draft-ietf-monami6-multihoming-motivation-scenario-02.txt   draft-ietf-monami6-multihoming-motivation-scenario-03.txt 
Monami6 Working Group T. Ernst Monami6 Working Group T. Ernst
Internet-Draft INRIA Internet-Draft INRIA
Expires: January 13, 2008 N. Montavont Expires: November 4, 2008 N. Montavont
GET/ENST-B IT/Telecom Bretagne
R. Wakikawa R. Wakikawa
Keio University Toyota ITC/Keio Univ.
C. Ng C. Ng
Panasonic Singapore Labs Panasonic Singapore Labs
K. Kuladinithi K. Kuladinithi
University of Bremen University of Bremen
July 12, 2007 May 3, 2008
Motivations and Scenarios for Using Multiple Interfaces and Global Motivations and Scenarios for Using Multiple Interfaces and Global
Addresses Addresses
draft-ietf-monami6-multihoming-motivation-scenario-02.txt draft-ietf-monami6-multihoming-motivation-scenario-03.txt
Status of this Memo Status of this Memo
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Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract Abstract
In this document, multihoming is investigated from an end-node point In this document, multihoming is investigated from an end-node point
of view, and not from a site point of view as the term "multihoming" of view, and not from a site point of view as the term "multihoming"
is commonly understood so far. The purpose of this document is to is commonly understood so far. The purpose of this document is to
explain the motivations for fixed and mobile nodes (hosts and explain the motivations for fixed and mobile nodes (hosts and
routers) using multiple interfaces and the scenarios where this may routers) using multiple interfaces and the scenarios where this may
end up using multiple global addresses on their interfaces. Such end up using multiple global addresses on their interfaces. Such
multihoming configurations can bring a number of benefits once multihoming configurations can bring a number of benefits once
appropriate support mechanisms are put in place. Interestingly, this appropriate support mechanisms are put in place. Interestingly, this
analysis is generic, i.e. motivations and benefits of node analysis is generic, i.e. motivations and benefits of node
multihoming apply to both fixed end nodes and mobile end nodes. multihoming apply to both fixed end nodes and mobile end nodes.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Scenarios and Motivations . . . . . . . . . . . . . . . . . . 4
3.1. Need for Ubiquitous Access to the Internet . . . . . . . . 4
3. Scenarios and Motivations . . . . . . . . . . . . . . . . . . 6 3.2. Need to Redirect Established Sessions . . . . . . . . . . 5
3.1. Need for Ubiquitous Access to the Internet . . . . . . . . 6 3.3. Need to Set Up Preferences . . . . . . . . . . . . . . . . 5
3.2. Need to Redirect Established Sessions . . . . . . . . . . 6 3.4. Need to Select the Best Access Technology . . . . . . . . 5
3.3. Need to Set Up Preferences . . . . . . . . . . . . . . . . 6 3.5. Need to Dispatch Traffic over Distinct Paths . . . . . . . 6
3.4. Need to Select the Best Access Technology . . . . . . . . 7 3.6. Need for Reliability . . . . . . . . . . . . . . . . . . . 7
3.5. Need to Dispatch Traffic over Distinct Paths . . . . . . . 8 3.7. Need to Accelerate Transmission . . . . . . . . . . . . . 7
3.6. Need for Reliability . . . . . . . . . . . . . . . . . . . 8 4. Goals and Benefits of Multihoming . . . . . . . . . . . . . . 8
3.7. Need to Accelerate Transmission . . . . . . . . . . . . . 9 4.1. Permanent and Ubiquitous Access . . . . . . . . . . . . . 9
4.2. Reliability . . . . . . . . . . . . . . . . . . . . . . . 9
4. Goals and Benefits of Multihoming . . . . . . . . . . . . . . 10 4.3. Flow Redirection . . . . . . . . . . . . . . . . . . . . . 9
4.1. Permanent and Ubiquitous Access . . . . . . . . . . . . . 11 4.4. Load Sharing . . . . . . . . . . . . . . . . . . . . . . . 9
4.2. Reliability . . . . . . . . . . . . . . . . . . . . . . . 11 4.5. Load Balancing/Flow Distribution . . . . . . . . . . . . . 9
4.3. Flow Redirection . . . . . . . . . . . . . . . . . . . . . 12 4.6. Preference Settings . . . . . . . . . . . . . . . . . . . 10
4.4. Load Sharing . . . . . . . . . . . . . . . . . . . . . . . 12 4.7. Aggregate Bandwidth . . . . . . . . . . . . . . . . . . . 10
4.5. Load Balancing/Flow Distribution . . . . . . . . . . . . . 12 5. Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.6. Preference Settings . . . . . . . . . . . . . . . . . . . 12 5.1. Case 1: One Interface, Multiple Prefixes . . . . . . . . . 10
4.7. Aggregate Bandwidth . . . . . . . . . . . . . . . . . . . 12 5.2. Case 2: Several Interfaces . . . . . . . . . . . . . . . . 12
6. Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
5. Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 6.1. Address Selection . . . . . . . . . . . . . . . . . . . . 14
5.1. Case 1: One Interface, Multiple Prefixes . . . . . . . . . 13 6.2. Failure Discovery and Recovery Delay . . . . . . . . . . . 15
5.2. Case 2: Several Interfaces . . . . . . . . . . . . . . . . 15 6.3. Change of Traffic Characteristics . . . . . . . . . . . . 15
6.4. Transparency . . . . . . . . . . . . . . . . . . . . . . . 15
6. Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 7. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 16
6.1. <!--Source-->Address Selection . . . . . . . . . . . . . . 18 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 16
6.2. Failure Discovery and Recovery Delay . . . . . . . . . . . 18 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16
6.3. Change of Traffic Characteristics . . . . . . . . . . . . 19 10. Informative References . . . . . . . . . . . . . . . . . . . . 16
6.4. Transparency . . . . . . . . . . . . . . . . . . . . . . . 19 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17
7. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Intellectual Property and Copyright Statements . . . . . . . . . . 20
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 20
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 20
10. Informative References . . . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 22
Intellectual Property and Copyright Statements . . . . . . . . . . 24
1. Introduction 1. Introduction
New equipments shipped on the market now often integrate several New equipments shipped on the market now often integrate several
access technologies (both wired and wireless). The main purpose of access technologies (both wired and wireless). The main purpose of
this integration is to federate all means of communications in order this integration is to federate all means of communications in order
to access the Internet ubiquitously (from everywhere and at any time) to access the Internet ubiquitously (from everywhere and at any time)
as no single technology can be expected to be deployed everywhere. as no single technology can be expected to be deployed everywhere.
Flows may thus be redirected from one interface to the other Flows may thus be redirected from one interface to the other
following the loss of connectivity or change of the network following the loss of connectivity or change of the network
conditions. Besides providing an Internet access of wide spread and conditions in different access mediums. Besides enabling ubiquitous
reach, integrating several access technologies also allow to increase Interent access, integrating several access technologies also allows
bandwidth availability or to select the the most appropriate increased bandwidth availability and selection of the the most
technology according to the type of flow or choices of the user, appropriate technology according to the type of flow or choices of
since each network interface has different cost, performance, the user, since each access medium has different cost, performance,
bandwidth, access range, and reliability. bandwidth, access range, and reliability.
Once multiple accesses are offered, users may want to select the most Once multiple accesses are offered, users may want to select the most
appropriate set of network interface(s) depending on the network appropriate set of network interface(s) depending on the network
environment, particularly in wireless networks which are mutable and environment, particularly in wireless networks which are mutable and
less reliable than wired networks. Users may also want to select the less reliable than wired networks. Users may also want to select the
most appropriate interface per communication type or to combine a set most appropriate interface per communication type or to combine a set
of interfaces to get sufficient bandwidth. of interfaces to get sufficient bandwidth.
The purpose of this document is to emphasize the goals and benefits The purpose of this document is to emphasize the goals and benefits
of multihoming for fixed and mobile hosts and routers in a generic of multihoming for fixed and mobile hosts and routers in a generic
fashion, i.e. without focusing on issues pertaining to hosts, or fashion, i.e. without focusing on issues pertaining to hosts, or
routers, nor mobility. This document is indeed completing other routers, or mobility. There are other documents focusing on these.
documents focusing on these latter issues: Issues pertaining to site issues pertaining to site multihoming in fixed networks are discussed
multihoming in fixed networks are discussed in [1]. Mobility issues in [1]. Mobility issues pertaining to mobile nodes and mobile
pertaining to mobile nodes and mobile networks are respectively networks are respectively discussed in companion drafts [2] and [3].
discussed in companion drafts [2] and [3]. Our document is targetted Our document is targetted at IPv6, although our analysis may be
to IPv6, although our analysis may be applicable to IPv4 as well. applicable to IPv4 as well. The readers may refer to [4] for a
The readers may refer to [4] for a description of the problem description of the problem specific to Mobile IPv4.
specific to Mobile IPv4.
This document is organized as follows: first, the terms used in the This document is organized as follows. First, the terms used in the
document are defined before illustrating the motivations by means of document are defined before illustrating the motivations by means of
some scenarios in Section 3. These scenarios are then used to some scenarios in Section 3. These scenarios are then used to
emphasize the goals and benefits of multihoming in Section 4. Next emphasize the goals and benefits of multihoming in Section 4.
follows in Section 5 an analysis of the achievable goals in two Following which, Section 5 provides an analysis of the achievable
multihoming configurations, i.e. when the node either has a single goals in two multihoming configurations, i.e. when the node either
interface or when it has multiple interfaces. Section 6 concludes has a single interface or when it has multiple interfaces. Section 6
this document with a number of generic issues that will have to be concludes this document with a number of generic issues that will
solved in order to effectively meet multihoming goals and benefits. have to be solved in order to effectively meet multihoming goals and
benefits.
2. Terminology 2. Terminology
This draft is based on the terminology defined in [5]. For the This draft is based on the terminology defined in [5]. For the
purpose of clarity, we remind the definition of interface. Terms purpose of clarity, we remind the definition of interface. Terms
related to multihoming are not known to be defined in existing IETF related to multihoming are not known to be defined in existing IETF
RFCs. RFCs.
Interface Interface
A node's point of attachment to a link (as defined in [5]) A node's point of attachment to a link (as defined in [5])
Multihomed Node Multihomed Node
A node (either a host or a router) is multihomed when it has A node (either a host or a router) is multihomed when it has
several IPv6 addresses to choose between, i.e. in the following several global IPv6 addresses to choose between, i.e. in the
cases when it is either: following cases when it is either:
* multi-prefixed: multiple prefixes are advertised on the link(s) * multi-prefixed: multiple prefixes are advertised on the link(s)
the node is attached to, or. the node is attached to, or.
* multi-interfaced: the node has multiple interfaces to choose * multi-interfaced: the node has multiple interfaces to choose
between, on the same link or not. between, on the same link or not.
3. Scenarios and Motivations 3. Scenarios and Motivations
The following real-life scenarios highlight the motivations for The following real-life scenarios highlight the motivations for
multihoming. Each scenario usually yields more than one of the goals multihoming. Each scenario usually yields more than one of the goals
and benefits outlined in Section 4. All scenarios focus on wireless and benefits which are later outlined in Section 4. Although most
technologies though no mobility management may be involved (one can scenarios focus on wireless technologies, mobility management may not
use wireless access at office). be involved (one can use wireless access at office).
3.1. Need for Ubiquitous Access to the Internet 3.1. Need for Ubiquitous Access to the Internet
Mona is just getting out of a meeting with customers in a building. Mona is just getting out of a meeting with customers in a building.
She calls her head office. This audio communication is initiated via She calls her head office. This audio communication is initiated via
a private wireless local area network (WLAN) link realized over one a private wireless local area network (WLAN) link realized over one
of the available Wi-Fi hot-spots in the building. This is going to of the available Wi-Fi hot-spots in the building. This is going to
be a long call and she must attend another meeting a few minutes be a long call and she must attend another meeting a few minutes
drive from here. She walks to a taxi stand, and boards a taxi. The drive from here. She walks to a taxi stand, and boards a taxi. The
audio communication is automatically transferred to the public audio communication is automatically transferred to the public
wireless metropolitan area network (WMAN) over the Wi-Max wireless metropolitan area network (WMAN) over the Wi-Max
metropolitan network deployed, with no interruption of the metropolitan network deployed, with no interruption of the
communication. communication.
This scenario illustrates the need to use multiple types of access This scenario illustrates the need to use multiple types of access
technologies in order to maintain ongoing communications when a user technologies in order to maintain ongoing communications when a user
is moving out of the coverage area of a specific technology. is moving out of the coverage area of a specific technology.
3.2. Need to Redirect Established Sessions 3.2. Need to Redirect Established Sessions
Oliver is in the passenger lounge waiting at his train. He uses this Oliver is in the passenger lounge waiting for his train. He uses
opportunity and the presence of a WLAN hot-spot to download the news this opportunity and the presence of a WLAN hot-spot to download the
from his favorite on-line news channel. While Oliver is downloading news from his favorite on-line news channel. While Oliver is
the news, he receives a video call over his wide area 3G cellular downloading the news, he receives a video call over his wide area 3G
link. The bandwidth and traversal delay of the wide area cellular cellular link. The bandwidth and traversal delay of the wide area
link is not adequate for high quality video-conference, so both flows cellular link is not adequate for high quality video-conference, so
(video/audio) are transferred to the WLAN link provided by the hot- both flows (video/audio) are transferred to the WLAN link provided by
spot. This transfer occurs transparently and without affecting the the hot-spot. This transfer occurs transparently and without
other active flows. affecting the other active flows.
This scenario illustrates the need for a nomadic user to dynamically This scenario illustrates the need for a nomadic user to dynamically
redirect flows from one type of access technology to another based on redirect flows from one type of access technology to another based on
some user preferences or traffic requirements. some user preferences or traffic requirements.
3.3. Need to Set Up Preferences 3.3. Need to Set Up Preferences
Nami works at home for a publishing company using her connection to Nami works at home for a publishing company using her connection to
the Internet via a low-speed dial up connection, a public and the Internet via a low-speed dial up connection, a public and
unrealiable 802.11b WLAN from the street and her 3G cellular phone. unrealiable 802.11b WLAN from the street and her 3G cellular phone.
Because the public WLAN is not secure, and the dial-up connection too Since the public WLAN is not secure, and the dial-up connection too
slow, she checks her company's email using her 3G phone even though slow, Nami checks her company's email using her 3G phone even though
it is expensive. She uses the WLAN service for non-confidential it is expensive. The WLAN service is used for non-confidential
activities such as web-browsing and video-conferencing. The dial-up activities, such as web-browsing and video-conferencing, and the
connection is moslty used to transmit her completed work securely and dial-up connection is moslty used to transmit her completed work
synchronizing her file system. securely and synchronizing her file system.
This scenario illustrates the need in a fixed environment to This scenario illustrates the need in a fixed environment to
simultaneously use multiple access technologies and to select the simultaneously use multiple access technologies and to select the
most appropriate one according to user preferences. No assumptions most appropriate one according to user preferences. No assumptions
are made whether flows need to be redirected or not from one access are made whether flows need to be redirected or not from one access
technology to another. These preferences can be dynamic (e.g. the technology to another. These preferences can be dynamic (e.g. the
WLAN link is only used if the signal is good and there is no unusual WLAN link is only used if the signal is good and there is no unusual
latency) or configured once for each application (e.g. applications latency) or configured once for each application (e.g. applications
exchanging confidential data always over the most secure link). exchanging confidential data always over the most secure link).
3.4. Need to Select the Best Access Technology 3.4. Need to Select the Best Access Technology
Alice is a paramedic. Her ambulance is called to the scene of a car Alice is a paramedic. Her ambulance is called to the scene of a car
accident. She initiates a communication to a hospital via a wide accident. She initiates a communication to a hospital via a wide
area cellular link for the relay of low bit-rate live video from the area cellular link for the relay of low bit-rate live video from the
site of the crash to assess the severity of the accident. It is site of the crash to assess the severity of the accident. It is
identified that one of the passengers has suffered a severe head identified that one of the passengers has suffered a severe head
injury. Alice decides to consult a specialist via video injury. Alice decides to consult a specialist via video
conferencing. This session is initiated from the specialist via the conferencing. This session is initiated from the specialist via the
same wide area cellular link. Meanwhile, Alice requests for the same wide area cellular link. Meanwhile, Alice requests for the
download of the patient medical records from the hospital servers. download of the patient's medical records from the hospital servers.
The wide area cellular link is too slow for this download, so the The wide area cellular link is too slow for this download, so the
download is transfered to the ambulance satellite link. Even though download is transfered to the ambulance satellite link. Even though
this link provides a significantly faster bit rate it has a longer this link provides a significantly faster bit rate it has a longer
traversal delay and only down-link is available. For this, only the traversal delay and only downlink is available. Thus, only the
down-stream of the download is transferred while up-stream proceeds downstream of the download is transferred while upstream proceeds
over the wide area cellular link. Connectivity between the parametic over the wide area cellular link. Connectivity between the parametic
and the ambulance is managed over a WLAN link. Even though Alice has and the ambulance is managed over a WLAN link. Even though Alice has
performed a partial hand-off for the transfer of the download down- performed a partial hand-off for the transfer of the downstream to
stream to the satellite link, the upstream and the video conferencing the satellite link, the upstream and the video conferencing session
session remains on the wide area cellular link. This serves best the remains on the wide area cellular link. This serves best the time
time constraint requirements of the real time communications. constraint requirements of the real time communications.
This scenario illustrates the need in a mobile environment for both This scenario illustrates the need in a mobile environment for both
ubiquitous access to the Internet using whatever available interface ubiquitous access to the Internet using whatever available interface
and the need to dispatch flows to particular access media according and the need to dispatch flows to particular access media according
to traffic characteristics or preferences. It also illustrates that to traffic characteristics or preferences. It also illustrates that
flows can be directed to separate media downlink and uplink. The flows can be directed to separate media downlink and uplink. The
fact that the actual connection to the Internet is maintained via the fact that the actual connection to the Internet is maintained via the
ambulance to which the paramedic is connected to via a WLAN link ambulance to which the paramedic is connected to via a WLAN link
illustrates to need to express preferences on the path to be taken illustrates to need to express preferences on the path to be taken
from a remote computer (i.e. a mobile router in the ambulance in this from a remote computer (i.e. a mobile router in the ambulance in this
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When his car passes an area where only a wide coverage-range cellular When his car passes an area where only a wide coverage-range cellular
network is available, safety related sessions are maintained via the network is available, safety related sessions are maintained via the
cellular network whereas infotainment data is buffered and cellular network whereas infotainment data is buffered and
transmitted over high data rate network access when one becomes transmitted over high data rate network access when one becomes
available. Toll bills and road sign data are transmitted over a available. Toll bills and road sign data are transmitted over a
dedicated radio interface, whereas data exchanged between vehicles is dedicated radio interface, whereas data exchanged between vehicles is
transmitted over a preferred media. Time-critical safety sessions transmitted over a preferred media. Time-critical safety sessions
are always given priority. are always given priority.
This scenario illustrates the applicability of multihoming in road This scenario illustrates the applicability of multihoming in road
transportation and emphasizes more particularly the need to save transportation and emphasizes more particularly the need to
traffic transiting in a particular access network when there is a prioritize traffic transiting in a particular access network when
possibility to send data over an alternative route. The availability there is a possibility to send data over an alternative route. The
of multiple access medium and the variety of on-board units availability of multiple access medium and the variety of on-board
illustrates a NEMO [6] scenario as currently considered in the CALM units illustrates a NEMO [6] scenario as currently considered in the
Architecture designed by ISO TC204 WG16 for Intelligent CALM Architecture [7] designed by ISO TC204 WG16 for Intelligent
Transportations Systems (ITS). The exchange of safety data Transportations Systems (ITS) [8]. The exchange of safety data
illustrates the ongoing work of the car-to-car communication illustrates the ongoing work of the car-to-car communication
consortium (C2C-CC) consortium (C2C-CC) [9].
3.6. Need for Reliability 3.6. Need for Reliability
Ingrid, a doctor, performs an operation via long-distance medical Ingrid, a doctor, performs an operation via long-distance medical
system. She watches a patient in a battle field over the screen system. She watches a patient in a battle field over the screen
which delivers real-time images of the patient. Sensors on her arms which delivers real-time images of the patient. Sensors on her arms
deliver her operational actions and a robot performs the actual deliver her operational actions and a robot performs the actual
operation in the battle field. Since the operation is critical, the operation in the battle field. Since the operation is critical, the
delivery of patient images and Dr. Ingrid's action is done by bi- delivery of patient images and Dr. Ingrid's action is done by bi-
casting from/to multiple interfaces bound to a distinct technology or casting from/to multiple interfaces bound to a distinct technology or
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WLAN interface. This additional WLAN interface is then used to WLAN interface. This additional WLAN interface is then used to
connect to another access point, and the different download flows are connect to another access point, and the different download flows are
distributed between the two wireless interfaces. distributed between the two wireless interfaces.
This scenario illustrates the need to use multiple accesses to the This scenario illustrates the need to use multiple accesses to the
Internet in order to accelerate the amount of data that could be Internet in order to accelerate the amount of data that could be
transmitted over a period of time. transmitted over a period of time.
4. Goals and Benefits of Multihoming 4. Goals and Benefits of Multihoming
The scenarios presented in the previous section are now used to From the scenarios presented in the previous section, we can
highlight the goals and benefits of node multihoming. The goals highlight the goals and benefits of node multihoming. The goals
cannot really be distinguished from the benefits, but there are cannot really be distinguished from the benefits, but there are
several situations where multihomed is either advisable or several situations where multihomed is either advisable or
beneficial. These benefits and goals listed here are by no means beneficial. These benefits and goals listed here are by no means
distinct and separate; most of them overlap with one another. It is distinct and separate; most of them overlap with one another. It is
not the objective here to classify the benefits and goals into not the objective here to classify the benefits and goals into
different non-overlapping consituents. Instead the objective is to different non-overlapping consituents. Instead the objective is to
list the possible benefits and goals different people have in mind list the possible benefits and goals different people have in mind
when deploying a multihomed node. when deploying a multihomed node.
Figure 1 summarizes which goal applies to the scenarios introduced in
Section 3. Note that all these goals and benefits apply to both
fixed end nodes and mobile end nodes, though the scenarios may either
focus on a fixed used (F), or nomadic usage (N), or a mobile usage
(M). Nomadic and mobile users are both on the move, while a fixed
user doesn't physically move. The difference between nomadic usages
and mobile usages is that sessions are not required to be maintained
when the access network is changed as a result of physical move
within the topology. No assumptions are made whether mobility
support mechanims may be useful or not in any of the fixed, nomadic
and mobile usages in order to maintain sessions. This is out of
scope of the present document.
+===================================+===========================+ +===================================+===========================+
| | Scenarios | | | | Scenarios |
| +---+---+---+---+---+---+---+ | +---+---+---+---+---+---+---+
| Goals | 1 | 2 | 3 | 4 | 5 | 6 | 7 | | Goals | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
+===================================+===+===+===+===+===+===+===+ +===================================+===+===+===+===+===+===+===+
| Ubiquitous Access | o | | | o | o | | | | Ubiquitous Access | o | | | o | o | | |
+-----------------------------------+---+---+---+---+---+---+---+ +-----------------------------------+---+---+---+---+---+---+---+
| Flow Redirection | o | o | o | o | o | | | | Flow Redirection | o | o | o | o | o | | |
+-----------------------------------+---+---+---+---+---+---+---+ +-----------------------------------+---+---+---+---+---+---+---+
| Reliability | | | o | o | o | o | | | Reliability | | | o | o | o | o | |
+-----------------------------------+---+---+---+---+---+---+---+ +-----------------------------------+---+---+---+---+---+---+---+
| Load Sharing | | | | | o | | | | Load Sharing | | | | | o | | |
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+-----------------------------------+---+---+---+---+---+---+---+ +-----------------------------------+---+---+---+---+---+---+---+
| Preference Settings | | o | o | o | | | | | Preference Settings | | o | o | o | | | |
+-----------------------------------+---+---+---+---+---+---+---+ +-----------------------------------+---+---+---+---+---+---+---+
| Aggregate Bandwidth | | | | o | | | o | | Aggregate Bandwidth | | | | o | | | o |
+===================================+===+===+===+===+===+===+===+ +===================================+===+===+===+===+===+===+===+
| Usage: F=Fixed N=Nomadic M=Mobile | M | N | F | M | M | F | N | | Usage: F=Fixed N=Nomadic M=Mobile | M | N | F | M | M | F | N |
+===================================+===+===+===+===+===+===+===+ +===================================+===+===+===+===+===+===+===+
Figure 1: Goals Applying to Each Scenario Figure 1: Goals Applying to Each Scenario
Figure 1 summarizes which goal applies to the scenarios introduced in
Section 3. Note that all these goals and benefits apply to both
fixed end nodes and mobile end nodes, though the scenarios may either
focus on a fixed used (F), or nomadic usage (N), or a mobile usage
(M). Nomadic and mobile users are both on the move, while a fixed
user doesn't physically move. The difference between nomadic usages
and mobile usages is that sessions are not required to be maintained
when the access network is changed as a result of physical move
within the topology. No assumptions are made whether mobility
support mechanims may be useful or not in any of the fixed, nomadic
and mobile usages in order to maintain sessions. This is out of
scope of the present document.
4.1. Permanent and Ubiquitous Access 4.1. Permanent and Ubiquitous Access
To provide an extended coverage area via distinct access To provide an extended coverage area via distinct access
technologies. technologies.
Multiple interfaces bound to distinct technologies can be used to Multiple interfaces bound to distinct technologies can be used to
ensure a permanent connectivity is offered, anywhere, anytime, with ensure a permanent connectivity is offered, anywhere, anytime, with
anyone. anyone.
4.2. Reliability 4.2. Reliability
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unavailable (e.g. failure). Connectivity is guaranteed as long as at unavailable (e.g. failure). Connectivity is guaranteed as long as at
least one connection to the Internet is maintained. least one connection to the Internet is maintained.
A potential means is to duplicate network component, another is to A potential means is to duplicate network component, another is to
duplicate a particular flow simultaneously through different routes. duplicate a particular flow simultaneously through different routes.
This minimizes packet loss typically for real-time communication and This minimizes packet loss typically for real-time communication and
burst traffic. It also minimizes delay of packet delivery caused by burst traffic. It also minimizes delay of packet delivery caused by
congestion and achieves more reliable real-time communication than congestion and achieves more reliable real-time communication than
single-casting. For mobile computing, bi-casting avoids dropping single-casting. For mobile computing, bi-casting avoids dropping
packets when a mobile node changes its interface during communication packets when a mobile node changes its interface during communication
[7]. [10].
4.3. Flow Redirection 4.3. Flow Redirection
To be able to redirect flows from one interface, or one address to To be able to redirect flows from one interface (or address) to
another one, without having to re-initiate the flow. This can be due another without having to re-initiate the flow. This can be due to
to preference changes or upon network failure. preference changes or upon network failure.
4.4. Load Sharing 4.4. Load Sharing
To spread network traffic load among several routes. This is To spread network traffic load among several routes. This is
achieved when traffic load is distributed among different connections achieved when traffic load is distributed among different connections
between the node and the Internet [8]. between the node and the Internet [11].
4.5. Load Balancing/Flow Distribution 4.5. Load Balancing/Flow Distribution
To separate a flow between multiple points of attachment To separate a flow between multiple points of attachment
(simultaneously active or not) of a node, usually chosing the less (simultaneously active or not) of a node, usually chosing the less
loaded connection or according to preferences on the mapping between loaded connection or according to preferences on the mapping between
flows and interfaces. flows and interfaces.
4.6. Preference Settings 4.6. Preference Settings
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going outside the coverage area of its access point). going outside the coverage area of its access point).
o Flow redirection: YES o Flow redirection: YES
The node might need to redirect a flow from one address to another The node might need to redirect a flow from one address to another
for several reasons. For example, if one of the IPv6 prefix for several reasons. For example, if one of the IPv6 prefix
becomes unavailable, flows using the address from this prefix becomes unavailable, flows using the address from this prefix
could be redirected to the address obtained on the other prefix. could be redirected to the address obtained on the other prefix.
o Reliability: MAYBE o Reliability: MAYBE
In case of failure of one IPv6 prefix, one of the address of the In case of failure of one IPv6 prefix, one of the address of the
node will not be valid anymore. Another available address built node will not be valid anymore. Another available address built
from other prefixes may allow the node to recover this sort of from other prefixes may allow the node to recover this sort of
failure. failure. Bi-casting can be performed to ensure the delivery of
packets on the node. To do so, more than one IPv6 address must be
Bi-casting can be performed to ensure the delivery of packets on used simultaneously for one flow. Bi-casting would allow the node
the node. To do so, more than one IPv6 address must be used to seamlessly change the address used on the node.
simultaneously for one flow. Bi-casting would allow the node to
seamlessly change the address used on the node.
o Load sharing: YES o Load sharing: YES
Load Sharing can be performed in the network, according to the Load Sharing can be performed in the network, according to the
address used by the node. The choice of the address used by the address used by the node. The choice of the address used by the
node and the router selection can be influenced by load sharing node and the router selection can be influenced by load sharing
rules. This mostly benefits the network side: if different access rules. This mostly benefits the network side: if different access
routers or routes can be used to forward the node's traffic, the routers or routes can be used to forward the node's traffic, the
traffic load will be shared in the network. traffic load will be shared in the network.
o Load balancing/Flow Distribution: NO o Load balancing/Flow Distribution: NO
Load balancing cannot be performed when the node has only one Load balancing cannot be performed when the node has only one
interface. interface.
o Preferences: YES o Preferences: YES
The source address can be chosen according to preferences set up The source address can be chosen according to preferences set up
by the user, or according to preferences set up in the network by the user, or according to preferences set up in the network
(such as with the default router preferences option introduced in (such as with the default router preferences option introduced in
Router Advertisement [9]), or by the ISP. Router Advertisement [12]), or by the ISP.
o Aggregated Bandwidth: MAYBE o Aggregated Bandwidth: MAYBE
With only one interface connected to a link, the node generally With only one interface connected to a link, the node generally
will not be able to benefit from an increased aggregated bandwidth will not be able to benefit from an increased aggregated bandwidth
with multiple prefixes. However, this benefit might be gained with multiple prefixes. However, this benefit might be gained
indirectly. For instance, by alternating between different indirectly. For instance, by alternating between different
addresses, the total throughput may be higher (eg. due to load addresses, the total throughput may be higher (eg. due to load
sharing). Also, some web and file transfer servers limit transfer sharing). Also, some web and file transfer servers limit transfer
bandwidths based on the client's address. By using different bandwidths based on the client's address. By using different
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+====================================+=====+=====+ +====================================+=====+=====+
| | Cases | | | Cases |
| +-----+-----+ | +-----+-----+
| Issues | (1) | (2) | | Issues | (1) | (2) |
+====================================+=====+=====+ +====================================+=====+=====+
| Source Address Selection | o = | o = | | Source Address Selection | o = | o = |
+------------------------------------+-----+-----+ +------------------------------------+-----+-----+
| Recovery Delay | o | o + | | Recovery Delay | o | o + |
+------------------------------------+-----+-----+ +------------------------------------+-----+-----+
| Change of e2e Path Characteristics | o - | o + | | Change of Traffic Characteristics | o - | o + |
+------------------------------------+-----+-----+ +------------------------------------+-----+-----+
| Transparency | o + | o + | | Transparency | o + | o + |
+====================================+=====+=====+ +====================================+=====+=====+
Figure 2: Issues and their Importance for Each Case Figure 2: Issues and their Importance for Each Case
6.1. <!--Source-->Address Selection 6.1. Address Selection
The multihomed node has several addresses, which implies the The multihomed node has several addresses, which implies the
appropriate address must be chosen when an IPv6 communication is appropriate address must be chosen when an IPv6 communication is
established (e.g. when a TCP connection is opened). An address established (e.g. when a TCP connection is opened). An address
selection mechanism is therefore needed. selection mechanism is therefore needed.
The choice of the address can be influenced by many parameters: user The choice of the address can be influenced by many parameters: user
preferences, ingress filtering, preference flag in Router preferences, ingress filtering, preference flag in Router
Advertisement, destination prefix, type of interface, link Advertisement, destination prefix, type of interface, link
characteristics, etc. characteristics, etc.
6.2. Failure Discovery and Recovery Delay 6.2. Failure Discovery and Recovery Delay
A particular access to the Internet may become unavailable while it A particular access to the Internet may become unavailable while it
is being used. The time needed for detecting an address has become is being used. The time needed for detecting an address has become
invalid and the time to redirect communications to one of its other invalid and the time to redirect communications to one of its other
addresses is considered critical. Efficient failure detection and addresses is considered critical. Efficient failure detection and
recovery mechanisms are therefore required. recovery mechanisms are therefore required.
Note that transport sessions with multihoming capabilies such as SCTP Note that transport sessions with multihoming capabilies such as SCTP
[10] may be able to continue easily since SCTP has built-in [13] may be able to continue easily since SCTP has built-in
transmission rate control mechanims to take into account the transmission rate control mechanims to take into account the
differences between two paths. differences between two paths.
6.3. Change of Traffic Characteristics 6.3. Change of Traffic Characteristics
The change of path for a specific session (e.g. due to change of The change of path for a specific session (e.g. due to change of
interface) may cause changes on the end-to-end path characteristics interface) may cause changes on the end-to-end path characteristics
(higher delay, different PMTU, etc). This could have an impact on (higher delay, different MTUs, etc). This could have an impact on
upper layer protocols such as transport protocols (particularly TCP) upper layer protocols such as transport protocols (particularly TCP)
or applications that are sensitive to changes. or applications that are sensitive to changes.
6.4. Transparency 6.4. Transparency
In some situations, it will be necessary to divert some or all of the In some situations, it will be necessary to divert some or all of the
sessions from one interface or prefix to another (e.g. due to loss of sessions from one interface or prefix to another (e.g. due to loss of
network connection or the access router becoming unreachable - this network connection or the access router becoming unreachable - this
could be particularly frequent for mobile nodes). With no support could be particularly frequent for mobile nodes). With no support
mechanism, an address change would cause on-going sessions using the mechanism, an address change would cause on-going sessions using the
invalid former address to terminate, and to be restarted using the invalid former address to terminate, and to be restarted using the
new address. To avoid this, a recovery mechanism allowing the new address. To avoid this, a recovery mechanism allowing the
redirection of all current communications to one of the other IPv6 redirection of all current communications to one of the other IPv6
addresses is needed. addresses is needed.
In the case of a mobile node changing its point of attachment using In the case of a mobile node changing its point of attachment using
the same interface, all flows must be redirected to the new location the same interface, all flows must be redirected to the new location
in order to maintain sessions. A mobility management solution may be in order to maintain sessions. A mobility management solution may be
required, such as Mobile IPv6 [11] for mobile hosts or NEMO Basic required, such as Mobile IPv6 [14] for mobile hosts or NEMO Basic
Support [6] for mobile routers. Additional mechanisms may be needed Support [6] for mobile routers. Additional mechanisms may be needed
if the node was using several addresses on its previous link, such as if the node was using several addresses on its previous link, such as
which flows shall be to redirected, which address must be associated which flows shall be to redirected, which address must be associated
with the new address(es). The scalability of the operations involved with the new address(es). The scalability of the operations involved
in the redirection of flows may also be an issue, if we consider that in the redirection of flows may also be an issue, if we consider that
the node had several addresses on the previous link and several flows the node had several addresses on the previous link and several flows
and/or correspondents. Issues pertaining to Mobile IPv6 and NEMO and/or correspondents. Issues pertaining to Mobile IPv6 and NEMO
Basic Support are explained in companion drafts [2] and [3] Basic Support are explained in companion drafts [2] and [3]
respectively. respectively.
7. Conclusion 7. Conclusion
In this document we studied multihoming at the level of the end node. In this document we studied multihoming at the level of an end node.
A node is multihomed in a situation where it has multiple addresses, A node is multihomed in a situation where it has multiple addresses,
usually due to the availability of multiple interfaces on the node, usually due to the availability of multiple interfaces on the node,
or the announcement of multiple prefixes on the link it is attached or the announcement of multiple prefixes on the link the node is
to. attached to. This satisfies a number of needs and brings a number of
potential benefits. The availability of multiple addresses allows
This fits a number of needs and brings a number of potential the use of an alternate address as the replacement of another
benefits. The availability of multiple addresses allows the use of (permanent and ubiquitous access to the Internet, reliability) or the
an alternate address as the replacement of another (permanent and transmission of multiple flows simultaneously over different routes
ubiquitous access to the Internet, reliability) or the transmission (flow redirection, load sharing, load balancing/flow distribution,
of multiple flows simultaneously over different routes (flow
redirection, load sharing, load balancing/flow distribution,
preference settings or aggregate bandwidth). preference settings or aggregate bandwidth).
This study is motivated for both fixed nodes and mobile nodes, but This study is motivated for both fixed nodes and mobile nodes, but
the motivation prevails for mobile nodes (hosts and routers). The the motivation prevails for mobile nodes (hosts and routers). The
benefits of multihoming can only be achieved once some issues are benefits of multihoming can only be achieved once some issues are
solved. Generic issues were outlined in the present document, solved. Generic issues were outlined in the present document,
whereas issues specific to mobile hosts and mobile routers are whereas issues specific to mobile hosts and mobile routers are
investigated in the associated documents [2] and [3] and, investigated in the associated documents [2] and [3] and,
respectively. respectively.
8. Contributors 8. Contributors
This document is based on an earlier document to which Thomas Noel This document is based on an earlier document to which Thomas Noel
(ULP, Strasbourg) and EunKyoung Paik (SNU, Seoul) also contributed in (ULP, Strasbourg) and EunKyoung Paik (SNU, Seoul) also contributed in
addition to the authors listed in the present document. addition to the authors listed in the present document.
9. Acknowledgments 9. Acknowledgments
We would like to extend our gratitude to Niko A. Fikouras, Ken We would like to extend our gratitude to Niko A. Fikouras, Ken
Nagami, Pekka Savola, Hesham Soliman, and many others who had Nagami, Pekka Savola, Hesham Soliman and many others who had provided
provided valuable comments to this document. valuable comments to this document.
10. Informative References 10. Informative References
[1] Abley, J., Black, B., and V. Gill, "Goals for IPv6 Site- [1] Abley, J., Black, B., and V. Gill, "Goals for IPv6 Site-
Multihoming Architectures", RFC 3582, August 2003. Multihoming Architectures", RFC 3582, August 2003.
[2] Montavont, N., Wakikawa, R., Ernst, T., Ng, C., and K. [2] Montavont, N., Wakikawa, R., Ernst, T., Ng, C., and K.
Kuladinithi, "Analysis of Multihoming in Mobile IPv6", Kuladinithi, "Analysis of Multihoming in Mobile IPv6",
draft-ietf-monami6-mipv6-analysis-03 (work in progress), draft-ietf-monami6-mipv6-analysis-05 (work in progress),
July 2007. May 2008.
[3] Ng, C., Paik, Ernst, and C. Bagnulo, "Analysis of Multihoming [3] Ng, C., Ernst, T., Paik, E., and M. Bagnulo, "Analysis of
in Network Mobility Support", Multihoming in Network Mobility Support", RFC 4980,
draft-ietf-nemo-multihoming-issues-06 (work in progress), October 2007.
June 2006.
[4] Fikouras, N., "Mobile IPv4 Flow Mobility Problem Statement", [4] Fikouras, N., "Mobile IPv4 Flow Mobility Problem Statement",
draft-nomad-mip4-flow-mobility-pb-00.txt (work in progress), draft-nomad-mip4-flow-mobility-pb-00.txt (work in progress),
Feb 2004. Feb 2004.
[5] Manner, J. and M. Kojo, "Mobility Related Terminology", [5] Manner, J. and M. Kojo, "Mobility Related Terminology",
RFC 3753, June 2004. RFC 3753, June 2004.
[6] Devarapalli, V., Wakikawa, R., Petrescu, A., and P. Thubert, [6] Devarapalli, V., Wakikawa, R., Petrescu, A., and P. Thubert,
"Network Mobility (NEMO) Basic Support Protocol", RFC 3963, "Network Mobility (NEMO) Basic Support Protocol", RFC 3963,
January 2005. January 2005.
[7] Malki, K. and H. Soliman, "Simultaneous Bindings for Mobile [7] "Official web page of ISO TC 204 Working Group 16",
URI: http://www.calm.hu/.
[8] "CALM - Medium and Long Range, High Speed, Air Interfaces
parameters and protocols for broadcast, point to point,
vehicle to vehicle, and vehicle to point communication in the
ITS sector - Networking Protocol - Complementary Element", ISO
Draft ISO/WD 21210, February 2005.
[9] "Car2Car Communication Consortium Official Website",
URI: http://www.car-2-car.org/.
[10] Malki, K. and H. Soliman, "Simultaneous Bindings for Mobile
IPv6 Fast Handovers", draft-elmalki-mobileip-bicasting-v6-06 IPv6 Fast Handovers", draft-elmalki-mobileip-bicasting-v6-06
(work in progress), July 2005. (work in progress), July 2005.
[8] Hinden, R. and D. Thaler, "IPv6 Host to Router Load Sharing", [11] Hinden, R. and D. Thaler, "IPv6 Host to Router Load Sharing",
draft-ietf-ipv6-host-load-sharing-04 (work in progress), draft-ietf-ipv6-host-load-sharing-04 (work in progress),
June 2005. June 2005.
[9] Draves, R. and D. Thaler, "Default Router Preferences and More- [12] Draves, R. and D. Thaler, "Default Router Preferences and More-
Specific Routes", RFC 4191, November 2005. Specific Routes", RFC 4191, November 2005.
[10] Stewart, R., Xie, Q., Morneault, K., Sharp, C., Schwarzbauer, [13] Stewart, R., Xie, Q., Morneault, K., Sharp, C., Schwarzbauer,
H., Taylor, T., Rytina, I., Kalla, M., Zhang, L., and V. H., Taylor, T., Rytina, I., Kalla, M., Zhang, L., and V.
Paxson, "Stream Control Transmission Protocol", RFC 2960, Paxson, "Stream Control Transmission Protocol", RFC 2960,
October 2000. October 2000.
[11] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in [14] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in
IPv6", RFC 3775, June 2004. IPv6", RFC 3775, June 2004.
Authors' Addresses Authors' Addresses
Thierry Ernst Thierry Ernst
INRIA INRIA
INRIA Rocquencourt INRIA Rocquencourt
Domaine de Voluceau B.P. 105 Domaine de Voluceau B.P. 105
Le Chesnay, 78153 Le Chesnay, 78153
France France
Phone: +33-1-39-63-59-30 Phone: +33-1-39-63-59-30
Fax: +33-1-39-63-54-91 Fax: +33-1-39-63-54-91
Email: thierry.ernst@inria.fr Email: thierry.ernst@inria.fr
URI: http://www.nautilus6.org/~thierry URI: http://www.nautilus6.org/~thierry
Nicolas Montavont Nicolas Montavont
Ecole Nationale Superieure des telecommunications de Bretagne Institut Telecom - Telecom Bretagne
2, rue de la chataigneraie 2, rue de la chataigneraie
Cesson Sevigne 35576 Cesson Sevigne 35576
France France
Phone: (+33) 2 99 12 70 23 Phone: (+33) 2 99 12 70 23
Email: nicolas.montavont@enst-bretagne.fr Email: nicolas.montavont@telecom-bretagne.eu
URI: http://www-r2.u-strasbg.fr/~montavont/ URI: http://www.rennes.enst-bretagne.fr/~montavont/
Ryuji Wakikawa Ryuji Wakikawa
Keio University Toyota ITC / Keio University
Department of Environmental Information, Keio University. 6-6-20 Akasaka, Minato-ku
5322 Endo Tokyo 107-0052
Fujisawa, Kanagawa 252-8520
Japan Japan
Phone: +81-466-49-1100 Phone: +81-3-5561-8276
Fax: +81-466-49-1395 Fax: +81-3-5561-8292
Email: ryuji@sfc.wide.ad.jp Email: ryuji@jp.toyota-itc.com
URI: http://www.wakikawa.org/
Chan-Wah Ng Chan-Wah Ng
Panasonic Singapore Laboratories Pte Ltd Panasonic Singapore Laboratories Pte Ltd
Blk 1022 Tai Seng Ave #06-3530 Blk 1022 Tai Seng Ave #06-3530
Tai Seng Industrial Estate Tai Seng Industrial Estate
Singapore 534415 Singapore 534415
SG Singapore
Phone: +65 65505420 Phone: +65 65505420
Email: chanwah.ng@sg.panasonic.com Email: chanwah.ng@sg.panasonic.com
Koojana Kuladinithi Koojana Kuladinithi
University of Bremen University of Bremen
ComNets-ikom,University of Bremen. ComNets-ikom,University of Bremen.
Otto-Hahn-Allee NW 1 Otto-Hahn-Allee NW 1
Bremen, Bremen 28359 Bremen, Bremen 28359
Germany Germany
Phone: +49-421-218-8264 Phone: +49-421-218-8264
Fax: +49-421-218-3601 Fax: +49-421-218-3601
Email: koo@comnets.uni-bremen.de Email: koo@comnets.uni-bremen.de
skipping to change at page 24, line 7 skipping to change at page 20, line 7
Bremen, Bremen 28359 Bremen, Bremen 28359
Germany Germany
Phone: +49-421-218-8264 Phone: +49-421-218-8264
Fax: +49-421-218-3601 Fax: +49-421-218-3601
Email: koo@comnets.uni-bremen.de Email: koo@comnets.uni-bremen.de
URI: http://www.comnets.uni-bremen.de/~koo/ URI: http://www.comnets.uni-bremen.de/~koo/
Full Copyright Statement Full Copyright Statement
Copyright (C) The IETF Trust (2007). Copyright (C) The IETF Trust (2008).
This document is subject to the rights, licenses and restrictions This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors contained in BCP 78, and except as set forth therein, the authors
retain all their rights. retain all their rights.
This document and the information contained herein are provided on an This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
skipping to change at page 24, line 44 skipping to change at line 886
attempt made to obtain a general license or permission for the use of attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr. http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any The IETF invites any interested party to bring to its attention any
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rights that may cover technology that may be required to implement rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at this standard. Please address the information to the IETF at
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Acknowledgment
Funding for the RFC Editor function is provided by the IETF
Administrative Support Activity (IASA).
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