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rfc:rfc1634

Network Working Group M. Allen Request For Comments: 1634 Novell, Inc. Obsoletes: 1551, 1362 May 1994 Category: Informational

             Novell IPX Over Various WAN Media (IPXWAN)

Status of this Memo

 This memo provides information for the Internet community.  This memo
 does not specify an Internet standard of any kind.  Distribution of
 this memo is unlimited.

Abstract

 This document describes how Novell IPX operates over various WAN
 media.  Specifically, it describes the common "IPX WAN" protocol
 Novell uses to exchange necessary router to router information prior
 to exchanging standard IPX routing information and traffic over WAN
 datalinks. This document supercedes RFC 1362 and RFC 1551. The
 changes from RFC 1551 are to correct a problem in the wording when an
 RFC 1362 router talks to an RFC 1551 router and to allow numbers to
 be specified in a Router Name.

Table of Contents

 1.  Introduction ................................................. 2
 1.1 Operation Over PPP ........................................... 2
 1.2 Operation Over X.25 Switched Virtual Circuits ................ 2
 1.3 Operation Over X.25 Permanent Virtual Circuits ............... 3
 1.4 Operation Over Frame Relay ................................... 3
 1.5 Operation Over Other WAN Media ............................... 3
 2.  Glossary Of Terms ............................................ 4
 3.  IPX WAN Protocol Description ................................. 4
 3.1 The Initial Negotiation ...................................... 5
 3.2 Information Exchange ......................................... 9
 3.3 NAK Packets .................................................. 10
 4.  Information Exchange Packet Formats .......................... 10
 4.1 Timer Request Packet ......................................... 12
 4.2 Timer Response Packet ........................................ 15
 4.3 Information Request Packet ................................... 16
 4.4 Information Response Packet .................................. 19
 5.  Running Unnumbered RIP ....................................... 20
 6.  Workstation Connectivity ..................................... 20
 7.  On-demand, Statically Routed Links ........................... 20
 8.  References ................................................... 22
 9.  Security Considerations ...................................... 22
 10. Author's Address.............................................. 23

Allen [Page 1] RFC 1634 IPXWAN May 1994

1. Introduction

 This document describes how Novell IPX operates over various WAN
 media. It is strongly motivated by a desire for IPX to treat ALL wide
 area links in the same manner. Sections 3 and 4 describe this common
 "IPX WAN" protocol.
 The IPX WAN protocol operation begins immediately after link
 establishment. While IPX is a connectionless datagram protocol, WANs
 are often connection-oriented.  Different WANs have different methods
 of link establishment. The subsections of section 1 of this document
 describe what link establishment means to IPX for different media.
 They also describe other WAN-media-dependent aspects of IPX
 operation, such as protocol identification, frame encapsulation, and
 link tear down.

1.1 Operation Over PPP

 IPX uses PPP [1] when operating over point-to-point synchronous and
 asynchronous networks.
 With PPP, link establishment means the IPX NCP [4] reaches the Open
 state. NetWare IPX will negotiate down to a null set of NCP options,
 and uses normal frame encapsulation as defined by PPP. The IPXWAN
 protocol MUST NOT occur until the IPX NCP reaches the Open state.
 Options negotiated by the IPXWAN protocol MUST supercede any options
 negotiated by the IPXCP.
 PPP allows either side of a connection to stop forwarding IPX if one
 end sends an IPXCP or an LCP Terminate-Request. When a router detects
 this, it will immediately reflect the lost connectivity in its
 routing information database instead of naturally aging it out.

1.2 Operation over X.25 Switched Virtual Circuits

 With X.25, link establishment means successfully opening an X.25
 virtual circuit.  As specified in RFC-1356, "Multiprotocol
 Interconnect on X.25 and ISDN in the Packet Mode" [2], the protocol
 identifier 0x800000008137 is used in the X.25 Call User Data field of
 the Call Request frame, and indicates that the virtual circuit will
 be devoted to IPX.
 Furthermore, each IPX packet is encapsulated directly in X.25 data
 frame sequences without additional framing.
 Either side of the virtual circuit may close it, thereby tearing down
 the IPX link. When a router detects this, it will immediately reflect
 the lost connectivity in its routing information database instead of

Allen [Page 2] RFC 1634 IPXWAN May 1994

 naturally aging it out.

1.3 Operation over X.25 Permanent Virtual Circuits

 The nature of X.25 PVC's is that no call request is made.  When the
 router is informed that X.25 Layer 2 is up, the router should assume
 that link establishment is complete.
 Each IPX packet is encapsulated in an X.25 data frame sequence
 without additional framing. Novell IPX assumes a particular X.25
 permanent circuit is devoted to the use of IPX.
 If a router receives a layer 2 error condition (e.g., X.25 Restart),
 it should reflect lost connectivity for the permanent circuits in its
 routing information database and re-perform the necessary steps to
 obtain a full IPX connection.

1.4 Operation over Frame Relay Permanent Virtual Circuits

 To determine when a permanent virtual circuit (PVC) has become active
 or inactive, the router interacts periodically with either a private
 Frame Relay switch or a public Frame Relay network. The method used
 depends on the switch or service provider. Some support [7], section
 6l others support [3], Annex D. Novell supports both methods.
 When a router is restarted, IPXWAN exchanges over active Frame Relay
 PVCs (that is, PVCs that have remained active before and after
 restart) can begin immediately.
 Each IPX packet is encapsulated in a Frame Relay frame sequence as
 defined in [3] without additional framing.
 When a router detects that a Frame Relay PVC has transitioned from an
 inactive to an active state, link establishment is considered
 complete and IPXWAN exchange over this newly activated link begins.
 When an active PVC becomes inactive, the router reflects the lost
 connectivity in its routing information database.

1.5 Operation over other WAN media

 Additional WAN media will be added here as specifications are
 developed.

Allen [Page 3] RFC 1634 IPXWAN May 1994

2. Glossary Of Terms

 Primary Network Number:
    Every IPX WAN router has a "primary network number". This is an
    IPX network number unique to the entire internet.  This number
    will be a permanently assigned network number for the router.
    Those readers familiar with NetWare 3.x servers should realize
    that this is the "Internal" network number.
 Router Name:
    Every IPX WAN router must have a "Router Name". This is a symbolic
    name given to the router. Its purpose is to allow routers to know
    who they are connected to after link establishment - particularly
    for network management purposes.  A symbolic name conveys more
    information to an operator than a set of numbers. The symbolic
    name should be between 1 and 47 characters in length containing
    the characters 'A' through 'Z', '0' through '9', underscore (_),
    hyphen (-) and "at" sign (@). The string of characters should be
    followed by a null character (byte of zero) and padded to 48
    characters using the null character.  Those readers familiar with
    NetWare 3.x servers should realize that the file server name is
    the Router Name.
    For workstation (client) connectivity, it is useful if the client
    connection software is configured with a symbolic name reflecting
    the name of the client. This allows a router management utility to
    determine which connection connects with which client/router.  If
    no name is configured, it is recommended that a default string
    such as "DIAL-IN-CLIENT" is used.

3. IPX WAN Protocol Description

 After the underlying data link connection is established as described
 in the preceding media dependant description, the IPXWAN protocol is
 activated to exchange identities and determine certain operational
 charactaristics of the link.
 There are two steps in the IPXWAN operation:
  1. Negotiating master/slave role and choice of routing protocol.

The master/slave roles persist for the IPXWAN exchanges only;

  1. Information exchange of final router configuration.
 After these steps are concluded, transmission of IPX routing packets
 begins - using the routing protocol negotiated - as well as

Allen [Page 4] RFC 1634 IPXWAN May 1994

 transmission of IPX data traffic.

3.1 The Initial Negotiation

 The first exchange of packets decides the master/slave roles and the
 routing protocol to be used on the link and gauges the link delay for
 the routing metrics. The initial negotiation is the same for all
 protocols.
      +---------------+                 +---------------+
      | Timer Request |                 | Timer Request |
      +---------------+                 +---------------+
                       \---->\   /<----/
                              \ /
                               x
                              / \
                 /\    /<----/   \---->\    /\
               /    \                     /    \
             /        \                 /        \
           / My primary \             / My primary \
         / network address\         / network address\
         \    is larger   /         \   is smaller   /
           \            /             \            /
             \        /                 \        /
               \    /                     \    /
                 \/                         \/
               MASTER                      SLAVE
                                        +----------------+
                       <----------------+ Timer Response +
                                        +----------------+
 After link establishment, both sides of the link send Timer Request
 packets and start a timer waiting for a Timer Response. These Timer
 Requests are sent every 20 seconds until a response is received or a
 descision is made that the remote node is not responding. This could
 be after a predefined time (min. 60 seconds) or a number of retries
 (e.g., 16).
 In composing the Timer Request, the router or workstation takes into
 consideration:
  1. Which types of routing protocols it supports;
  1. Whether it is prepared to assign a network address to the link;
  1. For workstations, whether they require the ability to specify

their network/NIC address on a reconnect;

Allen [Page 5] RFC 1634 IPXWAN May 1994

  1. Whether it is able to support IPX header compression [6].
 For each routing protocol supported, place an option in the Timer
 Request packet. The Routing Type options should be added in the
 originator's order of preference with the most preferred option
 first.
 Some of the newer (or modified) IPX routing protocols do not have the
 requirement to allocate a network number on a WAN link. This type of
 routing protocol has the advantage of potentially simpler
 configuration as no network number pools are necessary for WAN links.
 However, these router implementations may still wish to interoperate
 with the older IPXWAN implementations which are able to allocate
 network numbers for the WAN link. In this case, the following method
 is used to force the older implementation to become the link master.
 It should be noted that a router implementation capable of supporting
 workstation dial-in MUST be able to supply AT LEAST ONE network
 number on which the workstation can reside.
 If the router is prepared to assign an IPX network number to the
 link, it sends its primary network number in the Timer Request
 WNodeID field, and omits the Extended Node ID option. On the other
 hand, if the router is NOT prepared to assign an IPX network number
 to the link, it sets the Timer Request WNodeID field to zero, and
 includes its primary network number in an Extended Node ID option.
 Workstations follow a similar, but slightly different set of rules
 for setting the WNodeID field. If this is the first time the work-
 station is connecting to the router, the workstation will set the
 WNodeID to zero indicating the router should be the link master and
 allocate a network number for the new link. In this case, the work-
 station will respond to the router's Timer Request and acknowledge
 only the Workstation Routing Type option. Note that a workstation
 does NOT include an Extended Node ID option in  it's timer request.
 If the workstation is reconnecting a link after an earlier inactivity
 disconnect, it is necessary for the workstation to be able to specify
 its network, NIC address and "Router Name" field (so that file server
 connections can be maintained after the reconnect).  In this case,
 the workstation will set its WNodeID field to FFFFFFFFh forcing
 itself to be the link master. In this case, the router will respond
 to the workstation's Timer Request with only the Workstation Router
 Type acknowledged.
 Further packets in the IPXWAN exchange MUST use the correct WNodeID
 (workstations will always use zero).

Allen [Page 6] RFC 1634 IPXWAN May 1994

 On receiving a Timer Request packet, a router determines its role -
 master or slave - for the remainder of the IPXWAN exchanges. The
 master role does not denote special privileges, it merely means that
 the router is the requestor in the ensuing request/response
 exchanges. The descision is made as follows:
    a) If the WNodeID field is zero in the sent and the received Timer
       Requests
       i) If both Timer Requests include an Extended Node ID, the
          router with the higher numeric value of this field is the
          Master. If the two Extended Node ID fields are equal, a
          configuration error has occurred. After reporting the error,
          the router issues a disconnect on the underlying data-link
          connection. Manual intervention is needed to correct the
          error condition.
       ii) If only one Timer Request includes the Extended Node ID,
           the router sending it is the Master.
       iii) If neither Timer Request includes the Extended Node ID, a
            connection cannot be established. The data-link circuit is
            cleared by the system that initiated it.
    b) If either the sent or received Timer Request (or both) contains
       a nonzero WNodeID field, the router with the higher WNodeID is
       the Master.
    c) If the two WNodeID fields are equal and nonzero, a
       configuration error has occurred. After reporting the error,
       the router issues a disconnect on the underlying data-link
       connection. Manual intervention is needed to correct the error
       condition.
    Note: The Primary Network Number for a workstation when
    determining master/slave roles depends on whether the workstation
    requires itself to be the master of slave. It should compare the
    received WNodeID to that sent in it's own Timer Request.
 The numeric comparisons are done by considering each byte of the
 WNodeID or Extended Node ID fields as an unsigned integer, and the
 first byte as most significant.
 The link slave responds to the Timer Request with a Timer Response.
 To do so, each option in the received Timer Request is parsed. If an
 option is not supported (or recognized), that option is rejected by
 changing the WAccept field to "NO" for that option.

Allen [Page 7] RFC 1634 IPXWAN May 1994

 When selecting the router type which will be used on the link, the
 first option in the Timer Request which can be supported should be
 accepted. All other router types should have the WAccept field set to
 "NO". A router MUST NOT accept workstation connectivity to a node
 which is another router.
 Note: It is permitted for a router to support a numbered routing
 type, but not be able to assign the network number. In this case,
 that routing type can be selected only if the other router supports
 it and is able to assign the network number. This can be determined
 by the value of the received WNodeID field. If the router is unable
 to assign a network number to the link, it MUST support Unnumbered
 RIP and include this option in the Timer Requests.
 If a router wishes to provide WAN Client access without supporting
 other WAN routing types, a potential problem arises since a router
 and WAN client would both just be sending a single Routing Type
 option indicating the use of WAN Client. The IPXWAN specification
 does not allow a WAN workstation to connect to another WAN
 workstation. The method for detecting this is that the sent and
 received Timer Requests have a single Routing Type defined of WAN
 Client. To overcome this problem, IPXWAN defines that a router MUST
 NOT send a single Routing Type if that type is just WAN Client. The
 router MUST additionally include one (or more) of the defined routing
 types (like WAN RIP) with the WAccept option set to NO. This is so
 that a workstation may detect that this is actually a router sending
 the Timer Request and not just another workstation trying to call a
 workstation. The extra option will serve to be a counted Routing Type
 that will be ignored. If a workstation detects it is connecting to
 another workstation, it should disconnect the link.
 Note that a router supporting a workstation will need to be able to
 supply AT LEAST one network number for workstations. All dial-in
 workstations could share the same network, and be assigned unique
 node numbers by the router, or each workstation could be assigned a
 different network number. This is a router specific implementation
 detail. Use of a single network for all clients is prefered, however,
 this does involve extra work by the router when dealing with
 broadcast frames. When the router is the link master and allocating
 NIC addresses on a single network,it should ALWAYS use a unique value
 - by incrementing the NIC address for each client connection. This
 allows a workstation which is reconnecting the ability to specify his
 old network and NIC address. It is unlikely with a 6 byte NIC
 address, that there will be wrap-around in the numbers that would
 cause a problem. Router Node Number allocation should follow a few
 simple rules. The six byte NIC address SHOULD have the first byte set
 to 2.

Allen [Page 8] RFC 1634 IPXWAN May 1994

       Byte # +--1----2----3----4----5----6-+
              | 02 | XX | XX | XX | XX | XX |
              +-----------------------------+
 In an IEEE address space, this would represent a non-multicast,
 locally defined address. Node numbers of zero or -1 are not allowed.
 If a slave determines it cannot support any of the supplied routing
 protocols in the received Timer Request, it MUST issue a disconnect
 on the connection being established. The master of the link
 (determined when a Timer Response packet is received) is responsible
 for defining the network number that is to be used as a common
 network number for the new WAN link, and for calculating the RIP
 transport time that will be advertized to other RIP routers for the
 new link. This is calculated by stopping the timer which was started
 when a Timer Request was initiated and applying the algorithm in
 section 4.3.

3.2 Information Exchange

 After exchanging Timer Request packets, the link master and slave
 have been determined, and the Routing Protocol to be used on the link
 is negotiated. The link master is now responsible for sending an
 Information Request packet to the slave specifying the network number
 to be used on the new link (zero for unnumbered RIP and On Demand),
 the calculated transport time to be used in the routing metric, the
 Router Name (for management purposes), and for a workstation
 connection, the NIC address the workstation will be adopting. The NIC
 address option is a separate option added in the Information
 Request/Response for workstation connectivity. It is NOT present for
 router to router connections.
 If a router receives an inappropriate Information Request from a
 workstation trying to set the common network number and NIC address
 the router MUST overwrite these values with preferred values. When
 the workstation receives the Information Response, it MUST note the
 new values. If the workstation is unable to adjust to the new values,
 it MUST issue a disconnect on the link. If a workstation is the link
 master (i.e., it is reconnecting), the router is additionally
 responsible for ensuring the "Router Name" field matches that of the
 original connection. If the values differ, the call should be
 disconnected.
 If a router detects an error for which no suitable protocol response
 exists (e.g., unable to allocate a network number), the link should
 be terminated according to the relevant media specification.

Allen [Page 9] RFC 1634 IPXWAN May 1994

 Under certain circumstances, particularly on X.25 permanent circuits,
 it is only possible to detect the remote router went away when it
 comes back up again.  In this case, one side of the link receives a
 Timer Request packet when IPX is in a fully connected state.  The
 side receiving the Timer Request MUST realize that a problem
 occurred, and revert to the IPX link establishment phase.
 Furthermore, the routing information learned from this connection
 should be immediately discarded.
 When Unnumbered RIP, On-demand or Workstation options are negotiated,
 Information Request packets are repeated every 20 seconds until a
 response is received. For the Numbered RIP links, the Information
 Request is NOT resent. Instead, the link is disconnected after a
 suitable delay (min. 60 seconds) - this requirement ensures
 interoperabilty with earlier versions of IPXWAN.  When Information
 Requests are repeated, they should continue for a preconfigured time
 (min. 60 seconds) or a preconfigured number of retries (e.g., 16).
 Each retry uses an incremented sequence number.

3.3 NAK Packets

 The IPXWAN protocol uses a NAK packet to indicate the received IPXWAN
 packet was not acceptable. A NAK packet is an exact copy of the
 received packet with the WPacketType field set to NAK. There are two
 anticipated uses of this packet.
  1. The received WPacketType is invalid or not recognized;
  1. A badly formed IPXWAN packet is received.
 Returning a NAK packet allows the sender a chance to work out what
 was wrong. If the sender was unable to determine the problem, the
 call can then be disconnected.
 The value of the NAK WPacketType is FFh.

4. Information Exchange Packet Formats

 All IPX WAN protocol exchanges utilize the standard Novell IPX packet
 format. The packets use the IPX defined packet type 04 defining a
 Packet Exchange Packet. The socket number 0x9004 is a Novell reserved
 socket number for exclusive use with IPX WAN protocol exchange. IPX
 defines that a network number of zero (0) is interpreted as being a
 local network of unknown number that requires no routing. This
 feature is of use to us in transferring these packets before the
 common network number is exchanged. Some routers need to know a "Node
 Number" (or MAC address) for each node on a link. Node numbers will

Allen [Page 10] RFC 1634 IPXWAN May 1994

 be formed from the "WNode ID" field.  The node number will be the 4
 bytes of WNode ID followed by 2 bytes of zero. For a workstation, the
 node number will be explicitly assigned by the router and notified to
 the workstation in the Information Request packet.
 Router Type number assignment. Other vendors IPX routing protocols
 can make use of the IPXWAN protocol definition by obtaining Router
 Types from Novell. This document will then include the new Router
 Types (with the references to vendor protocol description documents).
 Current Routing Types are:
    00      Numbered RIP/SAP
    01      NLSP (no RIP/SAP - defined in [8])
    02      Unnumbered RIP/SAP
    03      On Demand, static routing (no RIP/SAP or NLSP)
    04      Workstation (no RIP/SAP)
    05-FF   Currently undefined
 WOption Number assignment. These numbers only need to be assigned
 from Novell for the "Timer Request" and "Timer Response" packets.
 Packet Types also need to be assigned by Novell. However, the options
 within these packets are dependant on the "Router Type" negotiated.
 WOption numbers in these packets are then defined by the vendor
 defining the Routing Type. The same packet format should still be
 maintained.
 Router Type 01 will not be described in this document since it
 involves knowledge of the NLSP protocol to implement. Please refer to
 [8] for a complete specification of these NLSP IPXWAN exchanges and
 the NLSP protocol.

Allen [Page 11] RFC 1634 IPXWAN May 1994

4.1 Timer Request Packet

  +---------------------------------------------------------------+
  | Checksum         | FF FF             | Always FFFF            |
  | Packet Length    | 02 40             | Max IPX size (576 bytes|
  |                  |                   | Hi Lo order)           |
  | Trans Control    | 00                | Hops traversed         |
  | Packet Type      | 04                | Packet Exchange Packet |
  | Dest Net #       | 00 00 00 00       | Local Network          |
  | Dest Node #      | FF FF FF FF FF FF | Broadcast              |
  | Dest Socket #    | 90 04             | Reserved WAN socket    |
  | Source Net #     | 00 00 00 00       | Local Network          |
  | Source Node #    | 00 00 00 00 00 00 | Set to zero            |
  | Source Socket #  | 90 04             | Reserved WAN socket    |
  |------------------+-------------------+------------------------|
  | WIdentifier      | 57 41 53 4D       | Confidence identifier  |
  | WPacket Type     | 00                | Timer Request          |
  | WNode ID         | xx xx xx xx       | Primary Net # of       |
  |                  |                   | sending router         |
  |                  |                   | (Hi Lo order)          |
  | WSequence #      | xx                | Sequence start at 0    |
  | WNum Options     | xx                | Number of options      |
  |------------------+-------------------+------------------------|
  | WOption Number   | xx                | Option Identifier      |
  | WAccept Option   | xx                | 0=No,1=Yes,3=Not Applic|
  | WOption Data Len | xx xx             | Number of following    |
  |                  |                   | option bytes (Hi Lo)   |
  | WOption Data     | nn                | Option specific data   |
  +---------------------------------------------------------------+

Routing Type Option:

  One or more of the following router type options should be included
  in a Timer Request packet. A router should ALWAYS include Routing
  Type zero (0) if full interoperability is required with an older
  implementation. The router types MUST be included in the senders
  order of preference. If a router receives a Timer Response with more
  than one Router Type having WAccept set to Yes, the link MUST be
  disconnected.
  +---------------------------------------------------------------+
  | WOption Number   | 00                | Define Routing Type    |
  | WAccept Option   | 01                | 0=No,1=Yes,3=Not Applic|
  | WOption Data Len | 00 01             | Option length (Hi Lo)  |
  | WOption Data     | 00                | IPX RIP/SAP Routing    |
  +---------------------------------------------------------------+

Allen [Page 12] RFC 1634 IPXWAN May 1994

  +---------------------------------------------------------------+
  | WOption Number   | 00                | Define Routing Type    |
  | WAccept Option   | 01                | 0=No,1=Yes,3=Not Applic|
  | WOption Data Len | 00 01             | Option length (Hi Lo)  |
  | WOption Data     | 01                | NLSP                   |
  +---------------------------------------------------------------+
  +---------------------------------------------------------------+
  | WOption Number   | 00                | Define Routing Type    |
  | WAccept Option   | 01                | 0=No,1=Yes,3=Not Applic|
  | WOption Data Len | 00 01             | Option length (Hi Lo)  |
  | WOption Data     | 02                | Unnumbered RIP/SAP     |
  +---------------------------------------------------------------+
  +---------------------------------------------------------------+
  | WOption Number   | 00                | Define Routing Type    |
  | WAccept Option   | 01                | 0=No,1=Yes,3=Not Applic|
  | WOption Data Len | 00 01             | Option length (Hi Lo)  |
  | WOption Data     | 03                | On-demand, static Rting|
  +---------------------------------------------------------------+
  +---------------------------------------------------------------+
  | WOption Number   | 00                | Define Routing Type    |
  | WAccept Option   | 01                | 0=No,1=Yes,3=Not Applic|
  | WOption Data Len | 00 01             | Option length (Hi Lo)  |
  | WOption Data     | 04                | Client - No RIP/SAP    |
  |                  |                   | except on request      |
  +---------------------------------------------------------------+

Extended Node ID Option:

  The extended node ID should only be included if the WNodeID field is
  set to zero AND the node constructing the packet is a router. Note
  that an older version of IPXWAN will just reject this option and
  automatically become the link master as the WNodeID is zero.
  +---------------------------------------------------------------+
  | WOption Number   | 04                | Extended Node ID       |
  | WAccept Option   | 01                | 0=No,1=Yes,3=Not Applic|
  | WOption Data Len | 00 04             | Pad data length (Hi Lo)|
  | WOption Data     | xx xx xx xx       | Real primary network # |
  |                  |                   | of this router (Hi-Lo) |
  +---------------------------------------------------------------+

Header Compression Option:

  Although more than one header compression option may be specified in
  a Timer Request packet, it is important that a MAXIMUM of ONE header
  compression option is accepted. If an implementation receives a
  Timer Response with more than one header compression option with the
  accept option set to Yes, the link MUST be disconnected. [Ref 6]
  defines the full Telebit Header Compression method.

Allen [Page 13] RFC 1634 IPXWAN May 1994

  +---------------------------------------------------------------+
  | WOption Number   | 80                | Header Compression     |
  | WAccept Option   | 01                | 0=No,1=Yes,3=Not Applic|
  | WOption Data Len | 00 03             | Variable - at least 1  |
  | WOption Data     | 00                | 0 = Telebit Hdr Compr. |
  |                  | xx                | Compression Options    |
  |                  | xx                | Compression Slots      |
  +---------------------------------------------------------------+

PAD Option:

  The PAD option is used to fill the Timer Request up to the 576 byte
  limit. This field will be of variable length depending on the number
  of other options in the packet. This option will normally be the
  last entry in the packet.  Its sole purpose is to fill the IPX
  packet to be 576 bytes.  The pad option data should be filled with a
  selection of totally random numbers to avoid compression modems or
  PPP data compression from destroying the link delay calculation.
  Note that this is different from the original RFC 1362
  specification. This should not affect implementations.
  Implementations should not attempt to verify the contents of a PAD
  option.
  +---------------------------------------------------------------+
  | WOption Number   | FF                | Pad option             |
  | WAccept Option   | 01                | 0=No,1=Yes,3=Not Applic|
  | WOption Data Len | xx xx             | Pad data length (Hi Lo)|
  |                  |                   | (enough to fill packet)|
  | WOption Data     | Random numbers    |                        |
  +---------------------------------------------------------------+
  Note:
          Timer Request packets will always be 576 bytes. However,
          there should be no assumption made about the number of
          options specified in this packet.
 After link establishment, Timer Request packets are sent by both
 sides of the link. Each end starts their sequence number at zero.
 Subsequent retries (every 20 seconds) will increment the value of
 this sequence number.  Only a Timer Response packet with a sequence
 number matching the last sent sequence number will be acted upon.
 As mentioned earlier, the WNodeID field may be set to zero for a
 router if it is unable to provide a network number for the link.  If
 a router ONLY supports the Numbered RIP/SAP option, it MUST be
 capable of proving a network number for a WAN link.

Allen [Page 14] RFC 1634 IPXWAN May 1994

 Packets received on the reserved socket number not having the
 WIdentifier set to the hexadecimal values noted above should be
 discarded.

4.2 Timer Response Packet

  +---------------------------------------------------------------+
  | Checksum         | FF FF             | Always FFFF            |
  | Packet Length    | 02 40             | Max IPX size (576 bytes|
  |                  |                   | Hi Lo order)           |
  | Trans Control    | 00                | Hops traversed         |
  | Packet Type      | 04                | Packet Exchange Packet |
  | Dest Net #       | 00 00 00 00       | Local Network          |
  | Dest Node #      | FF FF FF FF FF FF | Broadcast              |
  | Dest Socket #    | 90 04             | Reserved WAN socket    |
  | Source Net #     | 00 00 00 00       | Local Network          |
  | Source Node #    | 00 00 00 00 00 00 | Set to zero            |
  | Source Socket #  | 90 04             | Reserved WAN socket    |
  |------------------+-------------------+------------------------|
  | WIdentifier      | 57 41 53 4D       | Confidence identifier  |
  | WPacket Type     | 01                | Timer Response         |
  | WNode ID         | xx xx xx xx       | Primary Net # of       |
  |                  |                   | sending router         |
  |                  |                   | (Hi Lo order)          |
  | WSequence #      | xx                | Same as Timer Request  |
  |                  |                   | received               |
  | WNum Options     | xx                | Number of options      |
  |------------------+-------------------+------------------------|
  | WOption Number   | xx                | Option Identifier      |
  | WAccept Option   | xx                | 0=No,1=Yes,3=Not Applic|
  | WOption Data Len | xx xx             | Number of following    |
  |                  |                   | option bytes (Hi Lo)   |
  | WOption Data     | nn                | Option specific data   |
  +---------------------------------------------------------------+
 The options contained within this packet are as described in section
 4.1 Any unknown options or not supported options within the Timer
 Request MUST have the WAccept Option set to NO in the Timer Response.
 If the Timer Request packet contained more than one Router Type
 option and the "Slave" supports all the options, the "Slave" MUST set
 the WAccept Option to YES on the FIRST Router Type supported and NO
 to ALL other Router Types. This is the Router Type which is to be
 adopted by both ends of the link. Information exchanges will then
 proceed by the link master based on the accepted Router Type.
 This packet must contain the same sequence number as the received
 Timer Request. This packet should ONLY be sent by the router or

Allen [Page 15] RFC 1634 IPXWAN May 1994

 workstation determining themselves to be the "Slave" of the link.
 (Workstations are ALWAYS the link slave).
 Routers MUST set the WNodeID to their correct value when responding
 with the Timer Response. A value of zero must NOT be used.

4.3 Information Request Packet

  +---------------------------------------------------------------+
  | Checksum         | FF FF             | Always FFFF            |
  | Packet Length    | 00 63             | Size of header+data    |
  |                  |                   | (Hi Lo order)          |
  | Trans Control    | 00                | Hops traversed         |
  | Packet Type      | 04                | Packet Exchange Packet |
  | Dest Net #       | 00 00 00 00       | Local Network          |
  | Dest Node #      | FF FF FF FF FF FF | Broadcast              |
  | Dest Socket #    | 90 04             | Reserved WAN socket    |
  | Source Net #     | 00 00 00 00       | Local Network          |
  | Source Node #    | 00 00 00 00 00 00 | Set to zero            |
  | Source Socket #  | 90 04             | Reserved WAN socket    |
  |------------------+-------------------+------------------------|
  | WIdentifier      | 57 41 53 4D       | Confidence identifier  |
  | WPacket Type     | 02                | Information Request    |
  | WNode ID         | xx xx xx xx       | Primary Net # of       |
  |                  |                   | sending router         |
  |                  |                   | (Hi Lo order)          |
  | WSequence #      | 00                | Sequence start at 0    |
  | WNum Options     | 01                | 1 Option to follow     |
  | WOption Number   | 01                | Define IPX RIP/SAP     |
  |                  |                   | info exchange          |
  | WAccept Option   | 01                | 0=No,1=Yes,3=Not Applic|
  | WOption Data Len | 00 36             | Option length (Hi Lo)  |
  | WOption Data     |                   |                        |
  |  Link Delay      | xx xx             | Hi Lo link delay in    |
  |                  |                   | milli seconds (see     |
  |                  |                   | below for calculation) |
  |  Common Net #    | xx xx xx xx       | Hi Lo Common Network # |
  |  Router Name     | xx (x 48 decimal) | Router name - as defned|
  |                  |                   | in section 2.          |
  +---------------------------------------------------------------+
 Routers MUST set the WNodeID to their correct value when sending an
 Information Request. A value of zero must NOT be used.
 A workstation should replace the Router Name with the configured
 name, or a constant descriptor string as described in section 2.

Allen [Page 16] RFC 1634 IPXWAN May 1994

 For a Workstation Information Request, an extra option is added which
 specifies the NIC address for the workstation. In this case, the
 number of options will be set to two (2).
  +---------------------------------------------------------------+
  | WOption Number   | 05                | Define NIC Address     |
  | WAccept Option   | 01                | 0=No,1=Yes,3=Not Applic|
  | WOption Data Len | 00 06             | Option length (Hi Lo)  |
  | WOption Data     | 02 xx xx xx xx xx | NIC Address for W/S    |
  +---------------------------------------------------------------+
 Routers or workstations should not refuse to use a NIC address having
 a first byte with a value other than 02.
 Calculation of link delay is performed as follows:
  // Start_time is a time stamp when Timer Request sent out
  // End_time is a time stamp when a Timer Response is
  // received.
  link_delay = end_time - start_time; // 1/18th second
  if (link_delay < 1)
  {
      link_delay = 1;
  }/*IF*/
  // We are on a slow net, so add some biasing to help stop
  // multiple workstation sessions timing out on the link
  link_delay *= 6;   /* Add the biasing  for multiple sessions */
  link_delay *= 55;  /* Convert link delay to milliseconds */
  If a higher resolution timer is available, better results may be
  obtained using the following algorithm:
  conversion_factor = number of timer units in 1/18th second;
  link_delay = ((end_time - start_time) * 6) / conversion_factor;
  if (link_delay == 0)
  {
      link_delay = 1;
  }/*IF*/
  link_delay *= 55; /* Convert link delay to milliseconds */
 The "Link Delay" is used as the network transport time when
 advertized in the IPX RIP packet tuple for the network entry "Common
 Net #". For a consistent network, a common link delay is required at
 both ends of the link and is calculated by the link "Master". Link
 Delay is specified in milli seconds.

Allen [Page 17] RFC 1634 IPXWAN May 1994

 The Common Net # is supplied by the link "Master". This number must
 be unique in the connected internetwork. Each WAN call requires a
 separate number. If the negotiated Router Type was Unnumbered RIP,
 On-demand, or NLSP, the specified Common Net # will be zero.
 This packet should contain a sequence number starting at zero. This
 packet should ONLY be sent by the router or workstation determining
 themselves to be the "Slave" of the link.
 If extra options are included in this packet, they should be silently
 discarded.If the information option is missing, the link MUST be
 disconnected.

Allen [Page 18] RFC 1634 IPXWAN May 1994

4.4 Information Response Packet

  +---------------------------------------------------------------+
  | Checksum         | FF FF             | Always FFFF            |
  | Packet Length    | 00 63             | Size of header+data    |
  |                  |                   | (Hi Lo Order)          |
  | Trans Control    | 00                | Hops traversed         |
  | Packet Type      | 04                | Packet Exchange Packet |
  | Dest Net #       | 00 00 00 00       | Local Network          |
  | Dest Node #      | FF FF FF FF FF FF | Broadcast              |
  | Dest Socket #    | 90 04             | Reserved WAN socket    |
  | Source Net #     | 00 00 00 00       | Local Network          |
  | Source Node #    | 00 00 00 00 00 00 | Set to zero            |
  | Source Socket #  | 90 04             | Reserved WAN socket    |
  |------------------+-------------------+------------------------|
  | WIdentifier      | 57 41 53 4D       | Confidence identifier  |
  | WPacket Type     | 03                | Information Response   |
  | WNode ID         | xx xx xx xx       | Primary Net # of       |
  |                  |                   | sending router         |
  |                  |                   | (Hi Lo order)          |
  | WSequence #      | 00                | Same as Info Request   |
  | WNum Options     | 01                | 1 Option to follow     |
  | WOption Number   | 01                | Define IPX RIP/SAP     |
  |                  |                   | info exchange          |
  | WAccept Option   | 01                | 0=No,1=Yes,3=Not Applic|
  | WOption Data Len | 00 36             | Option length (Hi Lo)  |
  | WOption Data     |                   |                        |
  |  Link Delay      | xx xx             | Hi Lo link delay (as   |
  |                  |                   | received in Info Requ) |
  |  Common Net #    | xx xx xx xx       | Hi Lo Common Network # |
  |                  |                   | (as received in Info   |
  |                  |                   | request)               |
  |  Router Name     | xx (x 48 decimal) | Router name - as defned|
  |                  |                   | in section 2.          |
  +---------------------------------------------------------------+
 The responses contained within this packet are as described in
 section 4.3.
 A link slave will additionally respond with the received  NIC address
 option as a confirmation of receipt. A workstation should replace the
 Router Name with the configured name, or a constant descriptor string
 as described in section 2. If the Information Request contained an
 inappropriate Common Net # or NIC address, the Information Response
 may set new values. The receiver of the Information Response is
 responsible for checking on the value and terminating the connection
 if the new values cannot be used.

Allen [Page 19] RFC 1634 IPXWAN May 1994

 Routers MUST set the WNodeID to their correct value when sending an
 Information Response. A value of zero must NOT be used.

5. Running Unnumbered RIP

 Unnumbered RIP refers to the case where two WAN routers are
 communicating using the RIP protocol across a link with NO physical
 IPX network address. The premise for this ability is that there is no
 need to address a packet to anything on that WAN link. RIP and SAP
 run in exactly the same way as before, except the source and
 destination network numbers should be set to zero.
 The advantage to running unnumbered RIP links is that it is not
 necessary to allocate/configure a pool of usable IPX network numbers
 which can be used on the WAN links. The other advantage is that when
 there is a large number of WAN links, it is not necessary to flood
 the network with an unnecessary set of extra RIP information.

6. Workstation Connectivity

 Workstations MUST reside on a network and have a unique NIC address
 on that network to be individually addressable. However, workstations
 do not need to periodically receive RIP and SAP broadcasts as they
 play no part in the routing process. This allows routers to reduce
 background traffic on the workstation link by not sending any
 periodic RIP and SAP data. Note that it will not cause a problem if
 the RIP and SAP is sent. It will just slow down the workstation
 access times.
 RIP and SAP information should ONLY be sent if the workstation makes
 a specific request for information - like a service or route request.
 It should also be noted that if multiple workstations are attached to
 a single WAN workstation network (per router), broadcasts on that
 network - whether originated from a workstation or the router - MUST
 reach ALL other workstations. This will involve the router
 duplicating the packet to all WAN workstation connections.

7. On-demand, Statically Routed Links

 On-demand, Static Routing serves two purposes. The "on-demand" part
 means that a router initiates communication to a destination only
 when there is data to be forwarded to that destination. "Inititating
 comunication" includes making a datalink call (where necessary) and
 performing the IPXWAN exchange. A transient connection is closed
 after a period of inactivity.

Allen [Page 20] RFC 1634 IPXWAN May 1994

 The "static routing" part means that no routing information is sent
 over the link - no RIP, no SAP, and no NLSP. Instead, the router at
 each end is configured with the routes and services accessible
 through the link.
 With on-demand, static routing, the called router must be able to
 identify the calling router so that statically configured routes and
 services can be attached to that connection. For example, with X.25
 switched virtual circuits, the calling DTE address can be used; with
 PPP, the PPP authentication can be used; after IPXWAN has completed,
 the "Router Name" can be used; with a persistent datalink connection,
 the physical port identifier or a permanent virtual circuit
 identifier can be used. The choice of identifier is an implementation
 decision. Whatever value the called router uses is called a Remote
 System Identifier, or RSI. For PPP links, Novell uses PPP PAP or CHAP
 authentication to determine the caller.
 A router implementing on-demand, static routing must maintain a
 database of RSIs, and lists describing the network numbers and
 services reachable through each RSI. These lists determine the
 reachability information it transmits to other routers in a routing
 area. Other routers treat each on-demand, static routing link as
 though it were permanently available.
 The on-demand exchange has a slight variation on the IPXWAN protocol.
 The differences are as follows.
 In the Timer Request, the calling router offers only the "On-demand,
 static routing" Routing Type. If the called router is capable of On-
 demand static routing, it offers "On-demand, static routing" in the
 Timer Request, along with any additional routing types it is willing
 to support on the link. The Master/Slave election and choice of
 routing type proceeds as described previously. If the Slave detects a
 mismatch in routing types, it disconnects the link.
 For a persistent datalink (like X.25 PVCs), there may be no
 descerable "link establishemnt" event. For such media, arrival of a
 Timer Request plays the role of detecting link establishment.
 As with Unnumbered RIP, there is no network number assigned to the
 link. NLSP Packets are not sent on the link. Moreover, periodic RIP
 and SAP packets are not sent on the link. However, a router must
 respond to RIP and SAP queries received on the link.

Allen [Page 21] RFC 1634 IPXWAN May 1994

8. References

 [1] Simpson, W., Editor, "The Point-to-Point Protocol (PPP) for the
     Transmission of Multi-protocol Datagrams over Point-to-Point
     Links", RFC 1548, Daydreamer, December 1993.
 [2] Malis, A., Robinson, D., and R. Ullman, "Multiprotocol
     Interconnect on X.25 and ISDN in the Packet Mode", RFC 1356,
     August 1992.
 [3] Bradley, T., Brown, C., and A. Malis, "Multiprotocol Interconnect
     over Frame Relay", RFC 1490, Wellfleet Communications, Inc.,
     Ascom Timeplex, Inc., July 1993.
 [4] Simpson, W., "The PPP Internetwork Packet Exchange Control
     Protocol (IPXCP)", RFC 1552, Daydreamer, December 1993.
 [5] Novell IPX Router Specification.  Novell Part Number 107-000029-
     001. This document may be retrieved via Anonymous FTP to SJF-LWP
     (130.57.11.140) under /sys/ftpguest/dev_docs/ipx_rtr/ipxrtr.zip
 [6] Mathur, S., and M. Lewis, "Compressing IPX Headers Over WAN Media
     (CIPX)", RFC 1553, Telebit Corporation, December 1993.
 [7] ANSI, "Integrated Services Digital Network (ISDN) - Digital
     Subscriber Signalling System Number 1 (DSS1) - Signalling
     Specification for Frame Relay", ANSI T1.617-1991, June 1991.
 [8] Novell NetWare Link Services Protocol (NLSP) Specification.
     Novell part number 100-001708-002. This document may be retrieved
     via Anonymous FTP to SJF-LWP (130.57.11.140) under
     /sys/ftpguest/dev_docs/ipx_rtr/nlsp.zip.

9. Security Considerations

 Security issues are not discussed in this memo.

Allen [Page 22] RFC 1634 IPXWAN May 1994

10. Author's Address

 Michael Allen
 Novell, Inc.
 2180 Fortune Drive
 San Jose, CA 95131
 EMail: mallen@novell.com
 The working group can be contacted via the current chair:
 Fred Baker
 Advanced Computer Communications
 315 Bollay Drive
 Santa Barbara, California, 93111
 EMail: fbaker@acc.com

Allen [Page 23]

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