Internet Area M. Hui
Internet-Draft H. Deng
Intended status: Informational China Mobile
Expires: January 8, 2009 July 7, 2008
Problem Statement and Requirement of Simple IP Multi-homing of the Host
draft-hui-ip-multiple-connections-ps-00
Status of this Memo
By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79.
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.
This Internet-Draft will expire on January 8, 2009.
Hui & Deng Expires January 8, 2009 [Page 1]
Internet-Draft IP Multi-Connect July 2008
Abstract
This document discusses current problems with simple IP multi-homing.
In order to have deep understanding of the issue, the document also
analyzes related works in IETF. In the end gives the requirements of
the simple IP multi-homing in concern of technical implements.
Simple IP multi-homing focuses on simultaneous multiple IP
connections of the host.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Problem statements of Simple IP Multi-homing . . . . . . . . . 4
2.1. Default Gateway . . . . . . . . . . . . . . . . . . . . . 4
2.2. Metric Rules . . . . . . . . . . . . . . . . . . . . . . . 4
2.3. Weak and Strong Host Model . . . . . . . . . . . . . . . . 5
3. Analysis of Related Work in IETF . . . . . . . . . . . . . . . 6
3.1. Multi6 . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.2. Shim6 . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.3. Monami6 . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.4. Proxy Mobile IPv6 . . . . . . . . . . . . . . . . . . . . 7
4. Requirements for Simple IP Multi-homing . . . . . . . . . . . 8
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
6. Security Considerations . . . . . . . . . . . . . . . . . . . 10
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
7.1. Normative References . . . . . . . . . . . . . . . . . . . 11
7.2. Informative References . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
Intellectual Property and Copyright Statements . . . . . . . . . . 13
Hui & Deng Expires January 8, 2009 [Page 2]
Internet-Draft IP Multi-Connect July 2008
1. Introduction
Simple IP Multi-homing means the host connects to more than one
physical network through different network interfaces, and assigns
different network flows to each interface, and ensure all the
interfaces can deliver the flow simultaneously.
Simple IP Multi-homing is a necessary part of daily life, i.e., you
must connect with the VPN by your Ethernet interface when you are at
work, at the same time you want to watch the stock market, which is
forbidden in the VPN, so you need another connection to the GPRS
network simultaneously.
Current host operating systems allow one default connection at once.
If there are multiple connections of the host, all the flows will go
to the default gateway, although you can find several !o0.0.0.0!+/-
routs in the host route table. One default gateway guarantees the
host always has one exit to the network, but cause the multiple
connections be impossible. The most convenient way to make the host
work under several networks at the same time is to add specific
static route in the host route table, so that certain flow can use
the assigned interface while others use the default one, but it is
too hard for the ordinary users to handle it.
Hui & Deng Expires January 8, 2009 [Page 3]
Internet-Draft IP Multi-Connect July 2008
2. Problem statements of Simple IP Multi-homing
As description above, simple IP multi-homing can not work currently,
there are several reasons cause it invalid, the specifics are listed
as follows:
2.1. Default Gateway
The Windows operating system in the host obeys the default gateway
mechanism, which will choose the unify gateway among more than one
default routes (!o0.0.0.0!+/-), it can be seen in the last row of the
host route table. The default gateway guarantees there always has a
route to network when the host can not find a specific route for a
datagram in the route table.
But when it comes to multi-homing, the default gateway also causes
all the flows go out through one interface, although there has more
than one network connections. Nowadays there are diverse networks
can be chosen by the user, and the terminal have the capability and
interfaces to connect to more than one networks at the same time. It
is possible and necessary for the user to require connecting to
different networks to ensure the best user experiences of different
services, but the default gateway will invalidate the requirement.
Although you can connect your host to several networks physically,
and each network has already assigned a IP address for your host
interface, even you can see different default routes in the route
table, all the flow goes to the unify default gateway chosen by the
operation system other than different gateways actually.
2.2. Metric Rules
The default gateway is chosen based on the metric rule. The one have
the lowest metric value becomes to the default gateway among several
connected gateways, and the interface correspond to this gateway
turns to be the default interface.
Current metric rules define the 100M bps Ethernet network card to be
20 and 10M bps to be 30. But it is not a strict definition, and the
user can change the metric value manually. The problem is not every
network card obey the metric rules, which represents the lower metric
value is, the faster route is, so that the operating system can
always choose the best performance route as the default one for the
user. For example, CDMA data card set its metric value as 1,
although its speed is lower than 100M bps Ethernet network card. In
this situation, the operating system will choose the CDMA connection
as the default one, so the user is forced to use the slower
connection, which violates the aim of the metric rule.
Hui & Deng Expires January 8, 2009 [Page 4]
Internet-Draft IP Multi-Connect July 2008
2.3. Weak and Strong Host Model
There exists two different host model today, which are weak host
model and strong host model, described in RFC 1122. The weak host
model causes the default gateway behavior is possible, for the
destination is host other than a specific interface. Reversely, the
strong host model divides the host to several separated hosts
logically, what means the flow can only use the specific interface.
The problem is current host operating system such as Windows 2000/XP
all apply weak host model on its network interface, so the host can
not differ the flow to different interfaces, only the default gateway
is applied.
Hui & Deng Expires January 8, 2009 [Page 5]
Internet-Draft IP Multi-Connect July 2008
3. Analysis of Related Work in IETF
Multi-homing is a wide topic contains different aspects, and there
are some work groups in IETF worked on a certain aspect of multi-
homing.
This section explains their work, and compares the covered field with
the simple IP multi-homing. In the end we will find the simple IP
multi-homing is still a problem which is not solved yet.
3.1. Multi6
Multi6 WG in IETF focuses on the multi-homed site, which has more
than one connection to the public internet with those connections
through either the same or different ISPs. The reasons to choose
site multi-homing are to improve fault tolerance, perform load
balancing, etc.
The Multi6 WG mainly focuses on multi-homing solutions that tend to
minimize adverse impacts on the end-to-end routing system and limit
the number of prefixes that need to be advertised in the Default-Free
Zone (DFZ). The background is site multi-homing today is done
largely by having a site obtain a dedicated block of address space
and then advertising a route for its prefix through each of its ISP
connections. A site's ISPs in turn advertise the prefix to some or
all of their upstream connections and the route for the prefix may
propagate to all of the routers connected to the default-free zone.
As the number of sites multi-homing in this manner increase, the
number of routes propagated throughout the DFZ increases and overall
routing stability decreases because of the burden on convergence
time.
Multi6 WG tries to solve this by defining a set of goals for IPv6
site multi-homing architecture, and analyzing the current limitations
and the approaches to the site multi-homing. What!_s need to notice
is that the working group is not chartered to make significant
changes to the nature of IP addresses or to inter-domain routing.
Obviously, the site multi-homing does not consider the host multiple
connection which is the key problem in simple IP multi-homing.
3.2. Shim6
Shim6 is another WG in IETF aims at site multi-homing. Shim6 work is
based on the architecture developed by the Multi6 WG, and completes
the required protocol developments and the architecture and security
analysis of the required protocols. Different with Multi6, Shim6
focuses on surviving hosts on the multi-homing site from the changes
or for creating new associations, when one or more of the site!_s
Hui & Deng Expires January 8, 2009 [Page 6]
Internet-Draft IP Multi-Connect July 2008
address prefixes becomes unreachable.
Shim6 WG produces specifications for an IPv6-based site multi-homing
solution that inserts a new sub-layer (shim) into the IP stack of
end-system hosts. It enables hosts on multi-homed sites to use a set
of provider-assigned IP address prefixes and switch between them
without upsetting transport protocols or applications. But it can
not support connecting to all the ISPs simultaneously.
3.3. Monami6
The objective of the Monami6 WG is to produce a clear problem
statement and to produce standard track specifications to the
straight-forward problems associated with the simultaneous use of
multiple addresses for either mobile hosts using Mobile IPv6 or
mobile routers using NEMO Basic Support and their variants (FMIPv6,
HMIPv6,etc).
The WG does not define a tunnel selection mechanism, but document how
to use existing mechanisms based upon preferences or policies. They
explain the limitations for mobile hosts using multiple simultaneous
Care-of Addresses and Home Agent addresses using Mobile IPv6, whether
issues are specific to Mobile IPv6 or not. They also deliver a
protocol extension to Mobile IPv6 (RFC 3775) and NEMO Basic Support
(RFC 3963) to support the registration of multiple Care-of Addresses
at a given Home Agent address [Standard Track]. What!_s more,
Monami6 WG makes a "Flow/binding policies exchange" solution for an
exchange of policies from the mobile host/router to the Home Agent
and from the Home Agent to the mobile host/router influencing the
choice of the Care-of Address and Home Agent address.
Monami6 focus the same field with simple IP multi-homing, which is
ensuring simultaneous use of multiple addresses for the host. The
difference is Monami6 puts this aim to under a certain condition, the
mobile host using MIP6, while the simple IP multi-homing focuses on
ordinary host using IPv4/6.
3.4. Proxy Mobile IPv6
Hui & Deng Expires January 8, 2009 [Page 7]
Internet-Draft IP Multi-Connect July 2008
4. Requirements for Simple IP Multi-homing
Based on problem statements and related work analysis, the
requirements for simple IP multi-homing is concluded and listed as
follows:
1) The host with multiple network interfaces should be capable to
connect with different networks simultaneously.
2) The default gateway mechanism needs to be improved to support
several gateways working at the same time.
3) New metric rules must be defined to adapt to divers network cards
nowadays.
4) The policies to assign different flows to the appropriate
interface are required, and how to apply the policies to the host
need to be considered as well.
Hui & Deng Expires January 8, 2009 [Page 8]
Internet-Draft IP Multi-Connect July 2008
5. IANA Considerations
This document doesn't require any new number from IANA.
Hui & Deng Expires January 8, 2009 [Page 9]
Internet-Draft IP Multi-Connect July 2008
6. Security Considerations
This document doesn't propose any new protocol.
Hui & Deng Expires January 8, 2009 [Page 10]
Internet-Draft IP Multi-Connect July 2008
7. References
7.1. Normative References
[RFC1122] Braden, R., "Requirements for Internet Hosts -
Communication Layers", STD 3, RFC 1122, October 1989.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3582] Abley, J., Black, B., and V. Gill, "Goals for IPv6 Site-
Multihoming Architectures", RFC 3582, August 2003.
[RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
in IPv6", RFC 3775, June 2004.
[RFC4177] Huston, G., "Architectural Approaches to Multi-homing for
IPv6", RFC 4177, September 2005.
7.2. Informative References
[MONAMI6] Ernst, T., "Motivations and Scenarios for Using Multiple
Interfaces and global Addresses", May 2008, <draft-ietf-
monami6-multihoming-motivation-scenario-03(work in
progress)>.
Hui & Deng Expires January 8, 2009 [Page 11]
Internet-Draft IP Multi-Connect July 2008
Authors' Addresses
Min Hui
China Mobile
53A,Xibianmennei Ave.,
Xuanwu District,
Beijing 100053
China
Email: huimin.wti@gmail.com
Hui Deng
China Mobile
53A,Xibianmennei Ave.,
Xuanwu District,
Beijing 100053
China
Email: denghui02@gmail.com
Hui & Deng Expires January 8, 2009 [Page 12]
Internet-Draft IP Multi-Connect July 2008
Full Copyright Statement
Copyright (C) The IETF Trust (2008).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Intellectual Property
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
Hui & Deng Expires January 8, 2009 [Page 13]