One document matched: draft-ietf-mobileip-cellular-requirements-01.txt

Differences from draft-ietf-mobileip-cellular-requirements-00.txt

Mobile IP Working Group              Eva Gustafsson, Ericsson, Editor
INTERNET-DRAFT                                             April 1999
Expires October 1999
                                             Annika Jonsson, Ericsson
                                             Elisabeth Hubbard, Telia
                                               Jonas Malmkvist, Telia
                                                   Anders Roos, Telia
				

        Requirements on Mobile IP from a Cellular Perspective
         <draft-ietf-mobileip-cellular-requirements-01.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@smallworks.com mailing list. Distribution of this 
memo is unlimited.

This document is an Internet-Draft and is in full conformance with all 
provisions of Section 10 of RFC2026. 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 
and may be updated, replaced, or obsoleted by other documents at any 
time.  It is inappropriate to use Internet- Drafts as reference 
material or to cite them other than as "work in progress."

The list of current Internet-Drafts can be accessed at 
http://www.ietf.org/ietf/1id-abstracts.txt

The list of Internet-Draft Shadow Directories can be accessed at 
http://www.ietf.org/shadow.html.


Abstract

The increasing interest in Mobile IP as a potential macro-mobility 
solution for cellular networks leads to new solutions and extensions 
to the existing protocol. As part of this work, there is a need to put 
together the requirements on Mobile IP from a cellular perspective. 
This draft lists a set of requirements on Mobile IP for use in cellular 
networks, for instance IMT-2000, and relates the requirements to 
proposed solutions. These requirements consider Mobile IPv4, but the 
list will be extended for Mobile IPv6 as well.





<draft-ietf-mobileip-cellular-requirements-01.txt>           [Page 1]


Table of contents

1. Introduction......................................................2
2. General considerations............................................3
3. Authentication....................................................4
4. Registration requests generated on behalf of a mobile node........5
5. Private networks..................................................6
6. Reverse tunnelling................................................7
7. Route optimization................................................7
8. Dynamic home address assignment...................................8
9. Temporary home....................................................8
10. Handover performance.............................................9
11. Conclusions......................................................9
12. Intellectual property considerations............................10
13. Acknowledgements................................................10
14. References......................................................10
15. Author's address................................................12





1. Introduction

Recently, there has been an increasing interest in Mobile IP as a 
potential future mobility standard, common to cellular systems and the 
Internet as a whole [3][16][17]. The benefits of adopting a common 
mobility solution would include independence of access network 
technologies and common solutions for fixed and wireless networks.

The purpose of this document is to state a first version of the 
requirements on Mobile IP as a potential macro-mobility solution for 
future cellular networks. In particular, we consider third generation 
mobile systems fulfilling the requirements from ITU for International 
Mobile Telecommunications - 2000 (IMT-2000). The Universal Mobile 
Telecommunication System (UMTS) and the Enhanced Data rates for GSM 
Evolution (EDGE), which both evolve from the GSM/GPRS standard, as well 
as Cdma2000, are such IMT-2000 systems. One important aspect when 
considering Mobile IP for cellular networks, is to provide interworking 
with existing solutions.

Parts of the requirements presented in this document are specific for 
Mobile IP in cellular networks, while others consider mobile users in 
general. However, we have chosen to include all kinds of requirements 
necessary for a cellular operator to deploy Mobile IP. The requirements 
in this document mainly refer to Mobile IPv4 [20], but will be extended 
for Mobile IPv6 [18] as well.






<draft-ietf-mobileip-cellular-requirements-01.txt>            [Page 2]


We start in Section 2 with some general, system-level requirements for 
IP mobility in cellular networks. Then we list more specific 
requirements in Section 3 through Section 10. Section 11 concludes the 
document.

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 RFC 2119 [6].


2. General considerations

This section describes some general considerations and requirements on 
a system using Mobile IP. Note that these requirements are not specific 
requirements on the Mobile IP protocol, but point out important aspects 
on a system level.

To allow Mobile IP to be a mobility solution which supports many 
different kinds of access networks/technologies, the Mobile IP 
functionality shall be independent of the access network technology. For 
Mobile IP to be deployed in future cellular networks, it also needs to 
provide interworking with existing protocols.

Mobile IP provides authentication of the signalling messages [20]. For 
security reasons, such as keeping the current location of a user unknown 
to other users, it should also be possible to provide encryption of the 
Mobile IP signalling. This may be implemented through, for instance, 
IPSec tunnels and security associations established on a permanent basis 
inside and between different administrative domains. It should also be 
possible to provide encryption of the traffic. A solution is to employ 
IPSec together with Mobile IP, as suggested in [25].

As emerging Internet quality-of-service mechanisms are expected to 
enable a wide-spread use of real-time services between stationary nodes, 
for instance voice over IP and videoconferencing, there will be a demand 
for using the same kind of services when being mobile. Promising a 
certain level of quality of service to a mobile user is generally 
difficult, since there may not be enough resources available in the part 
of the network that the mobile node is moving into. However, when network 
resources allow, there should be mechanisms to handle quality of service 
for mobile users, particularly in case of handover and route 
optimization. The differences between stationary and mobile nodes making 
use of quality-of-service mechanisms should also be minimized, and 
network operators should not need to employ different quality of service 
platforms for stationary and mobile users. The emerging quality-of-
service architectures, Differentiated Services and Integrated Services 
[4][5][23][24], do not consider mobile nodes. Additions or changes may 
be needed.






<draft-ietf-mobileip-cellular-requirements-01.txt>            [Page 3]


Quality-of-service mechanisms enforce a differentiated sharing of 
bandwidth among different services and different users. Thus, there must 
be mechanisms available to identify traffic flows with different 
quality-of-service attributes, and to make it possible to charge the 
different users accordingly.

It is well known that mobile nodes are more complex to handle than 
stationary ones. Anyway, the extra handling of mobile nodes should be 
based on the same basic mechanisms as the stationary ones, rather than 
on separate mechanisms. Among these basic mechanisms are (i) an 
Authentication, Authorization, Accounting (AAA) infrastructure; (ii) 
quality of service and policy control; and (iii) directory services and 
gateway services like IP telephony.

Lastly, as more and more users become mobile, the need for a uniform 
service delivery across various access technologies increases. 
Ultimately, the user should not need to know what kind of access 
technology is in use at a particular moment. When bandwidth and other 
network capabilities allow, IP-based services should appear the same way 
independently of the access technology. Moreover, a normal user will try 
to employ the most efficient access, considering capacity and cost, 
which means that changes of access technology can be expected during 
active sessions. Thus, the change of access technology should be as 
smooth and as transparent to the user as possible.

These are general considerations and requirements; some of them may 
apply to Mobile IP and some may be fulfilled through other protocols and 
solutions. The following sections address more specific requirements on 
Mobile IP, in order to provide solutions satisfactory for operators as 
well as end users.


3. Authentication

The authentication of a mobile node or user can be performed at different 
locations and be based upon different parameters. We may also consider 
two phases of the authentication procedure: full or initial 
authentication and subsequent authentications. Full authentication is 
performed when the existing security associations are insufficient, for 
instance at initial registration, or when a mobile node requests a new 
home agent. Subsequent authentications are performed at handover, that 
is, when a mobile node changes its point of attachment within the same 
administrative domain, or to renew bindings before they are timed out.

The Mobile IP protocol specifies authentications to be performed at the 
home agent, and the identifications to be based on the home IP address 
of the mobile node [20]. However, additional solutions and extensions 
to Mobile IP have introduced identification and authentication based on 
the Network Access Identifier (NAI) [1][2][8][9][10][11][12][13]. 
Basing the authentication on the IP address means that it is the host 
that is authenticated, while authentication based on the NAI results in 



<draft-ietf-mobileip-cellular-requirements-01.txt>            [Page 4]


authentication of the mobile user. The latter alternative would 
alleviate the connection between a specific user and a specific host, 
and provide a secure way for dynamic allocation of IP addresses. Thus, 
the full authentication must be based on a unique user identity, for 
example the NAI. 

For reasons of subscription handling and charging, the full 
authentication must always be performed at the home domain or by the 
home operator, that is, where the user has its subscription. Such 
authentication procedures have been suggested in [8][10], and may, for 
instance, be performed through AAA functionality. The full 
authentication should not be performed at the home agent, since the home 
agent may be dynamically allocated. 

However, once a mobile node is connected to a visited network, 
performing subsequent authentications at the home domain could result 
in significant signalling delay. To minimize the signalling delay, and 
to reduce the signalling between the visited and the home network, it 
should be possible to perform subsequent authentications in the visited 
network, as described in [8].

Finally, since the Mobile IP protocol shall allow independence of the 
access network technology, the Mobile IP authentication should be 
independent of the authentication for the access, for instance the radio 
resources. A separation of the authentication procedures is motivated 
by the fact that radio resources are scarce, and an access network 
operator may not want to allow Mobile IP signalling until the access 
network in itself has accepted to provide resources for a mobile node. 
Also, different access networks with, for instance, radio-based or fixed 
access, experience different types of security threats, and may address 
them differently.

The requirements for the authentication procedure are:

 1. There MUST be a generic Mobile IP authentication procedure, 
specifying full and subsequent authentication, as well as authentication 
for registration requests generated on behalf of a mobile node.

 2. Full authentication MUST be performed with the home network, the 
home administrative domain or with the home operator of the mobile user.

 3. There MUST be a unique user identity for full authentication.

 4. It SHOULD be possible to perform subsequent authentication locally 
at the visited network.

 5. Mobile IP SHOULD use the same authentication infrastructure as 
stationary Internet nodes.






<draft-ietf-mobileip-cellular-requirements-01.txt>            [Page 5]



4. Registration requests generated on behalf of a mobile node

There may be cases when a mobile node does not support Mobile IP 
signalling. If so, the signalling between the mobile node and the 
foreign agent could be handled by lower-level functionality in the 
access network. Then, the foreign agent could generate a registration 
request on behalf of the mobile node. This was described in [9] as 
surrogate registrations.

For reasons of backward compatibility with existing systems, it must be 
possible to implement Mobile IP without introducing Mobile IP signalling 
in the terminal. Registration requests generated by the foreign agent 
on behalf of a mobile node provide such a solution. They also provide a 
means to minimize the signalling over the radio link, and shall be 
included in Mobile IP. Lastly, secure full and subsequent authentication 
for registration requests generated on behalf of a mobile node must be 
ensured according to the generic authentication procedure for Mobile IP.

The requirements for registration requests generated on behalf of a 
mobile node are:

 1. It MUST be possible to employ Mobile IP in a network without 
introducing Mobile IP signalling in the terminal.


5. Private networks

Since private networks are an important part of the communication 
network structure, Mobile IP must support private networks and private 
address spaces. A proposed solution is to support private address spaces 
through proxy home and foreign agents [8]. This solution also supports 
hierarchical foreign agents within a network. Such a hierarchy may be 
valuable in order to improve handover performance. It may also be 
important for security reasons, since it allows the existence of agents 
without direct connection to external agents, that is, agents external 
to for instance a private network. Since most private networks are 
protected by firewalls, Mobile IP must provide a means for signalling 
and traffic to pass these firewalls.

Larger private networks may provide their own home agents, but there is 
also the case where one operator provides a home agent which is shared 
by several smaller private networks. Then, a mobile node may want access 
to a private network which is not its home network. In this case, we 
recognize a need for, for instance, the VPN Identifier Extension in the 
registration request [9]. The NAI of a mobile user points out the home 
network of the user and the VPN Identifier Extension points out the final 
destination of the tunnel.







<draft-ietf-mobileip-cellular-requirements-01.txt>            [Page 6]


The requirements for support of private networks are:

 1. Support of private address spaces MUST be included in Mobile IP.

 2. Mobile IP MUST provide a means for signalling and traffic to pass 
through firewalls.

 3. Mobile IP MUST provide a means for a mobile node, or an agent 
generating registration requests on behalf of a mobile node, to request 
access to a network which is not the home network of the mobile node.


6. Reverse tunnelling

The Mobile IP protocol, as specified in [20], is built on the concept 
of triangular routing. Reverse tunnelling has been suggested as an 
addition to Mobile IP, to support topologically correct reverse tunnels 
[19]. For reasons of security and charging, it must be possible for a 
network operator to employ reverse tunnelling, and to refuse mobile 
nodes, or agents generating registration requests on behalf of mobile 
nodes, which do not request reverse tunnelling when required. It must 
also be possible to employ encryption of the traffic with reverse 
tunnelling. Lastly, it should be possible to choose how to employ 
reverse tunnelling: all the way to the home agent, or to a firewall or 
gateway somewhere between the foreign agent and the home agent.

The requirements for reverse tunnelling are:

 1. It MUST be possible to employ reverse tunnelling together with Mobile 
IP.

 2. A network operator MUST be able to refuse mobile nodes, or agents 
generating registration requests on behalf of mobile nodes, which do not 
request reverse tunnelling.


7. Route optimization

New access techniques are expected to give users significantly more 
bandwidth than today, which will lead to more traffic in the backbone 
networks. Thus, it is important to minimize the load on the backbone, 
as well as the delay, through efficient routing. In the Mobile IP 
protocol, datagrams destined to a mobile node are sent to its home 
address and are tunnelled by the home agent to the current care-of 
address [20]. Route optimization is a suggested addition, which allows 
correspondent nodes to send datagrams directly to a mobile node 
[22][21]. In order to minimize the delay, and to optimize the 
utilization of network resources, it must be possible for an operator 
to employ route optimization. Especially, this would improve the 
performance for two mobile nodes located in a visited network, which are 
communicating with each other.



<draft-ietf-mobileip-cellular-requirements-01.txt>            [Page 7]

The authentication procedure for route optimization must be according 
to the generic authentication procedure for Mobile IP, and there must 
be a secure way to distribute information of the current address of a 
mobile node. If requested, encryption must also be ensured for the 
traffic. Integrated and differentiated services [4][5][23][24] do not 
always handle the change from triangular to optimized routing in a 
smooth way, and Mobile IP extensions or changes may be needed. Lastly, 
choosing the optimal route, with respect to the number of hops, may 
result in a lower level of quality of service. In order to maintain a 
negotiated quality of service, the quality-of-service mechanisms may 
need to interact with the route optimization mechanisms.

The requirements for route optimization are:

 1. It MUST be possible to employ route optimization together with Mobile 
IP.


8. Dynamic home address assignment

In many networks, including home networks of mobile nodes, addresses are 
assigned dynamically. Dynamic address assignment provides a means to 
better utilize the IP addresses in a network. It must be possible to 
assign an address to a mobile node, which belongs to a home network that 
usually employs dynamic address assignment. Furthermore, if the home 
agent is dynamically assigned, the home address needs to be dynamically 
assigned as well, since the home address must belong to the same sub-
network as the home agent [20]. A solution for dynamic home address 
assignment was proposed in [12].

The requirements for dynamic home address assignment are:

 1. Dynamic home address assignment MUST be included in Mobile IP.


9. Temporary home

According to Mobile IP, as specified in [20], the home agent is allocated 
in the home network. However, mobile users may have a need for a 
temporary home, not necessarily through a home agent assigned in the 
home network. The need could be to have an anchor point for some period 
of time, and the most optimal solution, considering routing performance, 
would be to have a home agent dynamically assigned in the visited 
network.

It must be possible for a mobile node, or an agent generating 
registration requests on behalf of a mobile node, to request and obtain 
a dynamically assigned home agent in the home network or in the visited 
network. It should also be possible for a mobile node which has obtained 
a dynamically assigned home agent in a visited network, to keep this 
home agent when moving to another network. A solution for dynamic home 
agent assignment, fulfilling these requirements, has been suggested in 
[13].


<draft-ietf-mobileip-cellular-requirements-01.txt>            [Page 8]


The requirements for a temporary home solution are:

 1. It MUST be possible for a mobile node, or an agent generating 
registration requests on behalf of a mobile node, to request and be 
assigned a dynamic home agent either in the home network or in the 
visited network.

 2. A mobile node which has been assigned a dynamic home agent in a 
visited network SHOULD be able to keep this home agent when moving to 
another network.


10. Handover performance

Mobile IP, as specified in [20], does not provide seamless/loss-less 
handover between different foreign agents within the same administrative 
domain. The existing solution may be acceptable for certain non-delay-
sensitive and loss-tolerant applications, but needs to be improved in 
order to support for instance real-time applications.

There have been suggestions on how to improve the handover performance, 
in terms of making the signalling procedure faster [8][14][15][22]. 
However, the handover performance still needs to be improved in order 
to support for instance real-time applications, or to support loss-less 
handover.


11. Conclusions

This draft provides a list of requirements on Mobile IPv4 for use in 
cellular networks. Beside the general requirements on functionality and 
security, there are specific requirements on authentication, address 
assignment, routing and issues providing interworking with existing 
cellular solutions.

All the requirements provided in this draft may not be necessary in a 
first step of introducing Mobile IP in cellular networks. However, we 
believe that they all need to be considered to eventually support all 
various demands from different operators and end users. The requirements 
list will also be extended for Mobile IPv6.













<draft-ietf-mobileip-cellular-requirements-01.txt>            [Page 9]



12. Intellectual property considerations

Ericsson has a patent US 5708655 which might be relevant to the issues 
considered in this document. If access to this patent should become 
necessary for implementing any standard or standards proposal based on 
this document, Ericsson is willing to license this patent and any 
foreign counterparts on fair and reasonable terms and conditions to 
anybody for such use. If somebody asking for such a license from Ericsson 
owns or controls a patent also necessary for implementing the standard, 
Ericsson consider fair and reasonable terms and conditions to include a 
grant back license on such patent and any foreign counterparts. For the 
avoidance of doubt Ericsson supports the handling of IPR issues 
according to RFC 2026 [7].


13. Acknowledgements

The authors would like to thank Henrik Basilier, Martin Korling, Lars 
Westberg, Anders Herlitz, Yuri Ismailov, Ulf Olsson, Thomas Eklund and 
Georg Chambert at Ericsson for their valuable comments.


14. References

[1] B. Aboba: "Support for Mobile IP in Roaming", Internet draft 
(expired), draft-ietf-roamops-mobileip-01.txt, March 1998.

[2] B. Aboba, M. Beadles: "The Network Access Identifier", RFC 2486, 
January 1999.

[3] C.B. Becker, B. Patil, E. Qaddoura: "IP Mobility Architecture 
Framework", Internet draft (work in progress), draft-ietf-mobileip-ipm-
arch-00, February 1999.

[4] S. Blake, Editor: "A Framework for Differentiated Services", 
Internet draft (work in progress), draft-ietf-diffserv-framework-01, 
October 1998.

[5] S. Blake, Editor: "An Architecture for Differentiated Services", RFC 
2475, December 1998.

[6] S. Bradner: "Key words for use in RFCs to Indicate Requirements 
Levels", RFC 2119, March 1997.

[7] S. Bradner: "The Internet Standards Process -- Revision 3", RFC 
2026, October 1996.




<draft-ietf-mobileip-cellular-requirements-01.txt>            [Page 10]



[8] P.R. Calhoun, G. Montenegro, C.E. Perkins: "Mobile IP Regionalized 
Tunnel Management", Internet draft (work in progress), draft-ietf-
mobileip-reg-tunnel-00.txt, November 1998.

[9] P.R. Calhoun, G. Montenegro, C.E. Perkins: "Tunnel Establishment 
Protocol", Internet draft (expired), draft-ietf-mobileip-calhoun-tep-
01.txt, March 1998.

[10] P.R. Calhoun, C.E. Perkins: "DIAMETER Mobile IP Extensions", 
Internet draft (work in progress), draft-calhoun-diameter-mobileip-
01.txt, November 1998.

[11] P.R. Calhoun, C.E. Perkins: "Mobile IP Challenge/Response 
Extensions", Internet draft (work in progress), draft-ietf-mobileip-
chal-01.txt, February 1999.

[12] P.R. Calhoun, C.E. Perkins: "Mobile IP Dynamic Home Address 
Allocation Extension", Internet draft (work in progress), draft-ietf-
mobileip-home-addr-alloc-00.txt, November 1998.

[13] P.R. Calhoun, C.E. Perkins: "Mobile IP Foreign Agent 
Challenge/Response Extension", Internet draft (work in progress), 
draft-ietf-mobileip-challenge-00.txt, November 1998.

[14] M. Chuah, A. Yan, Y. Li: "Distributed Registrations Enhancements 
to Mobile IP", Internet draft (work in progress), draft-chuali-mobileip-
dremip-02.txt, November 1998.

[15] S.F. Foo, K.C. Chua: "Regional Aware Foreign Agent (RAFA) for Fast 
Local Handoffs", Internet draft (work in progress), draft-chuafoo-
mobileip-rafa-00.txt, November 1998.

[16] E. Gustafsson, A. Herlitz, A. Jonsson, M. Korling: "UMTS/IMT-2000 
and Mobile IP/DIAMETER Harmonization", Internet draft (work in 
progress), draft-gustafsson-mobileip-imt-2000-00.txt, November 1998.

[17] T. Hiller, Editor: "3G Wireless Data Provider Architecture Using 
Mobile IP and AAA", Internet draft (work in progress), draft-hiller-
3Gwireless-00.txt, March 1999.

[18] D.B. Johnson, C. Perkins: "Mobility Support in IPv6", Internet 
draft (work in progress), draft-ietf-mobileip-ipv6-07.txt, November 
1998.

[19] G. Montenegro: "Reverse Tunneling for Mobile IP", RFC 2344, May 
1998.


<draft-ietf-mobileip-cellular-requirements-01.txt>           [Page 11]


[20] C. Perkins, Editor: "IP Mobility Support", RFC 2002, October 1996.

[21] C. Perkins, D.B. Johnson: "Registration Keys for Route 
Optimization", Internet draft (expired), draft-ietf-mobileip-regkey-
00.txt, November 1997.

[22] C. Perkins, D.B. Johnson: "Route Optimization in Mobile IP", 
Internet draft (work in progress), draft-ietf-mobileip-optim-08.txt, 
February 1999.

[23] S. Shenker, J. Wroclawski: "General Characterization Parameters for 
Integrated Service Network Elements", RFC 2215, September 1997.

[24] S. Shenker, J. Wroclawski: "Network Element Service Specification 
Template", RFC 2216, September 1997.

[25] J.K. Zao, M. Condell: "Use of IPSec in Mobile IP", Internet draft 
(expired), draft-ietf-mobileip-ipsec-use-00.txt, November 1997.


15. Author's address

Eva Gustafsson, Annika Jonsson	
Ericsson Radio Systems AB
Network and Systems Research
SE-164 80 Stockholm
SWEDEN

{eva.m.gustafsson | annika.jonsson}@era.ericsson.se


Elisabeth Hubbard, Jonas Malmkvist, Anders Roos
Telia Research AB
Network Research
Vitsandsgatan 9
SE-123 86 Farsta
SWEDEN

{elisabeth.a.hubbard | jonas.x.malmkvist | anders.g.roos}@telia.se













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                             Expires October 1999