Mobile IP Working Group Pat R. Calhoun
INTERNET DRAFT Sun Microsystems Laboratories
5 January 2000 Charles E. Perkins
Nokia Research Center
Mobile IP Network Access Identifier Extension for IPv4
draft-ietf-mobileip-mn-nai-06.txt
Status of This Memo
This document is a submission by the mobile-ip Working Group of the
Internet Engineering Task Force (IETF). Comments should be submitted
to the MOBILE-IP@STANDARDS.NORTELNETWORKS.COM mailing list.
Distribution of this memo is unlimited.
This document is an Internet-Draft and is in full conformance with
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Abstract
AAA servers are in use within the Internet today to provide
authentication and authorization services for dial-up computers.
Such services are likely to be equally valuable for mobile nodes
using Mobile IP when the nodes are attempting to connect to foreign
domains with AAA servers. AAA servers today identify clients by
using the Network Access Identifier (NAI). Our proposal defines a way
for the mobile node to identify itself, by including the NAI along
with the Mobile IP Registration Request. This draft also updates
RFC2290 which specifies the Mobile-IPv4 Configuration option for
IPCP, by allowing the Mobile Node's Home Address field of this option
to be zero.
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1. Introduction
AAA servers are in use within the Internet today to provide
authentication and authorization services for dial-up computers.
Such services are likely to be equally valuable for mobile nodes
using Mobile IP when the nodes are attempting to connect to foreign
domains with AAA servers. AAA servers today identify clients
by using the Network Access Identifier (NAI) [1]. This document
specifies the Mobile Node NAI extension to the Mobile IP Registration
Request [7] message from the mobile node.
Since the NAI is typically used to uniquely identify the mobile
node, the mobile node's home address is not always necessary to
provide that function. Thus, it is possible for a mobile node to
authenticate itself, and be authorized for connection to the foreign
domain, without even having a home address. A message containing
the Mobile Node NAI extension MAY set the Home Address field to zero
(0) in the Registration Request, to request that a home address be
assigned.
The "Mobile-IPv4 Configuration" option to IPCP has been specified
in RFC 2290 [9] for proper interaction between a mobile node and a
peer, through which the mobile node connects to the network using
PPP. According to that specification the Mobile Node's Home Address
field of the option MUST not be zero. However, in the context of
this draft which allows a mobile node to be identified by its NAI and
to obtain an address after the PPP phase of connection establishment,
the Home Address field is allowed to be zero while maintaining all
other aspects of RFC 2290. Interpretation of various scenarios from
RFC 2290 is given in section 4.
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 [3].
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2. Mobile Node NAI Extension
The Mobile Node NAI extension, shown in figure 1, contains the user
and/or host name following the format defined in [1]. When it is
present in the Registration Request, the Home Address field MAY be
set to zero (0). The Mobile Node NAI extension MUST appear in the
Registration Request before both the Mobile-Home Authentication
extension and Mobile-Foreign Authentication extension, if present.
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 | MN-NAI ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: The Mobile Node NAI Extension
Type 131 (skippable) [7]
Length The length in bytes of the MN-NAI field
MN-NAI A string in the NAI format defined in [1].
3. Foreign Agent Considerations
If Home Address is zero in the Registration Request, the foreign
agent MUST use the NAI instead in its pending registration request
records, along with the Identification field as usual. If the
foreign agent cannot manage pending registration request records in
this way, it MUST return a Registration Reply with Code indicating
NONZERO_HOMEADDR_REQD (see section 5).
If the mobile node includes the Mobile Node NAI extension in its
Registration Request, then the Registration Reply from the home
agent MUST include the Mobile Node NAI extension. If not, the
foreign agent SHOULD send the Registration Reply to the mobile node,
changing the Code to the value MISSING_NAI (see section 5). The
Registration Reply MUST include a nonzero Home Agent address and
mobile node's Home Address. If not, the foreign agent SHOULD send
the Registration Reply to the mobile node, changing the Code to the
value MISSING_HOME_AGENT or MISSING_HOMEADDR, respectively (see
section 5).
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4. Interactions with Mobile-IPv4 Configuration Option to IPCP
In the Mobile-IPv4 Configuration Option to IPCP [9], the Mobile
Node's Home Address field may be zero. In this section, we specify
the action to be taken in that case, when the mobile node is using
the Mobile Node NAI extension in the Mobile IP Registration Request.
Whether or not the IP Address Configuration Option contains a nonzero
IP address, the mobile node will subsequently attempt to obtain a
home address from the Mobile IP Registration Reply.
If the IP Address Configuration Option to IPCP has IP address equal
to zero, the PPP peer is expected to allocate and assign a co-located
care-of address to the Mobile Node. If, on the other hand, the IP
Address Configuration Option to IPCP has a nonzero IP address, the
PPP peer is expected to assign that address to the Mobile Node as its
co-located care-of address.
5. Error Values
Each entry in the following table contains the name and value for the
Code [7] to be returned in a Registration Reply, and the section in
which the error Code is first mentioned in this specification.
Error Name Value Section of Document
---------------------- ----- -------------------
NONZERO_HOMEADDR_REQD 96 3
MISSING_NAI 97 3
MISSING_HOME_AGENT 98 3
MISSING_HOMEADDR 99 3
6. IANA Considerations
The number for the Mobile Node NAI extension is taken from the
numbering space defined for Mobile IP registration extensions defined
in RFC 2002 [7] as extended in RFC 2356 [6]. The numbering for
the extension also SHOULD NOT conflict with values specified in
the Internet Draft for Route Optimization [8]. The Code values
specified for errors, listed in section 5, MUST NOT conflict with any
other code values listed in RFC 2002, RFC 2344 [5], or RFC 2356 [6].
They are to be taken from the space of error values conventionally
associated with rejection by the foreign agent (i.e., 64-127).
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7. Security Considerations
Mobile IP registration messages are authenticated, and the
authentication verified by the recipient. This proposal does not
prohibit the mobile node from sending its NAI in the clear over the
network, but that is not expected to be a security issue.
8. IPv6 Considerations
Supporting NAI-based registrations for Mobile IPv6 [4] is outside
the scope of this document. This section contains some ideas how
Stateless Address Autoconfiguration [10] and DHCPv6 [2] might be
extended to support NAI-based Mobile IPv6 registrations.
For mobile nodes using IPv6, there are no commonly deployed
mechanisms by which a mobile node may present its credentials, such
as exist today with IPv4. Nevertheless, a mobile node using IPv6
mobility may wish to specify the domain in which their credentials
may be checked, by using a NAI just as this specification proposes
for IPv4. In the case of IPv6, however, there is no foreign agent
in place to manage the connectivity of the mobile node, and thus to
manage the verification of the credentials offered by the mobile
node. To identify the HDAF (see appendix A) that has the expected
relationship with the mobile node, the NAI would have to be forwarded
to a local AAA by the local agent involved with configuring the
care-of address of the mobile node.
This agent can either be a router sending out Router
Advertisements [10], or a DHCPv6 server. In the former case,
the router could signal its ability to handle the NAI by attaching
some yet to be defined option to the Router Advertisement. In the
latter case, for managed links, the mobile node could include a
yet to be defined NAI extension in its DHCP Solicitation message.
Such an NAI extension and appropriate authentication would also
be required on the subsequent DHCP Request sent by the mobile
node to the DHCP Server selected on the basis of received DHCP
Advertisements. Once a care-of address on the foreign network has
been obtained, the mobile node can use regular MIPv6 [4].
9. Acknowledgements
The authors would like to thank Gabriel Montenegro and Vipul
Gupta for their useful discussions. Thanks to Basaravaj Patil and
Pete McCann for text describing actions to be taken when the home
address is zero but the mobile node wishes to use the Mobile-IPv4
Configuration Option to IPCP defined in RFC 2290.
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References
[1] B. Aboba and M. Beadles. The Network Access Identifier.
Request for Comments (Proposed Standard) 2486, Internet
Engineering Task Force, January 1999.
[2] J. Bound and C. Perkins. Dynamic Host Configuration Protocol
for IPv6 (DHCPv6). Internet Draft, Internet Engineering Task
Force.
draft-ietf-dhc-dhcpv6-14.txt, February 1999. Work in progress.
[3] S. Bradner. Key words for use in RFCs to Indicate Requirement
Levels. Request for Comments (Best Current Practice) 2119,
Internet Engineering Task Force, March 1997.
[4] D. Johnson and C. Perkins. Mobility Support in IPv6.
draft-ietf-mobileip-ipv6-08.txt, June 1999. (work in progress).
[5] G. Montenegro. Reverse Tunneling for Mobile IP. Request for
Comments (Proposed Standard) 2344, Internet Engineering Task
Force, May 1998.
[6] G. Montenegro and V. Gupta. Sun's SKIP Firewall Traversal for
Mobile IP. Request for Comments (Informational) 2356, Internet
Engineering Task Force, June 1998.
[7] C. Perkins. IP Mobility Support. Request for Comments
(Proposed Standard) 2002, Internet Engineering Task Force,
October 1996.
[8] C. Perkins and D. Johnson. Route Optimization in Mobile IP.
Internet Draft, Internet Engineering Task Force.
draft-ietf-mobileip-optim-08.txt, February 1999. Work in
progress.
[9] J. Solomon and S. Glass. Mobile-IPv4 Configuration Option
for PPP IPCP. Request for Comments (Proposed Standard) 2290,
Internet Engineering Task Force, February 1998.
[10] S. Thomson and T. Narten. IPv6 Stateless Address
Autoconfiguration. Request for Comments (Draft Standard) 2462,
Internet Engineering Task Force, December 1998.
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A. Home Domain Allocation Function (HDAF)
This appendix introduces a new function named the Home Domain
Allocation Function (HDAF) that can dynamically assign a Home Address
to the mobile node.
Figure 2 illustrates the Home HDAF, which receives messages from
foreign agents (e.g., FA) and assigns a Home Address within the Home
Domain. The HDAF does not perform any Mobile IP processing on the
Registration Request, but simply forwards the request to a Home Agent
(HA) within the network that is able to handle the request.
+------+
| |
+---+ HA-1 |
+------+ +------+ +------+ | | |
| | | | | | | +------+
| MN |-------| FA |-------| HDAF +---+ ...
| | | | | | | +------+
+------+ +------+ +------+ | | |
+---+ HA-n |
| |
+------+
Figure 2: Home Domain Allocator Function (HDAF)
Upon receipt of the Registration Request from the mobile node (MN),
FA extracts the NAI and finds the domain name associated with it.
FA then finds the HDAF that handles requests for the mobile node's
domain. The discovery protocol is outside of the scope of this
specification. As an example, however, FA might delegate the duty of
finding a HDAF to a local AAA server. The local AAA server may also
assist FA in the process of verifying the credentials of the mobile
node, using protocols not specified in this document.
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Addresses
The working group can be contacted via the current chairs:
Basavaraj Patil Phil Roberts
Nortel Networks Inc. Motorola
2201 Lakeside Blvd. 1501 West Shure Drive
Richardson, TX. 75082-4399 Arlington Heights, IL 60004
USA USA
Phone: +1 972-684-1489 Phone: +1 847-632-3148
EMail: bpatil@nortelnetworks.com EMail: QA3445@email.mot.com
Questions about this memo can be directed to:
Charles E. Perkins Pat R. Calhoun
Nokia Research Center Sun Microsystems Laboratories
313 Fairchild Drive 15 Network Circle
Mountain View, California 94043 Menlo Park, California 94025
USA USA
Phone: +1-650 625-2986 Phone: +1 650-786-7733
EMail: charliep@iprg.nokia.com EMail: pcalhoun@eng.sun.com
Fax: +1 650 625-2502 Fax: +1 650-786-6445
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