Mobile IP Working Group Alpesh Patel
INTERNET DRAFT Kent Leung
10 September 2004 Cisco Systems
Experimental Message, Extension and Error Codes for Mobile IPv4
draft-ietf-mip4-experimental-messages-02.txt
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Copyright (c) The Internet Society (2004). All Rights Reserved.
Abstract
Mobile IPv4 message types range from 0 to 255. This document
reserves a message type for use by an individual, company, or
organization for experimental purpose, to evaluate enhancements
to Mobile IPv4 messages before formal standards proposal.
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Table of Contents
1. Introduction.............................................2
2. Terminology..............................................3
3. Experimental Message.....................................3
4. Experimental Extensions..................................4
4.1 Non-skippable Mobile IPv4 Experimental Extension........5
4.2 Non-skippable ICMP Router Discovery Exp. Extension......5
4.3 Skippable Mobile IPv4 Experimental Extension............6
4.4 Skippable ICMP Router Discovery Experimental Extension..7
5. Experimental Error Codes.................................7
6. Mobility Entity Considerations...........................7
7. IANA Considerations......................................8
7.1 New Message Type........................................8
7.2 New Extension Values....................................8
7.3 New Error Codes.........................................8
9. Backward Compatibility Considerations....................9
10. Acknowledgements........................................9
11. References..............................................9
11.1 Normative References..................................10
11.2 Informative References................................10
12. Authors' Addresses.....................................10
Intellectual Property Statement............................11
Disclaimer of Validity.....................................11
Copyright Statement........................................11
1. Introduction
Mobile IPv4 message types range from 0 to 255. This document
reserves a message type for experimental purposes, to evaluate
enhancements to Mobile IPv4 messages before formal standards
proposal.
Without experimental message capability, one would have to
select a type value from the range defined for IANA assignment,
which may result in collisions.
Within a message, Mobile IP defines a general extension
mechanism to allow optional information to be carried by Mobile
IP control messages. Extensions are not skippable if defined in
the range [0-127] and skippable if defined in the range [128-
255]. This document reserves extension types in both the
skippable and non-skippable ranges for experimental use.
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Mobile IPv4 defines error codes for use by the FA [64-127] and
HA [128-192]. This document reserves an error code in both
these ranges for experimental use.
The definition of experimental numbers in this document is done
according to the recommendation of Section 2.2 of BCP 82,
RFC 3692.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described
in [1].
In addition, this document frequently uses the following terms:
EXP-MSG-TYPE: A Mobile-IPv4 message number in the range [0-255]
to be assigned by IANA for experimental use.
EXP-SKIP-EXT-TYPE: A Mobile-IPv4 and ICMP router discovery
Agent Advertisement extension number in the range [128-255] to
be assigned by IANA for experimental use.
EXP-NONSKIP-EXT-TYPE: A Mobile-IPv4 and ICMP router discovery
Agent Advertisement extension number in the range [0-127] to be
assigned by IANA for experimental use.
EXP-HA-ERROR-CODE: A Mobile-IPv4 error code in the range [128-
192] for use by HA in MIPv4 reply messages to indicate an error
condition.
EXP-FA-ERROR-CODE: A Mobile-IPv4 error code in the range [64-
127] for use by FA in reply messages to indicate error
condition.
Mobility Entity: Entities as defined in [2] (home agent,
foreign agent and mobile node).
3. Experimental Message
Since the nature and purpose of an experimental message cannot
be known in advance, the structure is defined as having an
opaque payload. Entities implementing the message can interpret
the message as per their implementation. One suggestion is to
interpret based on extensions present in the message.
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These messages may be used between the mobility entities (Home
Agent, Foreign Agent, and Mobile Node). Experimental messages
MUST be authenticated using any of the authentication mechanism
defined for Mobile IP ([2], [5]).
This message MAY contain extensions defined in Mobile IP,
including vendor specific extensions [4].
IP fields:
Source Address: Typically the interface address from which
the message is sent.
Destination Address: The address of the agent or the Mobile
Node.
UDP fields:
Source Port Set according to RFC 768 (variable)
Destination Port Set to the value 434
Mobile IP fields shown below follow the UDP header:
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 | Opaque. . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type EXP-MSG-TYPE (To be assigned by IANA)
Opaque Zero or more octets of data, with structure defined
only by the particular experiment it is used for.
Once an experimental message has been tested and shown to be
useful, a permanent number should be obtained through the
normal IANA numbers assignment procedures.
A single experimental message type is defined. This message can
contain extensions based on which the message can be
interpreted.
4. Experimental Extensions
This document reserves Mobile IPv4 extensions in both the
skippable and non-skippable ranges for experimental purposes.
The long extension format (for non-skippable extensions) and
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short extension format (for skippable extensions), as defined
by [2], are used for Mobile IPv4 experimental extensions.
Also, ICMP router discovery extension numbers in both the
skippable and non-skippable ranges are reserved for
experimental use.
4.1 Non-skippable Mobile IPv4 Experimental Extension
This format is applicable for non-skippable extensions and may
carry information more than 256 bytes.
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 | Sub-Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opaque. . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type EXP-NONSKIP-EXT-TYPE (to be assigned by IANA) is
the type, which describes an experimental extension.
Sub-Type is a unique number given to each member in the
aggregated type.
Length Indicates the length (in bytes) of the data field
within this extension. It does NOT include the Type,
Sub-Type and Length fields.
Opaque Zero or more octets of data, with structure defined
only by the particular experiment it is used for.
Since the length field is 16 bits wide, the extension data can
exceed 256 bytes in length.
4.2 Non-skippable ICMP Router Discovery Exp. Extension
This format is applicable for non-skippable extensions.
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 | Opaque . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Type EXP-NONSKIP-EXT-TYPE (to be assigned by IANA) is
the type, which describes an ICMP router discovery
experimental extension.
Length Indicates the length (in bytes) of the data field
within this extension. It does NOT include the Type
and Length fields.
Opaque Zero or more octets of data, with structure defined
only by the particular experiment it is used for.
A node which receives a router advertisement with this
extension should ignore the extension if it does not recognize
it.
A mobility entity which understands this extension, but does
not recognize it, should drop (ignore) the router
advertisement.
4.3 Skippable Mobile IPv4 Experimental Extension
This format is applicable for skippable extensions, which carry
information less than 256 bytes.
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 | Sub-Type | Opaque. . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type EXP-SKIP-EXT-TYPE (to be assigned by IANA) is the
type, which describes an experimental extension.
Length Indicates the length (in bytes) of the data field
within this extension. It does NOT include the Type
and Length fields.
Sub-Type is a unique number given to each member in the
aggregated type.
Opaque Zero or more octets of data, with structure defined
only by the particular experiment it is used for.
Since the length field is 8 bits wide, the extension data
cannot exceed 256 bytes in length.
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4.4 Skippable ICMP Router Discovery Experimental Extension
This format is applicable for skippable ICMP router discovery
extensions. This extension should be ignored if an
implementation does not understand it.
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 | Opaque. . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type EXP-SKIP-EXT-TYPE (to be assigned by IANA) is the
type, which describes an experimental extension.
Length Indicates the length (in bytes) of the data field
within this extension. It does NOT include the Type
and Length fields.
Opaque Zero or more octets of data, with structure defined
only by the particular experiment it is used for.
5. Experimental Error Codes
This document reserves reply error code EXP-FA-ERROR-CODE for
use by the FA. This document also reserves reply error code
EXP-HA-ERROR-CODE for use by the HA.
These experimental error codes may be used in registration
reply messages.
It is recommended that experimental error codes be used
with experimental messages and extensions whenever none of the
standardized error codes are applicable.
6. Mobility Entity Considerations
Mobility entities can send and receive experimental messages.
Implementations that don't understand the message type SHOULD
silently discard the message.
Experimental extensions can be carried in experimental messages
and standards defined messages. In the latter case, it is
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suggested that experimental extensions MUST NOT be used in
deployed products and usage be restricted to experimentations
only.
7. IANA Considerations
This document defines a control message to be used between
mobility entities, two new extension formats and two new error
codes. To ensure correct interoperation based on this
specification, IANA has reserved values in the Mobile IPv4
number space, as defined in [2] for one new message type, two
new extensions and two error codes.
7.1 New Message Type
A new Mobile IPv4 control message using UDP port 434, type EXP-
MSG-TYPE has been defined by IANA. This value has been taken
from the same number space as Mobile IP Registration Request
(Type = 1), and Mobile IP Registration Reply (Type = 3). (The
value 255 is suggested in this case).
7.2 New Extension Values
The following extension types are introduced by this
specification:
Experimental non-skippable extension: The value for EXP-
NONSKIP-EXT-TYPE has been assigned from the numbering space for
non-skippable extensions, which may appear in Mobile IPv4
control messages.
Also, the same number, EXP-NONSKIP-EXT-TYPE has been assigned
from the numbering space for non-skippable extensions, which
may appear in ICMP router discovery messages. (The value 127
is suggested in both cases.)
Experimental skippable extension: The value EXP-SKIP-EXT-TYPE
has been assigned from the numbering space for skippable
extensions, which may appear in Mobile IPv4 control messages.
Also, the same number, EXP-SKIP-EXT-TYPE has been assigned from
the numbering space for skippable extensions which may appear
in ICMP router discovery messages. (The value 255 is suggested
in both cases.)
7.3 New Error Codes
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The value EXP-HA-ERROR-CODE has been defined by IANA to be used
as code field in messages generated by HA. (The value 192 is
suggested for this code.)
Also, value EXP-FA-ERROR-CODE has been defined by IANA to be
used as the code field in messages generated by the FA. (The
value 127 is suggested for this code.)
8. Security Considerations
Like all Mobile IP control messages, the experimental messages
MUST be authenticated as per the requirements specified in [2]
or [5]. Experimental messages without a valid authenticator
SHOULD be discarded.
9. Backward Compatibility Considerations
Mobility entities that don't understand the experimental
message MUST silently discard it.
Mobility entities that don't understand the experimental
skippable extensions MUST ignore them. Mobility entities that
don't understand the non-skippable experimental extensions
MUST silently discard the message containing them. This
behavior is consistent with section 1.8 of [2].
Foreign Agents and Home Agents SHOULD include an experimental
error code in a reply message only if they have a general
indication that the receiving entity would be able to parse it.
An indication of this is if the request message was of type
EXP-MSG-TYPE or contained at least one experimental extension.
10. Acknowledgements
The authors would like to acknowledge Henrik Levkowetz for his
detailed review of the draft and suggestion to incorporate
experimental extensions in this draft.
The authors would also like to acknowledge Thomas Narten for
his initial review of the draft and reference to [6] for
general guidelines.
11. References
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11.1 Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Perkins, C., "IP Mobility Support", RFC 3344, August 2002.
[3] Reynolds, J. and J. Postel, "Assigned Numbers", STD 2,
RFC 1700, October 1994.
11.2 Informative References
[4] G. Dommety, K. Leung, "Mobile IP Vendor/Organization-Specific
Extensions" RFC 3115, April 2001
[5] C. Perkins, P. Calhoun, "Mobile IPv4 Challenge/Response
Extensions", RFC 3012, November 2000
[6] T. Narten, "Assigning Experimental and Testing Numbers
Considered Useful", BCP 82, RFC 3692, January, 2004
12. Authors' Addresses
Questions and comments about this draft should be directed at
the Mobile IPv4 working group:
mip4@ietf.org
Questions and comments about this draft may also be directed to
the authors:
Alpesh Patel
Cisco Systems
170 W. Tasman Drive,
San Jose, CA 95134
USA
Email: alpesh@cisco.com
Phone: +1 408-853-9580
Kent Leung
Cisco Systems
170 W. Tasman Drive,
San Jose, CA 95134
USA
Email: kleung@cisco.com
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Phone: +1 408-526-5030
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Acknowledgement
Funding for the RFC Editor function is currently provided by
the Internet Society.
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