Network Working Group Y. Hong
Internet-Draft ETRI
Intended status: Informational J. Youn
Expires: September 2, 2009 DONG-EUI Univ.
March 1, 2009
Analysis and scenarios of multiple interfaces in a host
draft-hong-mif-analysis-scenario-00
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Abstract
This document is an analysis of multiple interfaces in a host and
description of scenarios of multiple interfaces with the respect of
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TCP/IP layer. The current TCP/IP mechanism and networking methods
are suitable for a single network interface. When a host has
multiple interfaces, the current TCP/IP mechanism and networking
methods cannot directly be used for them. In this document, we
describe some problems for a host which has multiple network
interfaces as an aspect of host's operations and some usage scenarios
of multiple interfaces in a host.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Problem Statements . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Relation between network interface and destination
address . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Considerations for heterogeneous environments with
different IP version . . . . . . . . . . . . . . . . . . . 5
3. Scenarios of host with multiple interfaces . . . . . . . . . . 5
3.1. Multiple interfaces but none layer do not support . . . . 5
3.2. Multiple interfaces and only network layer support . . . . 6
3.3. Multiple interfaces and network layer and transport
layer support . . . . . . . . . . . . . . . . . . . . . . 7
3.4. Multiple interfaces and all layer support . . . . . . . . 8
3.5. Multiple interfaces and specific layer support . . . . . . 8
4. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 9
5. Security Considerations . . . . . . . . . . . . . . . . . . . 9
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
7.1. Normative References . . . . . . . . . . . . . . . . . . . 10
7.2. Informative References . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
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1. Introduction
In future ubiquitous networks, many services and many access
technologies are expected to be interworked and harmonized for better
services. To do so, a host must have different access technologies
and different network interfaces for each access technology.
Mobile IPv6 [RFC3775][1] and NEMO Basic Support [RFC3963] [2] can
solve the problem of the change of IPv6 network address when a mobile
node or a mobile router moves. But these protocols are developed for
a mobile node with a single network interface and a mobile router
with a single egress network interface. Due to multiple interfaces,
there are many things to be considers such as multiple CoA, multiple
HoA, and multiple HA. We cannot directly use basic Mobile IPv6 for a
mobile node with multiple network interfaces. IETF MEXT working
group are targeting to solve these problems and have developed many
solutions.
If a host has multiple interfaces, this situation influences not only
mobility issues (e.g., extending Mobile IPv6/NEMO Basic Support) but
also general networking operations and TCP/IP mechanism
[I-D.blanchet-mif-problem-statement][3] [I-D.hui-ip-multiple-
connections-ps][4].
This document describes the problems of multiple interfaces in a host
as an aspect of host's operations. Because of the change of network
interface in communication, it needs the proper update between
destination address and network interfaces, and consideration for
heterogeneous environment with different IP version. And this
document describes the scenarios of multiple interfaces in a host
with the respect of TCP/IP stack. Because of the difference of
overhead and cost of each layer to support multiple interfaces, there
may be various scenarios of multiple interfaces in a host to use.
2. Problem Statements
2.1. Relation between network interface and destination address
The problem of multiple network interfaces in a host is the relation
between a destination address and a network interface. In the
following case, we assume a host with two network interfaces I1 and
I2 of different access technologies. Each interface is configured
with a global IPv6 address, respectively IP1 and IP2, and the address
of a correspondent node is IP3.
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_________
| CN |
|_________|
| IP3
/|\
+------------------+ +------------------+
| Network 1 (N1) | | Network 2 (N2) |
| | | |
+------------------+ +------------------|
Interface 1 (I1) \|/ \|/ Interface 2 (I2)
IP1 | | IP2
|_________|
| host |
|_________|
Figure 1: A host with two interfaces
+-------------+-----------------------+-----------------------------+
| Location | (Source Address, | Relation btw a Destination |
| (Used I/F) | Destination Address) | Addr. and a network I/F |
+-------------+-----------------------+-----------------------------+
| N1 (I1) | (IP1, IP3) | IP3 -> I1 |
| N2 (I2) | (IP2, IP3) | IP3 -> ? |
+-------------+-----------------------+-----------------------------+
Table 1: Relation between destination address and network interfaces
The host may change its interface for communication with a
correspondent node due to movement or change of network environments.
Before the change of network interface, when the host uses (I1, IP1)
and sends packets to a correspondent node, the source address and
destination address of packets is (IP1, IP3) and the used network
interface is I1. If the host moves other network N2, and then the
host uses (I2, IP2) and the used network interface is I2. Before the
change of network interface, the destination address (IP3) of the
correspondent node is mapped to a network interface I1. However
after the change of network interface, when an application tries to
send packets to the correspondent node, it continually tries to use a
network interface I1 if the relation of destination address IP3 and
network interface I1 is not properly updated. If this situation
happens, even though, the network interface is changed to I2, packets
are delivered to I1 at the link layer or L2 layer. The communication
sessions will be disrupted.
To solve this problem, a host must properly update the relation
between a destination address and a network interface when it changes
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a network interface.
2.2. Considerations for heterogeneous environments with different IP
version
If a host moves between networks with a single network interface or
access technology, the change may be only a network address. Because
the host has an access technology of the single network interface, it
doesn't need to consider other aspects such as the change of access
technology and IP version.
If a host moves between networks with multiple network interfaces or
access technologies, other changes may happen. If a host has
multiple network interfaces (one is a WLAN interface and the other is
a CDMA interface) in heterogeneous environments, changes include the
network address, network interface and access technologies of the
selected network interface after moving. Particularly, the main
issue is the network address. Currently in Korea, we can use IPv6
based WLAN service but it is impossible to use IPv6 based CDMA
service. The deployment of IPv6 based CDMA service will be done
sooner or later. Until the deployment of IPv6 based CDMA service, if
we want to use IPv6 service with a CDMA network interface, we must
consider how to use IPv6 service in IPv4 based CDMA network.
3. Scenarios of host with multiple interfaces
If a host has multiple interfaces, it influences not only PHY/MAC
layer but also other layer such as network layer, transport layer,
and application layer (and a user). As the deployment of multiple
interfaces to a host, there may be various scenarios of the usage of
host with multiple interfaces. At the beginning time, even though a
host adapts multiple interfaces, other layers could not have
capability to support multiple interfaces. Also, a user who uses a
host with multiple interfaces could not acknowledge the existence of
multiple interfaces. As the deployment of multiple interfaces, other
layer could have capability to support multiple interfaces. But, in
some cases, a specific layer could not have capability to support
multiple interfaces in a host.
3.1. Multiple interfaces but none layer do not support
At the beginning time, a host adapts multiple interfaces but other
layers do not support multiple interfaces. (Other layers are not
aware of the existence of multiple interfaces.) Because the overhead
and cost of modification of original network layer, transport layer,
and application layer, it is difficult to modify other layer all at
once to support multiple interfaces in a host. For specific
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applications and/or specific OS, it could be difficult to modify them
to support multiple interfaces. In this case, the connection manager
must provide method to use multiple interfaces even though other
layers do not support multiple interfaces. There are typical works
to support this case [5], [6].
+-------------------------------+
| Original Applications |
|-------------------------------|
| Original TCP/UDP/SCTP/DCCP |
|-------------------------------|
| Original IPv6/IPv4 |
|-------------------------------|
| +-------------------+
| | Connection Manager|
| +-------------------+
| |
| +------------+ +------------+ |
| | Interface 1| | Interface n| |
| | (I1) | | (In) | |
| +------------+ +------------+ |
+-------------------------------+
Figure 2: A host with multiple interfaces when other layer does not
support
3.2. Multiple interfaces and only network layer support
As time goes on, a host adapts multiple interfaces and network layer
support multiple interfaces. (transport layer, application layer, and
user are not aware of the existence of multiple interfaces.) The
Mobile IPv6 which is extended to support multiple interfaces could be
in this case [7]. In this case, the connection manager must provide
method to use multiple interfaces with the help of the network layer.
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+-------------------------------+
| Original Applications |
|-------------------------------|
| Original TCP/UDP/SCTP/DCCP |
|-------------------------------|
| Modified |
| IPv6/IPv4 +-------------------+
|---------------------| Connection Manager|
| +-------------------+
| |
| +------------+ +------------+ |
| | Interface 1| | Interface n| |
| | (I1) | | (In) | |
| +------------+ +------------+ |
+-------------------------------+
Figure 3: A host with multiple interfaces when network layer supports
3.3. Multiple interfaces and network layer and transport layer support
In this case, a host adapts multiple interfaces and network layer and
transport layer support multiple interfaces. (application layer, and
user are not aware of the existence of multiple interfaces.) Until
now, it seems that existing TCP/UDP could not have the capability to
support multiple interfaces. And it seems that SCTP could have the
capability to support multiple interfaces but it needs to be more
enhanced. In this case, the connection manager must provide the
method to use multiple interfaces with the help of the network layer
and the transport layer.
+-------------------------------+
| Original Applications |
|-------------------------------|
| Modified |
| TCP/UDP/SCTP/DCCP +-------------------+
|---------------------| |
| Modified | Connection Manager|
| IPv6/IPv4 | |
|---------------------| |
| +-------------------+
| +------------+ +------------+ |
| | Interface 1| | Interface n| |
| | (I1) | | (In) | |
| +------------+ +------------+ |
+-------------------------------+
Figure 4: A host with multiple interfaces when network layer and
transport layer support
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3.4. Multiple interfaces and all layer support
In this case, a host adapts multiple interfaces and all layers
including network layer, transport layer, and application layer
support multiple interfaces. And all layers are aware of the
existence of multiple interfaces. In this case, the connection
manager must provide the method to use multiple interfaces with the
help of the network layer, the transport layer, and the application
layer.
+-------------------------------+
| Modified +-------------------+
| Applications | |
|---------------------| |
| Modified | |
| TCP/UDP/SCTP/DCCP | Connection Manager|
|---------------------| |
| Modified | |
| IPv6/IPv4 | |
|---------------------| |
| +-------------------+
| +------------+ +------------+ |
| | Interface 1| | Interface n| |
| | (I1) | | (In) | |
| +------------+ +------------+ |
+-------------------------------+
Figure 5: A host with multiple interfaces when all layer support
3.5. Multiple interfaces and specific layer support
In this case, a host adapts multiple interfaces and one or two
specific layers support multiple interfaces. Because it seems that
it is difficult to modify network layer and transport layer to
support multiple interfaces (typically, network layer and transport
layer are in kernel space and application layer is in user space in
Linux OS), application layer could be easily modified to support
multiple interfaces. In this case, the connection manager must
provide the method to support multiple interfaces with the help of
specific layer even though intermediate layer does not support it.
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+-------------------------------+
| Modified --+-+ +-------------------+
| Applications | +--| Connection Manager|
|-------------------------------| | +-------------------+
| Original TCP/UDP/SCTP/DCCP | |
|-------------------------------| |
| Original IPv6/IPv4 | |
|-------------------------------| |
| --+-+
| +------------+ +------------+ |
| | Interface 1| | Interface n| |
| | (I1) | | (In) | |
| +------------+ +------------+ |
+-------------------------------+
Figure 6: A host with multiple interfaces when application layer
supports
4. Conclusions
When a host has multiple interfaces, the host can use heterogeneous
network interfaces and it can provide ubiquitous access. In this
document, we showed the issues when a host has multiple network
interfaces as an aspect of host's operations. If a host is able to
use multiple network interfaces, the host must update dynamically the
relation of a destination address of a correspondent node and a
network interface after the change of a network interface. Because
the host may use different access technologies in heterogeneous
networks with different IP version, some access networks of a
selected network interface do not support IPv6. In this case we must
consider how to support IPv6 service in IPv4 based networks. Because
of the difference of deployment of multiple interfaces in a host,
there may be various scenarios of multiple interfaces in a host to
use. We should clarify considerations and issues of each scenario
for further study.
5. Security Considerations
If a host has multiple interfaces and does not properly update the
relation between network interfaces and destination address, the
communication may disrupt.
6. IANA Considerations
This document has no actions for IANA.
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7. References
7.1. Normative References
[1] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in
IPv6", RFC 3775, June 2004.
[2] Devarapalli, V., Wakikawa, R., Petrescu, A., and P. Thubert,
"Network Mobility (NEMO) Basic Support Protocol", RFC 3963,
January 2005.
7.2. Informative References
[3] Blanchet, M., "Multiple Interfaces Problem Statement,
draft-blanchet-mif-problem-statement-00 (work in progress)",
December 2009.
[4] Hui, M. and H. Deng, "Problem Statement and Requirement of
Simple IP Multi-homing of the Host,
draft-hui-ip-multiple-connections-ps-01 (work in progress)",
November 2008.
[5] Hong, Y. and J. Youn, "Virtual network interface model for
multiple network interfaces in a host
draft-hong-mif-virtual-interface-00 (work in progress)",
February 2009.
[6] "SHISA, An implementation of Mobile IPv6",
<http://www.mobileip.jp/>.
[7] Wakikawa, R., Devarapalli, V., Ernst, T., and K. Nagami,
"Multiple Care-of Addresses Registration,
draft-ietf-monami6-multiplecoa-11 (work in progress)",
January 2009.
Authors' Addresses
Yong-Geun Hong
ETRI
161 Gajeong-Dong Yuseung-Gu
Daejeon, 305-700
Korea
Phone: +82 42 860 6557
Email: yonggeun.hong@gmail.com
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Joo-Sang Youn
DONG-EUI Univ.
Busan,
Korea
Phone: +82 51 890 1993
Email: joosang.youn@gmail.com
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