GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


rfc:rfc1378

Network Working Group B. Parker Request for Comments: 1378 Cayman Systems

                                                         November 1992
             The PPP AppleTalk Control Protocol (ATCP)

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 the
 AppleTalk Protocol [3] over PPP.
 This memo is a joint effort of the AppleTalk-IP Working Group and the
 Point-to-Point Protocol Working Group of the Internet Engineering
 Task Force (IETF).  Comments on this memo should be submitted to the
 ietf-ppp@ucdavis.edu mailing list.

Table of Contents

 1.     Introduction ..........................................    2
 2.     A PPP Network Control Protocol (NCP) for AppleTalk ....    2
 2.1    Sending AppleTalk Datagrams ...........................    3
 2.2    Half-Routers ..........................................    4
 3.     ATCP Configuration Options ............................    4
 3.1    AppleTalk-Address .....................................    5
 3.2    Routing-Protocol ......................................    7
 3.3    Suppress-Broadcasts ...................................    8
 3.4    AT-Compression-Protocol ...............................    9
 3.5    Server-information ....................................   10
 3.6    Zone-Information ......................................   12
 3.7    Default-Router-Address ................................   13
 APPENDICES ...................................................   14
 A.     ATCP Recommended Options ..............................   14
 REFERENCES ...................................................   15

Parker [Page 1] RFC 1378 PPP ATCP November 1992

 ACKNOWLEDGEMENTS .............................................   15
 SECURITY CONSIDERATIONS ......................................   16
 CHAIR'S ADDRESS ..............................................   16
 AUTHOR'S ADDRESS .............................................   16

1. Introduction

 PPP has three main components:
    1. A method for encapsulating datagrams over serial links.
    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.
 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).

2. A PPP Network Control Protocol (NCP) for AppleTalk

 The AppleTalk Control Protocol (ATCP) is responsible for configuring,
 enabling, and disabling the AppleTalk protocol modules on both ends
 of the point-to-point link.  ATCP uses the same packet exchange
 machanism as the Link Control Protocol (LCP).  ATCP packets may not
 be exchanged until PPP has reached the Network-Layer Protocol phase.
 ATCP packets received before this phase is reached should be silently
 discarded.
 The AppleTalk 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.

Parker [Page 2] RFC 1378 PPP ATCP November 1992

 Data Link Layer Protocol Field
    Exactly one ATCP packet is encapsulated in the Information field
    of a PPP Data Link Layer frame where the Protocol field indicates
    type hex 8029 (AppleTalk 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
    ATCP 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
    ATCP has a distinct set of Configuration Options, which are
    defined below.

2.1. Sending AppleTalk Datagrams

 Before any AppleTalk packets may be communicated, PPP must reach the
 Network-Layer Protocol phase, and the AppleTalk Control Protocol must
 reach the Opened state.
 Unless otherwise negotiated (via option 4), exactly one AppleTalk
 packet is encapsulated in the Information field of a PPP Data Link
 Layer frame where the Protocol field indicates type hex 0029
 (AppleTalk).
 Note that the negotiation of compression may imply the use of
 different encapsulation and hence different protocol fields.  These
 different protocol fields imply packet types which are sub-protocols
 of the base AppleTalk NCP.
 An encapsulated AppleTalk packet begins with an extended DDP
 (Datagram Delivery Protocol) header -- also known as a Long DDP
 header.  The maximum length of a DDP datagram is 599 octets.
 Since there is no standard method for fragmenting and reassembling

Parker [Page 3] RFC 1378 PPP ATCP November 1992

 AppleTalk datagrams, it is required that PPP links supporting
 AppleTalk allow at least 599 octets in the information field of a
 data link layer frame.

2.2. Half-Routers

 One model for routers in [3] is two remote AppleTalk routers linked
 as "half-routers" without a Node ID or Network number assigned to
 either side of the link.  When acting as half-routers, the only
 effect on transported packets is that the hop count is incremented
 when it is received over the link.  Routing updates received over a
 half-router link should also increment the hop count of routing table
 updates.
 As part of normal operation, AppleTalk will send RTMP Routing updates
 every 10 seconds.

3. ATCP Configuration Options

 ATCP Configuration Options allow negotiation of desirable AppleTalk
 parameters.  ATCP uses the same Configuration Option format defined
 for LCP [1], with a separate set of Options.
 The most up-to-date values of the ATCP Option Type field are
 specified in the most recent "Assigned Numbers" RFC [2].  Current
 values are assigned as follows:
 1       AppleTalk-Address
 2       Routing-Protocol
 3       Suppress-Broadcasts
 4       AT-Compression-Protocol
 5       RESERVED
 6       Server-information
 7       Zone-information
 8       Default-Router-Address

Parker [Page 4] RFC 1378 PPP ATCP November 1992

3.1. AppleTalk-Address

 Description
    This Configuration Option provides a way to negotiate the
    AppleTalk network and node number to be used on the local end of
    the link.  It allows the sender of the Configure-Request to state
    which AppleTalk-address is desired, or to request that the peer
    provide the information.  The peer can provide this information by
    NAKing the option, and returning a valid AppleTalk-address.
    If negotiation about the remote AppleTalk-address is required, and
    the peer did not provide the option in its Configure-Request, the
    option SHOULD be appended to a Configure-Nak.  The value of the
    AppleTalk-address given must be acceptable as the remote
    AppleTalk-address, or indicate a request that the peer provide the
    information.
    By default, no AppleTalk address is assigned.  A network or node
    number specified as zero in a Configure-Request shall be
    interpreted as requesting the remote end to specify a value via a
    Configure-Nak.  A network or node number specified as zero in a
    Configure-Ack shall be interpreted as agreement that no value
    exists.
    An implementation which requires that no AppleTalk addresses be
    assigned (such as a intermediate system to intermediate system
    "half-routing") MUST Configure-Reject all AppleTalk-Address
    Configuration Options.
    An implementation which requires that AppleTalk addresses be
    assigned to it (such as a end system) MUST fail configuration if
    the remote side Configure-Rejects all AppleTalk-Address requests,
    or fails to provide a valid value.
    If this option is negotiated, the two sides MUST negotiate a
    common AppleTalk network number and two unique Appletalk node
    numbers.  The network number MAY be zero but the Appletalk node
    numbers MUST be non-zero.  Values selected for network and node
    numbers must adhere to the ranges defined in [3].
    The AppleTalk protocol, phase 2, defines the concept of "extended"
    and "non-extended" networks.  Extended networks can support a
    large number (hundreds) of nodes, and requires multiple network
    numbers and multiple zone names to be managed effectively.  Non-
    extended networks can only support a small number of devices, and
    require only a single network number and zone name to be managed
    effectively.

Parker [Page 5] RFC 1378 PPP ATCP November 1992

    If a PPP link transporting AppleTalk is assigned an AppleTalk
    address, it must have the "non-extended" characteristics as
    defined in [3].
    The format of the network and node data is defined to be the same
    as the "AppleTalk address" in [3], chapter 3, "AppleTalk AARP
    packet formats on Ethernet and token ring".
 A summary of the AppleTalk-Address Configuration Option format is
 shown below.  The fields are transmitted from left to right.
  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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |     Type      |    Length     |    Reserved   |     AT-Net    |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |     AT-Net    |    AT-Node    |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 Type
    1
 Length
    6
 Reserved
    This octet is reserved and MUST be set to zero on transmission and
    ignored on reception.
 AT-Net
    The two octet AT-Net is the desired local AppleTalk network number
    of the sender of the Configure-Request.  This two octet quantity
    represents a 16 bit unsigned number sent "network byte order"
    (most significant octet first).
 AT-Node
    The one octet AT-Node is the desired local AppleTalk node ID of
    the sender of the Configure-Request.

Parker [Page 6] RFC 1378 PPP ATCP November 1992

3.2. Routing-Protocol

 Description
    This Configuration Option provides a way to negotiate the use of a
    specific routing protocol.  In particular, "half-routers" may want
    to exchange routing information using a protocol optimized for the
    PPP connection.  By default, AppleTalk RTMP (Routing Table
    Maintenance Protocol) routing information is sent over the PPP
    connection.
    By default, AppleTalk RTMP routing information is sent over the
    PPP connection.
 A summary of the Routing-Protocol Configuration Option format is
 shown below.  The fields are transmitted from left to right.
  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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |     Type      |    Length     |       Routing-Protocol        |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |    Data ...
 +-+-+-+-+
 Type
    2
 Length
    >= 4
 Routing-Protocol
    The Routing-Protocol field is two octets and indicates the type of
    Routing-Protocol desired.  This two octet quantity represents a 16
    bit number sent "network byte order" (most significant octet
    first).
    Negotiation of some routing protocols implies that you will
    receive packet types which transport these protocols.
    For example, negotiating AppleTalk AURP to exchange routing
    information implies both sides will accept EDDP type packets,
    since this is the transport type used by AURP.

Parker [Page 7] RFC 1378 PPP ATCP November 1992

    Initial values are assigned as follows:
    Value       Protocol
      0         No routing information exchange
      1         AppleTalk RTMP is used to exchange routing information
      2         AppleTalk AURP is used to exchange routing information
      3         AppleTalk ABGP is used to exchange routing information
 Data
    The Data field is zero or more octets and contains additional data
    as determined by the routing protocol indicated in the Routing-
    Protocol field.
    None of the Routing-Protocol options defined here require
    additional data.

3.3. Suppress-Broadcasts

 Description
    This Configuration Option provides a way to negotiate the
    suppression of AppleTalk broadcast datagrams which might otherwise
    use up limitted PPP bandwidth.  This Configuration Option is used
    to inform the remote end that no AppleTalk broadcast datagrams of
    a given DDP type should be sent.
    This option is useful when negotiated by a single end system.  It
    allows the local end system to request that broadcast packets
    generated on a remote network not be propagated across the PPP
    link.  In the case of a single end system connected to a large
    network, this can be used to suppress regular NBP lookups
    generated by other end systems on the remote network.  This will
    mean that protocols such as NBP can no longer be used to find
    network entities on the local system, but since the option
    configuration is asymmetric, it does not inhibit the local
    system's ability to find network entities on the remote network.
    By default, no AppleTalk broadcast datagrams are suppressed.  Note
    that this option may conflict with other options (such as Routing
    Protocol).  If so, the Suppress-Broadcasts option takes
    precedence.
 A summary of the Suppress-Broadcasts Configuration Option format is
 shown below.  The fields are transmitted from left to right.

Parker [Page 8] RFC 1378 PPP ATCP 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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |     Type      |    Length     |  DDP-Type  1  |  DDP-Type  2  |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | etc...
 +-+-+-+-+
 Type
    3
 Length
    >= 2
 DDP-Types
    A vector of one or more single octet DDP type values, each of
    which are to be suppressed if sent to the broadcast address.
    If no data is present (the length = 2), all broadcast packets are
    to be suppressed, regardless of DDP type.

3.4. AT-Compression-Protocol

 Description
    This Configuration Option provides a way to negotiate the use of a
    specific compression protocol.  By default, compression is not
    enabled.
 A summary of the AT-Compression-Protocol Configuration Option format
 is shown below.  The fields are transmitted from left to right.
  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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |     Type      |    Length     |   AT-Compression-Protocol     |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |    Data ...
 +-+-+-+-+
 Type
    4

Parker [Page 9] RFC 1378 PPP ATCP November 1992

 Length
    >= 4
 AT-Compression-Protocol
    The AT-Compression-Protocol field is two octets and indicates the
    compression protocol desired.  Values for this field are always
    the same as the PPP Data Link Layer Protocol field values for that
    same compression protocol.
    The most up-to-date values of the AT-Compression-Protocol field
    are specified in the most recent "Assigned Numbers" RFC [2].
    Current values are assigned as follows:
       Value (in hex)          Protocol
                               none defined
 Data
    The Data field is zero or more octets and contains additional data
    as determined by the particular compression protocol.

3.5. Server-information

 Description
    This Configuration Option provides a way to obtain information
    about the communications server providing the remote side of the
    PPP connection.
    The nature of this option is advisory only.  It is provided as a
    means of improving an end system's ability to provide a simple
    user interface.
 A summary of the Server-Information Option format is shown below.
 The fields are transmitted from left to right.

Parker [Page 10] RFC 1378 PPP ATCP 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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |     Type      |    Length     |          Server-class         |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                   Server-implementation-id                    |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |  Server-name ...
 +-+-+-+-+-+-+-+-+-+-+-+-+
 Type
    6
 Length
    >= 8
 Server-class
    The Server-class field is two octets and indicates the class of
    the communication server providing the remote end of the PPP
    connection.
    Initial values are assigned as follows:
    Value        Class
      1          AppleTalk PPP Dial-in server.
                 The server-implementation-id is a four byte version
                 id, with the first byte defined as the major
                 version number (1-255) and the second byte defined
                 as the minor version number (1-255).
                 The third and fourth bytes are undefined and should
                 be zero.
      2          Generic AppleTalk PPP implementation.
                 The server-implementation-id is undefined and
                 vendor specific.
      3          Both dial-in server and router

Parker [Page 11] RFC 1378 PPP ATCP November 1992

 Server-implementation-id
    The Server-implementation-id field is four octets and indicates
    the version of the communication server providing the remote end
    of the PPP connection.
 Server-name
    This optional field contains the "AppleTalk ASCII" name of the
    server.  The character codes used in "AppleTalk ASCII" are defined
    in [3], appendix D, "Character codes".  The length of the name is
    bounded by the option length.

3.6. Zone-Information

 Description
    This Configuration Option provides a way to obtain information
    about the AppleTalk zone used for the PPP connection.
    The nature of this option is advisory only.  It is provided as a
    means of improving the end system's ability to provide a simple
    user interface.
 A summary of the Zone-Information Option format is shown below.  The
 fields are transmitted from left to right.
  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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |     Type      |    Length     |           Zone-name...        |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 Type
    7
 Length
    >= 3
 Zone-name
    This field contains the "AppleTalk ASCII" zone name in which the
    server resides.  The character codes used in "AppleTalk ASCII" are
    defined in [3], appendix D, "Character codes".  The length of the
    name is bounded by the option length.

Parker [Page 12] RFC 1378 PPP ATCP November 1992

3.7. Default-Router-Address

 Description
    This Configuration Option provides a way to obtain information
    about a "default" Appletalk router which may be used to obtain
    network information such as zone names.  It is provided as a means
    of obtaining the address of a router in the case both sides of the
    link are end systems.
    Any AppleTalk RTMP packets received should supercede information
    negotiated in this option.
    By default, no default router is present.
 A summary of the Default-Router-Address Option format is shown below.
 The fields are transmitted from left to right.
  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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |     Type      |    Length     |    Reserved   |     AT-Net    |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |     AT-Net    |    AT-Node    |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 Type
    8
 Length
    6
 Reserved
    This octet is reserved and MUST be set to zero on transmission and
    ignored on reception.
 AT-Net
    The two octet AT-Net is the AppleTalk network number of the
    default router.  This two octet quantity represents a 16 bit
    unsigned number sent in "network byte order" (most significant
    octet first).

Parker [Page 13] RFC 1378 PPP ATCP November 1992

 AT-Node
    The one octet AT-Node is the AppleTalk node ID of the default
    router.

A. ATCP Recommended Options

 The ATCP is designed to support three different modes of operation.
 Each mode places constraints on the configuration options used and
 the values negotiated.
 The options for server information, zone information and default
 router address are "informational" options provided by one end of the
 connection and are not intended to be negotiated.  These options are
 provided to support a higher level of service to dial-in end systems.
 The options which SHOULD be negotiated in each case are outlined
 below.  Any option not listed may be rejected.

End System to Intermediate System - "dial-in"

 This mode of operation is intended to support end system dial-in.
       1       AppleTalk-Address (required)
       2       Routing-Protocol (required, no routing protocol)
       3       Suppress-Broadcasts (optional)
       4       AT-Compression-Protocol (optional)
       6       Server-information (optional, request from end system)

Parker [Page 14] RFC 1378 PPP ATCP November 1992

Intermediate system to Intermediate system - with network number

 This mode of operation is intended to support WAN-to-WAN, i.e.,
 router to router, connections where the link is configured with a
 network number.
       1      AppleTalk-Address (required, nets must be zero or equal)
       2      Routing-Protocol (optional)
       3      Suppress-Broadcasts (optional)

Intermediate system to Intermediate system - without network number

 This mode of operation is intended to support WAN-to-WAN, i.e.,
 router to router, connections where the link is not configured with a
 network number.  Routers in this mode are referred to as "half-
 routers" in [3].
       1      AppleTalk-Address (optional, nets & nodes MUST be zero)
       2      Routing-Protocol (optional)
       3      Suppress-Broadcasts (optional, suppress all broadcasts)

References

 [1] 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] Sidhu G., Andrews, R., and A. Oppenheimer, "Inside AppleTalk,
     Second Edition", Addison-Wesley Publishing Company, Inc., May
     1990.

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).
 This document is derivative of drafts written by the following
 people.  Many thanks for their work, and for taking an initial stab
 at the protocol:
 Steve Senum (sjs@network.com), Network Systems Corporation
 Jim Muchow (muchow@anubis.network.com), Network Systems Corporation
 Frank Slaughter (fgs@Shiva.COM), Shiva Corporation

Parker [Page 15] RFC 1378 PPP ATCP November 1992

Security Considerations

 Security issues are not discussed in this memo.

Chair's Address

 The working groups can be contacted via the current chairs:
 Brian Lloyd
 Lloyd & Associates
 3420 Sudbury Road
 Cameron Park, California 95682
 Phone: (916) 676-1147
 EMail: brian@lloyd.com
 John Veizades
 Apple Computer, Inc.
 20525 Mariani Avenue
 Cupertino, CA 95014
 Phone: (408) 996-1010
 EMail: veizades@apple.com

Author's Address

 Questions about this memo can also be directed to:
 Brad Parker
 Cayman Systems, Inc.
 26 Landsdowne Street
 Cambridge, Ma 02139
 EMail: brad@cayman.com

Parker [Page 16]

/data/webs/external/dokuwiki/data/pages/rfc/rfc1378.txt · Last modified: 1992/11/05 00:46 by 127.0.0.1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki