Internet Area M.Hui
Internet Draft H.Deng
Intended status: Informational China Mobile
Expires: April 27, 2009 October 27, 2008
Scenario and Solution: Simple IP Multi-homing of the Host
draft-hui-ip-multiple-connections-00.txt
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Copyright (C) The IETF Trust (2008).
Abstract
Current host routing mechanism doesn't allow simple IP multi-homing
for the default gateway consideration. This document proposes a
solution to make multiple connections can work simultaneously.
Conventions used in this document
In examples, "C:" and "S:" indicate lines sent by the client and
server respectively.
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
.
Table of Contents
1. Introduction...................................................3
2. Scenario.......................................................3
3. Solution.......................................................3
3.1. Routing policy............................................3
3.2. DHCP extension............................................4
3.3. Configuration procedure...................................5
4. Security Considerations........................................5
5. IANA Considerations............................................5
6. References.....................................................5
6.1. Normative References......................................5
6.2. Informative References....................................6
Author's Addresses................................................6
Intellectual Property Statement...................................6
Disclaimer of Validity............................................7
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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.
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 ''0.0.0.0'' 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. We analyze this problem statement in
another IETF draft ' draft-hui-ip-multiple-connections-ps-01'.
In this document we will illustrate the specific scenario and give a
probable solution by extending DHCPv4.
2. Scenario
Simple IP Multi-homing is a necessary part of daily life. For example,
Mike must connect with the VPN by Ethernet interface when he is at
work, at the same time he wants to watch the stock market, which is
forbidden in the VPN, so he needs another connection to the GPRS
network simultaneously.
The problem is Mike can not use two connections at the same time for
his different service requirement, because all the IP flows go to the
same interface which related to the default gateway in the host
routing table. That is the point need to be solved in simple IP
multi-homing.
3. Solution
The default gateway problem can be solved by applying routing policy
in the host.
3.1. Routing policy
The routing policy can applied in the host so that different IP flows
can go to different interfaces depending on the polices. To maintain
a simple host routing table, the policy can be allocated by the
network side, i.e. the gateway. The policy is distributed to the host
as soon as it attaches to the gateway, and the policy will be applied
in the initial procedure of the host.
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The routing policy information should contain the proper interface
allocation according to IP destination and service type. For doing
this, IP flows can go to the appropriate network, and all connections
can work simultaneously.
3.2. DHCP extension
DHCP is a proper message to carry the host routing policy information,
for DHCP take effect when host first attach to the network, and DHCP
is a universal protocol used in the host IP deployment between
network gateway and host.
To carry the host routing information, DHCP should make an extension
in the DHCP option field. The format is showed as follow:
Code Len Destination 1 Mask 1
+-----+-----+-----+-----+-----+-----+-----+
| x | n | d1 | d2 | d3 | d4 | m1 |
+-----+-----+-----+-----+-----+-----+-----+
TOS1 Router1 Destination 2
+-----+-----+-----+-----+-----+-----+-----+
| t1 | r1 | r2 | r3 | r4 | d1 | d2 |
+-----+-----+-----+-----+-----+-----+-----+
Mask 2 TOS2 Router2
+-----+-----+-----+-----+-----+-----+-----+
| d3 | d4 | m2 | t2 | r1 | r2 | r3 |
+-----+-----+-----+-----+-----+-----+-----+
+-----+-----
| r4 | ...
+-----+-----
Figure 1 DHCP extension format.
Code is a number represents the specific DHCP option, which needs to
be assigned by IANA.
Len represents the length of the option form the byte after the Len
field.
Destination is the Destination IP address of the datagram, occupying
4 byte. Mask represents the subnet mask digit of the destination.
TOS follows the definition in RFC1349, and it represents the
requirement of specific IP flow, such as bandwidth and delay.
Router is the next hop IP address. Either the router interface
address or the corresponding host interface address is suitable.
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3.3. Configuration procedure
The DHCP routing policy is carried in the DHCP message, when host
requires IP configuration as soon as it first attaches the network,
DHCP server will send the routing policy together with the IP
configuration to the host.
Then the routing policy carried on the DHCP message is obtained by
the host, and applied as the static routing entries in the host
routing table, which constrain specific IP flow to certain interface.
Depending on the destination and TOS, the IP flow can find a proper
router as the next hop, and goes out through the corresponding
interface. Thus different IP flows can use multiple connections
properly and simultaneously.
4. Security Considerations
This document doesn't propose any new protocol.
5. IANA Considerations
This document requires a new number for DHCP option code x described
in section 3.2.
6. References
6.1. 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.
[RFC2132] S. Alexander, Silicon Graphics, Inc., and R. Droms, " DHCP
Options and BOOTP Vendor Extensions ", RFC 2132, 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.
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[RFC4191] R. Draves, D. Thaler, ''Default Router Preferences and
More-Specific Routes'', RFC4191, November 2005
6.2. 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)>.
Author's Addresses
Min Hui
China Mobile
53A,Xibianmennei Ave.,
Xuanwu District,
Beijing 100053
China
Email: huimin.cmcc@gmail.com
Hui Deng
China Mobile
53A,Xibianmennei Ave.,
Xuanwu District,
Beijing 100053
China
Email: denghui02@gmail.com
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