommunications and information exchange between systems--Intermediate system to Intermediate system Intra-Domain routeing exchange protocol for use in conjunction with the protocol for providing the connectionless-mode network service (ISO 8473)", DP 10589, 1990. [6] ISO, "Information processing systems--Data communications--X.25 packet level protocol for Data terminal equipment", ISO 8208, 1984. [7] ISO, "Information technology--Telecommunications and information exchange between systems--Protocol identification in the Network layer", ISO/TR 9577, to be published. Security Considerations Security issues are not discussed in this memo. Acknowledgments Some of the text in this document is taken from previous documents produced by the Point-to-Point Protocol Working Group of the Internet Engineering Task Force (IETF), formerly chaired by Drew Perkins of Carnegie Mellon University, by Russ Hobby of the University of California at Davis, and by Steve Knowles of FTP Software. Editted and formatted by Bill Simpson. Katz [Page 4] RFC DRAFT PPP OSINLCP July 1991 Chair's Address The working group can be contacted via the current chair: Brian Lloyd Telebit Corporation 1315 Chesapeake Terrace Sunnyvale, CA 94089-1100 Phone: (408) 745-3103 EMail: brian@telebit.com Author's Address Questions about this memo can also be directed to: Dave Katz Merit/NSFNET 1075 Beal Ave. Ann Arbor, MI 48109 Phone: (313) 763-4898 EMail: dkatz@merit.edu Katz [Page 5] RFC DRAFT PPP OSINLCP July 1991 Table of Contents 1. Introduction .......................................... 1 1.1 OSI Network Layer Protocols ..................... 1 2. A PPP Network Control Protocol (NCP) for OSI .......... 2 2.1 Sending OSI NPDUs ............................... 2 2.2 Exchanging Network Layer Addressing Information ....................................................... 3 REFERENCES ................................................... 4 SECURITY CONSIDERATIONS ...................................... 4 ACKNOWLEDGEMENTS ............................................. 4 CHAIR'S ADDRESS .............................................. 5 AUTHOR'S ADDRESS ............................................. 5