NEMOv4 Prefix Allocation: Dynamic Prefix Allocation for Network Mobility for Mobile IPv4 (NEMOv4)
How a Mobile Router asks its home agent to hand out network prefixes instead of configuring them by hand.
Tsirtsis, G., Park, V., Narayanan, V., and K. Leung, "Dynamic Prefix Allocation for Network Mobility for Mobile IPv4 (NEMOv4)", RFC 6626, DOI 10.17487/RFC6626, May 2012, <https://www.rfc-editor.org/info/rfc6626>.
@misc{rfc6626,
series = {Request for Comments},
number = 6626,
howpublished = {RFC 6626},
publisher = {RFC Editor},
doi = {10.17487/RFC6626},
url = {https://www.rfc-editor.org/info/rfc6626},
author = {G. Tsirtsis and V. Park and V. Narayanan and K. Leung},
title = {{Dynamic Prefix Allocation for Network Mobility for Mobile IPv4 (NEMOv4)}},
pagetotal = 5,
year = 2012,
month = may,
} RFC text
Contents
Internet Engineering Task Force (IETF) G. Tsirtsis
Request for Comments: 6626 V. Park
Updates: 5177 V. Narayanan
Category: Standards Track Qualcomm
ISSN: 2070-1721 K. Leung
Cisco
May 2012
Dynamic Prefix Allocation for
Network Mobility for Mobile IPv4 (NEMOv4)
Abstract
The base Network Mobility for Mobile IPv4 (NEMOv4) specification
defines extensions to Mobile IPv4 for mobile networks. This
specification defines a dynamic prefix allocation mechanism for
NEMOv4.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6626.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction ....................................................2
2. Requirements Notation ...........................................2
3. Dynamic Mobile Prefix Allocation ................................2
3.1. Mobile Client Considerations ...............................2
3.2. Home Agent Considerations ..................................3
4. Security Considerations .........................................4
5. IANA Considerations .............................................4
6. Acknowledgements ................................................4
7. Normative References ............................................4
1. Introduction
The base NEMOv4 specification [RFC5177] defines extensions to Mobile
IPv4 [RFC5944] for mobile networks. This specification adds support
for dynamic allocation of mobile prefixes by the home agent.
2. Requirements Notation
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 [RFC2119].
3. Dynamic Mobile Prefix Allocation
The following extension is defined according to this specification.
3.1. Mobile Client Considerations
According to this specification, the Prefix field of the Mobile
Network Request extension MUST be set to zero to indicate that the
Mobile Router requests mobile network prefix(es) be assigned to it by
the home agent. In this case, the Mobile Router MAY set the prefix
length field of such extensions to zero or to a length of its choice
as a hint to the home agent. According to this specification, Mobile
Network Request extensions with the Prefix field set to zero MAY be
included in a registration request message either during initial
registration or during a subsequent registration.
When a Mobile Router receives a registration reply, it MUST process
it as defined in Mobile IPv4 [RFC5944] and [RFC5177]. If one or more
network acknowledgement extensions are included with the Code field
set to "Success", the Mobile Router SHOULD treat the prefixes in the
corresponding Prefix fields as allocated prefixes and create the
appropriate bindings as defined in [RFC5177].
In response to a registration request with a Mobile Network Request
extension with the Prefix field set to zero, if a Mobile Router
receives a registration reply with a network acknowledgement
extension including Code field set to 1 "invalid prefix", it may use
it as a hint that the home agent does not support dynamic prefix
allocation.
3.2. Home Agent Considerations
A home agent receiving a Mobile Network Request extension with the
Prefix field set to zero MAY return a Mobile Network Acknowledgement
extension [RFC5177] with the Prefix field set to the prefix allocated
to the Mobile Router. The length of that prefix is at the discretion
of the home agent. The home agent MAY take into account the prefix
length hint if one is included in the Mobile Network Request
extension. Once the home agent allocates a prefix, it MUST maintain
the prefix registration table as defined in [RFC5177].
Alternatively, the home agent MAY return a Mobile Network
Acknowledgement extension with the Code field set to one of the
negative codes defined in [RFC5177].
Dynamic mobile prefix allocation, as defined in this specification,
MAY be combined with dynamic home address allocation, as defined in
[RFC5177]. In other words, the home address field of the
registration request message MAY be set to zero while the message
also includes one or more Mobile Network Request extensions with the
Prefix field also set to zero.
Once the home agent allocates a prefix, it MUST maintain the prefix
registration table as defined in [RFC5177]. The lifetime of the
allocated prefix will be equal to the lifetime of the binding cache
entry. The Mobile Router may request for multiple mobile network
prefixes to be assigned by the home agent. For a Mobile Network
Prefix for which the assignment was unsuccessful, the Code field in
the corresponding Mobile Network Acknowledgement extension should be
set to 4 (MOBNET_UNASSIGNED).
For dynamic prefix allocation, the Mobile Router's home address MAY
be used to identify the client if it is not set to zero. Otherwise,
as defined in the Network Access Identifier (NAI) extension [RFC2794]
of Mobile IPv4 [RFC2794], the NAI extension needs to be included in
the registration request, in which case the same extension SHOULD be
used to identify the Mobile Router for prefix allocation purposes.
4. Security Considerations
This specification operates in the security constraints and
requirements of Mobile IPv4 [RFC5944], NAI [RFC2794], and [RFC5177].
Home agent implementations SHOULD take steps to prevent address
exhaustion attacks. One way to limit the effectiveness of such an
attack is to limit the number and size of prefixes any one Mobile
Router can be allocated.
5. IANA Considerations
A new value has been assigned in the Mobile Network Acknowledgement
Extension registry: 4 - Home Agent cannot assign a mobile network
prefix (MOBNET_UNASSIGNED).
6. Acknowledgements
The authors would like to thank Pete McCann, Alexandru Petrescu,
Ralph Droms, and Jari Arkko for their reviews and comments.
7. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2794] Calhoun, P. and C. Perkins, "Mobile IP Network Access
Identifier Extension for IPv4", RFC 2794, March 2000.
[RFC5177] Leung, K., Dommety, G., Narayanan, V., and A. Petrescu,
"Network Mobility (NEMO) Extensions for Mobile IPv4",
RFC 5177, April 2008.
[RFC5944] Perkins, C., "IP Mobility Support for IPv4, Revised",
RFC 5944, November 2010.
Authors' Addresses
George Tsirtsis
Qualcomm
EMail: tsirtsis@googlemail.com
Vincent Park
Qualcomm
Phone: +908-443-8141
EMail: vpark@qualcomm.com
Vidya Narayana
Qualcomm
Phone: +858-845-2483
EMail: vidyan@qualcomm.com
Kent Leung
Cisco
Phone: +408-526-5030
EMail: kleung@cisco.com
AI ELI5
On this page
§1Introduction
The base NEMOv4 specification, RFC 5177, defines extensions to Mobile IPv4 for mobile networks. This document adds support for dynamic allocation of mobile prefixes by the home agent.
It is a Standards Track document and updates RFC 5177.
A moving network used to have to bring its own addresses. Now it can ask its home base to assign them.
§3.1The Mobile Router Side
To ask for a prefix, the Mobile Router MUST set the Prefix field of the Mobile Network Request extension to zero. It MAY set the prefix length field to zero, or to a length of its choice as a hint to the home agent. Such extensions MAY appear in the initial registration or a later one.
On a registration reply, the router processes it as Mobile IPv4 and RFC 5177 require. If network acknowledgement extensions carry the Code Success, the router SHOULD treat the listed prefixes as allocated and create the bindings defined in RFC 5177. If it gets Code 1, "invalid prefix", it may take that as a hint that the home agent does not support dynamic allocation.
The router says 'give me some addresses, any will do' by leaving the address blank. It may suggest a size, and then uses whatever it is given.
- Registration RequestMobile Network Request extension with Prefix set to zero.
- Registration ReplyNetwork acknowledgement with the allocated prefix, or a negative code.
§3.2The Home Agent Side
A home agent that receives a request with a zero Prefix MAY reply with a Mobile Network Acknowledgement whose Prefix field holds the allocated prefix. The length is the home agent's choice, though it MAY consider the hint. Once it allocates a prefix, it MUST maintain the prefix registration table from RFC 5177. The prefix lifetime equals the lifetime of the binding cache entry.
The home agent may instead return one of the negative codes from RFC 5177. A router may ask for several prefixes, and for any that could not be assigned the Code should be set to 4 (MOBNET_UNASSIGNED).
This can be combined with dynamic home address allocation: the home address field may be zero while the request also carries zero-Prefix extensions. If the home address is not zero it MAY identify the client; otherwise the NAI extension needs to be included and SHOULD be used to identify the Mobile Router.
The home office picks the addresses, decides how many fit, and keeps a list of who got what. If it has none to give, it says so with a special code.
§4Security and IANA
The specification works within the security constraints of Mobile IPv4, the NAI extension and RFC 5177. Home agents SHOULD take steps to prevent address exhaustion attacks, for example by limiting the number and size of prefixes any one Mobile Router can be allocated.
IANA assigned value 4, MOBNET_UNASSIGNED (Home Agent cannot assign a mobile network prefix), in the Mobile Network Acknowledgement Extension registry.
A greedy router could ask for every address. So the home office should put a limit on how much each one may take.