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Network Working Group Simpson
Internet Draft Daydreamer
expires in six months October 1992
The PPP Internetwork Packet Exchange Control Protocol (IPXCP)
Status of this Memo
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 ietf-ppp@ucdavis.edu mailing list.
Distribution of this memo is unlimited.
This document is an Internet Draft. Internet Drafts are working
documents of the Internet Engineering Task Force (IETF), its Areas,
and its Working Groups. Note that other groups may also distribute
working documents as Internet Drafts. Internet Drafts are draft
documents valid for a maximum of six months. Internet Drafts may be
updated, replaced, or obsoleted by other documents at any time. It
is not appropriate to use Internet Drafts as reference material or to
cite them other than as a ``working draft'' or ``work in progress.''
Please check the 1id-abstracts.txt listing contained in the
internet-drafts Shadow Directories on nic.ddn.mil, nnsc.nsf.net,
nic.nordu.net, ftp.nisc.sri.com, or munnari.oz.au to learn the
current status of any Internet Draft.
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.
The IPX protocol was originally used in Novell's NetWare products
[3], and is now supported by numerous other vendors. This document
defines the NCP for establishing and configuring the IPX protocol
over PPP.
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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).
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2. A PPP Network Control Protocol (NCP) for IPX
The IPX Control Protocol (IPXCP) is responsible for configuring,
enabling, and disabling the IPX protocol modules on both ends of the
point-to-point link. IPXCP uses the same packet exchange machanism
as the Link Control Protocol (LCP). IPXCP packets may not be
exchanged until PPP has reached the Network-Layer Protocol phase.
IPXCP packets received before this phase is reached should be
silently discarded.
The IPX 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 IPXCP packet is encapsulated in the Information field
of a PPP Data Link Layer frame where the Protocol field indicates
type hex 802B (IPX 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
IPXCP 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
IPXCP has a distinct set of Configuration Options, which are
defined below.
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2.1. Sending IPX Datagrams
Before any IPX packets may be communicated, PPP must reach the
Network-Layer Protocol phase, and the IPX Control Protocol must reach
the Opened state.
Exactly one IPX packet is encapsulated in the Information field of a
PPP Data Link Layer frame where the Protocol field indicates type hex
002B (IPX).
The maximum length of an IPX datagram transmitted over a PPP link is
the same as the maximum length of the Information field of a PPP data
link layer frame. Since there is no standard method for fragmenting
and reassembling IPX datagrams, PPP links supporting IPX MUST allow
at least 576 octets in the information field of a data link layer
frame.
2.2. IPX-WAN protocol
Novell has recently announced a new specification called IPX-WAN [4],
which is intended to provide mechanisms similar to IPXCP negotiation
over all types of wide area links. As viewed by PPP, IPX-WAN is a
part of IPX, and IPX-WAN packets are indistinguishable from other IPX
packets.
2.3. Co-existance with IPX-WAN
Previous drafts of this specification have introduced a NCP with
several configuration options, and another NCP having no
configuration options, with some NCP functions moved to the IPX-WAN
protocol. This version proposes the union of the previous proposals,
with instructions for interoperating between the two environments.
As time has progressed, Novell has improved IPX-WAN by adding the
functional equivalent of every feature proposed in earlier drafts of
this document.
Currently, Novell has implemented IPXCP without any Configuration
Options, and requires successful IPX-WAN negotiation, even when all
required parameters have been hand configured. This makes it
impossible for the Novell products to interoperate with
implementations which do not already include support for IPX-WAN.
Therefore, it is the intent of this document to accomodate versions
of IPX and IPXCP which are implemented by other vendors, and to
provide features and functionality for those implementations which
are not directly connected to a NetWare network. It is hoped that
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future Novell releases will support the complete IPXCP specification.
If unable to negotiate some required parameter, all non-IPX-WAN-
capable implementations MUST NOT reach Opened state. Conversely, an
IPX-WAN-capable implementation SHOULD reach Opened state, even when
no Configuration Options are successfully negotiated.
IPX-WAN uses a "Timer Request" packet to set up the link. These MUST
NOT be sent until IPXCP has Opened the link.
An implementation which provides both IPX-WAN and IPXCP Configuration
Options capability SHOULD only send a Timer Request packet when a
Timer Request packet is received, or upon failure to successfully
negotiate a required parameter.
If unable to complete IPX-WAN setup when a required parameter is
unknown, by default IPXCP SHOULD terminate the link. However, some
implementations (such as half routers) might be capable of operating
without all indicated required parameters, in which case the
termination MUST be configurable.
2.4. Required Configuration Parameters
Where applicable, each Configuration Option indicates the environment
where the parameter which is negotiated MAY be required by the
implementation for proper operation. This determination is highly
implementation dependent.
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3. IPXCP Configuration Options
IPXCP Configuration Options allow negotiation of desirable IPX
parameters. IPXCP uses the same Configuration Option format defined for
LCP [1], with a separate set of Options.
The most up-to-date values of the IPXCP Option Type field are specified
in the most recent "Assigned Numbers" RFC [2]. Current values are
assigned as follows:
1 IPX-Network-Number
2 IPX-Node-Number
3 IPX-Compression-Protocol
4 IPX-Routing-Protocol
5 IPX-Router-Name
6 IPX-Configuration-Complete
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3.1. IPX-Network-Number
Description
This Configuration Option provides a way to negotiate the IPX
network number to be used on the local end of the link. It allows
the sender of the Configure-Request to state which network number
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 IPX-Network-Number.
If negotiation about the remote network number 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
IPX-Network-Number given must be acceptable as the remote IPX-
Network-Number, or indicate a request that the peer provide the
information.
By default, no IPX-Network-Number is assigned to either end. A
network 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 specified as zero in a Configure-Ack
shall be interpreted as agreement that no value exists.
This is a required parameter when the implementation is operating
as a router, but not as a half-router or end-system. By default,
this parameter SHOULD NOT be negotiated when statically
configured, unless requested by the peer. Any IPX-WAN packets
received MUST supercede information negotiated in this option.
A summary of the IPX-Network-Number 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 | IPX-Network-Number
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPX-Network-Number (cont.) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
1
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Length
6
IPX-Network-Number
The four octet IPX-Network-Number is the desired local IPX network
number of the sender of the Configure-Request. This number may be
zero, which is interpreted as being a local network of unknown
number that requires no routing.
Both ends of the link MUST have the same network number. In the
event of conflict, the end having the highest node number wins.
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3.2. IPX-Node-Number
Description
This Configuration Option provides a way to negotiate the IPX node
number to be used on the local end of the link. It allows the
sender of the Configure-Request to state which node number 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 IPX-Node-Number.
If negotiation about the remote node number 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
IPX-Node-Number given must be acceptable as the remote IPX-Node-
Number, or indicate a request that the peer provide the
information.
By default, no IPX-Node-Number is assigned to either end. A 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 node number specified as zero in a Configure-Ack
shall be interpreted as agreement that no value exists.
This is a required parameter when the implementation is
originating traffic as an end-system, but not when operating as a
router or half-router. By default, this parameter SHOULD NOT be
negotiated when statically configured, unless requested by the
peer. Any IPX-WAN packets received MUST supercede information
negotiated in this option.
A summary of the IPX-Node-Number 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 | IPX-Node-Number
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPX-Node-Number (cont.) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
2
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Length
8
IPX-Node-Number
The six octet IPX-Node-Number is the desired local IPX node number
of the sender of the Configure-Request. The node number MUST be
unique within the same network number.
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3.3. IPX-Compression-Protocol
Description
This Configuration Option provides a way to negotiate the use of a
specific compression protocol. By default, compression is not
enabled.
The sender of this Configuration Option indicates that it can
receive packets with the specified compression technique. A
Configure-Ack MAY obligate the peer to send such packets,
depending on the protocol negotiated.
Information negotiated in this option MUST supercede any IPX-WAN
packets received, since IPX-WAN packets could be affected by the
compression technique.
A summary of the IPX-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 | IPX-Compression-Protocol |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data ...
+-+-+-+-+
Type
3
Length
>= 4
IPX-Compression-Protocol
The IPX-Compression-Protocol field is two octets and indicates the
compression protocol desired. Odd values for this field are
always the same as the PPP Data Link Layer Protocol field values
for that same compression protocol. Even values are used when the
compression protocol is interleaved with IPX packets.
The most up-to-date values of the IPX-Compression-Protocol field
are specified in the most recent "Assigned Numbers" RFC [2].
Current values are assigned as follows:
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Value (in hex) Protocol
0002 Telebit Compressed IPX
0235 Shiva Compressed NCP/IPX
Data
The Data field is zero or more octets and contains additional data
as determined by the particular compression protocol.
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3.4. IPX-Routing-Protocol
Description
This Configuration Option provides a way to negotiate the use of a
specific routing protocol (or no routing protocol, if desired).
The sender of this option is specifying that it wishes to receive
information of the specified routing protocol. Multiple protocols
MAY be requested by sending multiple IPX-Routing-Protocol
Configuration Options.
By default, Novell's combination of Routing Information Protocol
(RIP) and Server Advertising Protocol (SAP) is expected.
This is a required parameter when the implementation is operating
as an end-system, and in that case SHOULD be negotiated even when
statically configured. Any IPX-WAN packets received MAY add to
information negotiated in this option.
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
4
Length
>= 4
Routing-Protocol
The Routing-Protocol field is two octets and indicates the type of
Routing-Protocol desired. This two octet quantity is sent most
significant octet first.
Initial values are assigned as follows:
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Value Protocol
0 No routing protocol required
1 RESERVED
2 Novell RIP/SAP required
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.
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3.5. IPX-Router-Name
Description
This Configuration Option provides a way to convey information
about the IPX server name.
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. This option MUST NOT be included in a Configure-
Nak.
A summary of the IPX-Router-Name 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 | Name...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
5
Length
>= 3
Name
This field contains the name of the IPX entity on this end of the
link. The symbolic name should be between 1 and 47 ASCII
characters in length, containing the characters 'A' through 'Z',
underscore (_), hyphen (-) and "at" sign (@). The length of the
name is bounded by the option length.
On reception, the name SHOULD be padded to 48 characters using the
NUL character. Those readers familiar with NetWare 3.x servers
will realize that this is equivalent to the file server name.
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3.6. IPX-Configuration-Complete
Description
This Configuration Option provides a way to indicate that all
implementation dependent required configuration parameters are
satisfied. It is provided as a means of detecting when
convergence will occur in a heterogeneous environment.
This option MUST be included in a Configure-Request when the
combination of statically configured parameters and offered
Configuration Options will result in successful configuration.
The nature of this option is advisory only. This option MUST NOT
be included in a Configure-Nak.
Implementation Note: An implementation which does not support
IPX-WAN can immediately detect that link setup will not be
successful if this option is not present in the peer's
Configure-Request, or this option is Rejected. This avoids
timeout delays.
An implementation which supports IPX-WAN may improve link setup
time by skipping IPX-WAN when this option has been Ack'd in
both directions.
A summary of the IPX-Configuration-Complete Option format is shown
below. The fields are transmitted from left to right.
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
6
Length
2
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4. Telebit IPX header compression
Telebit IPX header compression [5] reduces the size of the IPX headers
to as few as five bytes. This can be a significant improvement on slow
serial lines, particularly for interactive traffic.
The IPX-Compression-Protocol Configuration Option is used to indicate
the ability to receive compressed packets. Each end of the link must
separately request this option if bi-directional compression is desired.
The PPP Protocol field is set to the same value as the usual IPX
packets, and all IPX packets sent over the link MUST conform to the
compressed format.
4.1. Configuration Option Format
A summary of the IPX-Compression-Protocol Configuration Option format
to negotiate Telebit IPX header compression 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 | IPX-Compression-Protocol |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Max-Slot-Id | Options |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
3
Length
6
IPX-Compression-Protocol
0002 (hex) for Telebit Compressed IPX headers.
Max-Slot-Id
The Max-Slot-Id field is one octet and indicates the maximum slot
identifier. This is one less than the actual number of slots; the
slot identifier has values from zero to Max-Slot-Id.
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Options
The Options field is one octet, and is comprised of the
"logical or" of the following values:
0 No options.
1 The slot identifer may be compressed.
The slot identifier must not be compressed if there is no
ability for the PPP link level to indicate an error in
reception to the decompression module. Synchronization
after errors depends on receiving a packet with the slot
identifier.
2 A length field must be included.
The length field MUST be included if there is no ability for
the PPP link level to determine the amount of padding. It
SHOULD NOT be included when there is no padding on the link,
or the Self-Describing-Pad Configuration Option has been
negotiated.
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Security Considerations
Security issues are not discussed in this memo.
References
[1] Simpson, W. A., "The Point-to-Point Protocol (PPP)", RFC 1331,
May 1992.
[2] Reynolds, J.K., Postel, J.B., "Assigned Numbers", RFC 1340,
July 1992.
[3] Novell Inc., "NetWare System Interface Technical Overview",
Novell Part Number 883-001143-001
[4] Allen, M., "Novell IPX Over Various WAN Media", Novell Inc.,
June 1992.
[5] Mathu, Saroop, Lewis, Mark, "Compressing IPX Headers Over WAN
Media (CIPX)", September 1992.
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:
Michael Allen (mallen@novell.com)
Dave McCool (dave@shiva.com)
Robert D Vincent (bert@shiva.com)
Marty Del Vecchio (marty@shiva.com)
Chair's Address
The working group can be contacted via the current chair:
Brian Lloyd
Lloyd & Associates
3420 Sudbury Road
Cameron Park, California 95682
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Phone: (916) 676-1147
EMail: brian@lloyd.com
Author's Address
Questions about this memo can also be directed to:
William Allen Simpson
Daydreamer
Computer Systems Consulting Services
P O Box 6205
East Lansing, MI 48826-6205
EMail: Bill.Simpson@um.cc.umich.edu
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Table of Contents
1. Introduction .......................................... 1
2. A PPP Network Control Protocol (NCP) for IPX .......... 2
2.1 Sending IPX Datagrams ........................... 3
2.2 IPX-WAN protocol ................................ 3
2.3 Co-existance with IPX-WAN ....................... 3
2.4 Required Configuration Parameters ............... 4
3. IPXCP Configuration Options ........................... 5
3.1 IPX-Network-Number .............................. 6
3.2 IPX-Node-Number ................................. 8
3.3 IPX-Compression-Protocol ........................ 10
3.4 IPX-Routing-Protocol ............................ 12
3.5 IPX-Router-Name ................................. 14
3.6 IPX-Configuration-Complete ...................... 15
4. Telebit IPX header compression ........................ 16
4.1 Configuration Option Format ..................... 16
SECURITY CONSIDERATIONS ................................... 18
REFERENCES ................................................... 18
ACKNOWLEDGEMENTS ............................................. 18
CHAIR'S ADDRESS .............................................. 18
AUTHOR'S ADDRESS ............................................. 19