RFC 1377 – The PPP OSI Network Layer Control Protocol (OSINLCP)

Network Working Group                                            D. Katz
Request for Comments: 1377                                         cisco
                                                           November 1992


          
The PPP OSI Network Layer Control Protocol (OSINLCP)

Status of this Memo

   This RFC specifies an IAB standards track protocol for the Internet
   community, and requests discussion and suggestions for improvements.
   Please refer to the current edition of the "IAB Official Protocol
   Standards" for the standardization state and status of this protocol.
   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.

   This memo 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 [email protected] mailing list.

Table of Contents

   1.     Introduction ..........................................    2
   1.1    OSI Network Layer Protocols over PPP ..................    2
   2.     A PPP Network Control Protocol (NCP) for OSI ..........    5
   2.1    Sending OSI NPDUs .....................................    6
   2.2    NPDU Alignment ........................................    6
   2.3    Network Layer Addressing Information ..................    6
   3.     OSINLCP Configuration Options .........................    7
   3.1    Align-NPDU ............................................    7
   REFERENCES ...................................................    9
   ACKNOWLEDGEMENTS .............................................    9
   SECURITY CONSIDERATIONS ......................................   10
   CHAIR'S ADDRESS ..............................................   10
   AUTHOR'S ADDRESS .............................................   10






Katz                                                            [Page 1]

RFC 1377 PPP OSINLCP November 19921 . Introduction1.1 . OSI Network Layer Protocols over PPP3], the End System to Intermediate System routing protocol (ES-IS,
   ISO 9542) [4], the Intermediate System to Intermediate System routing
   protocol (IS-IS, ISO 10589) [5], and the Inter-Domain Routeing
   Protocol (IDRP, CD 10747) [6].  Generally, these protocols were
   designed to run over non-reliable data link protocols such as PPP.

   Network Layer Protocol Identifier (NLPID)

      OSI Network Layer protocols can be discriminated according to the
      first octet in each Network Protocol Data Unit (NPDU, that is,
      packet), known as the Network Layer Protocol Identifier (NLPID),
      which is 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 2]

RFC 1377 PPP OSINLCP November 19928],
      effectively the Packet Layer of CCITT X.25, is intended to be run
      over a reliable data link, such as IEEE 802.2 type II or LAPB.
      Therefore, the unreliable data link service provided by PPP is not
      appropriate for use with ISO 8208.

   ConnectionLess Network Protocol (CLNP)

      The ConnectionLess Network Protocol offers a simple non-reliable
      datagram service very similar to IP, and is designed to run over a
      non-reliable data link service, such as provided by PPP.

   End-System to Intermediate-System Protocol (ES-IS)

      ES Hellos and IS Hellos are retransmitted on a periodic timer-
      driven basis (based on expiration of the "Configuration Timer").
      The resulting ES and IS configuration information is invalidated
      on a timer driven basis, based on expiration of the "Holding
      Timer" for each piece of information.  The value of a Holding
      Timer is set by the source of the information, and transmitted in
      the Holding Time field of the appropriate ES-IS packet.  ISO 9542
      recommends that the holding time field is set to approximately
      twice the Configuration Timer parameter, such that even if every
      other Hello packet is lost the configuration information will be
      retained (implying that the Holding Timer is actually set to
      slightly more than twice the Configuration Timer).

      Generally, the recommendation in ISO 9542 is sufficient for PPP
      links.  For very unreliable links, it may be necessary to set the
      Holding Timer to be slightly more than three times the
      Configuration Timer to ensure that loss of configuration
      information is an unusual event.

      Redirect information is not transmitted on point-to-point links,
      but may be transmitted on general topology subnetworks, which in
      turn may make use of PPP.  Redirect information is sent on a
      event-driven basis (based on a CLNP packet being forwarded by a
      router out the incoming interface), but redirect information is



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RFC 1377 PPP OSINLCP November 1992
Katz                                                            [Page 4]

RFC 1377 PPP OSINLCP November 19922 . A PPP Network Control Protocol (NCP) for OSI1] with the following exceptions:

   Frame Modifications

      The packet may utilize any modifications to the basic frame format
      which have been negotiated during the Link Establishment phase.

   Data Link Layer Protocol Field

      Exactly one OSINLCP packet is encapsulated in the Information
      field of a PPP Data Link Layer frame 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



Katz                                                            [Page 5]

RFC 1377 PPP OSINLCP November 19929] is being defined in ISO to add support
   for dynamic address assignment.  This addendum has currently passed
   the formal "Committee Draft" (CD) letter ballot.

3 . OSINLCP Configuration Options1], with a separate set of Options.

   The most up-to-date values of the OSINLCP Option Type field are
   specified in the most recent "Assigned Numbers" RFC [2].  Current
   values are assigned as follows:

      1       Align-NPDU

3.1 . Align-NPDU
Katz                                                            [Page 7]

RFC 1377 PPP OSINLCP November 1992
Katz                                                            [Page 8]

RFC 1377 PPP OSINLCP November 19921] Simpson, W., "The Point-to-Point Protocol (PPP)", RFC 1331,
       Daydreamer, May 1992.

   [2] Reynolds, J., and J. Postel, "Assigned Numbers", STD 2, RFC 1340,
       USC/Information Sciences Institute, July 1992.

   [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)", ISO 10589,
       1990.

   [6] ISO, "Protocol for Exchange of Inter-domain Routeing
       Information among Intermediate Systems to Support Forwarding of
       ISO 8473 PDUs", ISO CD 10747, 1991.

   [7] ISO, "Information technology -- Telecommunications and
       information exchange between systems -- Protocol identification
       in the network layer", ISO/IEC TR9577:1990.

   [8] ISO, "Information processing systems -- Data communications --
       X.25 packet level protocol for Data terminal equipment", ISO
       8208, 1984.

   [9] Taylor, E., "Addendum to ISO 9542 (PDAM 1 - Dynamic Discovery
       of OSI NSAP Addresses by End Systems)", SC6/N7248.

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).

   Special thanks to Ross Callon (DEC), and Cyndi Jung (3Com), for
   contributions of text and design suggestions based on implementation



Katz                                                            [Page 9]

RFC 1377 PPP OSINLCP November 1992