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Network Working Group                                           S. SenumRequest for Comments: 1376                   Network Systems Corporation                                                           November 1992The PPP DECnet Phase IV Control Protocol (DNCP)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   Digital's DNA Phase IV Routing protocol (DECnet Phase IV) over PPP.   This document applies only to DNA Phase IV Routing messages (both   data and control), and not to other DNA Phase IV protocols (MOP, LAT,   etc.).1.  Introduction   There are two basic approaches to running the DNA Phase IV Routing   protocol over a serial line:   1. The approached that several router vendors have taken which is to      treat the serial link as an Ethernet, using the same data and      control messages an Ethernet would use.   2. The approach defined by Digital, which uses DDCMP and slightly      different control messages.   This document will define a method that uses the first approach.Senum                                                           [Page 1]

RFC 1376                        PPP DNCP                   November 19922.  Overview Of Phase IV DNA Protocols   The Phase IV DNA protocols which act as data link clients are:      o  DNA Phase IV Routing         The Phase IV Digital Network Architecture (DNA) Routing         protocol is a network layer protocol providing services similar         to that of DoD IP.  It routes messages in Phase IV DECnet         networks and manages the packet flow.  The complete definition         of the DNA Phase IV Routing protocol can be found in [2].      o  DNA System Console         The Digital Network Architecture (DNA) System Console protocol         is a maintenance protocol providing low level access to a         system for the functions of:          .  Identify processor          .  Read data link counters          .  Boot system          .  Console carrier (a general purpose i/o channel)         The complete definition of the DNA System Console protocol can         be found in [3].      o  Digital Customer Use         The Digital Customer Use protocol type is a value reserved for         use by Digital customers.  It allocates a type for private use         which will not conflict with Digital or other vendor protocols.      o  DNA Diagnostics         The Digital Network Architecture (DNA) Diagnostics protocol         type is reserved to allow diagnostic software communications in         parallel with other data link clients.      o  DNA Naming Service (DNS)         The Digital Network Architecture Naming Service (DNS) provides         a distributed naming service.  It allows clients to register         named objects and to bind a set of attributes to the objects in         a distributed database.      o  DNA Time Service (DTS)         The Digital Network Architecture Time Service (DTS) is a         protocol providing global clock synchronization in a         distributed environment.      o  DNA Load/Dump         The Digital Network Architecture (DNA) Load/Dump protocol is a         maintenance protocol for copying the contents of processorSenum                                                           [Page 2]

RFC 1376                        PPP DNCP                   November 1992         memory to or from a remote system.  For example, a system         manager can load an operating system into an unattended, remote         system.  The complete definition of the Phase IV DNA Load/Dump         protocol can be found in [3].      o  DNA Experimental Use         The Digital Network Architecture (DNA) Experimental Use         protocol type allows Digital experimental protocols to share a         data link with other data link clients.  It is for use by         Digital Equipment Corporation only.      o  DNA Communications Test         The Digital Network Architecture (DNA) Communications Test         protocol is a maintenance protocol for testing the data link         communications path.  The complete definition of the DNA         Communications Test protocol can be found in [3].      o  Digital Protocol X1         The Digital X1 protocol is a network layer protocol currently         private to Digital.   This document defines the NCP for establishing and configuring   Digital's DNA Phase IV Routing protocol (DECnet Phase IV) over PPP.   This document applies only to DNA Phase IV Routing messages (both   data and control), and not to other DNA Phase IV protocols (MOP, LAT,   etc.).3.  A PPP Network Control Protocol for DNA Phase IV Routing   The DNA Phase IV Routing Control Protocol (DNCP) is responsible for   configuring, enabling, and disabling the DNA Phase IV Routing   protocol modules on both ends of the point-to-point link.  DNCP uses   the same packet exchange mechanism as the Link Control Protocol   (LCP).  DNCP packets may not be exchanged until PPP has reached the   Network-Layer Protocol phase.  DNCP packets received before this   phase is reached should be silently discarded.   The DNA Phase IV Routing Control Protocol is exactly the same as the   Link Control Protocol [1] 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 DNCP packet is encapsulated in the Information fieldSenum                                                           [Page 3]

RFC 1376                        PPP DNCP                   November 1992      of a PPP Data Link Layer frame where the Protocol field indicates      type hex 8027 (DNA Phase IV 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      DNCP 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      DNCP has no Configuration Options.4.  Sending DNA Phase IV Routing Packets   Before any DNA Phase IV Routing packets may be communicated, PPP must   reach the Network-Layer Protocol phase, and the DNA Phase IV Routing   Control Protocol must reach the Opened state.   Exactly one octet-count field and one DNA Phase IV Routing packet are   encapsulated in the information field of a PPP Data Link Layer frame   where the Protocol field indicates type hex 0027 (DNA Phase IV   Routing).  The octet-count contains a count of the number of octets   in the DNA Phase IV Routing packet.  It is two octets in length   itself, and is stored in VAX byte ordering, to be more consistent   with DNA Phase IV Routing over Ethernet (i.e. least significant byte   first).  It is needed to disambiguate optional padding octets from   real information.   The maximum length of an DNA Phase IV Routing packet transmitted over   a PPP link is the same as the maximum length of the Information field   of a PPP data link layer frame minus 2 octets (for the Length field).   The format of the packets themselves is the same as the format used   over Ethernet, without the Ethernet header, Pad, and FCS fields.   A summary of the information field is shown below.  The fields are   transmitted from left to right.Senum                                                           [Page 4]

RFC 1376                        PPP DNCP                   November 1992    0                   1                   2                   3    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |   Length LSB  |   Length MSB  |      DATA     |      ...      |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                              ...                              |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   Length LSB      Least significant byte of length field   Length MSG      Most significant byte of length field   DATA      DNA Phase IV Routing data, as specified in [2]5.  General Considerations   When a topology change in the network occurs, DNA Phase IV Routing   nodes immediately propagate changes via Level 1 and Level 2 Routing   messages, with a 1 second minimum delay between updates.  DNA Phase   IV Routing nodes also periodically retransmit the complete Level 1   and Level 2 distance vectors to guard against data corruption in host   memory, and (in the case of Ethernet) loss of packets due to media   errors.  Because Digital's serial links run a protocol that   guarantees delivery of packets (DDCMP), the recommended default   retransmit time is long (600 seconds), whereas for Ethernet, where   packet delivery is not guaranteed, the recommended default is short   (10 seconds), as documented in [2].  To achieve convergence of routes   within a satisfactory time, the interval between updates should be   based upon the error rate of underlying data link.  As such, it is   recommended that the time between routing updates be user   configurable per PPP interface.   The Hello timer and Listen timer should be set according to the   recommendations for broadcast links (15 and 45 seconds,   respectively).   Routers are not required to send routing updates if the remote node   connected via the PPP link is an endnode.  Endnodes are required to   discard all routing updates received over a PPP link.  The type of a   node (endnode versus routing) can be determined from the hello   messages received from it.Senum                                                           [Page 5]

RFC 1376                        PPP DNCP                   November 1992References   [1] Simpson, W., "The Point-to-Point Protocol (PPP)",RFC 1331,       Daydreamer, May 1992.   [2] Digital Equipment Corporation, "DNA Routing Layer Functional       Specification", Version 2.0.0, Order No. AA-X435A-TK.   [3] Digital Equipment Corporation, "DNA Maintenance Operations       Functional Specification", Version 3.0.0, Order No.  AA-X436A-TK.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).   The author wishes to thank Jim Muchow (Network Systems Corporation),   and Arthur Harvey (Digital Equipment Corporation) for their input to   this memo.Security Considerations   Security issues are not discussed in this memo.Chair's Address   The working group can be contacted via the current chair:   Brian Lloyd   Lloyd & Associates   3420 Sudbury Road   Cameron Park, California 95682   Phone: (916) 676-1147   EMail: brian@lloyd.comAuthor's Address   Questions about this memo can also be directed to the author:   Steven J. Senum   Network Systems Corporation   7600 Boone Avenue North   Minneapolis, Minnesota 55428   Phone: (612) 424-4888   EMail: sjs@network.comSenum                                                           [Page 6]